Parallel vortex shedding at Re $\;{=}{\bm {O(10^4)}$ – a transverse control cylinder technique approach

Abstract

The effects of the end conditions of a circular cylinder on its wake at a fairly high Reynolds number of Re = 1.57 x 10 4 were studied. The transverse control cylinder technique (TCCT) was previously reported to be able to induce parallel vortex shedding at Re = O(10 2 ). In the present work, experimental results showed that the TCCT is still effective in inducing parallel vortex shedding at Re = O(10 4 ). Initially, before the inclusion of the control cylinders, vortices shed by the main cylinder were curved (all shapes referred to are time-averaged shapes) owing to the influence of the cylinder end conditions. Later, two larger control cylinders of diameter D were included and were located normal and upstream of the main cylinder near its ends to change its end conditions. By manipulating the control distance (the gap between the control cylinders and the main cylinder), different vortex-shedding patterns could be induced. With both control cylinders fixed at the optimum control distance of L 1 = L 2 = L 0 = 1.26D, the main cylinder was induced to shed parallel vortices. For the cases of curved vortex shedding (without control cylinders) and parallel vortex shedding (with control cylinders at the optimum distance of L 1 = L 2 = L 0 = 1.26D), various aerodynamic parameters of the main cylinder were measured and compared