Suppression of Fluid Forces of Rectangular Cylinders by Passive Control of Flow. 2nd Report. On Rectangular Cylinder with Fully Separated Flow.

Abstract

Objective of the present study is to investigate the suppression of the fluid forces acting on rectangular cylinders by passive control of flow around it. The width-to-height ratio B/H of the section is varied from 0.3 to 2.0. Flow control is established by introducing a fine flat plate in the upstream of rectangular cylinder. Measurements are carried out to change systematically the position of the plate, and then the steady and unsteady fluid forces are examined to estimate the magnitude of the reduction themselves. Also, such matters as the mechanism of the flow control, the structure of the controlled wake and the behavior of the separated shear layer are investigated. As a result, it is found that the steady and unsteady fluid forces and vortex shedding of the rectangular cylinders with aspect ratio B/H beyond 0.5 can be substantially suppressed using a flat plate with a width of one tenth of the cylinder height.