Large eddy simulation of film cooling flow from cylindrical hole with dielectric barrier discharge plasma actuators

Abstract

Large eddy simulation was applied for studying the effects of plasma aerodynamic actuation on the coherent structures and cooling efficiency of a cylindrical cooling hole. Two arrangement-typed plasma actuators were placed immediately downstream of the cooling hole exit and a phenomenological plasma model was employed to provide plasma force vectors. Results show that the single plasma actuator installed in streamwise direction exerts downward force and streamwise momentum injection effects on film cooling flow. Therefore, the coolant is deflected to the wall and stretched farther downstream, and hairpin vortices are reduced in number and size, and then happen to breakup. The pair of plasma actuators installed in spanwise direction acts a predominant spanwise momentum injection effect on the film cooling flow, thus inducing the coolant flows along spanwise direction. The beneficial vortex pair created by plasma aerodynamic actuation mitigates the detrimental entrainment and lift-off effect of counter rotating vortex pair. Moreover, hairpin vortices stay much closer to the wall thanks to the reduction of the Kutta-Joukowski lift and mutual vortex induction, and soon break into much smaller-scale vortices. Eventually, both the streamwise and spanwise coverage of the coolant are expanded, and thus improved the cooling efficiency.