有关DPM的问题.docx
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有关DPM的问题
1.DPM
I'dliketoset3particleinjections(e.g,30particlesforeachinjections)fordifferentdiameterof20um,1um,0.01umandcomparethedepositionvelocity.iamusingtheunsteadytracking,theproblemiswhenistartingtheiteration,Fluentmixthe3injectionstogether,thatis,itwillshowontheconsolewindows:
numbertracked=90,trapped=15,escaped75,sthlikethis,soican'tgetthetrappednumberofparticlesforeachdiameter.Canyouhelpme?
thanks
Hi
Iwasthinkinginyourcase!
Whydoyouwanttorunthethreediametersinonlyoneiteration?
Ithinkyoucanruneachdiameterseparatelyinordertomeasurethevariablethatyourequest,afteralltheparticletrackingisindividualforeachparticleanditisnotaffectedbyotherparticles!
InadditionIthinkthat3pointofinjectionaretolow!
Perhapsmorepointperareacouldbemorerepresentativeforyourcasethan30particleslaunchedfromonepoint!
GiveyourcommentbackIaminterestedinyourcase!
Alex
thanksforyourresponding!
ImeanifIcansubmit3injections(justtheparticlediameterisdifferent,theotherparametersarethesame)inonetimestepsandgettheresultsseperately.butnowicanonlyputoneinjectionatonetime.forexample,ineedtheresultsduring20timesteps,onetimestepcosts1hour,thenforoneinjectionineed20hours,ifiputtheinjectiononebyone,thenihavetospendn*20hours!
soiwonderificanputalltheinjectionstogether,andthenthetimeneedisonly20hours.
hopeiexplainitclealy,thanks!
HICandy
YesIcanhelpyou!
Solution
MadeThreefileswiththefollowingformatandinformationdata
((x,y,z,v,v,w,d,T,mass-flow)injectionID:
particleID)wherex,y,zarethecordinatesu,v,w,aretheabsolutevelocityoftheparticlesddiametermTtemperatureKelvinMass-flowKg/sInjectionID:
particleID=Injectioni:
jwhereithenumberofpointforinjection(inyourcase0to2)andjthenumberofparticleperinjectionpoint(inyourcase0to29)
Thenreadthatfilesinyourinjectionwindow(belowsingle,group,surfaceyouwillseefile)Thenatthebottomoftheinjectionwindowyouwillseaboxwiththenamefile..Clickonthefile..boxandselectthefile(namethefilecandy0.inj,candy1.injandcandy2.inj)Then,runtheparticletrackingforyousteadycaseMakesurethatyouaregettingreasonableresultsThen,writeaUDFdpmOutlettowriteafilewiththevariablethatyouwishThen,openreport>discretephase>sample>selectyousurface,injectionandoutputfilecompute,plotthehistogramreport>discretephase>histogrammakesurethatyourstatisticalmomentsforthevariablesofconcerndoesnotchangeafterincresingthenumberofparticlesThen,runtheunsteadycasewithallyouinjectionsImporttheoutput.dpmfiletoExcelThen,youcanseethevariableofconcernforeachinjectionID:
particleIDFinallyyoucanplaywithyourresultsasyouwant!
Havefun!
Ifimisssomethingthinksmart!
Regards
Alex
Hicandy
Now,Ineedyouhelp
Ihavenotrununsteadyparticletracking!
couldyoupleaseexplainmehowyoudoit
Thankyou
Alex
1.OpenDISCRETEPAHSEMODELpanel,selectUnsteadytracking.
2.GotoInjections-setinjectionproperty-creat,ifyouselectasurfaceasinjection,thenonthebelowofthepanel,therewillexist"pointproperties"forunsteadytracking,itwillappeartheitem“starttime"and"stoptime",particlewillbereleasedateverytimestepduringtheperiodoftimeyoudefined.Aftertheperiodoftimeyouset,particlewillstillbetrackeduntilalltheparticlearetrappedorescapedor....3.notethatunsteadytrackingiscalculatedtogetherwiththefluiditeration,thatis,open"iterate"panel,and"iterating",aftereachtimestepiteration,theparticlewillbereleasedandcaculated.
hopetheaboveisuseful,goodluck!
unsteadyparticletrackingisonlyactivewhenyouselecttheunsteadyoptioninthesolver.
helloCandyandHedonist
Thankyouforyourinformation!
Regards
AlexMUnoz
Hicandy
Iforgettoaskyouonedetail.
isyourDPMcouplewiththecontinuousfluid?
becuasemycaseisnotcouplewiththecontinuousflow,andIwonderifIneedtoiteteratetheflow.
Thankyouforanswermethesequestions!
Bestregards
AlexMunoz
Mycaseisalsonotcoupletoo,butitisalsoneededtoiteratetheflow,otherwisehowcanyoudotheunsteadytrackingsincethecaseanddatafileonlyrecordtheflowinadefinitetime?
HiCandy
Thanksalotforyourreply,Ithoughtaboutit!
JustIwanttobesure
Thankyou
AlexMunoz
Hicandy
Iwanttoaskyouanotherquestion!
Perhaps,youwonderWhyIdon'trunFluentandIcheckformyself,Currently,wearemakingmodificationandIcannotrunaniterationformorethan5minutesusingtheGUI,ifIruniterationformorethan5minutesIhavetodoitunderbatchmode.Idon'tknowifyouhaveworkingunderthismodebutIhavetobe100%surewhatIamdoing.
