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Longitudinal and transverse structure functions in decaying nearly homogeneous and isotropic turbulenceLongitudinal and transverse structure functions in decaying nearly homogeneous and isotropic turbulenceLongitudinal and transverse structure functions in decaying nearly homogeneous and isotropic turbulence 下载免费PDF全文
Streamwise evolution of longitudinal and transverse velocity structure functions in a decaying homogeneous and nearly isotropic turbulence is reported for Reynolds numbers Re;t up to 720. First, two theoretical relations between longitudinal and transverse structure functions are examined in the light of recently derived relations and the results show that the low-order transverse structure functions can be well approximated by longitudinal ones within the sub-inertial range. Reconstruction of fourth-order transverse structure functions with a recently proposed relation by Grauer et al. is comparatively less valid than the relation already proposed by Antonia et al. Secondly, extended self-similarity methods are used to measure the scaling exponents up to order eight and the streamwise evolution of scaling exponents is explored. The scaling exponents of longitudinal structure functions are, at first location, close to Zybin's model, and at the fourth location, close to She-Leveque model. No obvious wend is found for the streamwise evolution of longitudinal scaling exponents, whereas, on the contrary, transverse scaling exponents become slightly smaller with the development of a steamwise direction. Finally, the stremwise variation of the order-dependent isotropy ratio indicates the turbulence at the last location is closer to isotropic than the other three locations. 相似文献
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IntroductionDuetotheimportanceofglobalandlocalscalingexponents,theyattractmanyturbulentresearchersduringthepasttwentiesyears.Butresultsobtaineduptonowaremainlyonisotropicturbulence ,bothinexperimentsandnumericsimulations[1].Itisfoundthatξpisnonlinearfunc… 相似文献
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I.IntroductionItisaveryinlportulltdiscoveryofcoherentstrLICturcinshetlrturbulellt11owsbyexperimentinthelate1950s,whichleadsustoseekthenaturall,ropertiesofturbulcllcefromthenewideaandilladifferentway.ThestudyofthecoherclltstrLlcttlrcisofgreatimportallcetounderstandthegeneration,developmentanddecayof'tLlrbulellce,allditlsoconstructsInorerealisticturbulencemodeltheory.Meanwhile,itwillbeor11elpIYomengineerillgpoint,suchaslllassandheattrallslbr,dl'agI.eductiolland11oisecontrolproblems.Soinlnlel… 相似文献
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在文献「1」、「2」的启发下,本文建立一个零压梯度下,考虑局部产生以及外来扰动涡旋的壁湍流边界层大涡拟序结构的统计及动力学模型,在此基础上对充分发展的宽明渠流动中壁面附近的热扩散进行了数值模拟,建立了边界层拟序脉动速度和温度的数据库,发现了与速度快慢条相对应的高低温流条及其随时间的展向的摆动,数值模拟结果与前人的计算和实验结果吻合很好。 相似文献
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Three dimensional large eddy simulation (LES) is performed in the investigation of stably stratified turbulence with a sharp thermal interface. Main results are focused on the turbulent characteristic scale, statistical properties, transport properties, and temporal and spatial evolution of the scalar field. Results show that the buoyancy scale increases first, and then goes to a certain constant value. The stronger the mean shear, the larger the buoyancy scale. The overturning scale increases with the flow, and the mean shear improves the overturning scale. The flatness factor of temperature departs from the Gaussian distribution in a fairly large region, and its statistical properties are clearly different from those of the velocity fluctuations in strong stratified cases. Turbulent mixing starts from small scale motions, and then extends to large scale motions. 相似文献