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本文研制了脉冲热线空间速度探针,对其空间结构及特性进行了分析,给出了测量雷诺应力的方法与应用实例 相似文献
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湍流运动本身的不规则性使得湍流测量中得到信号的可靠性成为一个较难检查的问题,使用天津大学流体力学实验室编的湍流测量软件对一些标准信号进行分析,由所得结果可以检查出软件的可靠性. 相似文献
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研究的目的是确立用单一倾斜热线探头进行三维湍流测试的基础技术.在阐明基本原理,基础方程式的基础上,对比实验结果,证明应用所阐明的方法、用单一倾斜热线探头进行三维湍流测试是切实可行的.对边界层壁面附近的测试结果表明考虑平均速度和变动速度的高次相关项后可以得到更加精确的实验结果. 相似文献
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在风速为6~30m/s的范围内,许多研究表明可近似认为热线探针的偏角因子K1和倾角因子K2不随风速变化,倾角θ对K1及偏角ψ对K2也近似认为没有影响,一般采用k1≈0.2,K2≈1.02.然而在极低风速下,特别是1m/s以下,由于热线的传热机理发生变化,所以K1和K2也出现了显著的变化.本文对单丝探针和双丝探针方向特性进行了探讨性的研究,实验表明,风速小于3m/s时,K1和K2随速度发生变化,且θ对K1以及ψ对K2都有影响.当取ψ和θ为90°时,K1和K2在整个角度范围内计算速度的误差较小. 相似文献
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本文介绍了用一半圆电极对同时测量壁面上轴向与横向速度梯度湍流脉动的方法,并对电化学法测量的频率响应进行分析和实验验证,提出对测量结果修正的方法。 相似文献
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本文阐述了新研究的一种在甘油介质中可产生0~1 GPa 压力宽脉冲的加载装置,以及用于该装置测量的相应锰铜计测试系统。同时对锰铜计在1 GPa以下的压阻系数进行了动态标定。实验结果表明,所研制的装置可产生脉宽10微秒以内,压力脉值为0~1 GPa的脉冲,与理论设计基本相符。 相似文献
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文章以流体科学进入二十一世纪后,在大规模超算、云存储、数据通信和人工智能为支撑的大数据时代背景下,结合目前在复旦大学航空航天系所构建的热流体湍流直接数值仿真数据库,以及复旦大学团队近期与美国德州大学刘超群教授、上海理工大学蔡小舒教授以及国内水动力学杂志编辑部所合作开展的第三代涡识别技术研究,初步概念性地展示旋涡和湍流,特别是针对有工程实际背景和直接应用价值的壁湍流,在这两个流体力学关键基础议题上的最新认知,和基于大数据深度学习的相关湍流工程模拟实践成果.这些成果包括:(1) 基于第三代涡识别技术的尾迹湍流中的涡运动学和动力学探索;(2) 流-热统一完整的类-1、类-2湍流边界层壁面律构建;(3) 基于第三代涡识别量对Kolmogorov 幂次律的再认知;(4) 基于DNS统计数据和神经网络深度学习构建新型湍流封闭模型及RANS计算实践.通过这些成果展示,论证解决这两个基础流体科学议题的技术路径,进而促进流体及相关学科研究在现代大数据背景下取得实质性进展和突破,并惠及现代流体、气动、水利、动力和化工等工程领域. 相似文献
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On the basis of a numerical simulation of the turbulent steady-state flow past a thick airfoil with vortex cells built into the body contour, an unconventional technique for controlling flow separation by means of distributed suction from central bodies embedded in the cells is analyzed over a wide range of Reynolds numbers and suction velocities. 相似文献
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气固两相流场的湍流颗粒浓度理论模型 总被引:8,自引:0,他引:8
本文进行了气固两相流动颗粒湍流扩散现象的理论分析,提出了颗粒湍流扩散系数和气流弥散效应二个颗粒湍流模化新概念,在此基础上建立了气固两相流场湍流颗粒浓度模型。理论模型包括离心力和其它外加力场作用下颗粒运动和浓度分布的计算方法。运用湍流颗粒浓度模型,对直管气固两相流动、受限射流气固两相流动和90°弯管气固两相流动等三种流动做了数值模拟,计算获得颗粒速度、颗粒浓度等主要流动参数。讨论了湍流颗粒浓度模型的适用性。 相似文献
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Simulation and Modelling of Turbulent Trailing-Edge Flow 总被引:1,自引:0,他引:1
Computations of turbulent trailing-edge flow have been carried out at a Reynolds number of 1000 (based on the free-stream
quantities and the trailing-edge thickness) using an unsteady 3D Reynolds-Averaged Navier–Stokes (URANS) code, in which two-equation
(k–ε) turbulence models with various low-Re near wall treatments were implemented. Results from a direct numerical simulation
(DNS) of the same flow are available for comparison and assessment of the turbulence models used in the URANS code. Two-dimensional
URANS calculations are carried out with turbulence mean properties from the DNS used at the inlet; the inflow boundary-layer
thickness is 6.42 times the trailing-edge thickness, close to typical turbine blade flow applications. Many of the key flow
features observed in DNS are also predicted by the modelling; the flow oscillates in a similar way to that found in bluff-body
flow with a von Kármán vortex street produced downstream. The recirculation bubble predicted by unsteady RANS has a similar
shape to DNS, but with a length only half that of the DNS. It is found that the unsteadiness plays an important role in the
near wake, comparable to the modelled turbulence, but that far downstream the modelled turbulence dominates. A spectral analysis
applied to the force coefficient in the wall normal direction shows that a Strouhal number based on the trailing-edge thickness
is 0.23, approximately twice that observed in DNS. To assess the modelling approximations, an a priori analysis has been applied using DNS data for the key individual terms in the turbulence model equations. A possible refinement
to account for pressure transport is discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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A direct numerical simulation (DNS) of a recirculating, swirling flow is performed at a Reynolds number of 5000. Detailed
one and two point statistics are presented in this paper. Flow visualization and frequency analysis are used to identify a
