Vortex shedding and turbulent wake from a square cylinder of finite length placed on a ground plane.

Abstract

This paper describes the formation and decay of vortex shedding, turbulent eddies, and turbulent wakes from a square cylinder of finite length placed on a ground plane. The experiment was carried out in an N. P. L. blowdown-type wind tunnel having a working section of 500mm×500mm×2000mm in size at the Reynolds number 2.5×104. As a result, it was found that (i) the vortices shed from a square cylinder are arch vortices for H/D=1 and 2, and change into Karman vortices at H/D=4∼7; (ii) the number of turbulent eddies of a large scale contained in the turbulent near wake increases as the downstream distance increases, and the scale of eddies in the near wake enlarges with an increase in the value of H/D; and (iii) the effect of the free end of a square cylinder on the near and far wake was determined from the velocity measurement.