DISCRETE SHEDDING MODES OF THE CYLINDER WAKE IN A JET WITH A HOMOGENEOUS CORE

The von Karman vortex street behind a circular cylinder in a laminar homogeneous jet core is experimentally investigated. The Strouhal-Reynolds number relationships are measured for various shear-layer thicknesses and aspect ratios. The experimental Strouhal number values are found to collapse with the discrete vortex shedding modes, which were observed for boundary-layer end conditions. The results indicate that the shedding modes are independent from the end conditions, but are an intrinsic feature of the shedding process of an infinitely long cylinder. The experimentally assumed shedding mode, however, is strongly dependent of the geometric parameters, like the shear-layer thickness and the aspect ratio. The observed tendencies can be made physically plausible.