Table Of Content

ANSYS CFX-Solver Modeling Guide ANSYS, Inc. Release 15.0 Southpointe November 2013 275 Technology Drive Canonsburg, PA 15317 ANSYS, Inc. is [email protected] certified to ISO 9001:2008. http://www.ansys.com (T) 724-746-3304 (F) 724-514-9494 Copyright and Trademark Information © 2013 SAS IP, Inc. All rights reserved. Unauthorized use, distribution or duplication is prohibited. ANSYS, ANSYS Workbench, Ansoft, AUTODYN, EKM, Engineering Knowledge Manager, CFX, FLUENT, HFSS and any and all ANSYS, Inc. brand, product, service and feature names, logos and slogans are registered trademarks or trademarks of ANSYS, Inc. or its subsidiaries in the United States or other countries. ICEM CFD is a trademark used by ANSYS, Inc. under license. CFX is a trademark of Sony Corporation in Japan. All other brand, product, service and feature names or trademarks are the property of their respective owners. Disclaimer Notice THIS ANSYS SOFTWARE PRODUCT AND PROGRAM DOCUMENTATION INCLUDE TRADE SECRETS AND ARE CONFID- ENTIAL AND PROPRIETARY PRODUCTS OF ANSYS, INC., ITS SUBSIDIARIES, OR LICENSORS.The software products and documentation are furnished by ANSYS, Inc., its subsidiaries, or affiliates under a software license agreement that contains provisions concerning non-disclosure, copying, length and nature of use, compliance with exporting laws, warranties, disclaimers, limitations of liability, and remedies, and other provisions.The software products and documentation may be used, disclosed, transferred, or copied only in accordance with the terms and conditions of that software license agreement. ANSYS, Inc. is certified to ISO 9001:2008. U.S. Government Rights For U.S. Government users, except as specifically granted by the ANSYS, Inc. software license agreement, the use, duplication, or disclosure by the United States Government is subject to restrictions stated in the ANSYS, Inc. software license agreement and FAR 12.212 (for non-DOD licenses). Third-Party Software See the legal information in the product help files for the complete Legal Notice for ANSYS proprietary software and third-party software. If you are unable to access the Legal Notice, please contact ANSYS, Inc. Published in the U.S.A. Table of Contents 1. Basic Capabilities Modeling.................................................................................................................... 1 1.1. Domains........................................................................................................................................... 2 1.2. Physical Models................................................................................................................................ 2 1.2.1. Steady State and Transient Flows.............................................................................................. 3 1.2.2. Mesh Deformation................................................................................................................... 4 1.2.2.1. None............................................................................................................................... 4 1.2.2.2. Regions of Motion Specified............................................................................................ 4 1.2.2.2.1. Displacement Relative To........................................................................................ 4 1.2.2.2.2. Mesh Stiffness......................................................................................................... 5 1.2.2.2.2.1. Increase Near Small Volumes.......................................................................... 5 1.2.2.2.2.2. Increase Near Boundaries............................................................................... 6 1.2.2.2.2.3.Value (Specified Stiffness)............................................................................... 6 1.2.2.2.3. Mesh Motion Options............................................................................................. 7 1.2.2.2.3.1. Conservative Interface Flux............................................................................. 8 1.2.2.2.3.2. Unspecified.................................................................................................... 8 1.2.2.2.3.3. Stationary...................................................................................................... 8 1.2.2.2.3.4. Specified Displacement.................................................................................. 8 1.2.2.2.3.5. Specified Location.......................................................................................... 9 1.2.2.2.3.6. Periodic Displacement.................................................................................... 9 1.2.2.2.3.7. Parallel to Boundary..................................................................................... 10 1.2.2.2.3.8. Surface of Revolution................................................................................... 10 1.2.2.2.3.9. ANSYS MultiField.......................................................................................... 11 1.2.2.2.3.10. Rigid Body Solution.................................................................................... 11 1.2.2.3. Junction Box Routine..................................................................................................... 11 1.2.3. Laminar Flow......................................................................................................................... 12 1.2.4.Turbulence and Turbulence Models........................................................................................ 12 1.2.5. Heat Transfer.......................................................................................................................... 12 1.2.5.1. None............................................................................................................................. 12 1.2.5.2. Isothermal..................................................................................................................... 12 1.2.5.3.Thermal Energy............................................................................................................. 12 1.2.5.4.Total Energy .................................................................................................................. 13 1.2.5.5.Turbulent Flux Closure................................................................................................... 13 1.2.6. Conjugate Heat Transfer......................................................................................................... 13 1.2.7. Compressible Flow................................................................................................................. 13 1.2.7.1. Mixed Subsonic/Supersonic Boundaries......................................................................... 14 1.2.8. Setting a Reference Pressure................................................................................................... 15 1.2.9. Buoyancy............................................................................................................................... 15 1.2.9.1. Full Buoyancy Model (Density Difference)...................................................................... 16 1.2.9.2. Boussinesq Model ......................................................................................................... 17 1.2.9.3. Buoyancy and Pressure.................................................................................................. 17 1.2.9.4. Buoyancy In Rotating Domains...................................................................................... 18 1.2.10. Immersed Solids................................................................................................................... 18 1.2.10.1. Immersed Boundary Tracking....................................................................................... 19 1.2.10.2. Limitations to using Immersed Solids........................................................................... 20 1.2.11. Multicomponent Flow.......................................................................................................... 21 1.2.11.1. Assumptions About Multicomponent Flow.................................................................. 21 1.2.11.2. Multicomponent Flow Terminology.............................................................................. 22 1.2.11.2.1. Pure Substance................................................................................................... 22 1.2.11.2.2. Component ........................................................................................................ 22 1.2.11.2.3. Multicomponent Fluid ........................................................................................ 22 Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates. iii Modeling Guide 1.2.11.2.4. Fluid................................................................................................................... 22 1.2.11.2.5. Additional Variable.............................................................................................. 22 1.2.11.2.6. Ideal Mixture....................................................................................................... 23 1.2.11.2.7.Transport Equation.............................................................................................. 23 1.2.11.2.8. Constraint Equation............................................................................................ 23 1.2.11.2.9. Algebraic Equation.............................................................................................. 23 1.2.11.3. Multicomponent Flow Examples.................................................................................. 23 1.2.11.3.1. Example 1: Multicomponent Multiphase.............................................................. 23 1.2.11.3.2. Example 2: Smoke in Air...................................................................................... 24 1.2.11.4. Component Domain Settings....................................................................................... 24 1.2.11.4.1. Algebraic Slip...................................................................................................... 25 1.2.11.4.2. Kinematic Diffusivity and Bulk Viscosity............................................................... 25 1.2.11.4.3.Turbulent Flux Closure......................................................................................... 25 1.2.11.5. Boundary Conditions................................................................................................... 25 1.2.11.6. Multicomponent Energy Diffusion............................................................................... 26 1.2.12. Additional Variables.............................................................................................................. 27 1.2.12.1. Kinematic Diffusivity.................................................................................................... 27 1.2.12.2.Turbulent Flux Closure................................................................................................. 27 1.2.12.3.Volumetric and Specific Additional Variable.................................................................. 28 1.2.12.4. Additional Variables In Units Other Than Mass.............................................................. 28 1.2.12.5. Unspecified Additional Variables.................................................................................. 29 1.2.12.6.Tensor Type................................................................................................................. 29 1.2.13. Non-Newtonian Flow ........................................................................................................... 29 1.2.14. Coordinate Frames............................................................................................................... 32 1.2.14.1. Global Coordinate Frame (Coord 0).............................................................................. 32 1.2.14.2. Local Coordinate Frames.............................................................................................. 33 1.2.14.3. Cartesian Coordinate Frames....................................................................................... 34 1.2.15. Rotating Frames of Reference (RFR)....................................................................................... 34 1.2.15.1. Alternate Rotation Model............................................................................................. 34 1.2.16. Electric Field......................................................................................................................... 35 1.3. Sources .......................................................................................................................................... 36 1.3.1. Locators for Sources............................................................................................................... 36 1.3.1.1. Subdomains.................................................................................................................. 36 1.3.1.2. Boundary Sources ......................................................................................................... 37 1.3.1.3. Point Sources ................................................................................................................ 37 1.3.2.Types of Sources..................................................................................................................... 37 1.3.2.1. General Sources ............................................................................................................ 37 1.3.2.1.1. Source Coefficient / Total Source Coefficient.......................................................... 37 1.3.2.2. Momentum Sources...................................................................................................... 38 1.3.2.2.1. Isotropic and Directional Loss Models.................................................................... 38 1.3.2.2.2. General Momentum Source.................................................................................. 39 1.3.2.2.2.1. Post-Processing the Momentum Sources...................................................... 40 1.3.2.2.3. Immersed Solids Sources....................................................................................... 