Near wakes of a circular cylinder in stratified flows

Near wakes of a circular cylinder in linearly stratified flows are experimentally investigated by means of flow visualization and measurements of vortex shedding frequencies, at Reynolds numbers 5 × 10 ³-10⁴ and stratification parameters K smaller than 1.0. The study demonstrates that as K increases from zero, the vortex shedding from a circular cylinder is progressively strengthened, while the Strouhal number becomes gradually lower than that for a homogeneous flow. At a certain critical value of K, the enhanced vortex shedding is suddenly weakened and the Strouhal number increases sharply to a high value.