Mean and Fluctuating Velocity Characteristics of a Separated Shear Layer Past a Surface Mounted Block

Abstract

The mean velocity, Reynolds stress, and mean vorticity regions of a separated shear layer over a surface mounted block are investigated by 2D Digital Particle Image Velocimetry (DPIV) for three Reynolds numbers (Rea=500, 1000, and 2500) and two channel-to-block height ratios (H∕a=1.825 and 4.6). The recirculation region’s height and length are determined for the separated shear layer by means of U¯=0 contours. It is observed that the high Reynolds stress regions lay just outside of the U¯=0 contours. The flow visualization and DPIV measurement of vorticity indicate that the differing normalized Reynolds stresses between Rea=500 and 1000 are most probably due to the initiation of the vortex shedding between these two Reynolds numbers while, differences are minimal between Rea=1000 and 2500. A sign change in the Reynolds shear stress distribution of the separated shear layer near the leading edge of the block was recognized for every Reynolds number and channel width.