The heat transfer enhancement with a flag-shaped flexible wing

The flow and heat transfer characteristics in a rectangular channel with a flag-shaped flexible wing are numerically investigated. The effects of Young's modulus of flexible wings and Reynolds number on the fluid dynamic and heat transfer characteristics are explored. Different from the previous investigations, the visualization of the flexible wings motion and vortex structure induced by the flexible wings are obtained. The influence of entrance effect on heat transfer is taken into account, and the dimensionless destruction time is introduced to measure the time scale of intermittent damage of the boundary layer. The results show that flexible wings have two motion modes, i.e. flapping and deflection modes under the considered conditions. In terms of the heat transfer enhancement, the flapping mode is superior to the deflection mode. It's found that the presence of nearwall vortex structure increases the local Nusselt number significantly, reaching up to 4.99 times of the spatiotemporal average Nusselt number. Furthermore, it's found that the increase of the dimensionless destruction time is highly consistent with the augment of Nusselt number and skin friction coefficient. The overall performance coefficient is used to evaluate the comprehensive heat transfer performance. Under the considered conditions, the optimal overall performance coefficient can reach 1.20, and Nusselt number increases by 23.38 %.