Near-wake effects of a heat input on the vortex-shedding mechanism

Abstract

This article presents the investigation on the vortex formation and shedding process behind a heated cylinder which is exposed to a cold cross flow. The Reynolds number is chosen to be 75 while the Grashof number is varied between 0 and 5000 (resulting in a variation from forced to mixed convection). The numerical results show that the addition of heat disturbs the vortex formation process. The vortices shed from the upper half of the cylinder become stronger for increasing heat input. Therefore, the shedding process at the upper half of the cylinder becomes more effective compared with the process at the lower half. Consequently, the vortices shed from the upper half of the cylinder have a higher vorticity extreme and a higher temperature. The results show that the difference in effectiveness is mainly caused by a decreasing effect of strain rate during the formation of an upper vortex. This change in strain rate is caused by a change in flow pattern around the cylinder for increasing Grashof number. For higher heat input more fluid flows underneath the cylinder, resulting in weaker shear layers at the upper part of the cylinder.