Suppression of Fluid Forces Acting on a Square Prism by Passive Control

Suppression of fluid forces acting on a square prism by passive control of the approaching flow was investigated in the present study. Flow was controlled using a small flat plate upstream of the prism. The position of the flat plate was varied within the range of S/W = 0 ~ 3.0 (S: distance between the flat plate and square prism, W: width of square prism) and the width h of the flat plate ranged from 2 mm to 8 mm (h/W = 0.05 ~ 0.19). Steady and unsteady fluid forces, vortex shedding frequency, and flow pattern were systematically investigated. The maximum reduction of time-averaged drag was 75 percent, and the maximum reduction in fluctuating lift and drag was 95 and 80 percent, respectively, using a flat plate 1/10 of the size of the square prism.