Velocity field of a bluff-body wake

The characteristics of shear-layer vortex shedding and toroidal wake behind a circular disc are experimentally studied. Five characteristic flow structures, laminar, subcritical, transitional, supercritical, and turbulent modes, are identified in the shear layer evolving from the edge of the disk. The Strouhal numbers of the vortex shedding are about 0.12 and 0.20 in the subcritical and supercritical shear layers, respectively. The Taylor integral length scales of the shed vortices in the subcritical and supercritical shear layers are about one and 0.5 disc diameters, respectively. The flow patterns, recirculation length, as well as turbulence properties are closely related to the characteristic modes of shear-layer structures in different ranges of Reynolds numbers. The measured distributions of Reynolds stresses show that the simple Boussinesq approximation of gradient-type stress model is inappropriate for this flow field. The intensity of turbulence fluctuation superimposed on the vortices dominates the distributions of the Reynolds stresses.