Abstract
Near wakes of a circular cylinder in linearly stratified flows of finite depth are experimentally investigated by means of flow visualization and measurements of vortex shedding frequencies, at Reynolds numbers 3.5 × 103-1.2 × 104 and stratification parameters kd smaller than 2.0. The nondimensional parameter kd is defined by kd=Nd/U, where N is the Brunt-Väisälä frequency, d, the cylinder's diameter, and U, the approaching velocity. The study demonstrates that as kd increases from zero, the vortex shedding from a circular cylinder is progressively strengthened, while the Strouhal number becomes gradually lower than that for a neutral flow. Of particular interest is the phenomenon in which at a certain value of kd, the enhanced vortex shedding is critically weakened, with a sharp rise in the Strouhal number.
