Computational Studies of Vortex Rings Interacting with a Constant-Wall-Temperature Heated Wall*

This study is motivated by understanding and controlling the cooling mechanisms arising from vortex-wall interaction in impinging jets. Three cases involving different configurations of axi-symmetric vortex rings interacting with a flat constant-temperature heated wall are studied computationally using ANSYS FLUENT. The cases represent simplified models of vortex-wall interaction scenarios during the evolution of jet vortices: before (Case I), during (Case II) and after (Case III) vortex pairing. The results show that the strongest wall interaction occurs during pairing (Case II), leading to significant instantaneous enhancement in Nusselt number (Nu) in comparison to that associated with a single vortex interacting with the wall (Cases I and III). However, the strong Nu enhancement in Case II has the shortest persistence in time because of the formation of a very strong secondary vortex, which leads the Nu enhancement to decay faster than in the other two cases. Overall, the results suggest that to gain the full potential of heat transfer enhancement in Case II, control of vortex-induced boundary-layer separation is necessary.