40 1.3.2.3. Mass (Continuity) Sources.............................................................................................. 40 1.3.2.3.1. Mass (Continuity) Source Coefficients.................................................................... 41 1.3.2.4. Bulk Sources.................................................................................................................. 42 1.3.2.5. Solid Sources................................................................................................................. 42 1.3.2.6. Radiation Sources.......................................................................................................... 42 1.3.2.7. Particle User Sources..................................................................................................... 42 1.3.3. Multiplying Sources by Porosity.............................................................................................. 42 1.4. Material Properties.......................................................................................................................... 42 1.4.1. CEL Expressions ..................................................................................................................... 43 Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information iv of ANSYS, Inc. and its subsidiaries and affiliates. Modeling Guide 1.4.2. Coordinate Frame .................................................................................................................. 43 1.4.3. Equation of State.................................................................................................................... 43 1.4.3.1. Option .......................................................................................................................... 43 1.4.3.1.1.Value .................................................................................................................... 43 1.4.3.1.2. Ideal Gas............................................................................................................... 44 1.4.3.1.3. Real Gas................................................................................................................ 44 1.4.3.1.4. IAPWS Library....................................................................................................... 44 1.4.3.2. Molar Mass.................................................................................................................... 45 1.4.4. Specific Heat Capacity............................................................................................................ 45 1.4.4.1.Value............................................................................................................................. 45 1.4.4.2. NASA Format................................................................................................................. 45 1.4.4.3. Zero Pressure Polynomial............................................................................................... 46 1.4.4.4. Real Gas........................................................................................................................ 47 1.4.4.5. Reference State Properties............................................................................................. 47 1.4.4.5.1. Reference Temperature and Reference Pressure..................................................... 47 1.4.4.5.2. Reference Specific Enthalpy and Entropy............................................................... 47 1.4.5. Density and Specific Heat Dependencies................................................................................ 47 1.4.6.Table Generation Pressure and Temperature Limits................................................................. 48 1.4.7.Transport Properties............................................................................................................... 48 1.4.7.1. Dynamic Viscosity.......................................................................................................... 48 1.4.7.1.1.Value .................................................................................................................... 48 1.4.7.1.2. Rigid Non Interacting Sphere and Interacting Sphere Models................................. 48 1.4.7.1.3. Non-Newtonian Model.......................................................................................... 49 1.4.7.1.4. Ideal Mixture ........................................................................................................ 49 1.4.7.1.5. Sutherland’s Formula............................................................................................ 49 1.4.7.2.Thermal Conductivity.................................................................................................... 50 1.4.7.2.1. Sutherland’s Formula............................................................................................ 50 1.4.7.2.2. Modified Euken Model.......................................................................................... 50 1.4.8. Radiation Properties............................................................................................................... 50 1.4.9. Buoyancy Properties.............................................................................................................. 51 1.4.9.1.Thermal Expansivity....................................................................................................... 51 1.4.10. Electromagnetic Properties.................................................................................................. 51 1.4.10.1. Electrical Conductivity................................................................................................. 51 1.4.10.2. Magnetic Permeability................................................................................................. 51 1.4.11. Library Materials................................................................................................................... 52 1.4.11.1. Adding to the MATERIALS file....................................................................................... 52 1.5. Mixture Properties (Fixed,Variable, Reacting)................................................................................... 53 1.5.1. Equation of State/Density....................................................................................................... 53 1.5.2. Molar Mass............................................................................................................................. 55 1.5.3. Specific Heat Capacity............................................................................................................ 55 1.5.4. Electromagnetic Properties.................................................................................................... 55 1.6. Efficiency Calculation...................................................................................................................... 56 1.6.1. Isentropic Efficiency and Total Enthalpy.................................................................................. 56 1.6.2. Polytropic Efficiency............................................................................................................... 57 1.6.3. Activating Efficiency Output................................................................................................... 59 1.6.3.1. CFX-Solver Manager Output Variables............................................................................ 59 1.6.3.2. Results File Output Variables.......................................................................................... 60 1.6.4. Restrictions............................................................................................................................ 60 1.7.Wall Condensation Model............................................................................................................... 61 1.7.1. CFX-Pre Setup........................................................................................................................ 61 1.7.1.1. Domain Fluid Model Specification.................................................................................. 61 1.7.1.2. Boundary Condition Specification.................................................................................. 62 Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates. v Modeling Guide 1.7.1.3. Restrictions ................................................................................................................... 62 1.7.1.4. Convergence Tip............................................................................................................ 62 1.7.2. Condensation Mass Flux in CFD-Post...................................................................................... 63 2. Boundary Condition Modeling............................................................................................................. 65 2.1.The Purpose of Boundary Conditions............................................................................................... 65 2.2. Available Boundary Conditions....................................................................................................... 66 2.2.1. Fluid Boundaries.................................................................................................................... 66 2.2.2. Solid Boundaries.................................................................................................................... 67 2.3. Using Boundary Conditions............................................................................................................. 67 2.3.1. Specifying Well-Posed Boundary Conditions........................................................................... 67 2.3.2. Recommended Configurations of Boundary Conditions.......................................................... 68 2.3.3. Using Inlets, Outlets and Openings......................................................................................... 68 2.3.3.1. Inlets............................................................................................................................. 68 2.3.3.2. Outlets.......................................................................................................................... 69 2.3.3.3. Openings ...................................................................................................................... 70 2.3.3.4. Using Pressure Specified Boundaries with Buoyant Flows............................................... 71 2.3.4. Using CEL Expressions With Boundary Conditions................................................................... 72 2.4. Inlet................................................................................................................................................ 72 2.4.1. Mesh Motion.......................................................................................................................... 72 2.4.2. Inlet (Subsonic)...................................................................................................................... 72 2.4.2.1. Mass and Momentum.................................................................................................... 72 2.4.2.1.1. Normal Speed....................................................................................................... 72 2.4.2.1.2. Cartesian Velocity Components............................................................................. 73 2.4.2.1.3. Cylindrical Velocity Components........................................................................... 73 2.4.2.1.4. Mass Flow Rate..................................................................................................... 73 2.4.2.1.5.Total Pressure (Stable)........................................................................................... 74 2.4.2.1.6. Stationary Frame Total Pressure (Stable)................................................................ 74 2.4.2.1.7. Static Pressure...................................................................................................... 74 2.4.2.1.8. Fluid Velocity........................................................................................................ 74 2.4.2.2. Flow Direction............................................................................................................... 74 2.4.2.3.Turbulence.................................................................................................................... 75 2.4.2.3.1. Default Intensity and Autocompute Length Scale.................................................. 75 2.4.2.3.2. Intensity and Autocompute Length Scale.............................................................. 75 2.4.2.3.3. Intensity and Length Scale.................................................................................... 76 2.4.2.3.4. Low (Intensity = 1%)............................................................................................. 76 2.4.2.3.5. Medium (Intensity = 5%)....................................................................................... 76 2.4.2.3.6. High (Intensity = 10%)........................................................................................... 76 2.4.2.3.7. Specified Intensity and Eddy Viscosity Ratio........................................................... 76 2.4.2.3.8. k and Epsilon........................................................................................................ 76 2.4.2.3.9. Zero Gradient....................................................................................................... 76 2.4.2.4. Heat Transfer................................................................................................................. 76 2.4.2.4.1. Static Temperature................................................................................................ 76 2.4.2.4.2.Total Temperature................................................................................................. 76 2.4.2.4.3. Stat. Frame Total Temperature............................................................................... 76 2.4.2.4.4.Total Enthalpy....................................................................................................... 