Dual cylinder inviscid vortex sound of low Mach number

Abstract

The unsteady motions of an inviscid vortex under the influence of a cylinder pair in the presence of a low Mach number mean flow and the corresponding sound generation are examined in the present study. The two cylinders are in close proximity. A semi-analytical approach using the conformal mapping together with the potential theory is adopted. The results show that the vortex will interact intensively with the cylinders under the right combinations of mean flow direction and initial vortex position. Such interactions result in a high rate of change of vortex propagation velocity, strong fluctuating forces on cylinder and strong sound radiations. However, it is found that much stronger acoustic energy radiation will result when the vortex approaches the cylinder pair from the bottom than from the top, unless the mean flow is nearly perpendicular to the horizontal cylinder pair axis. Stronger sound radiation is also observed for the identical cylinder cases in general, except the flow direction is close to some critical values.