Effect of rotating control cylinder location on vortex shedding behind a main cylinder

Abstract

The dynamic behavior of flow over a circular main cylinder (MC) in presence of single small rotating control cylinder (CC) has been studied numerically at Reynolds number, Re = 100 and 200. The CC location (r cc = 0.6D–1D), rotational direction (clockwise and counterclockwise) and rotational rate (α = 0–2) of CC are taken as the study parameters. The flow field variables are computed using Ansys Fluent 15.0, the vortex shedding characteristics such as Strouhal number (St), drag (C D ) and lift (C L ) coefficients are analyzed. It is identified that the fluid shearing between MC and CC significantly controls the vortex formation behind the MC and subsequent vortex shedding. Unlike existing study, which reports the vortex shedding suppression only for the very closer location of CC, the present work identified new locations of CC for vortex shedding suppression. At Re = 100, suppression is identified at three different locations of CC (r cc = 0.7D, 0.9D and 1D) with lower α (α = 0.5, 1) due to a favorable pressure gradient (FPG) over MC. But with increasing Re, CC at higher r cc and lower α does not generate FPG. At Re = 200, shedding suppression is observed only at higher α (α = 2) and closer location of CC ( θ = 75 ∘ , r c c = 0.7 D ), which is identified as an optimum location based on vortex shedding suppression on the MC with reduced drag (65.45%, 75.8%) respectively for Re = 100 and 200.