77 2.4.2.4.5. Stationary Frame Total Enthalpy............................................................................ 77 2.4.2.5.Thermal Radiation......................................................................................................... 77 2.4.2.5.1. Radiative Heat Flux (P1 Model).............................................................................. 77 2.4.2.5.2. Radiation Intensity (P1 Model)............................................................................... 77 2.4.2.5.3. External Blackbody Temperature........................................................................... 77 2.4.2.5.4. Local Temperature................................................................................................ 77 2.4.2.5.5. Sources (Discrete Transfer and Monte Carlo models).............................................. 78 Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information vi of ANSYS, Inc. and its subsidiaries and affiliates. Modeling Guide 2.4.2.6.Transported Additional Variables at an Inlet.................................................................... 78 2.4.3. Inlet (Supersonic)................................................................................................................... 78 2.4.3.1. Mass and Momentum.................................................................................................... 78 2.4.4. Inlet (Mixed Subsonic-Supersonic).......................................................................................... 79 2.4.4.1. Supported Material Types.............................................................................................. 80 2.4.4.2. Mass and Momentum.................................................................................................... 80 2.4.4.2.1. Cartesian Velocity Components and (Total) Pressure.............................................. 80 2.4.4.2.2. Cylindrical Velocity Components and (Total) Pressure............................................ 80 2.4.4.2.3. Normal Speed and (Total) Pressure........................................................................ 81 2.4.4.3. Heat Transfer................................................................................................................. 81 2.4.4.3.1. Static Temperature................................................................................................ 81 2.4.4.3.2.Total Temperature................................................................................................. 81 2.4.4.3.3.Total Enthalpy....................................................................................................... 81 2.4.4.4. Initial Guess Recommendation....................................................................................... 81 2.5. Outlet............................................................................................................................................. 81 2.5.1. Mass and Momentum............................................................................................................. 82 2.5.1.1. Static Pressure............................................................................................................... 82 2.5.1.2. Normal Speed............................................................................................................... 82 2.5.1.3. Cartesian Velocity Components..................................................................................... 82 2.5.1.4. Cylindrical Velocity Components.................................................................................... 82 2.5.1.5. Average Static Pressure.................................................................................................. 82 2.5.1.5.1. Average Over Whole Outlet................................................................................... 82 2.5.1.5.2. Average Above Specified Radius............................................................................ 83 2.5.1.5.3. Average Below Specified Radius............................................................................ 83 2.5.1.5.4. Circumferential..................................................................................................... 83 2.5.1.5.5. Radial Equilibrium................................................................................................. 83 2.5.1.6. Mass Flow Rate (Bulk Mass Flow Rate for Multiphase)..................................................... 84 2.5.1.7. Exit Corrected Mass Flow Rate........................................................................................ 84 2.5.1.8. Mass Flow Update......................................................................................................... 85 2.5.1.8.1. Scale Mass Flows................................................................................................... 85 2.5.1.8.2. Constant Flux........................................................................................................ 85 2.5.1.8.3. Shift Pressure with or without Pressure Profile....................................................... 85 2.5.1.8.4. Shift Pressure with Circumferential Pressure Averaging.......................................... 86 2.5.1.9. Degassing Condition (Multiphase only).......................................................................... 86 2.5.1.10. Fluid Velocity (Multiphase only).................................................................................... 87 2.5.1.11. Supercritical (Multiphase only)..................................................................................... 87 2.5.2.Turbulence, Heat Transfer, and Additional Variables................................................................. 87 2.5.3.Thermal Radiation.................................................................................................................. 87 2.5.4. Mesh Motion.......................................................................................................................... 87 2.5.5. Outlet (Supersonic)................................................................................................................ 87 2.6. Opening......................................................................................................................................... 87 2.6.1. Mass and Momentum............................................................................................................. 88 2.6.1.1. Cartesian Velocity Components..................................................................................... 88 2.6.1.2. Cylindrical Velocity Components.................................................................................... 88 2.6.1.3. Opening Pressure and Direction..................................................................................... 88 2.6.1.4. Static Pressure and Direction......................................................................................... 88 2.6.1.5. Entrainment.................................................................................................................. 88 2.6.1.6. Fluid Velocity................................................................................................................. 89 2.6.2. Loss Coefficient...................................................................................................................... 89 2.6.2.1. For a Pressure-Specified Opening................................................................................... 89 2.6.2.2. For a Static-Pressure-Specified Opening......................................................................... 89 2.6.3. Heat Transfer.......................................................................................................................... 89 Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates. vii Modeling Guide 2.6.4.Turbulence............................................................................................................................. 90 2.6.5.Thermal Radiation.................................................................................................................. 90 2.6.6. Additional Variables ............................................................................................................... 90 2.6.7. Mesh Motion.......................................................................................................................... 90 2.7.Wall................................................................................................................................................ 90 2.7.1. Mass and Momentum............................................................................................................. 91 2.7.1.1. No Slip Wall................................................................................................................... 91 2.7.1.2. Free Slip Wall................................................................................................................. 92 2.7.1.3. Finite Slip Wall............................................................................................................... 92 2.7.1.4. Specified Shear.............................................................................................................. 92 2.7.1.5. Counter-rotating Wall.................................................................................................... 92 2.7.1.6. Rotating Wall................................................................................................................. 93 2.7.2.Wall Roughness...................................................................................................................... 93 2.7.3.Wall Contact Model................................................................................................................ 93 2.7.4.Wall Adhesion........................................................................................................................ 94 2.7.5. Heat Transfer.......................................................................................................................... 94 2.7.5.1. Adiabatic....................................................................................................................... 94 2.7.5.2. Fixed Temperature......................................................................................................... 94 2.7.5.3. Heat Flux and Wall Heat Flux.......................................................................................... 94 2.7.5.4. Heat Transfer Coefficient and Wall Heat Transfer Coefficient............................................ 94 2.7.5.5. ANSYS Multi-field .......................................................................................................... 95 2.7.5.6. Results File Variables for Post-Processing........................................................................ 95 2.7.5.7.Wall Temperature (T ).................................................................................................... 96 w 2.7.5.8.Wall Heat Flux and Heat Flux (q )................................................................................... 96 w 2.7.5.9.Wall Heat Transfer Coefficient (h ) and Wall Adjacent Temperature (T ).......................... 97 c nw 2.7.5.10.Wall External Heat Transfer Coefficient and Wall External Temperature.......................... 97 2.7.6. Mesh Motion.......................................................................................................................... 97 2.7.7.Thermal Radiation.................................................................................................................. 98 2.7.7.1. Opaque......................................................................................................................... 98 2.7.7.2. Sources ......................................................................................................................... 98 2.7.8. Equations Governing Additional Variables............................................................................... 98 2.7.9. Additional Coupling Sent Data............................................................................................... 98 2.8. Symmetry Plane.............................................................................................................................. 98 2.8.1. Mesh Motion.......................................................................................................................... 99 2.9. Profile Boundary Conditions............................................................................................................ 99 2.9.1. Using a Profile From One Location at Another Location......................................................... 100 2.9.2. Standard Variable Names...................................................................................................... 101 2.9.3. Non-Standard Variable Names.............................................................................................. 102 2.9.4. Custom Variables.................................................................................................................. 102 2.9.5. Using r-Theta Profiles........................................................................................................... 102 2.9.6. Data Interpolation Method................................................................................................... 103 2.9.7. Extracting Profile Data from Results Files............................................................................... 103 3. Initial Condition Modeling.................................................................................................................. 105 3.1. Setting the Initial Conditions in CFX-Pre........................................................................................ 106 3.1.1. Automatic............................................................................................................................ 106 3.1.2. Automatic with Value........................................................................................................... 107 3.1.3. Using Expressions with Initial Conditions.............................................................................. 107 3.2. Initialization Parameters................................................................................................................ 