简介：Theaerodynamicdesignofastrategicweaponisofinterest,especiallywhentheradarsignaturesareincludedintheconceptualdesignphase.Thebasicsofstealthconfigurationsandstealthmechanismsformissilesarereviewed.TheRadarCrossSections(RCS)ofsomegenericmissilesarepredictedandcomparedtoanalyzethetrade-offsinvolvedbetweenlowRCSandaerodynamicperformance.TheconsiderationofRCSpredictionintheconceptualdesignphasegivesaquickinsightintothestealthperformancepriortodetaileddesign.

简介：Inthepresentwork,aparametricnumericalstudyisconductedinordertoassesstheeffectofairfoilcamberingontheaerodynamicperformanceofrigidheavingairfoils.TheincompressibleNavier-Stokesequationsaresolvedintheirvelocity-pressureformulationusingasecond-orderaccurateinspaceandtimefinite-differencescheme.Totackletheproblemofmovingboundaries,thegoverningequationsaresolvedonoverlappingstructuredgrids.ThenumericalsimulationsareperformedataReynoldsnumberofRe=1100andatdifferentvaluesofStrouhalnumberandreducedfrequency.Theresultsobtainedshowthattheairfoilcamberinggeometricparameterhasastronginfluenceontheaverageliftcoefficient,whileithasasmallerimpactontheaveragethrustcoefficientandpropulsiveefficiencyofheavingairfoils.

简介：在前翅和hindwing之间的阶段变化是从另外的昆虫使蜻蜓显得优越的一个不同特征。在这份报纸，我们调查了与60改变forewing-hindwing阶段差别的空气动力学的效果

简介：Accurateaerodynamicmeasurementsinthehypersonicflowoflargeaircraftmodelsintunnelshavepracticalsignificance,butposeasignificantchallenge.Novelaerodynamicforcemeasurementmethodshavebeenproposed,butlacktheoreticalsupport.Theformsoftheforcesignalstechniquesforsignalprocessingandcalculationofaerodynamicsareespeciallyproblematic.Atheoreticalstudyisconductedtoinvestigatethedynamicpropertiesbasedonmodelsofthedraw-rodsystemandslenderrods.Theresultsindicatethattheinertiaitemcanbeneglectedintherodgoverningequation;further,thesolutionsshowthatthesignalsofeachrodareacombinationofaerodynamicsignals(withaconstantvalue)andsinesignals,whichcanbeverifiedbyexperimentalshocktunnelresults.Signalprocessingandaerodynamicscalculationtechniquesarealsofoundtobeachievableviatheflatpartofthesignals.

简介：TheLongitudinalAerodynamicCharacteristics(LACs)ofawing-bodywithouttailunitiscomputedandtestedinwindtunnel.TheempiricalformulasofDatcomandsomeotherauthorsareappliedtoestimatethebasicAerodynamicCoefficients.Twowingoptionsarecoveredasanalysisspace,namely,thedouble-deltawingandstreakwing,gettingtwoanalysisgroupsrespectively.Goodagreementbetweenthecomputationresultsandthewindtunneltestsshowsthatthemethodologypresentedisasimpleandreliablewaytocalculatethiskindofnovelwing-bodyconfigurations.

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简介：Aerodynamicforcesandpowerrequirementsinforwardflightinabumblebee(Bombusterrestris)werestudiedusingthemethodofcomputationalfluiddynamics.Actualwingkinematicdataoffreeflightwereusedinthestudy(thespeedrangesfrom0m/sto4.5m/s;advanceratiorangesfrom0-0.66).Thebumblebeeemploysthedelayedstallmechanismandthefastpitching-uprotationmechanismtoproduceverticalforceandthrust.Theleading-edgevortexdoesnotshedinthetranslatoryphaseofthehalf-strokesandismuchmoreconcentratedthanthatofthefruitflyinapreviousstudy.Athoveringandlow-speedflight,theverticalforceisproducedbyboththehalf-strokesandiscontributedbywinglift;atmediumandhighspeeds,theverticalforceismainlyproducedduringthedownstrokeandiscontributedbybothwingliftandwingdrag.Atallspeedsthethrustismainlyproducedintheupstrokeandiscontributedbywingdrag.Thepowerrequirementatlowtomediumspeedsisnotverydifferentfromthatofhoveringandisrelativelylargeatthehighestspeed(advanceratio0.66),i.e.thepowercurveisJshaped.Exceptatthehighestflightspeed,storingenergyelasticallycansavepowerupto20%-30%.Atthehighestspeed,becauseofthelargeincreaseofaerodynamictorqueandtheslightdecreaseofinertialtorque(duetothesmallerstrokeamplitudeandstrokefrequencyused),thepowerrequirementisdominatedbyaerodynamicpowerandtheeffectofelasticstorageofenergyonpowerrequirementislimited.

