Large Eddy Simulation of Pulsed Film Cooling with a Dielectric Barrier Discharge Plasma Actuator

Abstract

The effects of the coolant pulsation and the plasma aerodynamic actuation (PAA) on the film cooling are herein explored via large eddy simulations. The electrohydrodynamic force derived from the PAA was solved through the phenomenological plasma model. The Strouhal number of the sinusoidal coolant pulsation and the averaged pulsation blowing ratio were 0.25 and 1.0, respectively. Comprehensive analyses were carried out on the time-averaged flow fields, and the results reveal that the pulsed cooling jet might cause a deeper penetration into the crossflow, and this phenomenon could be remarkably mitigated by the downward force of the PAA. Comparing steady film cooling to pulsed film cooling revealed a modest 15.1% reduction in efficiency, while the application of the dielectric barrier discharge plasma actuator (DBDPA) substantially enhanced the pulsed film cooling efficiency by 42.1%. Moreover, the counter-rotating vortex pair (CRVP) was enlarged and lifted off from the wall more poorly due to the coolant pulsation, and the PAA weakened the detrimental lift-off effect and entrainment of the CRVP. Then, the spatial–temporal development of the coherent structures was figured out by the alterations in the centerline temperature, reflecting the formation of the intermittent coherent structures rather than hairpin vortices due to the coolant pulsation, and their size and upcast behaviors were reduced by the PAA; thus, the turbulent integration of the coolant with the crossflow was suppressed fundamentally. Finally, the three-dimensional streamlines confirmed that the coherent structure dynamic behaviors were significantly regulated by the PAA for alleviating the adverse influences of the coolant pulsation. In summary, the PAA can effectively improve the pulsed film cooling efficiency by controlling the spatial–temporal development of the dominant coherent structures.