107 3.2.1. Coordinate Frame................................................................................................................. 108 3.2.2. Frame Type .......................................................................................................................... 109 3.2.2.1. Considerations for Multiple Domains and Global Initialization....................................... 109 3.2.3.Velocity Type........................................................................................................................ 109 Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information viii of ANSYS, Inc. and its subsidiaries and affiliates. Modeling Guide 3.2.3.1. Cartesian Coordinate Frame, Cartesian Velocity Components........................................ 109 3.2.3.2. Cartesian Coordinate Frame, Cylindrical Velocity Components...................................... 109 3.2.3.3. Cylindrical Coordinate Frame, Cartesian Velocity Components...................................... 109 3.2.3.4. Cylindrical Coordinate Frame, Cylindrical Velocity Components..................................... 109 3.2.4. Cartesian Velocity Components............................................................................................ 109 3.2.4.1. Automatic Values......................................................................................................... 109 3.2.4.2. Recommended Values................................................................................................. 111 3.2.5. Cylindrical Velocity Components........................................................................................... 112 3.2.5.1. Automatic Values......................................................................................................... 112 3.2.5.2. Recommended Values................................................................................................. 112 3.2.6.Velocity Scale....................................................................................................................... 112 3.2.7.Velocity Fluctuation.............................................................................................................. 112 3.2.8. Static Pressure...................................................................................................................... 112 3.2.8.1. Automatic Values......................................................................................................... 112 3.2.8.2. Recommended Values................................................................................................. 113 3.2.9.Temperature ........................................................................................................................ 113 3.2.9.1. Automatic Values......................................................................................................... 113 3.2.9.2. Recommended Values................................................................................................. 113 3.2.10. K (Turbulent Kinetic Energy)............................................................................................... 113 3.2.10.1. Automatic Values....................................................................................................... 113 3.2.10.2. Recommended Values ............................................................................................... 114 3.2.11. Epsilon (Turbulence Eddy Dissipation)................................................................................ 114 3.2.11.1. Automatic Values....................................................................................................... 114 3.2.11.2. Recommended Values ............................................................................................... 114 3.2.11.3. Manual Specification ................................................................................................. 114 3.2.12. Omega (Turbulence Eddy Frequency)................................................................................. 114 3.2.12.1. Automatic Values....................................................................................................... 114 3.2.12.2. Recommended Values ............................................................................................... 115 3.2.12.3. Manual Specification ................................................................................................. 115 3.2.13. Reynolds Stress Components.............................................................................................. 115 3.2.14. Initialization of Additional Variables.................................................................................... 115 3.2.15. Component........................................................................................................................ 115 3.2.16.Volume Fraction................................................................................................................. 116 3.2.17. Radiation Intensity............................................................................................................. 116 3.2.18. Initialization of Solid Domains............................................................................................. 116 3.2.19. Initial Conditions for a Multiphase Simulation..................................................................... 116 3.2.19.1.Volume Fraction......................................................................................................... 116 3.2.19.2.Velocity ..................................................................................................................... 117 3.2.20. Initialization Advice............................................................................................................ 117 3.3. Reading the Initial Conditions from a File....................................................................................... 117 3.3.1. Using Configuration Results to Provide Initial Values.............................................................. 118 3.3.2. Continuing the History......................................................................................................... 119 3.3.3. Using Multiple Files to Provide Initial Conditions................................................................... 122 3.3.4. Using the Mesh from the Initial Values File............................................................................ 122 3.3.5. Using an Initial Values File Which Contains Particles............................................................... 123 3.4. Using the CFX-Interpolator............................................................................................................ 125 3.4.1. Interpolating from a Single File............................................................................................. 126 3.4.1.1. Mapping Data from the Source File to the Target File.................................................... 128 3.4.2. Interpolating from Multiple Files........................................................................................... 131 3.4.3. Interpolation Mapping......................................................................................................... 132 3.4.3.1. Defining Transformations for use in Interpolation Mapping Alignment Transforma- tions....................................................................................................................................... 133 Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates. ix Modeling Guide 3.4.3.2. Creating Interpolation Mapping Objects...................................................................... 134 3.4.4. Adjusting the Bounding Box Tolerance.................................................................................. 135 3.4.5. Interpolating Onto a Solver Input File with Results Fields....................................................... 136 3.4.6. Miscellaneous Limitations of the CFX-Interpolator................................................................. 137 3.4.7. Using the CFX-Interpolator to Calculate Difference Variables................................................. 138 4.Turbulence and Near-Wall Modeling.................................................................................................. 139 4.1.Turbulence Models........................................................................................................................ 140 4.1.1.The Laminar Model............................................................................................................... 140 4.1.2.The Zero Equation Model...................................................................................................... 141 4.1.3.The k-epsilon Model............................................................................................................. 141 4.1.4.The RNG k-epsilon Model...................................................................................................... 141 4.1.5.The k-omega and SST Models............................................................................................... 141 4.1.6. Curvature Correction for Two-Equation Models..................................................................... 142 4.1.7.The Reynolds Stress Model................................................................................................... 142 4.1.8. Omega-Based Reynolds Stress Models.................................................................................. 144 4.1.9. Explicit Algebraic Reynolds Stress Model............................................................................... 144 4.1.10. CFX Transition Model.......................................................................................................... 145 4.1.10.1. Estimating when the Transition Model Should be Used............................................... 145 4.1.10.2. Grid Requirements..................................................................................................... 146 4.1.10.3. Specifying Inlet Turbulence Levels.............................................................................. 149 4.1.10.4. Summary................................................................................................................... 151 4.1.11.The Large Eddy Simulation Model (LES)............................................................................... 151 4.1.11.1. Using the LES model in CFX........................................................................................ 151 4.1.11.2. Introduction to LES.................................................................................................... 151 4.1.11.3.When to use LES........................................................................................................ 151 4.1.11.4. Setting up an LES Simulation..................................................................................... 152 4.1.11.4.1. Geometry for LES.............................................................................................. 152 4.1.11.4.2. Meshing ........................................................................................................... 152 4.1.11.4.3. Boundary Layers............................................................................................... 152 4.1.11.4.4. Analysis Type .................................................................................................... 152 4.1.11.4.5. Domains........................................................................................................... 152 4.1.11.4.6. LES Boundary Conditions: Inlet.......................................................................... 153 4.1.11.4.7. LES Boundary Conditions: Outlets and Openings................................................ 153 4.1.11.4.8. LES Initialization................................................................................................ 153 4.1.11.4.9. LES Solver Control............................................................................................. 154 4.1.11.4.10. LES Timestep Considerations........................................................................... 154 4.1.11.5. Solver Memory.......................................................................................................... 154 4.1.11.6. Useful Values For LES Runs......................................................................................... 154 4.1.11.6.1. Statistical Reynolds Stresses.............................................................................. 155 4.1.11.6.2. Delaying the Start of Reynolds Stress Calculations.............................................. 155 4.1.12.The Detached Eddy Simulation Model (DES)........................................................................ 155 4.1.12.1. Using the Detached Eddy Simulation Model in CFX.................................................... 155 4.1.12.1.1.When to use DES............................................................................................... 155 4.1.12.2. Setting up a DES Simulation....................................................................................... 156 4.1.12.2.1. Geometry for DES............................................................................................. 156 4.1.12.2.2. Meshing Requirements for DES......................................................................... 156 4.1.12.2.3. DES Timestep Considerations............................................................................ 156 4.1.12.2.4. Boundary Conditions........................................................................................ 157 4.1.12.2.5. DES Initialization............................................................................................... 157 4.1.12.2.6. Monitoring a DES Simulation............................................................................. 157 4.1.12.3. Limitations/Concerns of the DES Model...................................................................... 159 4.1.13.The Scale-Adaptive Simulation (SAS)................................................................................... 160 Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information x of ANSYS, Inc. and its subsidiaries and affiliates.

