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• Dyson’s acclaimed new fan that eliminates blades along with associated buffetingandturbulence
• ChevyVolt,anelectriccarthatboastssomeofthemostadvanced engineeringeverseeninamainstreamAmericanautomobile
• Terrafugia’sTransition®RoadableAircraft,whichhasaflightrangeof upto490milesandlandcruisingspeedof105mph
• Apple’siPad®andiPhone®,whichhaverevolutionizedthewaywe communicate
• Speedo’sLZRRACER®swimsuitthathelpedworld-classswimmersat theBeijingOlympicssetnewworldrecords
Whatengineeringdesigntoolshelpedspeedtheseproductstomarketaheadofthecompetition?Howdiddevelopersensurethatdesigned-infeatureswouldfunctionasexpectedunderreal-worldconditions?Oneofthekeyfactorscommontotheseproductsiscomputationalfluiddynamics,orCFD.Forover25years,engineershaveleveragedfluiddynamics advancestobringinnovativeproductstomarketfaster,morecost effectivelyandmoreefficiently.Andasendproductsbecomeevenmore intricate,asconsumersandgovernmentsdemandoptimizedperformancetomeetenvironmentaltargets,CFDtoolsmustalsoevolvetoaddress futureengineeringdesignneeds.
Forexample,heightenedproductcomplexitywilldemandgreaterdepthinphysicsmodels(suchasturbulence,chemistry,particulates,real-fluidproperties),physicsbreadth(structuralmechanics,fluiddynamics)andcoupling(forexample,flow-induceddeformation).Moreintricatedesignswillrequiretransientanalysisofmovingparts(suchasimpellers,valvesandpistons).Notjustanydesignwillserve:Itmustbetheoptimaldesign.AndnotjustanyCFDtoolwillserve.Technologywithlimitedscopecannotsustainpresent—letalonefuture—engineeringdesignneeds.ContinuedadvancesincoreCFDtechnology—especiallyinthecriticalareasof solutionfidelityandspeed,optimization,androbustnessandusability—promisetoofferinnovativesolutionstomeetevolvingproduct developmentneeds.
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Advances in Core CFD Technology: Meeting Your Evolving Product Development Needs
Product developers may see it as a perfect storm of challenges: increased product complexity, tighter quality requirements, and higher yield and productivity indexes. Even with such constraints, today’s most successful companies are bringing game-changing products to market. Consider these outside-the-box ideas that are now realities.
For over 25 years, engineers have leveraged fluid dynamics advances to bring innovative products to market faster, more cost effectively and more efficiently.Today, CFD tools must evolve to address future engineering design needs.
By Eric Bish, Ph.D. Software Development Manager ANSYS, Inc.
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Overall CFD BenefitsCFDtechnologyisaprovenandsophisticatedcomputationallybaseddesignandanalysistechnique.Itaidsinbuildingavirtualprototypeofthesystemordevice,ultimatelyprovidingimagesanddatathatpredicttheperformanceofaparticulardesign.Fromatop-downperspective,therearesolidbusinessreasonstouseCFDanalysis.
Insight: Applicabletoanydeviceorsystemdesignthatisdifficulttoproto-typeortestthroughexperimentation,CFDanalysisenablesvirtualinterro-gationtoseehowagivendesignperforms.TherearemanyphenomenathatCFDcancapture—someofthemcostprohibitiveorsimplyimpracticaltoinvestigateanyotherway.CFDprovidesdeeperinsightintodesigns. Foresight: BecauseCFDisatoolforpredictingwhatwillhappenunderagivensetofcircumstances,itcanreadilyanswerwhat-ifquestions.Theuserprovidesasetofboundaryconditions,andthesoftwareproducesout-comeswithinashorttime.Thedatacanbeusedtopredicthowthedesignwillperform,withtheabilitytotestmanyvariationstoreachanoptimalresult.CFDallowsengineerstoidentifypossibledesignflawsintheearlystagesofdevelopment,beforemore-costlyphysicalprototypingandlate-stagetesting.CFDtoolshelptominimizetheriskofcostlyandpotentiallyembarrassingproductfailures.