Thequestionisthefollowing
IhavetoreportparticletrackingunderReport>DPM>SampleandIhavetospeficytheStarttimeandStoptime.Fluentdocumentationsaysthe
"Forunsteadyparticletracking,clickingontheStartbuttonwillopenthefilesandwritethefileheadersections.Ifthesolutionisadvancedintimebycomputingsometimesteps,theparticletrajectorieswillbeupdatedandtheparticlestateswillbewrittentothefilesastheycrosstheselectedplanesorboundaries.ClickingontheStopbuttonwillclosethefilesandendthesampling"
Iamveryconfusewiththisinformationperhapsyoucanhelptounderstandthisissue.
Thankyouinadvance!
AlexMunoz
2.ProblemofDPM
Deareveryone:
IamusingDPMmethodtosimulatedropsdistributioninacompartment.Theresidualsarealwaysoscillatoryanddon'tconverge.Couldyoupleasetellmehowtomakemysolutionconvergence?
Thankyouverymuchforyourhelp.
Iamlookingforwardtoyourreply.
Withbestregards,
You
Ihaveexactlythesameproblemifitisanyconsolation!
Hiyou,
canyougivemoredetailonyourcase:
coupledorsegregatedsolver?
twowaycoupleddpmcalculationornot?
withstochasticparticletrack?
doesthecalculationforthecontinuousphaseconvergewithoutparticle,...
bestregards
Alain
HiAlain,
Thankyouverymuchforyourreply.Iamusingsegregatedsolverandcoupleddpmcalculationwithstochasticparticletrack.Thecalculationforthecontinuousphaseconvergeswithoutparticle.Thedropdiameteris1.2mm.
Doyouprovideenoughinformation?
Bestregards,You
Canithavesomethingtodowithhowoftenyouinjectparticles?
Christian
Dearyou
1)DropdiameterisfairlybigcomparedtothegeneralDPMapplication.So,Ithink,it'smomentumsourceisfairlylarge.Becauseyouusestochasticparticletracking,smallchangeinmomentumsourceinlocalarea(localcell)cancausefairlybigeffect.So,howabouttotrymeanparticletracking(withoutstochasticoption)?
2)WhenItryDPMandconvergenceisdifficult,Iincreasegasphaseiteration,thatis,50~100iterationpereachDPMiteration.Atthattime,Isetresidualconvergencecriteriaverylowvalue,e.g.,1.e-05.Then,iterationiscontinued.Aftermanyiterations(atleast50~100DPMinjectioniteration),Icheckeveryresidualwhethertheyareenoughlowornot.Withthisapproach,ingeneral(noteverycase),Iwassuccessful.
Hi,
Thankyouverymuchforyourreply.Ihavetriedinjectingparticlesevery5to20iterations.
Withbestregards,You
Ihopethatitmightbehelpfultoyou.
Sincerely,Jinwook
Dearyou
Iagreewithjimwook.
Yourlackofconvergenceiscertainlydotostochastictracking.
Notethatthiscanalsobetheresultofaphysicalphenomenon!
Stochastictrackingintroduceimplicitlyatemporalterminthemomentumequationduetofluctuationofthetermofexchange.
Thiscanbeobservedexperimentalyindensetwophaseflowsuchaspneumatictransportorfluidizedbed.
Takealookatyourmomemtumsourcetermandyourflowpressureandvelocityfield.Yoursourcetermcanfluctuatebutyourfieldcanbesteady.Inthispeculiarcaseyourflowis"converged"evenifyourresidualsremainshigh.
Atlast,ifyourflowdiverge,youcanalsounderrelaxthesourcetermcomingfromDPM.
Bestregards
Alain
Addtopreviouscomment:
Increasinginjectionnumbermightbehelpfulforconvergencebecausemomentumsourceofeachinjectionisrelativelysmallwithmanyinjectionnumber.
Sincerely,Jinwook
3.Usingfiletodefineinjectiondistribution!
!
(DPM)
Hello,
InfluentDPM,particleinitialconditionscanbereadfromanexternalfile.Thefilehasfollowingform:
((xyzuvwdiametertemperaturemass-flow)name)
Butwhat'sthefile'sformat?
?
Thankyouforyourhelp!
!
winnie
Hiwiinie
Thefilehastheformatthatyouwrite((xyzuvwdiametertemperaturemass-flow)injection0:
ID)((###########)injection0:
0)((###########)injection0:
1)((###########)injection0:
2).........((###########)injection0:
n)
where#isanumberundertheunitthatyouareusing.
Regards
AlexMunoz
Hi,AlexMunoz
Thankyouforyouranswer.Iwouldalsoliketoknowthefile'stype,anotherword,whatkindoffilescanbeaccessedbyfluent?
Ihavetried.txt,.candsoon,buttheycan'tbeinputtothefluent.
Waitingforyouranswer!
Bytheway,ifIhavefourinjections,canIusefoursingleinjections?
Doesithaveanydifferencewithafileinjection?
Regards
winnie
Hiwinnie
Thefileisatextfile,ForinstanceIgenerateafileusingaCcodethatIwrote,thenInameit"bach.inj"
YOucancreatefourfilesorIguessyoucanwritejustonefilecontaining4injecti