Computational Fluid Dynamics Computational Fluid Dynamics A Practical Approach Third Edition Jiyuan Tu RMIT University, Australia University of NewSouthWales,Australia TsinghuaUniversity, P.R. China Guan-Heng Yeoh Australian Nuclear Scienceand TechnologyOrganisation University of NewSouthWales,Australia Chaoqun Liu University of Texasat Arlington,USA Butterworth-HeinemannisanimprintofElsevier TheBoulevard,LangfordLane,Kidlington,OxfordOX51GB,UnitedKingdom 50HampshireStreet,5thFloor,Cambridge,MA02139,UnitedStates ©2018ElsevierLtd.Allrightsreserved. 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LibraryofCongressCataloging-in-PublicationData AcatalogrecordforthisbookisavailablefromtheLibraryofCongress BritishLibraryCataloguing-in-PublicationData AcataloguerecordforthisbookisavailablefromtheBritishLibrary ISBN:978-0-08-101127-0 ForinformationonallButterworth-Heinemannpublicationsvisit ourwebsiteathttps://www.elsevier.com/books-and-journals Publisher:KateyBirtcher AcquisitionEditor:SteveMerken EditorialProjectManager:PeterJardim ProductionProjectManager:SruthiSatheesh CoverDesigner:MarkRogers TypesetbySPiGlobal,India Preface for Third Edition TheacceptanceofthefirstandsecondeditionsofourbookbytheCFDcom- munity has certainly been overwhelming and most welcomed ever since its publication.Inresponsetothenumerousreviewsandsuggestions,ourthirdedi- tion aims to further enhance and update the fast-growing subject, significant developments,andimportantapplicationsofCFD.Inthisthirdedition,wehave retainedthematerialsthathavebeenincorporatedinthesecondeditionandpro- videdmorediscussiononsomekeytopics.Notstrayingawayfromtheprimary focus to offer CFD users with a suitable text for the right level of assumed knowledge, we have slightly reorganized the structure of the second edition while maintainingthe practical aspectinthe understandingofCFD. Thesignificantchangesinthethirdeditionliepredominantlyinthetreatment ofthe fundamental physicsoffluid flows and a new chapterfocusingonmesh generationforCFD.Derivationandthegenericformofthegoverningequations forcompressibleflowshavebeenprovidedinChapter3.Inretrospect,theform of equations is just an extension to the incompressible form of equations for CFD.TheintroductionofChapter4onmeshgenerationlooksintothekeyaspects relatingtotheuseofstructured,body-fitted,andunstructuredmeshes.Wehave alsoprovidedkeypracticalguidelinesofgridgenerationforCFD.Moreadvanced gridgenerationapproachsuchasmovingmeshesisalsodiscussed. Inthesecondedition,weprovidedasummaryofthebasicideasunderpin- ningtheutilizationoffiniteelementandspectralmethodstosolvethefluidflow equations.Inthisedition,wehavefurtherexpoundedonthedescriptionofthese methods since they are still prevalently used in the main stream of CFD. To solve the discretized form of the governing equations, we have made every effort to discuss the important aspects of transportiveness and boundedness, whichareimportanttowardsattainingstableandphysicalnumericalsolutions. Considering the fast-paced development of computer hardware, we have included discussions on the increasing utilization of the graphical processing unit (GPU) in CFD. Also included in this edition are discussions on the use of hybrid CPU-GPU systems with the purpose of exploiting all available processing power andCPU memory resourcesfor CFD calculations. Jiyuan Tu Guan-Heng Yeoh Chaoqun Liu xi Preface for Second Edition TheacceptanceofthefirsteditionofourbookbytheCFDcommunityhascer- tainlybeenoverwhelmingandmostwelcomed.Wewereextremelypleasedby thepositivefeedbackreceivedevenwithinashortperiodsinceitsinceptionof publication.Inresponsetothenumerouscomments,oursecondeditionaimsto furtherenhanceandupdatethefast-growingsubject,significantdevelopments, andimportantapplicationsofCFD.Notstrayingawaybytheprimaryfocusto offer CFD users with a suitable text that is being pitched at the right level of assumedknowledge,thestructureandsystematicapproachofthefirstedition have been retained inorder tomaintain practicalityin understandingCFD. Inthetreatmentofthe fundamentalphysics offluidflows,wehave added thegenericformoftheequationspertainingtocompressibleflowsthatinret- rospectiveisanextensiontotheincompressibleformoftheequationsforCFD. Atthetimeofwritingthefirstedition,wehavefocusedpredominantlyonthe descriptionofthemostpopulardiscretizationapproachesinCFDbasedonfinite differenceandfinitevolume.Recognizingthatotherdiscretizationmethodssuch asthefiniteelementandspectralmethodsthatarestillavailableinthemainstream ofCFD,wehaveprovidedasummaryofthebasicideasunderpinningtheutilization ofthesemethodstosolvethefluidflowequations.Toreflecttheiterativeapproach