TOMOGRAPHIC TRPIV MEASUREMENT OF ANISOTROPIC EDDY-VISCOSITY MODEL FOR COHERENT STRUCTURE REYNOLDS STRESS

The time sequences dataset of 3D-3C flow field of turbulent boundary layer in a water tunnel by tomographic TRPIV were employed to put forward the new concept of spatial locally-averaged velocity structure function of turbulence that describes the spacial dilation, compression, shear deformation and rotation of the multi-scale turbulent eddy structure. According to the physical characteristics of the multi-scale vortex structures' stretch and compression in turbulent flow, a new conditional sampling method of coherent structure, based on the concept of multi-scale spatial locally averaged velocity structure function along the longitudinal direction, was proposed to extract the spatial topology of physical quantities such as fluctuating velocity, mean velocity strain rate and Reynolds stress during the process of coherent structure burst in TRPIV dataset. In this paper, the relationship between mean velocity strain rate and Reynolds stress was studied. The validity of the anisotropic eddy viscosity model was confirmed for coherent structure Reynolds stress in wall-bounded turbulence through investigating the spatial phase difference between Reynolds stress components and mean velocity strain rate components.