简介：Thepaperpresentstheformulationtocomputenumericallytheunsteadyaerodynamicforcesonthevibratingannularcascadeblades.Theformulationisbasedonthefinitevolumemethod.ByapplyingtheTVDschemetothelinearunsteadycalculations,theprecisecalculationofthepeakofunsteadyaerodynamicforcesattheshockwavelocationlikethedeltafunctionsingularitybecomespossiblewithoutempiricalconstants.Asafurtherfeatureofthepresentpaper,resultsofthepresentnumericalcalculationarecomparedwiththoseofthedoublelinearizationtheory(DLT),whichassumessmallunsteadyandsteadydisturbancesbuttheunsteadydisturbancesaremuchsmallerthanthesteadydisturbances.SinceDLTrequiresfarlesscomputationalresourcesthanthepresentnumericalcalculation,thevalidationofDLTisquiteimportantfromtheengineeringpointofview.Undertheconditionsofsmallsteadydisturbances,agoodagreementbetweenthesetworesultsisobserved,sothatthetwocodesarecross-validated.ThecomparisonalsorevealsthelimitationontheapplicabilityofDLT.

简介：Thispaperperformsanumericalsimulationofthree-dimensionalflowfieldinacentrifugalcompressorwithlonginletandoutletpipesusingCFXsoftware.Byarrangingvirtualprobesatdifferentpositionsinbothinletandoutletplanes,theaerodynamicperformanceofthecentrifugalcompressorismeasuredandcomparedwitheachother.Theneffectsofmeasuringpositionsonmeasurementresultsarediscussed.Theresultsshowthatitwillgeneratenotablemeasuringerrorsofthepressureratioandefficiencyiftheinlettotalpressureismeasuredusingasingle-pointprobe.Theinlettotalpressuredatacanbeaccuratewhentheyaremeasuredusinga3-pointrake.Theoutlettotalpressureandtotaltemperaturedatacannotbeaccurateiftheyarerespectivelymeasuredatonecircumferentialpositionevenusingamulti-pointrake.Increasingtangentialmeasuringpositionsattheoutletiseffectivetoimprovethetestaccuracy.Whentheoutlettotalpressureandtotaltemperaturearerespectivelymeasuredat3tangentialpositions,thedatacanbealmostaccurate.

简介：Three-dimensionalnonlinearaerodynamicstabilityanalysiswasappliedtostudytheaerodynamicstabilityofacable-stayed-suspension(CSS)hybridbridgewithmainspanof1400meters,andtheeffectsofsomedesignparameters(suchasthecablesag,lengthofsuspensionportion,cableplanearrangement,subsidiarypiersinsidespans,thedeckform,etc.)ontheaerodynamicstabilityofthebridgeareanalyticallyinvestigated.Thekeydesignparameters,whichsignificantlyinfluencetheaerodynamicstabilityofCSShybridbridges,arepointedout,andbasedonthewindstabilitythefavorablestructuralsystemofCSShybridbridgesisdiscussed.

简介：Anexperimentalinvestigationonairfoil(NACA64-215)shockcontrolisperformedbyplasmaaerodynamicactuationinasupersonictunnel(Ma=2).Theresultsofschlierenandpressuremeasurementshowthatwhenplasmaaerodynamicactuationisapplied,thepositionmovesforwardandtheintensityofshockattheheadoftheairfoilweakens.Withtheincreaseinactuatingvoltage,thetotalpressuremeasuredattheheadoftheairfoilincreases,whichmeansthattheshockintensitydecreasesandthecontrolefectincreases.Thebestactuationefectiscausedbyupwind-directionactuationwithamagneticfield,andthendownwind-directionactuationwithamagneticfield,whilethecontrolefectofaerodynamicactuationwithoutamagneticfieldisthemostinconspicuous.Themeanintensityofthenormalshockattheheadoftheairfoilisrelativelydecreasedby16.33%,andthenormalshockintensityisrelativelyreducedby27.5%when1000Vactuatingvoltageandupwind-directionactuationareappliedwithamagneticfield.ThispapertheoreticallyanalyzestheJouleheatingefectgeneratedbyDCdischargeandtheLorentzforceefectcausedbythemagneticfield.Thedischargecharacteristicsarecomparedforallkindsofactuationconditionstorevealthemechanismofshockcontrolbyplasmaaerodynamicactuation.