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ANSYS CFX-Solver Modeling Guide ANSYS, Inc. Release 15.0 Southpointe November 2013 275 Technology Drive Canonsburg, PA 15317 ANSYS, Inc. is [email protected] certified to ISO 9001:2008. http://www.ansys.com (T) 724-746-3304 (F) 724-514-9494 Copyright and Trademark Information © 2013 SAS IP, Inc. All rights reserved. Unauthorized use, distribution or duplication is prohibited. ANSYS, ANSYS Workbench, Ansoft, AUTODYN, EKM, Engineering Knowledge Manager, CFX, FLUENT, HFSS and any and all ANSYS, Inc. brand, product, service and feature names, logos and slogans are registered trademarks or trademarks of ANSYS, Inc. or its subsidiaries in the United States or other countries. ICEM CFD is a trademark used by ANSYS, Inc. under license. CFX is a trademark of Sony Corporation in Japan. All other brand, product, service and feature names or trademarks are the property of their respective owners. Disclaimer Notice THIS ANSYS SOFTWARE PRODUCT AND PROGRAM DOCUMENTATION INCLUDE TRADE SECRETS AND ARE CONFID- ENTIAL AND PROPRIETARY PRODUCTS OF ANSYS, INC., ITS SUBSIDIARIES, OR LICENSORS.The software products and documentation are furnished by ANSYS, Inc., its subsidiaries, or affiliates under a software license agreement that contains provisions concerning non-disclosure, copying, length and nature of use, compliance with exporting laws, warranties, disclaimers, limitations of liability, and remedies, and other provisions.The software products and documentation may be used, disclosed, transferred, or copied only in accordance with the terms and conditions of that software license agreement. ANSYS, Inc. is certified to ISO 9001:2008. U.S. Government Rights For U.S. Government users, except as specifically granted by the ANSYS, Inc. software license agreement, the use, duplication, or disclosure by the United States Government is subject to restrictions stated in the ANSYS, Inc. software license agreement and FAR 12.212 (for non-DOD licenses). Third-Party Software See the legal information in the product help files for the complete Legal Notice for ANSYS proprietary software and third-party software. If you are unable to access the Legal Notice, please contact ANSYS, Inc. Published in the U.S.A. Table of Contents 1. Basic Capabilities Modeling.................................................................................................................... 1 1.1. Domains........................................................................................................................................... 2 1.2. Physical Models................................................................................................................................ 2 1.2.1. Steady State and Transient Flows.............................................................................................. 3 1.2.2. Mesh Deformation................................................................................................................... 4 1.2.2.1. None............................................................................................................................... 4 1.2.2.2. Regions of Motion Specified............................................................................................ 4 1.2.2.2.1. Displacement Relative To........................................................................................ 4 1.2.2.2.2. Mesh Stiffness......................................................................................................... 5 1.2.2.2.2.1. Increase Near Small Volumes.......................................................................... 5 1.2.2.2.2.2. Increase Near Boundaries............................................................................... 6 1.2.2.2.2.3.Value (Specified Stiffness)............................................................................... 6 1.2.2.2.3. Mesh Motion Options............................................................................................. 7 1.2.2.2.3.1. Conservative Interface Flux............................................................................. 8 1.2.2.2.3.2. Unspecified.................................................................................................... 8 1.2.2.2.3.3. Stationary...................................................................................................... 8 1.2.2.2.3.4. Specified Displacement.................................................................................. 8 1.2.2.2.3.5. Specified Location.......................................................................................... 9 1.2.2.2.3.6. Periodic Displacement.................................................................................... 9 1.2.2.2.3.7. Parallel to Boundary..................................................................................... 10 1.2.2.2.3.8. Surface of Revolution................................................................................... 10 1.2.2.2.3.9. ANSYS MultiField.......................................................................................... 11 1.2.2.2.3.10. Rigid Body Solution.................................................................................... 11 1.2.2.3. Junction Box Routine..................................................................................................... 11 1.2.3. Laminar Flow......................................................................................................................... 12 1.2.4.Turbulence and Turbulence Models........................................................................................ 12 1.2.5. Heat Transfer.......................................................................................................................... 12 1.2.5.1. None............................................................................................................................. 12 1.2.5.2. Isothermal..................................................................................................................... 12 1.2.5.3.Thermal Energy............................................................................................................. 12 1.2.5.4.Total Energy .................................................................................................................. 13 1.2.5.5.Turbulent Flux Closure................................................................................................... 13 1.2.6. Conjugate Heat Transfer......................................................................................................... 13 1.2.7. Compressible Flow................................................................................................................. 13 1.2.7.1. Mixed Subsonic/Supersonic Boundaries......................................................................... 14 1.2.8. Setting a Reference Pressure................................................................................................... 15 1.2.9. Buoyancy............................................................................................................................... 15 1.2.9.1. Full Buoyancy Model (Density Difference)...................................................................... 16 1.2.9.2. Boussinesq Model ......................................................................................................... 17 1.2.9.3. Buoyancy and Pressure.................................................................................................. 17 1.2.9.4. Buoyancy In Rotating Domains...................................................................................... 18 1.2.10. Immersed Solids................................................................................................................... 18 1.2.10.1. Immersed Boundary Tracking....................................................................................... 19 1.2.10.2. Limitations to using Immersed Solids........................................................................... 20 1.2.11. Multicomponent Flow.......................................................................................................... 21 1.2.11.1. Assumptions About Multicomponent Flow.................................................................. 21 1.2.11.2. Multicomponent Flow Terminology.............................................................................. 22 1.2.11.2.1. Pure Substance................................................................................................... 22 1.2.11.2.2. Component ........................................................................................................ 22 1.2.11.2.3. Multicomponent Fluid ........................................................................................ 22 Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates. iii Modeling Guide 1.2.11.2.4. Fluid................................................................................................................... 22 1.2.11.2.5. Additional Variable.............................................................................................. 22 1.2.11.2.6. Ideal Mixture....................................................................................................... 23 1.2.11.2.7.Transport Equation.............................................................................................. 23 1.2.11.2.8. Constraint Equation............................................................................................ 23 1.2.11.2.9. Algebraic Equation.............................................................................................. 23 1.2.11.3. Multicomponent Flow Examples.................................................................................. 23 1.2.11.3.1. Example 1: Multicomponent Multiphase.............................................................. 23 1.2.11.3.2. Example 2: Smoke in Air...................................................................................... 24 1.2.11.4. Component Domain Settings....................................................................................... 24 1.2.11.4.1. Algebraic Slip...................................................................................................... 25 1.2.11.4.2. Kinematic Diffusivity and Bulk Viscosity............................................................... 25 1.2.11.4.3.Turbulent Flux Closure......................................................................................... 25 1.2.11.5. Boundary Conditions................................................................................................... 25 1.2.11.6. Multicomponent Energy Diffusion............................................................................... 26 1.2.12. Additional Variables.............................................................................................................. 27 1.2.12.1. Kinematic Diffusivity.................................................................................................... 27 1.2.12.2.Turbulent Flux Closure................................................................................................. 27 1.2.12.3.Volumetric and Specific Additional Variable.................................................................. 28 1.2.12.4. Additional Variables In Units Other Than Mass.............................................................. 28 1.2.12.5. Unspecified Additional Variables.................................................................................. 29 1.2.12.6.Tensor Type................................................................................................................. 29 1.2.13. Non-Newtonian Flow ........................................................................................................... 29 1.2.14. Coordinate Frames............................................................................................................... 32 1.2.14.1. Global Coordinate Frame (Coord 0).............................................................................. 32 1.2.14.2. Local Coordinate Frames.............................................................................................. 33 1.2.14.3. Cartesian Coordinate Frames....................................................................................... 34 1.2.15. Rotating Frames of Reference (RFR)....................................................................................... 34 1.2.15.1. Alternate Rotation Model............................................................................................. 34 1.2.16. Electric Field......................................................................................................................... 35 1.3. Sources .......................................................................................................................................... 36 1.3.1. Locators for Sources............................................................................................................... 36 1.3.1.1. Subdomains.................................................................................................................. 36 1.3.1.2. Boundary Sources ......................................................................................................... 37 1.3.1.3. Point Sources ................................................................................................................ 37 1.3.2.Types of Sources..................................................................................................................... 37 1.3.2.1. General Sources ............................................................................................................ 37 1.3.2.1.1. Source Coefficient / Total Source Coefficient.......................................................... 37 1.3.2.2. Momentum Sources...................................................................................................... 38 1.3.2.2.1. Isotropic and Directional Loss Models.................................................................... 38 1.3.2.2.2. General Momentum Source.................................................................................. 39 1.3.2.2.2.1. Post-Processing the Momentum Sources...................................................... 40 1.3.2.2.3. Immersed Solids Sources....................................................................................... 