OPTIMUM SUPPRESSION OF FLUID FORCES ACTING ON A CIRCULAR-CYLINDER

The objective of this paper is to investigate the suppression of the fluid forces acting on a circular cylinder (hereafter called the main cylinder) by controlling the flow around it. Flow control was established by introducing a fine circular cylinder (hereafter called the control cylinder) near the main cylinder. Measurements were carried out with variation of the position of the control cylinder in the ranges of G/d = 0.004 approximately 0.20 (G is the gap between main cylinder and control cylinder, d is diameter of main cylinder) and alpha = 0 approximately 180 deg (alpha is the angle along circumference from the front stagnation point of main cylinder) at a Reynolds number of 6.5 x 10(4). Subsequently, the steady and unsteady fluid forces, vortex shedding frequency and flo w pattern were systematically examined. Furthermore, such matters as the mechanism of the flow control, the nature of the controlled wake, the relationship between the characteristics of the controlled fluid forces, and the behavior of the flow were discussed in detail on the basis of the obtained results regarding fluid forces, vortex shedding frequency and flow pattern.