Asymmetric disturbance effect on the flow over a wavy cylinder at a subcritical Reynolds number

Abstract

A new geometric disturbance giving the reductions of the drag and lift fluctuations for bluff body flows has been proposed by applying the asymmetry to a symmetric wavy (SW) geometry. This asymmetric wavy (ASW) disturbance is applied on a circular cylinder to identify its effect on the flow control, forming the asymmetric wavy (ASW) cylinder. The turbulent flow over an ASW cylinder is investigated at a subcritical Reynolds number of 3000 using large eddy simulation based on the finite volume method. The findings of the present study identify that the ASW disturbance achieves more reductions in the mean drag and the lift fluctuation than the optimal wavy cylinder. The branch-like formation of the additional streamwise and transverse vorticities observed in the ASW cylinder are dissipated farther upstream than the symmetric wavy (SW) cylinder, resulting in wider regions of the zero vorticities in the near-wake. The ASW cylinder formed the asymmetric distribution of flow and the extent of the coherent flow farther downstream. The vortex formation length of the ASW cylinder reveals the asymmetric distribution along the span and is much longer than that of the smooth and SW cylinders. This comparison of the vortex formation length also proves the capacity of the ASW geometric disturbance to reduce the drag and lift fluctuation than the SW cylinder.