Spatial Relaxation Effect between Reynolds Stress and Mean Velocity Strain for Cylinder Wake Flow
圆柱尾流雷诺应力与平均运动变形率的空间弛豫效应

In terms of the periodicity of Karman vortex-street along flow direction in cylindrical wake flow, an experimental investigation was carried out in a circular water channel to validate the spatial relaxation effect due to Reynolds stress and mean velocity strain by virtue of two-dimensional high time resolution particle image velocimetry (TRPIV). Cylindrical wake flow with different Reynolds numbers was implemented by placing cylindrical models with different diameters in a water channel. Time sequence of the spatially distributed images of two-dimension instantaneous velocity for cylinder wake flow was acquired based on TRPIV technology. Spatial distribution of the two-dimensional mean velocity, the mean velocity gradient, the mean velocity strain and Reynolds stress was obtained respectively by means of digital image processing. The rationality of complex eddy viscosity model in turbulent flow was verified by comparing the spatial phase difference between Reynolds-stress and mean velocity strain along flow direction.