Perturbation of Wall Boundary Condition to Trigger Vortex Shedding Over a Circular Cylinder

A circular cylinder placed in a uniform flow with its axis perpendicular to the flow direction can result in an unsteady flow caused by vortex shedding. Numerical simulations attempting to capture this phenomenon may lack a trigger to cause the appropriate vortex shedding, consequently, asymmetric vortex shedding can be delayed or may not occur. Therefore, an artificial disturbance can be introduced into the flow field to initiate an earlier onset of vortex shedding. Here, the wall boundary condition is used to perturb the local shear layer. It is tested for a circular cylinder at Reynolds numbers of 40, 60 and 150. Application of wall perturbation technique triggers the onset of asymmetrical vortex shedding and in the absence of a perturbation, asymmetrical vortex shedding does not occur. The effect of the patch size and duration of application of initial perturbation on the onset of vortex shedding for Re = 150 is reported.