EXPERIMENTAL INVESTIGATION OF ACTIVE WINGTIP VORTEX CONTROL USING SYNTHETIC JET ACTUATORS A Thesis presented to the Faculty of California Polytechnic State University San Luis Obispo In Partial Fulfillment of the Requirements for the Degree Master of Science in Aerospace Engineering by Peter J. Sudak August 2014 © 2014 Peter J. Sudak ALL RIGHTS RESERVED ii COMMITTEE MEMBERSHIP TITLE: Experimental Investigation of Active Wingtip Vortex Control Using Synthetic Jet Actuators AUTHOR: Peter J. Sudak DATE SUBMITTED: August 2014 COMMITTEE CHAIR: Jin Tso, Ph.D. Professor of Aerospace Engineering COMMITTEE MEMBER: Russell Westphal, Ph.D. Professor of Mechanical Engineering COMMITTEE MEMBER: Rob McDonald, Ph.D. Associate Professor of Aerospace Engineering COMMITTEE MEMBER: Faysal Kolkailah, Ph.D. Professor of Aerospace Engineering iii ABSTRACT Experimental Investigation of Active Wingtip Vortex Control using Synthetic Jet Actuators Peter J. Sudak An experiment was performed in the Cal Poly Mechanical Engineering 2x2 ft wind tunnel to quantify the effect of spanwise synthetic jet actuation (SJA) on the drag of a NACA 0015 semispan wing. The wing, which was designed and manufactured for this experiment, has an aspect ratio of 4.20, a span of 0.427 m (16.813”), and is built around an internal array of piezoelectric actuators, which work in series to create a synthetic jet that emanates from the wingtip in the spanwise direction. Direct lift and drag measurements were taken at a Reynolds Number of 100,000 and 200,000 using a load cell/slider mechanism to quantify the effect of actuation on the lift and drag. It was found that the piezoelectric disks used in the synthetic jet actuators cause structural vibrations that have a significant effect on the aerodynamics of the NACA 0015 model. The experiment was performed in a way as to isolate the effect of vibration from the effect of the synthetic jet on the lift and drag. Lift and drag data was supported with pressure readings from 60 pressure ports distributed in rows along the span of the wing. Oil droplet flow visualization was also performed to understand the effect of SJA near the wingtip. The synthetic jet and vibration had effects on the drag. The synthetic jet with vibration decreased the drag only slightly while vibration alone could decrease drag significantly from 11.3% at α = 4° to 23.4% at α = 10° and Re = 100,000. The lift was slightly increased with a slight increase due to the jet and showed a slight increase due to vibration. Two complete rows of pressure ports at 2y/b = 37.5% and 85.1% showed changes in lift due to actuation as well. The synthetic jet increased the lift near the wingtip at 2y/b = 85.1% and had little to no effect inboard at the 37.5% location, hence, the synthetic jet changes the lift distribution on the wing. Oil flow visualization was used to support this claim. Without actuation, the footprint of the tip vortex was present on the upper surface of the wing. With actuation on, the footprint disappeared suggesting the vortex was pushed off the wingtip by the jet. It is possible that the increased lift with actuation can be caused by the vortex being pushed outboard. Keywords: Active Flow Control, NACA 0015, Semispan Testing, Synthetic Jet, Piezoelectric Actuators, Design, Wingtip Vortex, Hot-wire. iv ACKNOWLEDGMENTS First of all, I would like to thank my parents for supporting me not only while I worked on my Thesis but throughout my college career. I could not have made it without you and I cannot even express how grateful I am. Thank you very much. Acknowledgments I would like to thank Dr. Tso for taking me on as his graduate student. Dr. Tso, thank you for always being readily available to offer your support and providing the resources I needed to complete my Thesis. It was a pleasure having you as an advisor. I would like to give a big thank you to Dr. Westphal for letting me use the Mechanical Engineering wind tunnel while the Aero tunnel was being repaired. Also, thank you for always being willing to share your expert advice and letting me use all the cool equipment in the ME tunnel. I would like to thank Dr. McDonald for serving on my committee and answering questions that I had. It was helpful to hear your perspective on various aspects of this project. I would like to thank Dr. Kolkailah for accepting a position on my committee last minute after one member became unavailable. I hope you found my work interesting. I would like to thank Cody Thompson for letting me use his machine shop and buying me supplies in a moment’s notice whenever needed. Your assistance helped me finish this project it a “timely” manner Finally yet importantly, I would like to thank Alan L’Esperance for his help in all aspects of this project from helping me with the manufacture of the wing to showing me how to use various pieces of test equipment that were used for this Thesis. v TABLE OF CONTENTS LIST OF TABLES ix LIST OF FIGURES x NOMENCLATURE xiv 1 Introduction 1 1.1 Literature Survey ............................................................................................................. 1 1.2 Purpose ............................................................................................................................ 3 1.3 Background ...................................................................................................................... 5 1.3.1 Wing Tip Vortices............................................................................................. 5 1.3.2 Lift-Induced Drag ............................................................................................. 6 1.3.3 Zero-Net Mass-Flux Actuators ......................................................................... 