40 1.3.2.3. Mass (Continuity) Sources.............................................................................................. 40 1.3.2.3.1. Mass (Continuity) Source Coefficients.................................................................... 41 1.3.2.4. Bulk Sources.................................................................................................................. 42 1.3.2.5. Solid Sources................................................................................................................. 42 1.3.2.6. Radiation Sources.......................................................................................................... 42 1.3.2.7. Particle User Sources..................................................................................................... 42 1.3.3. Multiplying Sources by Porosity.............................................................................................. 42 1.4. Material Properties.......................................................................................................................... 42 1.4.1. CEL Expressions ..................................................................................................................... 43 Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information iv of ANSYS, Inc. and its subsidiaries and affiliates. Modeling Guide 1.4.2. Coordinate Frame .................................................................................................................. 43 1.4.3. Equation of State.................................................................................................................... 43 1.4.3.1. Option .......................................................................................................................... 43 1.4.3.1.1.Value .................................................................................................................... 43 1.4.3.1.2. Ideal Gas............................................................................................................... 44 1.4.3.1.3. Real Gas................................................................................................................ 44 1.4.3.1.4. IAPWS Library....................................................................................................... 44 1.4.3.2. Molar Mass.................................................................................................................... 45 1.4.4. Specific Heat Capacity............................................................................................................ 45 1.4.4.1.Value............................................................................................................................. 45 1.4.4.2. NASA Format................................................................................................................. 45 1.4.4.3. Zero Pressure Polynomial............................................................................................... 46 1.4.4.4. Real Gas........................................................................................................................ 47 1.4.4.5. Reference State Properties............................................................................................. 47 1.4.4.5.1. Reference Temperature and Reference Pressure..................................................... 47 1.4.4.5.2. Reference Specific Enthalpy and Entropy............................................................... 47 1.4.5. Density and Specific Heat Dependencies................................................................................ 47 1.4.6.Table Generation Pressure and Temperature Limits................................................................. 48 1.4.7.Transport Properties............................................................................................................... 48 1.4.7.1. Dynamic Viscosity.......................................................................................................... 48 1.4.7.1.1.Value .................................................................................................................... 48 1.4.7.1.2. Rigid Non Interacting Sphere and Interacting Sphere Models................................. 48 1.4.7.1.3. Non-Newtonian Model.......................................................................................... 49 1.4.7.1.4. Ideal Mixture ........................................................................................................ 49 1.4.7.1.5. Sutherland’s Formula............................................................................................ 49 1.4.7.2.Thermal Conductivity.................................................................................................... 50 1.4.7.2.1. Sutherland’s Formula............................................................................................ 50 1.4.7.2.2. Modified Euken Model.......................................................................................... 50 1.4.8. Radiation Properties............................................................................................................... 50 1.4.9. Buoyancy Properties.............................................................................................................. 51 1.4.9.1.Thermal Expansivity....................................................................................................... 51 1.4.10. Electromagnetic Properties.................................................................................................. 51 1.4.10.1. Electrical Conductivity................................................................................................. 51 1.4.10.2. Magnetic Permeability................................................................................................. 51 1.4.11. Library Materials................................................................................................................... 52 1.4.11.1. Adding to the MATERIALS file....................................................................................... 52 1.5. Mixture Properties (Fixed,Variable, Reacting)................................................................................... 53 1.5.1. Equation of State/Density....................................................................................................... 53 1.5.2. Molar Mass............................................................................................................................. 55 1.5.3. Specific Heat Capacity............................................................................................................ 55 1.5.4. Electromagnetic Properties.................................................................................................... 55 1.6. Efficiency Calculation...................................................................................................................... 56 1.6.1. Isentropic Efficiency and Total Enthalpy.................................................................................. 56 1.6.2. Polytropic Efficiency............................................................................................................... 57 1.6.3. Activating Efficiency Output................................................................................................... 59 1.6.3.1. CFX-Solver Manager Output Variables............................................................................ 59 1.6.3.2. Results File Output Variables.......................................................................................... 60 1.6.4. Restrictions............................................................................................................................ 60 1.7.Wall Condensation Model............................................................................................................... 61 1.7.1. CFX-Pre Setup........................................................................................................................ 61 1.7.1.1. Domain Fluid Model Specification.................................................................................. 61 1.7.1.2. Boundary Condition Specification.................................................................................. 62 Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates. v Modeling Guide 1.7.1.3. Restrictions ................................................................................................................... 62 1.7.1.4. Convergence Tip............................................................................................................ 62 1.7.2. Condensation Mass Flux in CFD-Post...................................................................................... 63 2. Boundary Condition Modeling............................................................................................................. 65 2.1.The Purpose of Boundary Conditions............................................................................................... 65 2.2. Available Boundary Conditions....................................................................................................... 66 2.2.1. Fluid Boundaries.................................................................................................................... 66 2.2.2. Solid Boundaries.................................................................................................................... 67 2.3. Using Boundary Conditions............................................................................................................. 67 2.3.1. Specifying Well-Posed Boundary Conditions........................................................................... 67 2.3.2. Recommended Configurations of Boundary Conditions.......................................................... 68 2.3.3. Using Inlets, Outlets and Openings......................................................................................... 68 2.3.3.1. Inlets............................................................................................................................. 68 2.3.3.2. Outlets.......................................................................................................................... 69 2.3.3.3. Openings ...................................................................................................................... 70 2.3.3.4. Using Pressure Specified Boundaries with Buoyant Flows............................................... 71 2.3.4. Using CEL Expressions With Boundary Conditions................................................................... 72 2.4. Inlet................................................................................................................................................ 72 2.4.1. Mesh Motion.......................................................................................................................... 72 2.4.2. Inlet (Subsonic)...................................................................................................................... 72 2.4.2.1. Mass and Momentum.................................................................................................... 72 2.4.2.1.1. Normal Speed....................................................................................................... 72 2.4.2.1.2. Cartesian Velocity Components............................................................................. 73 2.4.2.1.3. Cylindrical Velocity Components........................................................................... 73 2.4.2.1.4. Mass Flow Rate..................................................................................................... 73 2.4.2.1.5.Total Pressure (Stable)........................................................................................... 74 2.4.2.1.6. Stationary Frame Total Pressure (Stable)................................................................ 74 2.4.2.1.7. Static Pressure...................................................................................................... 74 2.4.2.1.8. Fluid Velocity........................................................................................................ 74 2.4.2.2. Flow Direction............................................................................................................... 74 2.4.2.3.Turbulence.................................................................................................................... 75 2.4.2.3.1. Default Intensity and Autocompute Length Scale.................................................. 75 2.4.2.3.2. Intensity and Autocompute Length Scale.............................................................. 75 2.4.2.3.3. Intensity and Length Scale.................................................................................... 76 2.4.2.3.4. Low (Intensity = 1%)............................................................................................. 76 2.4.2.3.5. Medium (Intensity = 5%)....................................................................................... 76 2.4.2.3.6. High (Intensity = 10%)........................................................................................... 76 2.4.2.3.7. Specified Intensity and Eddy Viscosity Ratio........................................................... 76 2.4.2.3.8. k and Epsilon........................................................................................................ 76 2.4.2.3.9. Zero Gradient....................................................................................................... 76 2.4.2.4. Heat Transfer................................................................................................................. 76 2.4.2.4.1. Static Temperature................................................................................................ 76 2.4.2.4.2.Total Temperature................................................................................................. 76 2.4.2.4.3. Stat. Frame Total Temperature............................................................................... 76 2.4.2.4.4.Total Enthalpy....................................................................................................... 