Passive control of a front inclined hole on flow structures around a surface-mounted short cylinder

Abstract

Abstract To control the wake flow of a short cylinder, a passive flow control method, a front inclined hole in the cylinder was drilled from the front surface side to the free end surface. A cylinder of an aspect ratio H/D\u202f=\u202f1 with a height H\u202f=\u202f70\u202fmm and a diameter D\u202f=\u202f70\u202fmm is used. A circulation water tunnel is used to perform PIV measurements at Reynolds number of 8,570 for comparing the flow structures between the no hole and hole wakes. In order to consider the influence of the hole position, the different cylinder models of the hole height at the front from the wall are tested. Comparing with the flow structures around standard cylinder, it is found that the separation zone near the free end surface decreases and the rear separation ron increases because of the blown flow from the inclined hole. The vorticity and Reynolds shear stresses are also suppressed in the rear recirculation zone. The instantaneous large-scale eddies in the rear separation zone are divided into several small-scale eddies as increasing the angle of the inclined hole.