Productivity:TheforesightgainedfromCFDhelpsuserstodesignbetterandfaster,savemoney,meetenvironmentalregulations,andensureindus-trycompliance.CFDanalysisleadstoshorterdesigncyclesandacceleratednewproductdevelopment.Inaddition,changestoexistingequipmentcanbebuiltandinstalledwithminimaldowntime.CFDisatoolforcompressingthedesignanddevelopmentcycle,allowingforrapidprototyping.
CFD as a Catalyst for Continued InnovationProductdevelopmentorganizationstodayturntoCFDtechnologytohelpdeliverevergreaterefficienciesinbringingthenextworld-classproductstomarket.Inthefuture,commercialCFDsoftwaremustmeetandexceedrequirementsofdepth,breadthandscalabilitywithgreaterreliabilityandwithoutapplicationbarriers.Thisholisticviewwillenabletomorrow’sCFDpractitionerstoleverageCFDtechnologyinunprecedentedways—whilesimultaneouslymanagingproductdevelopmentriskandoptimizingfactorsthatimpactproductiontime,costandfinalproductquality.
Advances in Core CFD Technology: Meeting Your Evolving Product Development Needs
CFD allowed Centro Richerche Fiat in Italy to save time and money by reducing wind tunnel experiments. Use of ANSYS fluid dynamics technology during the design cycle of the fuel-efficient Fiat Panda MultiEco was instrumental in reaching aerodynamic goals.
CFD cross section of unique fan ring design showing contours of velocity magnitude. Dyson, a U.K. product innovator, used software from ANSYS to develop its acclaimed Air Multiplier™.
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ContinuedadvancesincoreCFDtechnologyincriticalareaspromisetoofferinnovativesolutionstomeetindustry’sevolvingandincreasinglydemandingproductdevelopmentneeds.
TherearethreecompellingtechnologyreasonstouseCFDasanR&Dsolu-tion:accuracyandspeed,optimization,androbustnessandusability.
Solution Accuracy and Speed CFDsolutionsmustproducemore-accurateresultsformore-realisticvirtualprototypes.Greaterfidelityallowstheengineertoexploreincreasinglyrealisticdesigns,whichcontributegreatlytomakingimportantdesigndecisions.Essentialtoimprovedaccuracyareadvancesinnumerical algorithmsandmainstreamuseofhigher-orderdiscretizationmethods. Inmanycases,propermodelingrequirestheabilitytopredictthedynamicbehavioroftheflowfieldasafunctionoftime.Astime-dependentsolutionmethodsbecomemoreaccurateandefficient,transientCFDsolutionswillbecomeanintrinsicpartofday-to-dayproductdevelopment.Theability tosimulatemodelswithmovingparts—inapplicationssuchasturbo- machinery(pumps,compressors,turbines),mixingtanks,valvesand reciprocatingmachineslikeICengines—hasbecomemorecommonplaceinmanyindustries.CFDoffersproductdevelopersintheseareasthe potentialforgreaterrealisminsimulation.
CFD’snumericalmodelsvirtuallyrepresentallthephysicshappeninginaprocessordeviceinreality.Moresophisticatedandaccuratephysicalmodelswilldrivemore-authenticCFDsimulationsthatcanrevealnewlevelsofinsightintoproductdesigns.Turbulenceandmultiphasemodelingareubiquitousinfluidsengineeringsimulation;thesecontinuetobeactiveareasforfurtherresearchanddevelopment.Andthoughaddedcomplexitysometimesleadstolongerturnaroundtime,engineersdon’thavetomaketradeoffs:ThebestCFDsoftwaresuitesofferbothspeedandaccuracy,whichareenabledbythespecializedadvancementsmadeinCFDcoretechnology.