6 1.3.4 Momentum Coefficient ..................................................................................... 8 1.3.5 Non-Dimensional Frequency, F+ ...................................................................... 9 2 Design and Manufacture of Experiment 10 2.1 Manufacturing Equipment ............................................................................................. 10 2.1.1 Haas VF-3 ....................................................................................................... 10 2.1.2 Haas Super Minimill 2 .................................................................................... 12 2.1.3 Haas TL-1 ....................................................................................................... 12 2.1.4 Universal Laser Systems VLS6.60 Laser cutter ............................................. 13 2.2 Synthetic Jet Actuator .................................................................................................... 14 2.3 NACA 0015 Semispan Model ....................................................................................... 18 2.3.1 Model Accuracy .............................................................................................. 36 2.4 Load Cell Support Structure .......................................................................................... 37 3 Experimental Apparatus 41 3.1 LabVIEW ...................................................................................................................... 41 3.2 Wind Tunnel .................................................................................................................. 43 3.3 Pressure Measurement System ...................................................................................... 44 vi 3.3.1 ZOC33/64Px ................................................................................................... 44 3.3.2 RADBASE 3200-EXT .................................................................................... 45 3.4 Linear Amplifier ............................................................................................................ 45 3.5 Bimorph Actuator Disk ................................................................................................. 46 3.6 Load Cell ....................................................................................................................... 47 3.7 NACA 0015 Semispan Model ....................................................................................... 47 3.8 Hotwire Anemometer System........................................................................................ 49 3.8.1 Thermal Anemometer ..................................................................................... 50 3.8.2 Hotwire Sensor ............................................................................................... 50 3.8.3 Automatic Velocity Calibrator ........................................................................ 51 3.8.4 Hotwire Fixture ............................................................................................... 52 4 Analysis 54 4.1 Momentum Coefficient Calculation .............................................................................. 54 4.2 Coefficient of Pressure Calculation ............................................................................... 54 4.2.1 Tunnel Calibration .......................................................................................... 55 4.2.2 Solid & Wake Blockage.................................................................................. 55 4.2.3 Buoyancy Correction ...................................................................................... 56 4.3 Sectional Force Coefficients .......................................................................................... 58 4.4 Direct Load Measurement ............................................................................................. 59 4.5 Uncertainty Analysis ..................................................................................................... 60 5 Experimental Procedure 62 5.1 Hotwire Calibration ....................................................................................................... 62 5.2 Hotwire Test Matrix ...................................................................................................... 63 5.3 Wing and Load Cell Apparatus Preparation .................................................................. 64 5.4 Calibrating Lift and Drag Directions ............................................................................. 65 5.5 Angle of Attack Calibration .......................................................................................... 65 5.6 Wind Tunnel Test Matrix .............................................................................................. 66 5.6.1 Additional Wind Tunnel Test Considerations ................................................ 67 5.7 Flow Visualization ......................................................................................................... 68 vii 5.8 Stethoscope Boundary Layer Investigation ................................................................... 69 6 Results and Discussion 70 6.1 Baseline Data Validation ............................................................................................... 70 6.2 Momentum Coefficient .................................................................................................. 76 6.3 Pressure Measurement Results ...................................................................................... 82 6.4 Load Cell Results........................................................................................................... 