简介：TheHongKongObservatory(HKO)provideslow-levelturbulencealertingservicefortheHongKongInternationalAirport(HKIA)throughthewindshearandturbulencewarningsystem(WTWS).IntheWTWS,turbulenceintensitiesalongtheflightpathsoftheairportareestimatedbaseduponcorrelationequationsestablishedbetweenthesurfaceanemometerdataandtheturbulencedatafromresearchaircraftbeforetheopeningoftheairport.Theresearchaircraftdataarenotavailableonday-to-daybasis.Theremotesensingmeteorologicalinstruments,suchastheDopplerlightdetectionandranging(LIDAR)andradar,maybeusedtoprovidedirectmeasurementsofturbulenceintensitiesovertherunwaycorridors.TheperformancesofLIDAR-andradar-basedturbulenceintensitydataarestudiedinthispaperbasedonactualturbulenceintensitymeasurementsmadeon423commercialjetsforatypicalcaseofterrain-inducedturbulenceinassociationwithatyphoon.Itturnsoutthat,withthetuningoftherelativeoperatingcharacteristic(ROC)curvebetweenhitrateandfalsealarmrate,theLIDAR-basedturbulenceintensitymeasurementperformsbetterthantheanemometer-basedestimationofWTWSforturbulenceintensityatmoderatelevelorabove.Ontheotherhand,theradar-basedmeasurementdoesnotperformaswellwhencomparedwithWTWS.BycombiningLIDAR-andradar-basedmeasurements,theperformanceisslightlybetterthanWTWS,mainlyasaresultofcontributionfromLIDAR-basedmeasurement.Asaresult,theLIDAR-basedturbulenceintensitymeasurementcouldbeusedtoreplaceanemometer-basedestimatefornon-rainyweatherconditions.Furtherenhancementsofradar-basedturbulenceintensitymeasurementinrainwouldbenecessary.

简介：Inthispaper,wepresentanextensivestudyofthelinearlyforcedisotropicturbulence.Byusinganalyticalmethod,weidentifytwoparametricchoices,ofwhichtheyseemtobenewasfarasourknowledgegoes.WeprovethattheunderlyingnonlineardynamicalsystemforlinearlyforcedisotropicturbulenceisthegeneralcaseofacubicLienardequationwithlineardamping.WealsodiscussaFokker–Planckapproachtothisnewdynamicalsystem,whichisbistableandexhibitstwoasymmetricandasymptoticallystablestationaryprobabilitydensities.

简介：Experimentswereconductedinawatertunnelbytomographictime-resolvedparticleimagevelocimetry(Tomo-TRPIV).TheReynoldsnumberReθis2460onthebaseofmomentumthickness.Accordingtothephysicalmechanismofthestretchandcompressionofmulti-scalevortexstructuresinthewall-boundedturbulence,thetopologicalcharacteristicsofturbulencestatisticsinlogarithmiclayerwereillustratedbylocal-averagedvelocitystructurefunction.Duringcoherentstructuresbursting,resultsrevealthatthetopologicalstructuresofvelocitygradients,velocitystrainratesandvorticitiesbehaveasantisymmetricquadrupolemodes.Athree-layerantisymmetricquadrupolevortexpacketconfrmsthatthereisatightrelationshipbetweentheouterlayerandthenear-walllayer.

简介：在精力平衡实验期间，patch-to-patch灌溉在一块纵贯的面向的棉花地里在土壤潮湿产生了坡度。从相对干燥的在上游的补丁由于强壮的水平移流开发相对弄湿下游的补丁的内部边界层(IBL)与占优势的在北方的风联系了。这产生了多重尺寸的大旋涡，它在IBL在骚乱的结构上有重要影响。在IBL以内在二高度测量的风速度，温度，湿度，和精力流动的力量系列和cospectra被介绍并且过去常在表面层骚乱上调查IBL的影响。系列和cospectra被外部骚乱极大地在低频率提高。这些骚乱的山峰频率没随着高度变化。系列和cospectra典型地收敛了并且与在高频率的堪萨斯光谱平行(在惯性的子域)。当表面层是稳定的时，在水平风速度的系列的清楚的差距在中间的频率存在。结果显示在在上游的对流边界层发源的大旋涡在表面层骚乱的系列和cospectra上有可观的影响。这些大旋涡的影响更大(1)当IBL比IBL什么时候没存在在近的表面层是开发得好的时，(2)在比在底层高级，并且(3)当大气的表面层(ASL)比ASL什么时候是稳定的不稳定时。这些大旋涡的长度规模与在实验地点的表面异质的主导的规模一致。