Mean Flow Generation near a Flat Surface by Direct Impingement of an Anisotropic Turbulence and Blocking Effect
Mean Flow Generation near a Flat Surface by Direct Impingement of an Anisotropic Turbulence and Blocking Effect
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通过各向异性湍流和阻塞效应的直接冲击在平坦表面附近生成平均流
DOI：
10.1299/kikaib.70.2776
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
J. Hunt
中科院分区：
文献类型：
--
作者：
K. Nagata;J. Hunt
利用边界层理论和线性快速变形理论，研究了无切变边界层中各向异性湍流直接撞击产生的第二类普朗特二次流。本文将齐次轴对称湍流的三维谱张量应用于Hunt&Graham(1978)发展的无切变边界层线性理论。得到了速度脉动和雷诺剪应力三分量湍流强度的全解析解。结果表明，在这种类型的轴对称自由流湍流中，垂直速度脉动的湍流强度在平坦表面附近的流向和展向上不是均匀分布的，而对于各向同性自由流湍流，垂直速度脉动的湍流强度在流向和展向上是均匀分布的。各向异性大尺度涡直接撞击表面所产生的雷诺应力梯度产生平均流动，但湍流轴线与表面方向平行的情况除外。该效应还解释了在刚性表面附近的复杂湍流中，各向异性涡旋结构如何影响平均流动。
Generation of Prandtl's secondary flow of the second kind by direct impingement of anisotropic turbulence is studied in a shear-free boundary layer using a boundary-layer theory and a linear Rapid Distortion Theory (RDT) . The three-dimensional spectral tensor for homogeneous axisymmetric turbulence is applied to the linear theory developed for shear-free boundary-layer by Hunt & Graham (1978) . Fully analytical solutions for the three-component turbulent intensities of velocity fluctuations and Reynolds shear stresses are obtained. The results show that the turbulence intensity of vertical velocity fluctuations is not distributed equally in streamwise and spanwise directions near a flat surface in this type of homogeneous axisymmetric free-stream turbulence whereas it is distributed equally in streamwise and spanwise directions for isotropic free-stream turbulence. Reynolds stress gradients caused by the direct impingement of the anisotropic large-scale eddies onto the surface generate the mean flow except in the case where the axis of the turbulence is parallel to the direction of the surface. The effect also explains how in complex turbulent flows near rigid surfaces the anisotropic eddy structures affect the mean flow.