CommercialCFDsoftwaremustalsoproduceresultsrobustlyandina minimumamountoftime.More-efficientsolutionalgorithmsforbothsteady-stateandtransientCFDsimulationsareessential.High-performancecomputing(HPC)andparallelcomputinghavebecomeindispensibleenablingtechnologies.ContinuedoptimizationofCFDalgorithmsforpeakscalabilitywillenableorganizationstoleveragehardwaretechnologyandperipheralsadvancesformulti-coremachinesanddistributedclusternetworks.Solution-steeringtechniquescanhelpinautomaticallyselectingand adjustingsolutionsettingsforimprovedsolverrobustnessandperfor-mancewithless“babysitting.”Inaddition,emergingadvanceshandle solutioninstabilities,especiallyonlow-qualitymeshes.Solution sensitivityanalyseshavethepotentialtoimprovetheprocessby identifyingoptimalchoicesforinputparameters,suchasboundary conditions,solutioncontrols,timestepsandlocalmeshdensity.
Advances in Core CFD Technology: Meeting Your Evolving Product Development Needs
As products grow more sophisticated, so do companies’ require-ments for engineering simulation tools. A decade ago, Zitron in Spain solved the characterization of a simple ventilation circuit under steady-state conditions using CFD tools from ANSYS. Today, all heat transfer modes — including spectral radiation and species combustions — are considered in a transient manner to accurately assess the time response to Zitron’s ventilation management system in the event of fire in a tunnel several kilometers long.
Tractebel in Brazil simulated a coal burner with ANSYS software to identify contributing erosion. The company estimated that the altered design will reduce boiler downtime from once every three years to once every five years.
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Advances in Core CFD Technology: Meeting Your Evolving Product Development Needs
Solution Optimization CFDsolutionsmustallowanengineertoeasilyandseamlesslyexploreawiderparameterspacefordesignoptimization.Traditionally,exploringoptimaldesignconfigurationshasinvolvedcomputingindividualsolu-tionstoasetofstrategicallychosenconfigurationsrepresenting“points”inaparameterspace.Thevariationinkeyengineeringoutputquantitiesforthesystemaremappedasafunctionofinputconditionstohelptargetanoptimizedconfigurationthatcanbefurtherexploredandrefined.Thesensitivityofproductperformanceto“off-design”conditionscanalsobeconsidered.Typically,however,onlyalimitednumberofinput/outputparametersandcasescanbeincludedintheanalysisfortimeandcostreasons,makingtheentireprocesspronetoerrorandhighlydependentontheexpertiseoftheengineeringteam.Theabilitytooptimizedesignsfornewproductswithoutthebenefitofpastoperationalexperiencecanbeprohibitivelycostly.
NewmethodsfordeterminingthederivativeofaCFDsolutionwithrespecttoinputparametersusingthesolutionofadjointshavethepotentialtotakedesignoptimizationtoapowerfulnewlevel.Anadjointsolutionisableprovidethederivativeofanengineeringobservation(forexample,lift,dragortotalpressuredropthroughasystem)withrespecttoaverylargenumberofinputparameterssimultaneouslyviaasinglecomputation.The adjoint solution can be used to guide the optimal adjustment that will improveasystem’sperformanceaspartofagradient-basedoptimiza-tionalgorithm.Anadjointsolutioncanbeusedtoestimatetheeffectofachangepriortoactuallymakingthechange.Thederivativeswithrespecttothegeometricshapeofthesystemcanalsobedetermined.Sensitivitydataderivedfromthesegradientscanbecombinedwithmeshmorphing,forexample,toguidesmoothmeshdeformationsforshapeoptimiza-tion.AutomationofoptimizationtoolsintotheCFDworkflowfrominitialconcepttofinaldesignisessentialtoleveragingthesetechniquestotheirgreatestadvantage.
Solution Robustness and Usability EngineersmustbeabletorelyonCFDsimulationtohelpguideincreas-inglycomplexandcriticalproductdevelopmentdecisions.Continuousimprovementsincodingpractices,alongwithcomprehensivecodeveri-ficationandvalidation,areneededtoensurehigh-qualityreliablecode.Codedefectsarealeadingriskfactor;theycanhaveasignificantnegativeimpactontheeffectivenessofCFDsimulationinproductdevelopment.Defectscanslowthepaceofproductdevelopmentandleadtoadditionalprojectcostsintermsofworkhoursandunrealizedproductivity.Whenproblemsdooccur,supportorganizationsmustbereadytohelpmitigatetheimmediateimpactanddeliverasolutioninatimelymanner.
