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1、AppliedMathematicsandMechanicsPublishedbySUT,(EnglishEdition,Vol.12,No.4,Apr.1991)Shanghai,ChinaPERTURBATIONSOLUTIONTOTHENONLINEARPROBLEMOFOBLIQUEWATEREXITOFANAXISYMMETRICBODYWITHALARGEEXIT-ANGLE*YeQu-yuan(~I~)HeYou-sheng(~I~)(ShanghaiJiaotongUniversity,ShanghaO(ReceivedFeb.26,1990)AbstractInthisp
2、aper,anonlinear,unsteady3-Dfreesurfaceproblemoftheobliquewaterexitofanaxisymmetricbodywithalargewaterexit-anglewasinvestigatedbymeansoftheperturbationmethodinwhichthecomplementaryangleaofthewaterexitanglewaschosenasasmallparameter.Theoriginal3-Dproblemwassolvedbyexpandingitintoapowerseriesofaandre
3、ducedtoanumberof2-Dproblems.Theintegralexpressionsforthefirstthreeordersolutionsweregivenintermsofthecompleteellipticfunctionsofthefirstandsecondkinds.Thezeroth-ordersolutiondidn'tturnouttobealinearproblemasusualbutanonlinearonecorrespondingtotheverticalwaterexitforthesamebody.Computationalresults
4、werepresentedforthefreesurfaceshapesandtheforcesexerteduptothesecondorderduringtheobliquewaterexitofaseriesofellipsoidswithvariousratiosoflengthtodiameteratdifferentFroudenumbers.Keywordswaterexit,nonlinearfreesurface,perturbationmethod,ellipticintegrals,boundaryelementmethod,FourierexpansionInves
5、tigatingthewaterexitproblem,whichisnonlinearandunsteadyowingtothepresenceofafreesurface,isofgreatimportanceinthedesignofanunderwaterweapon,especiallyinthehydroballisticspredictionofasubmarinelaunchingmissile.Theoriesandnumericalsimulationsonthisproblemhaveconcentratedmainlyon2-Dplanaroraxisymmetri
6、ccase.Moran(1964),Yim(1974),Wang(1977)tookitsimplyas.alinearproblem,whileMoran(1963),YeandHe(1986),DommermuthandYue(1987)simulateditonthebasisofamoreaccuratenonlineartheory.Inaddition,theeffectsoftwofluids,airandwater,ontheflowweretakenintoconsiderationbyMoran(1963).Inprinciple,theproceduredevelop
7、edfirstbyLonguet-HigginsandCokelet(1976)andthenutilizedbyYeandHe(1986),DommermuthandYue(1987)andothersmaybeextendedtothe3-D.waterexitproblem.However,thereseemsnosuccessfulresultforengineeringapplicationsduetothei