precessing vortex core and to characterize its position, extent and influence on the flow field. The results are compared
with laser Doppler velocimetry (LDV) measurements as well as large eddy simulation (LES) data reported in the literature.
The present work constitutes a first step in setting up a DNS data base for complex flows. 相似文献
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A time-dependent three-dimensionally skewed flow is investigated using direct numerical simulations of the incompressible
Navier-Stokes equations. The effect on the instantaneous and mean turbulent field is investigated. Instantaneous flowfields
reveal that the skewing has the effect of initially reducing the strength and height of quasi-streamwise vortices of both
signs of rotation with respect to the skewing. A mechanism for this process is put forward. The mean flowfields show drops
in turbulence quantities such as turbulence kinetic energy. In addition to this, two-equation turbulence modelling of the
flow is carried out. This highlights a deficiency, in that the standard turbulence models are unable to capture the drop in
turbulence intensity due to the skewing. A modification based on the exact dissipation equation is found to significantly
improve the model behaviour for this flow.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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M. V. Ustinov 《Fluid Dynamics》2005,40(6):897-910
The action of an artificially generated spanwise flow in the form of periodical longitudinal vortices on a plane turbulent mixing layer is investigated. It is shown that the disturbances result in a significant increase in the thickness of the mixing region. For two kinds of spanwise flow, namely, vortices whose centers lie in the plane separating the streams and vortices located above this plane, the dependence of the mixing layer thickness on the vortex amplitude and vertical dimension and on the longitudinal coordinate is found. 相似文献
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Low-order moments of the increments δu andδv where u and v are the axial and radial velocity fluctuations respectively, have been obtained using single and X-hot wires mainly on the
axis of a fully developed pipe flow for different values of the Taylor microscale Reynolds numberR
λ. The mean energy dissipation rate〉ε〈 was inferred from the uspectrum after the latter was corrected for the spatial resolution of the hot-wire probes. The corrected Kolmogorov-normalized
second-order structure functions show a continuous evolution withR
λ. In particular, the scaling exponentζ
v
, corresponding to the v structure function, continues to increase with R
λ in contrast to the nearly unchanged value of ζ
u
. The Kolmogorov constant for δu shows a smaller rate of increase with R
λ than that forδv. The level of agreement with local isotropy is examined in the context of the competing influences ofR
λ and the mean shear. There is close but not perfect agreement between the present results on the pipe axis and those on the
centreline of a fully developed channel flow.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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The transitional turbulent regime in confined flow between a rotating and a stationary disc is studied using direct numerical
simulation. Besides its fundamental importance as a three-dimensional prototype flow, such flows frequently arise in many
industrial devices, especially in turbomachinary applications. The present contribution extends the DNS simulation into the
turbulent flow regime, to a rotational Reynolds number Re =3 × 105. An annular rotor-stator cavity of radial extension ΔR and height H, is considered with L = 4.72(L = ΔR/H) and Rm = 2.33 (Rm = (R
1+ R
0)/ΔR). The direct numerical simulation is performed by integrating the time-dependent Navier–Stokes equations until a statistically
steady state is reached. A three-dimensional spectral method is used with the aim of providing both very accurate instantaneous
fields and reliable statistical data. The instantaneous quantities are analysed in order to enhance our knowledge of the physics
of turbulent rotating flows. Also, the results have been averaged so as to provide target turbulence data for any subsequent
modelling attempts at reproducing the flow.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献