乱流の非等方性と壁面のブロック効果による平板上での平均流の発生(流体工学,流体機械)

概要

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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.
一般社団法人日本機械学会の論文
2004-11-25