复杂形状船体剖面水动力系数计算方法研究(英文).docx

1、第15卷第9期2011年9月船舶力学JournalofShipMechanicsVol.15No.9Sep.2011ArticleID：1007-7294(2011)09-0988-08ResearchonCalculationMethodsofHydrodynamicCoefficientsfbrSectionswithComplexShapeGAONi,SUNShu-zheng,ZHAOXiao-dong,UJi-de(CollegeofShipbuildingEngineering,HarbinEngineeringUniversity,Harbin150001,China)Abstra

2、ct：Thesource/dipolemixed-distributionapproachbasedonpotentialtheoryissuitablefbrcalculatinghydrodynamicsofsomesectionswithspecialshapes,butthismethodcannotmeetirregularshipswithobviousviscouseffectverywell.Inthispaper,theCFDsoftwareFluentconsideringviscouseffectisusedforsimulatingthebodysurgingintan

3、k.TheRANSmethodisusedforcalculatingthesurgingforceofsections,andthenthehydrodynamicscanbeobtainedbyanalyzingtheforce.ThecomparisonoflongitudinalpredictionresultsoftheshipwithcomplexsectionsbetweenthemethodswithandwithoutcalculatingviscouseffectshowsthattheRANSmethodusedinthispaperisbetterforconsider

4、ingviscouseffect,andthephysicalcharactersofdampingcoefficientsareclosertoreality.Sothemethodisbetterthanregularpotentialmethodfbrshipswithcomplexsectionswhichhaveobviouslyviscouseffects.Keywords:complexshapesection;hydrodynamiccoefficient;potentialtheory;viscosityCLCnumber:U661.32Documentcode：AIntro

5、ductionCalculatinghydrodynamicsisthebaseofthemotionpredictionofships,andalargenumberofresearchbasedonpotentialtheoryhavebeendoneforalongtime,alsothereareseveralengineeringmethodsandtheoryforhydrodynamiccoefficientscalculationsuchassource/dipolemixed-distributionapproach,multipoleexpansionapproach,2.

6、5Dpotentialtheory,3-Dpotentialtheory,andsoon11"31.Themethodsabovecanmeettheengineeringprecisionalx)uttheregularship.Butasthedevelopingofthenewtypeofship,manyirregularshipsappear,likehighperformancemonohullsandmulti-hulledshipswithvariouskindsofappendage.Becauseviscousdamptakeslargeproportionint

7、hehydrodynamicforce,thecalculationofhydrodynamiccoefficientsshouldbemoreaccurate.Thepotentialflowsolvercannottakeviscouseffectintoaccount,asthedevelopingofcomputertechnologyandCFDtechnologyinrecentyearstheRANSmethodaccountingviscouseffecthasbeenusedwidelyinships*performancecomputa-tion,4-51.Received

8、date：2011-04-27Biography:GAONi(1982-),female,Ph.D.studentofHarbinEngineeringUniversity;SUNShu-zheng(1982-),male,Ph.D.,lecturer.Inthispaper,thesource/dipolemixed-distributionapproachand2DRANSmethodwereusedforcomputingthehydrodynamiccoefficientsofsectionswithandwithoutSSB(Semi-submergedBow)回.Theresult

9、scomputingbypotentialtheoryarecomparedtotheresultusingviscousmethod,thentheadvantageanddisadvantagearediscussedbetweenthesemethods.ThispapershowsthattheviscousdampisconsideredbyRANSmethod.Theprecisionofcalculationishigherwithobviousviscouseffect,buttheadvantageislittleofthenormaltypeofshipsbecauseth

10、eviscouseffectisalsolittle.Anywaythispaperadvancesanewwaytocomputethehydrodynamicsandimprovestheprecisionofviscousdampcoefficient.1 Calculatingof2Dsections'hydrodynamiccoefficientsSource/dipolemixed-distributionapproachSource/dipolemixed-distributionapproachissuitabletospecialsectionsuchascatama

11、ran,SWATH,underwatervehicle,andsoon.Fig.lshowsthecoordinatesforthe2Dsection'ssurge.The2DfrequencydomainGreenfunctionisintroducedtosolvetheproblemof2Dsectionsurging.dG搭G、+7(p，q)dydzp(y,z)isfieldpoint,§)issourcepoint华-kG=0(z=0)dzlimVG=0JlimmikG=0The2-DfrequencydomainGreenfunctioncouldbewritte

12、nas:mg)ecoszn(y-?7)dmok-m8G(p,q)=G(y,z;y,()=ln-+2p.v.j'pqc-2mecos«I=Gi+Gz+Gg+GJ221/2221/2where=(7-77)+(z-<)J'斯=履一吁)+(z+<)|Thevelocitypotentialofanypointpintheflowfieldcouldbeexpressedasbelow:dlThelinecpresentstheboundaryofflowfieldwiththenormaldirectionpointingoutsidetheflowfield,

