Drag Reduction of a Square Prism. 2nd Report, Strouhal Number and Flow Pattern.

To control the flow around a square prism, a small rod was set upstream of the prism. The side of the prism, D, was 20 mm and the Reynolds number ranged from 5. 3 × 103 to 3. 2 × 104. The effects of the diameter of the rod, d, the distance between the axes of the rod and prism, L, and the Reynolds number on the drag reduction of the prism were investigated. The value of the Strouhal number of the prism is classified into three groups. These groups correspond to the flow patterns around the prism, which are related to) the behavior of vortex shedding from the rod. The maximum reduction of drag coefficient is 70% compared with that without the rod at d/D=0.3 and L/D=2.5.