Investigation of bluff body asymmetry on the properties of vortex shedding

The influence of unequal strength opposing shear layers on periodically shed vortices is experimentally investigated in the wake of a two-dimensional triangular cylinder. The experiment was developed to isolate the influence of the intensity differential between two shear layers from other flow parameters. Phase-averaged velocity and surface pressure data were obtained for a Reynolds number of 22 500. The relative intensity of the shear layers was adjusted through the angle of incidence. It is found that the shedding frequency can be satisfactorily scaled using the projected obstacle width. The product of the drag and shedding frequency scales with the velocity parameter k, based on the base pressure, as predicted from existing theory. However, the predicted relationship between k and the shedding frequency no longer holds, indicating that the existing vortex shedding theory needs modification to account for unequal strength shear layers. (C) 2007 Published by Elsevier Ltd.