77 2.4.2.4.5. Stationary Frame Total Enthalpy............................................................................ 77 2.4.2.5.Thermal Radiation......................................................................................................... 77 2.4.2.5.1. Radiative Heat Flux (P1 Model).............................................................................. 77 2.4.2.5.2. Radiation Intensity (P1 Model)............................................................................... 77 2.4.2.5.3. External Blackbody Temperature........................................................................... 77 2.4.2.5.4. Local Temperature................................................................................................ 77 2.4.2.5.5. Sources (Discrete Transfer and Monte Carlo models).............................................. 78 Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information vi of ANSYS, Inc. and its subsidiaries and affiliates. Modeling Guide 2.4.2.6.Transported Additional Variables at an Inlet.................................................................... 78 2.4.3. Inlet (Supersonic)................................................................................................................... 78 2.4.3.1. Mass and Momentum.................................................................................................... 78 2.4.4. Inlet (Mixed Subsonic-Supersonic).......................................................................................... 79 2.4.4.1. Supported Material Types.............................................................................................. 80 2.4.4.2. Mass and Momentum.................................................................................................... 80 2.4.4.2.1. Cartesian Velocity Components and (Total) Pressure.............................................. 80 2.4.4.2.2. Cylindrical Velocity Components and (Total) Pressure............................................ 80 2.4.4.2.3. Normal Speed and (Total) Pressure........................................................................ 81 2.4.4.3. Heat Transfer................................................................................................................. 81 2.4.4.3.1. Static Temperature................................................................................................ 81 2.4.4.3.2.Total Temperature................................................................................................. 81 2.4.4.3.3.Total Enthalpy....................................................................................................... 81 2.4.4.4. Initial Guess Recommendation....................................................................................... 81 2.5. Outlet............................................................................................................................................. 81 2.5.1. Mass and Momentum............................................................................................................. 82 2.5.1.1. Static Pressure............................................................................................................... 82 2.5.1.2. Normal Speed............................................................................................................... 82 2.5.1.3. Cartesian Velocity Components..................................................................................... 82 2.5.1.4. Cylindrical Velocity Components.................................................................................... 82 2.5.1.5. Average Static Pressure.................................................................................................. 82 2.5.1.5.1. Average Over Whole Outlet................................................................................... 82 2.5.1.5.2. Average Above Specified Radius............................................................................ 83 2.5.1.5.3. Average Below Specified Radius............................................................................ 83 2.5.1.5.4. Circumferential..................................................................................................... 83 2.5.1.5.5. Radial Equilibrium................................................................................................. 83 2.5.1.6. Mass Flow Rate (Bulk Mass Flow Rate for Multiphase)..................................................... 84 2.5.1.7. Exit Corrected Mass Flow Rate........................................................................................ 84 2.5.1.8. Mass Flow Update......................................................................................................... 85 2.5.1.8.1. Scale Mass Flows................................................................................................... 85 2.5.1.8.2. Constant Flux........................................................................................................ 85 2.5.1.8.3. Shift Pressure with or without Pressure Profile....................................................... 85 2.5.1.8.4. Shift Pressure with Circumferential Pressure Averaging.......................................... 86 2.5.1.9. Degassing Condition (Multiphase only).......................................................................... 86 2.5.1.10. Fluid Velocity (Multiphase only).................................................................................... 87 2.5.1.11. Supercritical (Multiphase only)..................................................................................... 87 2.5.2.Turbulence, Heat Transfer, and Additional Variables................................................................. 87 2.5.3.Thermal Radiation.................................................................................................................. 87 2.5.4. Mesh Motion.......................................................................................................................... 87 2.5.5. Outlet (Supersonic)................................................................................................................ 87 2.6. Opening......................................................................................................................................... 87 2.6.1. Mass and Momentum............................................................................................................. 88 2.6.1.1. Cartesian Velocity Components..................................................................................... 88 2.6.1.2. Cylindrical Velocity Components.................................................................................... 88 2.6.1.3. Opening Pressure and Direction..................................................................................... 88 2.6.1.4. Static Pressure and Direction......................................................................................... 88 2.6.1.5. Entrainment.................................................................................................................. 88 2.6.1.6. Fluid Velocity................................................................................................................. 89 2.6.2. Loss Coefficient...................................................................................................................... 89 2.6.2.1. For a Pressure-Specified Opening................................................................................... 89 2.6.2.2. For a Static-Pressure-Specified Opening......................................................................... 89 2.6.3. Heat Transfer.......................................................................................................................... 89 Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates. vii Modeling Guide 2.6.4.Turbulence............................................................................................................................. 90 2.6.5.Thermal Radiation.................................................................................................................. 90 2.6.6. Additional Variables ............................................................................................................... 90 2.6.7. Mesh Motion.......................................................................................................................... 90 2.7.Wall................................................................................................................................................ 90 2.7.1. Mass and Momentum............................................................................................................. 91 2.7.1.1. No Slip Wall................................................................................................................... 91 2.7.1.2. Free Slip Wall................................................................................................................. 92 2.7.1.3. Finite Slip Wall............................................................................................................... 92 2.7.1.4. Specified Shear.............................................................................................................. 92 2.7.1.5. Counter-rotating Wall.................................................................................................... 92 2.7.1.6. Rotating Wall................................................................................................................. 93 2.7.2.Wall Roughness...................................................................................................................... 93 2.7.3.Wall Contact Model................................................................................................................ 93 2.7.4.Wall Adhesion........................................................................................................................ 94 2.7.5. Heat Transfer.......................................................................................................................... 94 2.7.5.1. Adiabatic....................................................................................................................... 94 2.7.5.2. Fixed Temperature......................................................................................................... 94 2.7.5.3. Heat Flux and Wall Heat Flux.......................................................................................... 94 2.7.5.4. Heat Transfer Coefficient and Wall Heat Transfer Coefficient............................................ 94 2.7.5.5. ANSYS Multi-field .......................................................................................................... 95 2.7.5.6. Results File Variables for Post-Processing........................................................................ 95 2.7.5.7.Wall Temperature (T ).................................................................................................... 96 w 2.7.5.8.Wall Heat Flux and Heat Flux (q )................................................................................... 96 w 2.7.5.9.Wall Heat Transfer Coefficient (h ) and Wall Adjacent Temperature (T ).......................... 97 c nw 2.7.5.10.Wall External Heat Transfer Coefficient and Wall External Temperature.......................... 97 2.7.6. Mesh Motion.......................................................................................................................... 97 2.7.7.Thermal Radiation.................................................................................................................. 98 2.7.7.1. Opaque......................................................................................................................... 98 2.7.7.2. Sources ......................................................................................................................... 98 2.7.8. Equations Governing Additional Variables............................................................................... 98 2.7.9. Additional Coupling Sent Data............................................................................................... 98 2.8. Symmetry Plane.............................................................................................................................. 98 2.8.1. Mesh Motion.......................................................................................................................... 99 2.9. Profile Boundary Conditions............................................................................................................ 99 2.9.1. Using a Profile From One Location at Another Location......................................................... 100 2.9.2. Standard Variable Names...................................................................................................... 101 2.9.3. Non-Standard Variable Names.............................................................................................. 102 2.9.4. Custom Variables.................................................................................................................. 102 2.9.5. Using r-Theta Profiles........................................................................................................... 102 2.9.6. Data Interpolation Method................................................................................................... 103 2.9.7. Extracting Profile Data from Results Files............................................................................... 103 3. Initial Condition Modeling.................................................................................................................. 105 3.1. Setting the Initial Conditions in CFX-Pre........................................................................................ 106 3.1.1. Automatic............................................................................................................................ 106 3.1.2. Automatic with Value........................................................................................................... 107 3.1.3. Using Expressions with Initial Conditions.............................................................................. 107 3.2. Initialization Parameters................................................................................................................ 