Enhancement of heat transfer by a self-oscillating inverted flag in a Poiseuille channel flow

Abstract

A flexible inverted flag immersed in a Poiseuille flow with heated walls was numerically modeled to investigate the dynamics of the flag and its effect on convective heat transfer. An immersed boundary method was used to analyze the interaction between the fluid and the inverted flag. This inverted flag readily becomes self-oscillating because of its configuration, in which the leading edge is free to move and the trailing edge is clamped. The inverted flag has three dynamic modes according to the characteristics of the surrounding fluid and the flag flexibility: deflected, flapping, and straight. In the flapping mode, nearly 6 pairs of vortical structures are generated in the wake of the inverted flag, which include counter vortical structures formed near the walls as well as structures generated by the interaction between the flag and the surrounding fluid. These vortical structures affect the thermal boundary layer near the walls and the temperature field in a manner that enhances the heat transfer performance of the channel flow.