Vortex Shedding from a Circular Cylinder Placed Vertically in a Laminar Boundary Layer

Abstract

Characteristics of vortex formed behind a circular cylinder placed in a laminar boundary layer have been investigated experimentally by flow visualization and analysis on fluctuating velocity signals. Three nondimensional paramerers of Re=U0d/v(U0 : freestream velocity, d : cylinder diameter, v : kinematic viscosity), h/δ(h : cylinder height, δ : boundary layer thickness) and h/d govern the flow field. In the present study, h/δ is kept constant to unity, and h/d and Re were varied. The following new results were obtained: (i) Within the range of Re=70∼613, separated shear layers from both sides and the free-edge of the cylinder were linked to form an arch-type vortex for h/d up to 4. (ii) At h/d=3 where an arch-type vortex is formed, the Strouhal number St(=fd/U0) against Re can be classified into three regions based on different time rates of intermittent vortex shedding. (iii) Simiraly, at h/d=6 where Karman-type vortex is formed, St against Re can be classified into two regions. © 1987, The Japan Society of Mechanical Engineers. All rights reserved.