thatisalsocommonlybeingadoptedtosolvethesystemsofdiscretizedequationsin commercialCFDcodes,adedicatedsectiononmultigridmethodhasbeenwritten. Inthefirstedition,wehavealsoidentifiedanumberofkeysectorswhereCFD has been firmly established. They are aerospace, biomedical science and engi- neering,chemicalandmineralprocessing,civilandenvironmentalengineering, power generation, and sports. In this second edition, we further illustrate the application of CFD in the areas of metallurgy and nuclear safety. Considering thewidespreadofCFDthroughoutanumberofsignificantengineeringindustries, theproperhandlingofcomplexgeometriesbecomesevermoreimportantinview ofdifferenttypesofmeshingapproachesthatcanbeemployed.Discussionson key aspects of structured, body-fitted, and unstructuredmeshes have been pro- videdwithinthepracticalguidelinesofgridgeneration. Lastly, an alternative numerical approach based on the discrete element method has been added tothe growing list ofadvanced topics inCFD. Jiyuan Tu Guan-Heng Yeoh Chaoqun Liu xiii Preface for First Edition Computational fluid dynamics (CFD), once the domain of academics, post- doctoral researchers, or trained specialists, is now progressively becoming more accessible to graduate engineers for research and development as well as design-oriented tasks in industry. Mastery of CFD in handling complex flowandheatindustrialproblemsisbecomingevermoreimportant.Compe- tencyinsuchaskillcertainlybringsaboutasteeplearningcurveforpracticing engineers,whoconstantlyfaceextremechallengestocomeupwithsolutions to fluid flow and heat-transfer problems without a priori knowledge of the basic concepts and fundamental understanding of fluid mechanics and heat transfer. Today’sengineersarealmostcertainlygearedmoretowardstheuseofcom- mercial CFD codes, such as ANSYS CFX, ANSYS FLUENT or STAR-CD. Withoutproperguidance,theuseofthesesoftwarepackagesposesriskslikened to placing potent weaponry in the hands of poorly trained soldiers. There is everypossibilityofuserswithinadequatetrainingcausingmoreharmthangood throughflawedinterpretationsofresultsproducedthroughsuchpackages.This makesitevermoreimportantthatasoundknowledgeandapplicationinCFDis acquired. Furthermore, changing workplace environment has imposed con- straintsonusersindiscerningthepitfallsofCFDbyosmosisandthroughfre- quent failures. The number of users who have had the luxury of being fully equipped and who were conscientious of the limitations of CFD from their own experiences isfast dwindling. ThepurposeofthisbookistoofferCFDuserswithasuitabletextpitchesat the rightlevel of assumed knowledge. CFD is a mathematically sophisticated discipline, and the authors’ aim of this book has been to provide simple-to- understand descriptions of fundamental CFD theories, basic CFD techniques, andpracticalguidelines.Ithasneverbeenouraimtooverwhelmthereaderwith excessive mathematical and theoretical illustrations of computational tech- niques.Everyefforthasbeenmadetodiscussthematerialinastyletocapture thereader’sattention.Thedominantfeatureofthepresentbookistomaintain practicalityinunderstandingCFD.InourlecturingexperienceonCFD,wehave identified what it takes to present elementary concepts to initiate the student. This book incorporates specially designed intuitive and systematic worked- outCFDexamplestoenhancethelearningprocessandalsoprovidesstudents withexamplesforpracticetobettercomprehendthebasicprinciples.Itishoped xv xvi PrefaceforFirstEdition that this approach will accomplish the purpose of offering beginners who are morefocused onthe engineering practiceof CFDtechniques. Thebasicstructure ofthisbook isas follows: ***Chapter1presentsanintroductiontocomputationalfluiddynamicsand isspecificallydesignedtoprovidethereaderwithanoverviewofCFDandits entailed advantages, the range of applications as a research tool on various facets ofindustrial problems, and the future use ofCFD. Chapter2aimstocultivateasenseofcuriosityforthefirst-timeuseronhow aCFDproblemiscurrentlyhandledandsolved.Thereaderwillbenefitthrough theguidanceofthesebasicprocessesusinganycommercial,shareware,andin- houseCFDcodes.Moreimportantly,itservesasaguidepostforthereaderto other chapters relating to the fundamental knowledge of CFD. Chapter 2 is a unique design compared with many traditional CFD presentations. The basic thoughts and philosophy associated with CFD, along with an extensive discussion of the governing equations of fluid dynamics and heat transfer,aretreatedinChapter3.Itisvitallyimportantthatthereadercanfully appreciate,understand,andfeelcomfortablewiththebasicphysicalequations andunderlyingprinciplesofthisdiscipline,astheyareitslifeblood.Byworking