93 6.5 Oil Film Interferometry Results................................................................................... 102 6.6 Stethoscope Boundary Layer Investigation Results .................................................... 103 7 Conclusion 105 Bibliography 107 Appendices A Sample Calculations .................................................................................................... 110 B Uncertainty Analysis ................................................................................................... 113 B.1 Pressure Coefficient ..................................................................................... 113 B.2 Sectional Lift Coefficient ............................................................................. 115 B.3 Lift and Drag Coefficient Error.................................................................... 117 B.4 Momentum Coefficient Error ....................................................................... 120 C LabVIEW Block Diagram ........................................................................................... 122 viii LIST OF TABLES Table 2.1 Peak jet velocities (m/s)21 .............................................................................................. 14 Table 2.2 Actuator Materials ......................................................................................................... 16 Table 2.3 Top pressure port locations ............................................................................................ 22 Table 2.4 Bottom pressure port locations ...................................................................................... 22 Table 3.1 Top pressure port locations ............................................................................................ 49 Table 3.2 Bottom pressure port locations ...................................................................................... 49 Table 3.3 TSI 1210-TI.5x hotwire sensor specifications ............................................................... 50 Table 6.1 Tabulated C values for f = 100 Hz ............................................................................... 82 µ Table 6.2 Laminar to turbulent transition locations α = 10o ....................................................... 103 ix LIST OF FIGURES Figure 1.1 Schematic of a piston cylinder synthetic jet actuator ..................................................... 7 Figure 1.2 Schematic of a voice coil synthetic jet actuator .............................................................. 7 Figure 1.3 Schematic of a piezoelectric synthetic jet actuator ......................................................... 8 Figure 2.1 Haas VF-3 ..................................................................................................................... 11 Figure 2.2 Wireless Probing System: Tool Setter (left) and Wireless Probe (right) ...................... 11 Figure 2.3 Haas Super Minimill 2 .................................................................................................. 12 Figure 2.4 Haas TL-1 ..................................................................................................................... 13 Figure 2.5 Universal Laser Systems VLS6.60 Laser Cutter .......................................................... 14 Figure 2.6 Dimensioned drawing showing half of an actuator casing ........................................... 15 Figure 2.7 Assembled synthetic jet actuator .................................................................................. 17 Figure 2.8 Peak and RMS velocities for Slit 1 and 2 .................................................................... 18 Figure 2.9 C estimate for spanwise actuation ............................................................................... 19 µ Figure 2.10 Dual synthetic jet concept .......................................................................................... 20 Figure 2.11 Combined actuator concept ........................................................................................ 20 Figure 2.12 Pressure port row locations......................................................................................... 21 Figure 2.13 Top half of the wing showing internal details ............................................................ 24 Figure 2.14 Bottom half of the wing showing pressure surface. ................................................... 26 Figure 2.15 Pressure surface actuator cover .................................................................................. 27 Figure 2.16 Wing longitudinal spar ............................................................................................... 27 Figure 2.17 Wingtip ....................................................................................................................... 28 Figure 2.18 Wingtip ....................................................................................................................... 29 Figure 2.19 Wingtip halves ............................................................................................................ 29 Figure 2.20 Screenshot showing selected toolpaths ....................................................................... 30 Figure 2.21 Screenshot showing toolpath simulation .................................................................... 31 Figure 2.22 Wing top half being machined.................................................................................... 32 Figure 2.23 Both halves of the wing .............................................................................................. 33 Figure 2.24 Both halves of wingtip ................................................................................................ 34 x