107 3.2.1. Coordinate Frame................................................................................................................. 108 3.2.2. Frame Type .......................................................................................................................... 109 3.2.2.1. Considerations for Multiple Domains and Global Initialization....................................... 109 3.2.3.Velocity Type........................................................................................................................ 109 Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information viii of ANSYS, Inc. and its subsidiaries and affiliates. Modeling Guide 3.2.3.1. Cartesian Coordinate Frame, Cartesian Velocity Components........................................ 109 3.2.3.2. Cartesian Coordinate Frame, Cylindrical Velocity Components...................................... 109 3.2.3.3. Cylindrical Coordinate Frame, Cartesian Velocity Components...................................... 109 3.2.3.4. Cylindrical Coordinate Frame, Cylindrical Velocity Components..................................... 109 3.2.4. Cartesian Velocity Components............................................................................................ 109 3.2.4.1. Automatic Values......................................................................................................... 109 3.2.4.2. Recommended Values................................................................................................. 111 3.2.5. Cylindrical Velocity Components........................................................................................... 112 3.2.5.1. Automatic Values......................................................................................................... 112 3.2.5.2. Recommended Values................................................................................................. 112 3.2.6.Velocity Scale....................................................................................................................... 112 3.2.7.Velocity Fluctuation.............................................................................................................. 112 3.2.8. Static Pressure...................................................................................................................... 112 3.2.8.1. Automatic Values......................................................................................................... 112 3.2.8.2. Recommended Values................................................................................................. 113 3.2.9.Temperature ........................................................................................................................ 113 3.2.9.1. Automatic Values......................................................................................................... 113 3.2.9.2. Recommended Values................................................................................................. 113 3.2.10. K (Turbulent Kinetic Energy)............................................................................................... 113 3.2.10.1. Automatic Values....................................................................................................... 113 3.2.10.2. Recommended Values ............................................................................................... 114 3.2.11. Epsilon (Turbulence Eddy Dissipation)................................................................................ 114 3.2.11.1. Automatic Values....................................................................................................... 114 3.2.11.2. Recommended Values ............................................................................................... 114 3.2.11.3. Manual Specification ................................................................................................. 114 3.2.12. Omega (Turbulence Eddy Frequency)................................................................................. 114 3.2.12.1. Automatic Values....................................................................................................... 114 3.2.12.2. Recommended Values ............................................................................................... 115 3.2.12.3. Manual Specification ................................................................................................. 115 3.2.13. Reynolds Stress Components.............................................................................................. 115 3.2.14. Initialization of Additional Variables.................................................................................... 115 3.2.15. Component........................................................................................................................ 115 3.2.16.Volume Fraction................................................................................................................. 116 3.2.17. Radiation Intensity............................................................................................................. 116 3.2.18. Initialization of Solid Domains............................................................................................. 116 3.2.19. Initial Conditions for a Multiphase Simulation..................................................................... 116 3.2.19.1.Volume Fraction......................................................................................................... 116 3.2.19.2.Velocity ..................................................................................................................... 117 3.2.20. Initialization Advice............................................................................................................ 117 3.3. Reading the Initial Conditions from a File....................................................................................... 117 3.3.1. Using Configuration Results to Provide Initial Values.............................................................. 118 3.3.2. Continuing the History......................................................................................................... 119 3.3.3. Using Multiple Files to Provide Initial Conditions................................................................... 122 3.3.4. Using the Mesh from the Initial Values File............................................................................ 122 3.3.5. Using an Initial Values File Which Contains Particles............................................................... 123 3.4. Using the CFX-Interpolator............................................................................................................ 125 3.4.1. Interpolating from a Single File............................................................................................. 126 3.4.1.1. Mapping Data from the Source File to the Target File.................................................... 128 3.4.2. Interpolating from Multiple Files........................................................................................... 131 3.4.3. Interpolation Mapping......................................................................................................... 132 3.4.3.1. Defining Transformations for use in Interpolation Mapping Alignment Transforma- tions....................................................................................................................................... 133 Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates. ix Modeling Guide 3.4.3.2. Creating Interpolation Mapping Objects...................................................................... 134 3.4.4. Adjusting the Bounding Box Tolerance.................................................................................. 135 3.4.5. Interpolating Onto a Solver Input File with Results Fields....................................................... 136 3.4.6. Miscellaneous Limitations of the CFX-Interpolator................................................................. 137 3.4.7. Using the CFX-Interpolator to Calculate Difference Variables................................................. 138 4.Turbulence and Near-Wall Modeling.................................................................................................. 139 4.1.Turbulence Models........................................................................................................................ 140 4.1.1.The Laminar Model............................................................................................................... 140 4.1.2.The Zero Equation Model...................................................................................................... 141 4.1.3.The k-epsilon Model............................................................................................................. 141 4.1.4.The RNG k-epsilon Model...................................................................................................... 141 4.1.5.The k-omega and SST Models............................................................................................... 141 4.1.6. Curvature Correction for Two-Equation Models..................................................................... 142 4.1.7.The Reynolds Stress Model................................................................................................... 142 4.1.8. Omega-Based Reynolds Stress Models.................................................................................. 144 4.1.9. Explicit Algebraic Reynolds Stress Model............................................................................... 144 4.1.10. CFX Transition Model.......................................................................................................... 145 4.1.10.1. Estimating when the Transition Model Should be Used............................................... 145 4.1.10.2. Grid Requirements..................................................................................................... 146 4.1.10.3. Specifying Inlet Turbulence Levels.............................................................................. 149 4.1.10.4. Summary................................................................................................................... 151 4.1.11.The Large Eddy Simulation Model (LES)............................................................................... 151 4.1.11.1. Using the LES model in CFX........................................................................................ 151 4.1.11.2. Introduction to LES.................................................................................................... 151 4.1.11.3.When to use LES........................................................................................................ 151 4.1.11.4. Setting up an LES Simulation..................................................................................... 152 4.1.11.4.1. Geometry for LES.............................................................................................. 152 4.1.11.4.2. Meshing ........................................................................................................... 152 4.1.11.4.3. Boundary Layers............................................................................................... 152 4.1.11.4.4. Analysis Type .................................................................................................... 152 4.1.11.4.5. Domains........................................................................................................... 152 4.1.11.4.6. LES Boundary Conditions: Inlet.......................................................................... 153 4.1.11.4.7. LES Boundary Conditions: Outlets and Openings................................................ 153 4.1.11.4.8. LES Initialization................................................................................................ 153 4.1.11.4.9. LES Solver Control............................................................................................. 154 4.1.11.4.10. LES Timestep Considerations........................................................................... 154 4.1.11.5. Solver Memory.......................................................................................................... 154 4.1.11.6. Useful Values For LES Runs......................................................................................... 154 4.1.11.6.1. Statistical Reynolds Stresses.............................................................................. 155 4.1.11.6.2. Delaying the Start of Reynolds Stress Calculations.............................................. 155 4.1.12.The Detached Eddy Simulation Model (DES)........................................................................ 155 4.1.12.1. Using the Detached Eddy Simulation Model in CFX.................................................... 155 4.1.12.1.1.When to use DES............................................................................................... 155 4.1.12.2. Setting up a DES Simulation....................................................................................... 156 4.1.12.2.1. Geometry for DES............................................................................................. 156 4.1.12.2.2. Meshing Requirements for DES......................................................................... 156 4.1.12.2.3. DES Timestep Considerations............................................................................ 156 4.1.12.2.4. Boundary Conditions........................................................................................ 157 4.1.12.2.5. DES Initialization............................................................................................... 157 4.1.12.2.6. Monitoring a DES Simulation............................................................................. 157 4.1.12.3. Limitations/Concerns of the DES Model...................................................................... 159 4.1.13.The Scale-Adaptive Simulation (SAS)................................................................................... 160 Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information x of ANSYS, Inc. and its subsidiaries and affiliates.

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