Flow control of vortex shedding by a short splitter plate asymmetrically arranged downstream of a cylinder

The flow around a circular cylinder (diameter d) was investigated, behind which a short thin splitter plate with a chord of 1.0d was inserted horizontally as an interference element. The plate was traversed upstream along the wake; hence its relative position is defined by gap G from the cylinder base to the plate tip and by level Z from the wake centerline. The variation in both base suction coefficient and Strouhal number with G/d significantly depends on Z/d. In the circular cylinder case with Z/d=0.5–1.3, as the plate approaches the cylinder, the base suction coefficient exhibits a critical fall in a similar fashion to Roshko’s experiment where Z/d=0. Interestingly, however, unlike his experiment, the Strouhal number exceeds the natural one for some range of G/d beyond the critical gap. To further examine the flow mechanism, a similar situation was investigated by using a rectangular cylinder (height h, depth 0.1h) in place of the circular cylinder. A rise in the Strouhal number is observed for Z/h=1.1. These rises in Strouhal number are explained by the flow mode in which the shear layer separated from the gap side is forced to flow into the gap and to interact in the nearer wake by the approach of the splitter plate.