简介:OnMarch26,2010anunderwaterexplosion(UWE)ledtothesinkingoftheROKSCheonan.TheofficialMultinationalCivilian-MilitaryJointInvestigationGroup(MCMJIG)reportconcludedthatthecauseoftheunderwaterexplosionwasa250kgnetexplosiveweight(NEW)detonationatadepthof69mfromaDPRK'CHT-02D'torpedo.KimandGitterman(2012a)determinedtheNEWandseismicmagnitudeas136kgatadepthofapproximately8mand2.04,respectivelyusingbasichydrodynamicsbasedontheoreticalandexperimentalmethodsaswellasspectralanalysisandseismicmethods.ThepurposeofthisstudywastoclarifythecauseoftheUWEviamoredetailedmethodsusingbubbledynamicsandsimulationofpropellersaswellasforensicseismology.Regardingtheobservedbubblepulseperiodof0.990s,0.976sand1.030swerefoundincaseofa136NEWatadetonationdepthof8musingtheboundaryelementmethod(BEM)and3Dbubbleshapesimulationsderivedfora136kgNEWdetonationatadepthof8mapproximately5mportsidefromthehullcenterline.Hereweshowthroughanalyticalequations,modelsand3Dbubbleshapesimulationsthatthemostprobablecauseofthisunderwaterexplosionwasa136kgNEWdetonationatadepthof8mattributabletoaROKlittoral'landcontrol'mine(LCM).
简介:Inordertostudycavitationcharacteristicsofa2-Dhydrofoil,themethodthatcombinesnonlinearcavitationmodelandmixed-iterationisusedtopredictandanalyzethecavitationperformanceofhydrofoils.ThecavitationelementsarenonlinearlydisposedbasedontheGreenformulaandperturbationpotentialpanelmethod.Atthesametime,themethodthatcombinescavityshapeforfixedcavitylength(CSCL)iterationandcavityshapeforfixedcavitationnumber(CSCN)iterationisusedtoworkoutthethicknessandlengthofhydrofoilcavitations.Throughanalysisofcalculationresults,itcanbeconcludedthatthejumpofpressureandvelocitypotentiallyexistbetweencavitationendareaandnon-cavitationsareaonsuctionsurfacewhencavitationoccursonhydrofoil.Incertainanglesofattack,thecavitationnumberhasanegativeimpactonthelengthofcavitations.Andunderthesameangleofattackandcavitationnumber,thebiggerthethicknessofthehydrofoil,theshorterthecavitationslength.
简介:Strongrestrictionsonemissionsfrommarinepowerplants(particularlySOx,NOx)willprobablybeadoptedinthenearfuture.Inthispaper,acombinedsolidoxidefuelcell(SOFC)andsteamturbinefuelledbynaturalgasisproposedasanattractiveoptiontolimittheenvironmentalimpactofthemarinesector.TheanalyzedvariantofthecombinedcycleincludesaSOFCoperatedwithnaturalgasfuelandasteamturbinewithasingle-pressurewasteheatboiler.ThecalculationswereperformedfortwotypesoftubularandplanarSOFCs,eachwithanoutputpowerof18MW.Thispaperincludesadetailedenergyanalysisofthecombinedsystem.Massandenergybalancesareperformednotonlyforthewholeplantbutalsoforeachcomponentinordertoevaluatethethermalefficiencyofthecombinedcycle.Inaddition,theeffectsofusingnaturalgasasafuelonthefuelcellvoltageandperformanceareinvestigated.Ithasbeenfoundthatahighoverallefficiencyapproaching60%maybeachievedwithanoptimumconfigurationusingtheSOFCsystem.Thehybridsystemwouldalsoreduceemissions,fuelconsumption,andimprovethetotalsystemefficiency.
简介:圆柱绕流问题对于研究海上浮基风电平台在波浪和海流作用下的动力特性以及开发深海风能具有重要的理论和工程应用价值,很多不可压缩流体力学数值模拟方法都基于圆柱绕流的实验或计算结果进行验证。基于自适应时间步长理论及小雷诺数(Re=100)情况下,采用有限体积法,借助FLUENT软件中的用户自定义(UDF)功能,通过二次开发在FLUENT中实现圆柱绕流的数值模拟,并对计算结果与先前的研究结果作了比较,依此来验证时间步长自适应技术和精细边界层网格设计的合理性。计算结果表明了该方法能有效获得准确的流体动力学参数并提高数值模拟计算精度,为该领域的深入研究提供依据。