Flow Structure Around A Finite-Length Square Prism

Abstract Turbulent flow structure around a square prism of finite length is experimentally investigated in a closed-circuit low speed wind tunnel. Hotwire and PIV data indicate that the near wake structure is dependent on the aspect ratio of the prism and characterized by vigorous interactions between base and tip vortices when the cylinder aspect ratio is 3 or less, but among spanwise vortices, tip vortices and base vortices at an aspect ratio of 5 and above. The counter-rotating base vortices dominate the near wake close to the prism base and attain maximum vorticity at 1d (prism width) downstream of the prism and decay rapidly downstream. Both the maximum strength and size of these vortices grow with increasing aspect ratio due to weakening interaction between the tip and base vortices. Based on the present data and those in the literature, the flow structure models for different prism aspect ratios are proposed.