13、andthedirectionisshownasFig.l.Theadditionalmassofsectionmk.anddampingcoefficient与canbeobtainedfromthefollowingequation:心E粉=f+渺RANSmethods2.2.1EstablishmentofgoverningequationReynolds-averagedNavier-Stokesequationsshouldbeexpressedasbelow:duJdxO(5)Momentumequationshouldbeexpressedasbelow:dp%枷，%_fdp印叫

14、电+叫履)可pQ%，)dt，3jCjidx：、dx.whereuiisthetimeaveragevelocitycomponent(u(=u,u2=v,u3=w)forCartesiancoordinates气(£=1,2,3)direction,pisfluiddensity,pistimeaveragepressure,/zisviscouscoefficient,fiisthecomponentofsurfacel)o(lyforceinxtdirectionwhichcanbeputintopressureitemifbodyforceonlycontainsthegrav

15、ity,u/isthefluctuationvelocitycomponentofx.(t=1,2,3)directioninCartesiancoordinates,andpu：il；isReynoldsstresstensor.Turbulenttensionisproportionaltoaveragevelocityandcouldbeexpressedasbelow:/dudu%蚌=*1安+忘1J1(8)(8)whereisturbulenceforceviscouscoefficientandcanbeexpressedasbelow:呻c三where,k,eareturbulen

16、ceenergyandturbulenceenergydissipationrespectively,andcanbecomputedfromthefollowingequation:也L+也吐=_L|*也(9)(10)dt、dx)JwherePkistheproducerofturbulenceenergy,anddx.阴dxiEmpiricalconstantsC=0.09,=1.44,Ct2=1.92,<rA=1.0and5=1.30.Theunknownquanlitiesu,0,u/,p,kand£canbecomputedfromthesixclosedequati

17、onsabove.2.2.2Calculationof2DsectionsurgingTheshipscalculatedinthispaperarethehybridmono-hullwithstabilizingappendageandthemono-hullwithdeep-Vsections,andthesectionsareshowninFig.2.(c)SectionwithSSBandfinFig.2Sectionsofships5001,奸0180*01，炊5e6601500r-01454W-0140D»SO-O1100010«*-

18、00Fig.3Thesketchofregion,meshandfreesurfaceforcalculationInthispaper,thehydrodynamiccoefficientsofthebowwerecalculatedusingRANSmethod.TheunsteadyforcewascalculatedbyFluentwhensectionissurgingslightly.Theflowfield,themeshandthefreesurfaceareshowninFig.3.TheflowfieldofthecomputingmodelisdiscretewithFV

19、M.Thesizeofflowfieldis10timesbreadthxlOtimesdraft;Themeshsizeis0.1monthesectionoftheship,whilethemeshoftheflowfieldistriangleunstructuredandintensivebesidetheshipabout6timesbreadthand4timesdraft.Theflowfieldisdividedintoairpartandwaterpart,andtheVOFmethodisusedforfreesurface;ThePISOarithmeticisemplo

20、yedandtheturbulentflowmodelisRNG-k-£,alsothedynamicmeshingtechniqueisused.Fig.4Verticalunsteadyforceforthesectionsoj=2ttTheresultofswayingforceofdeep-Vsection,sectionwithSSBandsectionwithSSBandfinwhilea)=2irisshowninFig.4.Theaddedmassanddampcoefficientofheavingcouldbegotbyverticalforcecomputing

21、,andtheprincipleisbelow:theheavingadditionalmassisA33,theheavingdampcoefficientis/z33,theheavingdisplacementisZ,theheavingvelocityisZ,theheavingaccelerationisZ,theheavingamplitudeisA,forthesatisfactionoflineartheoryinthispaperAissetas0.02m,theinitialphaseis0°,theradiationforceisF,therestoringfo

22、rceisF,theverticalunsteadyforceisF=F,+F,andtheamplitudeofverticalunsteadyforceisF.WhenZ=0,Z=0,assumingZ=4sin(a>£).2Then:Z=a)Acos(W),Z=-a)Asin(a)t)Because:/=-A33Z-/x33Z,F=-pgBZThustheverticalunsteadyforceisF=F：+F=-A.33Z-pgBZTheverticalunsteadyforceFcouldbecomputedbyFluent,afterdiscretizationi

23、tcanbeexpressedasbelow:F=Fcos(以+。0)=Fcosa>Zcos0-Fsind>Zsin()(11)(12)(11)(12)And:寸燃竺咄Ao,'33"And:FcostoZcos-TsinedfsinAylcoAsin(toz)-fjb33Aa)cos(ot)-pgBAsina)t)whereBisthewaterlinebreadth,Aistheheavingamplitude,Faistheheavingforceamplitude,0()istheinitialphase,p,g,B,Aando)isknown.Thehea

24、vingadditionalmassA33anddampcoefficient/z，33couldbegotwhenFand0()arecomputedfromtheverticalunsteadyforceF.1.1 CalculatingresultsofhydrodynamiccoefficientsFig.5Addedmassofsection(noSSB)Fig.6Dampingcoefficientofsection(noSSB)Fig.7Addedmassofsection(withSSB)Fig.8Dampingcoefficientofsection(withSSB)Fig.