throughtheworked-outexamples,thereaderwillhaveabetterunderstandingof the equationsgoverning the conservationof mass, momentum, andenergy. Computational solutions are obtained through two stages. The first stage deals with numerical discretization, which is examined in Chapter 4. Here, the basic numerics are illustrated with popular discretization techniques such as the finite-difference and finite-volume methods (adopted in the majority ofcommercialcodes)forsolvingflowproblems.Thesecondstagedealswith thespecifictechniquestosolvealgebraicequations.Thepressure–velocitycou- plingscheme(SIMPLEanditsderivatives)inthischapterformstheinforma- tion core of the book. This scheme invariably constitutes the basis of most commercialCFDcodesthroughwhichsimulationsofcomplexindustrialprob- lems have been successfully made. Thenumericalconceptsofstability,convergence,consistency,andaccuracy arediscussedinChapter5.Asanunderstandingofthefundamentalequationsof fluidflowandheattransferistheessenceofCFD,itfollowsthattheunderstand- ingofthetechniquesofachievingaCFDsolutionistheresultantsubstantive. This chapterwill enable the reader tobetter assess the results produced when different numerical methodologies are applied. TheauthorshaveincludedturbulencemodellinginCFD,asubjectnotordi- narilytreatedinabookofthisnature,butaftercarefulconsiderations,wehave feltitimperativetoincludeitsincereal-worldapplicationsofCFDareturbu- lent in nature after all. In Chapter 6, the authors have therefore devised some practical guidelines for the readertobetter comprehend turbulence modelling andothermodelscommonlyapplied.Theauthorshavealsocarefullydesigned worked-outexamplesthatwillassiststudentsintheunderstandingofthecom- plex modelling concept. PrefaceforFirstEdition xvii An increasing number of books and journals covering different aspects of CFDinmathematicallyabstrusetermsarereadilyavailablemainlyforspecial- ists associated with industry. It follows that it is more helpful to include in Chapter7illustrationsofthepowerofCFDthroughasetofindustriallyrelevant applications on a significant range of engineering disciplines. Special efforts havebeenmadeinthischaptertostimulatetheinquisitivemindsofthereader throughexposition ofsomepioneeringapplications. AlthoughthedetailedtreatmentofadvancedCFDtechniquesisusuallyout- sidethescopeofabookofthisnature,wehaveofferedageneralintroductionto the basic concepts in Chapter 8, hoping inthe process, toreap the benefits of whetting the appetite of readers for more to come in the evolutionary use of CFD in anynew emerging areas ofscience andengineering. Jiyuan Tu Guan-Heng Yeoh Chaoqun Liu Acknowledgements Thematerialpresentedinthisbookhasbeenpartlyaccumulatedfromteaching thecourseIntroductiontoComputationalFluidDynamicsforseniorundergrad- uate students at the School of Aerospace, Mechanical and Manufacturing EngineeringattheRoyalMelbourneInstituteTechnologyUniversity,Australia, and the course Computational Fluid Dynamics at the School of Mechanical and Manufacturing Engineering, University of New South Wales, Australia. Forthestudentswhohaveundertakenthecourse,wewouldliketothankthem for providing us with many feedbacks to better design particular project topicsandaidunderstandinginthissubject.Theauthorswouldalsoliketothank many research students and colleagues who have generously assisted us in variousways. Forthefirstedition,wethankMr.JonathanSimpson,seniorcommissioning editor,andhiscolleaguesatElsevierScienceandTechnologywhohaveoffered us immense help both in their academic elucidation and professional skills in thepublicationprocess.OurspecialthanksarealsogiventoDr.RisaRobinson, ProfessorofMechanicalEngineeringattheRochesterInstituteofTechnology, theUnitedStates,forreviewingthewholetextandgivingusinvaluablesugges- tions and comments thatwe have incorporated inthe book. For the second edition, we would like to thank Mr. Joe Hayton and Ms. Fiona Geraghty from Elsevier Science and Technology for managing the project. Forthethirdedition,weextendourappreciationtoMr.Steve Merkenand Mr. Peter Jardim from Elsevier Science and Technology for initiating the review process andguiding the project. Dr.Tuwouldliketoexpresshisdeepgratitudetohiswife,Xue,andhisson, Tian, who have provided their unflinching support in preparing and writing the text. Dr. Yeoh would also like to acknowledge the untiring support of hiswife, Natalie, and his daughters, Genevieve, Ellana, and Clarissa, for their understandingandencouragementduringtheseeminglyunendinghoursspent in preparing and writing. Toallthathavebeeninvolved,weextendourdeepestheartfeltappreciation. xix