Blade flutter with compressors and turbines is a serious cause of machine failure. Until recently, it has been beyond the design capability to satisfactorily investigate and avoid this phenomenon. Bidirectionally coupled CFD and structural tools from ANSYS can now predict vibration modes that occur over an entire wheel from a single-blade component model. Fluid–structure interaction accurately predicts how a design will function in a real-world environment. Courtesy PCA Engineers Ltd.
Advanced turbulence models offers tools that eliminate the tradeoffs between speed and accuracy. Zonal RANS-LES models in ANSYS software enable the user to define LES only in the region where it is needed for highest accuracy, while RANS is used to model the remaining region. This enables design teams to speed up the computation while maintaining a high accuracy in regions of highest interest.
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Advances in Core CFD Technology: Meeting Your Evolving Product Development Needs
Robust CFD tools are especially critical when the ability to perform physical testing is limited. In designing pulse jet mixers (PJMs) — for use in converting nuclear plant radioactive waste into stable, storable materials— U.S.-based Bechtel National engineers needed sufficient confidence that their fluid flow model would provide pass–fail judgments. Software from ANSYS enabled them to accurately predict the ability of the units to provide sufficient mixing for each of the different vessels in which the waste would be treated. This image shows contours of solid particle concentra-tion. During the suction phase, the solids were found to become more concentrated along the bottom of the vessel, as shown by the red color in the early suction.
Therefore,CFDcodequalitymustbeanongoingpriorityforcodevendors.Muchgoodhasbeendone—andisexpectedforthefuture—withtheadoptionofqualitystandardssuchasISO-9001andNQA-1.
ForCFDsimulationtohaveitgreatestimpactonthedesignprocess,itshouldgobeyondservingasapredictivetoolforagivenconfigurationandsetofconditions.Itmustalsoshedlightontherelative“goodness”ofanygivensolution.Onepromisingapproachistoestimatethesolutionerror usingsensitivityanalyses.Withthisprocess,thereliabilityofadesigncanbeinvestigatedalongwiththesensitivityofadesigntovariationsinoperatingconditions.Sensitivityanalysescanbeusedtoassesstradeoffsinasetofplausibledesigns.
CFDtechnologyprovidesevengreatervaluewhenitismorewidelyacces-siblewithinproductdevelopmentorganizations.DemocratizingsimulationforwiderdeploymentrequiresthatCFDcodesbemorereliable.Intuitiveandeasy-to-useinterfacesaremakingitpossibleformoreengineerswithlittleCFDexperiencetoeffectivelyutilizesimulationasavalue-addedengineeringtool.Expertusersneedtobeabletocollaboratewithotherstoshareknowledgeandincreaseproductivity.TheintegrationofCFDsimu-lationwithotherphysicsdisciplines—suchasstructuralmechanicsandelectromagnetics—isalreadyunderway.FurtherdevelopmentwillopenevenmorewindowsofopportunitytoleverageCFDsimulationinproductdevelopmentorganizations.
ANSYScombinesthemostrespectednamesinfluidsimulation—ANSYS®FLUENT®andANSYS®CFX®—toexpertlyaddressevolvingCFDneedsatatimewhenproductreliability,safetyandmarketperformancearepara-mount.ANSYSoffersthemostcompletesuiteofadvancedCFDsoftwaretoolsavailable,coupledwithunrivaledmodelingcapabilities,tohelpyouachieveafastertotaltimetosolution.Productdevelopmentleadersworld-widetrustANSYSsoftwareastheirfluiddynamicssimulationplatformforitsaccuracy,reliabilityandspeed.
For more information, visit: www.ansys.com/cfdinsight
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The adjoint solver in ANSYS software provides specific informa-tion about a fluid system that is very difficult to gather otherwise. This vector plot of an internal combustion engine’s inlet port shows sensitivity of geometry shape to pressure drop, created using the adjoint solver in ANSYS software. The vector direction and magnitude indicate the recommended geometry change to improve the design.
