Vortex shedding control by a rotating control cylinder located near the flow separation region

Vortex shedding due to flow over a main cylinder (MC) has been investigated numerically using a rotating control cylinder (CC) for the effective control of shedding characteristics and possible suppression. The state of the art concerning the investigation is "the location of control cylinder" which is kept in the "flow separation region of MC". The study is conducted in an unconfined, unsteady flow region, in which the flow is assumed to be two-dimensional at the Reynolds number (Re) 100. The rotational speed of CC (alpha = 0 to 2) and the radial distance between the centres of MC and CC (Rd/D = 0.6 to 1) are taken as the study parameters, where D is the diameter of the main cylinder. The instantaneous flow field variables are computed using the finite volume-based CFD solver Ansys Fluent (15.0). The vortex shedding characteristics are presented in the form of streamlines, Strouhal number (St), drag coefficient (CD) and lift coefficient (CL). It is interesting to note that the CC located away from the MC (Rd/D = 1) suppresses the shedding, whereas control cylinder located very close to the MC has less significant in shedding control, which depends mainly on the flow approaching the gap between MC and CC. At Rd /D = 1, the shedding is suppressed with reduced drag around 20% as compared to MC cylinder without CC; the reduction percentage increases with the increasing rotational speed of CC (alpha).