Large eddy simulation of saw tooth plasma actuator for improving film cooling efficiency

摘要

This paper presents results on a saw tooth plasma actuator for the inducement of flow topology and the improvement of flat plate film cooling efficiency. A phenomenological plasma model is constructed to generate the three-dimensional plasma force vectors of the saw tooth plasma actuator. The dynamics of airflow induced by the saw tooth plasma actuator on a flat plate in quiescent air are numerically investigated. The results show that the saw tooth plasma actuator pushes the fluids in all three directions and induces a three-dimensional jet flow with counter rotating streamwise oriented vortices that propagate downstream. The flow field characteristics of both cylindrical hole with and without the saw tooth plasma actuator are studied by large eddy simulation, and a comparison is made. The saw tooth plasma actuator improves the cold jet adherent performance and promotes the spanwise spreading rate of the coolant. Meanwhile, the streamwise vortices induced by the saw tooth plasma actuator suppress the development of counter-rotating vortex pair, thus delaying the diffusion of coolant in the crossflow. Accordingly, the centerline cooling efficiency and the spanwise-averaged cooling efficiency are improved by 36% and 144% at x/d = 15, compared with the baseline case without the saw tooth plasma actuator.