简介：在这篇文章，跑进一条单程的二小巷的道路隧道的货车的过程用动态网孔技术和RNGk数字地被模仿吗？骚乱模型。在货车附近的短暂空气动力学的特征在三种情况中被获得：一辆单个货车，二辆货车一起并且一个接一个分别地跑进隧道的二辆货车。通过有风隧道实验的结果的比较，短暂模拟方法被验证。结果看那一辆货车是否跑进隧道，空气动力学在隧道入口附近拖系数增加，并且在进入隧道以后，方面力量被产生，更近指向隧道墙到货车。当二辆货车一起跑进隧道时，他们在50%的drag系数增加，和方面力量严厉地变化，方向在隧道入口附近变化两次。当二辆货车一个接一个跑进隧道时，在在前面的货车附近的空气动力学的特征在货车在后面上类似于一辆单个货车，而是空气动力学的力量的没有明显的变化。在三个盒子之中，当二辆货车一起跑时，空气动力学的力量有一个锋利的变化，因此一起开进一条隧道应该为安全被避免。

简介：TheaerodynamicforcesandflowstructureofamodelinsectwingisstudiedbysolvingtheNavier-Stokesequationsnumerically.Afteraninitialstartfromrest,thewingismadetoexecuteanazimuthalrotation(sweeping)atalargeangleofattackandconstantangularvelocity.TheReynoldsnumber(Re)consideredinthepresentnoteis480(Reisbasedonthemeanchordlengthofthewingandthespeedat60%winglengthfromthewingroot).Duringtheconstant-speedsweepingmotion,thestallisabsentandlargeandapproximatelyconstantliftanddragcoefficientscanbemaintained.Themechanismfortheabsenceofthestallorthemaintenanceoflargeaerodynamicforcecoefficientsisasfollows.Soonaftertheinitialstart,avortexring,whichconsistsoftheleading-edgevortex(LEV),thestartingvortex,andthetwowing-tipvortices,isformedinthewakeofthewing.Duringthesubsequentmotionofthewing,abase-to-tipspanwiseflowconvertsthevorticityintheLEVtothewingtipandtheLEVkeepsanapproximatelyconstantstrength.ThispreventstheLEVfromshedding.Asaresult,thesizeofthevortexringincreasesapproximatelylinearlywithtime,resultinginanapproximatelyconstanttimerateofthefirstmomentofvorticity,orapproximatelyconstantliftanddragcoefficients.Thevariationoftherelativevelocityalongthewingspancausesapressuregradientalongthewingspan.Thebase-to-tipspanwiseflowismainlymaintainedbythepressure-gradientforce.

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简介：Unsteadyaerodynamiccharacteristicsofaseagullwinginlevelflightareinvestigatedusingaboundaryelementmethod.Anewno-penetrationboundaryconditionisimposedonthesurfaceofthewingbyconsideringitsdeformation.Thegeometryandkinematicsoftheseagullwingarereproducedusingthefunctionsanddatainthepreviouslypublishedliterature.Theproposedmethodisvalidatedbycomparingthecomputedresultswiththepublisheddataintheliterature.Theunsteadyaerodynamicscharacteristicsoftheseagullwingareinvestigatedbychangingflappingfrequencyandadvanceratio.Itisfoundthatthepeakvaluesofaerodynamiccoefficientsincreasewiththeflappingfrequency.Thethrustanddraggenerationsarecomplicatedfunctionsoffrequencyandwingstrokemotions.Theliftisinverselyproportionaltotheadvanceratio.Theeffectsofseveralflappingmodesontheliftandinduceddrag(orthrust)generationarealsoinvestigated.Amongthreesinglemodes(flapping,foldingandlead&lag),flappinggeneratesthelargestliftandcanproducethrustalone.Forthreecombinedmodes,bothflapping/foldingandflapping/lead&lagcanproduceliftandthrustlargerthantheflapping-alonemodecan.Foldingisshowntoincreasethrustwhencombinedwithflapping,whereaslead&laghasaneffectofincreasingtheliftwhenalsocombinedwithflapping.Whenthreemodesarecombinedtogether,thebirdcanobtainthelargestliftamongtheinvestigatedmodes.Eventhoughtheproposedmethodislimitedtotheinviscidflowassumption,itisbelievedthatthismethodcanbeusedtothedesignofflappingmicroaerialvehicle.

简介：Numericalinvestigationonthedynamicmechanismhasbeenmadeforanalbatrosstoflyeffectivelynearseasurface.Emphasizingontheeffectoftheseawave,thealbatrossissimplifiedasatwo-dimensionalairfoilandthepanelmethodbasedonthepotentialflowtheoryisemployedtocalculatethewaveeffectontheaerodynamicforces.Thenumericalresultshavebeenpresentedforthestatesofflyingatdifferentconstantspeedswithconstantheightsabovesealevel,andflyingatdifferentconstantspeedswiththecombinedoscillationsofpitchingandfreeheaving.Itisshownthatthealbatrossflightefficiencydependsonnotonlythespeedandheightofflightbutalsothewaveamplitudeandthewavelength.Thealbatrossbenefitsbywaveeffecttogetthrust,soastoreducetheresistanceinthecircumstancesofroughsea.