25、10Dampingcoefficientofsection(SSB+fin)Usetheabovemethodwecangettheaddedmassanddampingcoefficientofthesection,andthecalculatingresultsofsectionswithandwithoutSSBareshowninFigs.5-10.Thecalculationresultsshowthatviscousdamptakesasmallproportionofpitchingdampindeep-VsectionwithoutSSB,andtheresultcalcula

26、tedbyFluentisalmostthesametothehydrodynamiccoefficientsbysource/dipolemixed-distributionapproach.TheviscousdamptakesalargeproportioninsectionwithSSB,consequentlytheresultcalculatedbyFluentismoreaccuratethantheonebypotentialflowtheory.2 TheresultsofmotionpredictionThepredictionmodelusedinthispaperisS

27、TFmethod,whichisusefulforship'slongitudinalmotionprediction.TheviscousmodificationhydrodynamiccoefficientisthehydrodynamicsbyFluentsubtractingthehydrodynamicsbypotentialtheory,andtheverticalequationofmotioncouldbeexpressedasfollows:(13)M+Ai3+A33)Z+|B33+B33)Z+C33Z+(435+4*5吊+区+政)e+C350=F3e*)0+(%+K

28、)0+GW+3+兀)2+(%+房)2+%Z吼e*'wherethefactorwith*isviscouscorrectionhydrodynamiccoefficients.Oneofthetwoshipswhichwerepredictedinthispaperisadeep-Vmonohull,theotherisahybridmonohullwithSSBandfins.Andthetwoshipsarebothabout1200tonsweight,84meterslengthand10metersbreadth.Thelongitudinalpredictionresult

29、sofhybridmonohullwithSSBandfinsinheadwaves(7*r=0.32,0.43)areshowninFig.l1,andthelongitudinalpredictionresultsofdeep-VmonohullwithoutSSBinheadwaves(77=0.32,0.43)areshowninFig12.a.ComparisonofBowaccelerationbetweenFluentandpotentialmethod(Ar=0.32)OS101.5M.2.02.6b.ComparisonofheaveRAObetweenFluentandpo

30、tentialmethod(?r=0.32)c.ComparisonofpitchRAObetweenFluentandpotentialmethod(/r=0.32)1.0-1d.ComparisonofbowaccelerationbetweenFluentandpotentialmethod(Ar=0.43)Predictionresuit9(Rucnt)Fredtcuonmults(PoUntiaJ)Modeltearetuto0$1.0Predictionrwulu(F1ueet)-PredictionrwuhXPounbal)Modelrwultif.Comparisonofpit

31、chRAObetweenFluentandpotentialmethod(/r=0.43)Fig.11Predictionresultsofhybridmonohull(?r=0.32,0.43)e.ComparisonofheaveRAObetweenFluentandpotentialmethod(?=0.43)a.Comparisonofbowaccelerationbetweena.Comparisonofbowaccelerationbetweenb.ComparisonofheaveRAObetweenFluentandpotentialmethod(?r=0.32)Predict

32、ionrcsuhs(Fluent)Predictionrwuk<Potenual)Modelteatreauluc.ComparisonofpitchRAObetweFluentandpotentialmethod(Fr=032)d.ComparisonofbowaccelerationbetweenFluentandpotentialmethod(/r=0.43)e.ComparisonofheaveRAObetweenFluentand)x)lentialmethod(7r=0.43)Fig.12Predictionresultsof(leep-Vmonohull(&=0.3

33、2,0.43)f.ComparisonofpitchRAObetweenFluentandpotentialmethod(7*r=0.43)Predictionrcwlu(Fluent)Predictionreaulta(Polcntitl)ModeltatrwutaThecomparisonbetweenthetwocalculationmethodsandmodeltestresultsindicatesthat,forhybridmonohullthepredictedresultswithviscousmodificationarebetterthanpotentialmethod,w

34、hilefordeep-Vmonohullthepredictedresultswithviscousmodificationarealmostthesametopotentialmethod.3 ConclusionsFromtheresearchofthispaperwecanobtainthefollowingconclusions:(1)Fromthecomparisonofhydrodynamiccoefficientscalculationresultswecanseethat,theviscousdamptakesasmallproportionofpitchingdampind

35、eep-VsectionwithoutSSB,andtheresultcalculatedbyFluentisalmostthesametothehydrodynamiccoefficientsbysource/dipolemixed-distributionapproach.However,theviscousdamptakesalargeproportioninsectionwithSSBandfin,consequentlytheresultcalculatedbyFluentismoreaccuratethantheonebypotentialflowtheory.(2)Fromthe

36、comparisonofpredictionresultsandmodeltestresultswecanseethat,ibrdeep-Vmonohullthepredictionresultsofviscousmodificationmethodisalmostthesametopotentialtheory,andforhybridmonohullwithSSBandfinthepredictionresultsofviscousmodificationmethodarebetterthanpotentialtheory.Allinall,themethodusedinthispaperwithviscousmodificationisagoodwayforhydrodynamicscalculationespeciallyforsectionswithcomplexshapewettedsurface.References11LiJide.SeakeepingperformanceofshipsM.Beijing:Nation