Features of flow past a circular cylinder with a slit

The impact of a slit placed along a circular cylinder diameter, which is parallel to the incoming flow, is numerically investigated in order to nd a geometric modi cation that can help drag reduction, as well as vortex suppression, without any additional energy consumption. The drag reduction is achieved by diverting part of the fluid in the front stagnation region into the low pressure zone at the back of cylinder through the slit. The Reynolds number based on the cylinder diameter, D, ranges from 60 to 250. The e ect of the slit width ratio (s=D) on the drag and lift coecients, the Strouhal number, and the wake flow feature of the cylinder is presented. Favorable reduction of drag and lift coecients is observed with the rising of slit width ratio. The vortex shedding generated from the slit alters the wake flow thoroughly and drives the vortex shedding derived from the cylinder surface to further downstream.