简介：空气动力学的粗糙长度与nearsurface一起显著地变化，这以前被显示出大气的热力学的状态；目前，然而，这现象糟糕留下理解，并且很，有关这个话题的很少研究都没被进行。在这篇论文，由使用不同位于诺思中国下面的数据，表面在半干旱、干旱的区域上在由试验性的合作观察和不可分的研究提供了，空气动力学的粗糙长度(z0)在稳定、中立、不稳定的大气的层化的价值与对方相比，并且在z之间的关系0并且大气的热力学的稳定性()被分析。它被发现0显示出的那z大在稳定、中立、不稳定的大气的热力学的国家之中的差别，与在0在充分热力学的稳定的条件和中立条件之间珍视的z的差别到达60%吝啬的z0。而且，在风数据对z在哪个不太敏感为风速度变化0，0更显著地改变与，并且是的表面z高度与Monin-Obukhov稳定性(0)和全面理查森数字(Rib)相关，与两个他们在马厩和不稳定的大气的层化的比0.71和0.47大的关联系数分别地。与试验性的观察适合的实验关系与在稳定的空气的Zilitinkevich理论关系相当一致，但是二是在在不稳定的空气的变化趋势对面的相当不同、平的表演。然而，在申请，由使用试验性的数据的实验适合的关系的确认发现适合的关系是比在稳定的大气的层化的Zilitinkevich理论关系稍微更适用的，但是它是比在不稳定的大气的层化的Zilitinkevich关系更合适的。

简介：Acomputationalinvestigationwasperformedtopredicttheeffectsofaerodynamicperformancedegradationonaircraftswepttaperwingwithandwithout10minutesand22.5minutesglazeiceaccretions.Inthisstudy,thethree-dimensionalsimulatedglazeiceshapesweredefinedfromaseriesoftwo-dimensionalicesections.TheaerodynamicperformancesofglazeicedsweptwingswithC-Hstructuremulti-blockgridwereanalyzedandevaluated.ThesteadyReynolds-AveragedNavier-Stokes(RANS)equationsareemployedtocomputesolutionswithimplementationoftwoequationShear-StressTransport(SST)turbulencemodelandsecond-orderupwinddifferencingforentireicedwingflowfield.Computedresultswerecomparedwithavailableexperimentaldata.TheCFDcomputationcanalsoaccuratelypredicttheaerodynamicperformancedegradationoflift,dragandpressurecoefficientsoffinitesweptwingwithglazeiceaccretionswhichhavetwobigupperandlowerhorn.

简介：Pantographsystemofhigh-speedtrainsbecomesignificantsourceofaerodynamicnoisewhentravellingspeedexceeds300km/h.Inthispaper,ahybridmethodofnon-linearacousticsolver(NLAS)andFfowcsWilliams-Hawkings(FW-H)acousticanalogyisusedtopredicttheaerodynamicnoiseofpantographsysteminthisspeedrange.Whenthesimulationmethodisvalidatedbyabenchmarkproblemofflowsaroundacylinderoffinitespan,wecalculatethenearflowfieldandfaracousticfieldsurroundingthepantographsystem.Andthen,thefrequencyspectraandacousticattenuationwithdistanceareanalyzed,showingthatthepantographsystemnoiseisatypicalbroadbandonewithmostacousticpowerrestrictedinthemedium-highfrequencyrangefrom200Hzto5kHz.Theaerodynamicnoiseofpantographsystemsradiatesoutwardsintheformofsphericalwavesinthefarfield.Analysisoftheoverallsoundpressurelevel(OASPL)atdifferentspeedsexhibitsthattheacousticpowergrowsapproximatelyasthe4thpoweroftrainspeed.Thecomparisonofnoisereductioneffectsforfourtypesofpantographcoversdemonstratesthatonlycase1canlessenthetotalnoisebyabout3dBasbafflesonbothsidescanshieldsoundwaveinthespanwisedirection.ThecoversproduceadditionalaerodynamicnoisethemselvesintheotherthreecasesandleadtotheriseofOASPLs.

简介：飞机和鸟有类似。事实上气体动力学底是一样。以便做一些比较，这份报纸论述实验的二个系列：在与为有flapping翅膀的空气动力学的力量的大小的一个ornithopter模型一起的一条风隧道的。翅膀运动在模型的纵的轴附近有自由flapping的二度并且在翅膀轴附近羽饰。空气动力学的力量的大小：在在运动并且在动态情况中的许多周期期间平均价值的静态的情况中上升并且拖被执行了。纸的另外的部分有或没有不平的表面在一条风隧道在一口金属飞机墙喷气上使速度和骚乱大小担心，有或没有声学的颤动以便模仿一个飞机翅膀。空气动力学的特征在所有情况中被获得了。关键词风隧道-气体动力学特征-ornithopter模型-飞机墙喷气CLC数字V211.74