Abstract
Measurements of the base pressure of rectangular cylinders with different depth-to-height ratios, d/h=0.4-0.6 are presented. A cylinder with d/h=0.5 shows characteristic fluctuations in base pressure, with alternately high and low values, almost equal to those for d/h=0.4 and 0.6, respectively. This is caused by a sudden change in the flow pattern around a cylinder, associated with the vortex formation. Namely, the flow around rectangular cylinders initially changes gradually with increasing d/h, but, when d/h reaches a transitional range around d/h =0.5, there is an abrupt change in the flow pattern.
