Film cooling and aerodynamic loss performance of a flat plate with a saw tooth plasma actuator

The effects of the cylindrical holes, fan-shaped holes and saw-tooth plasma actuator (SPA) on the film cooling effectiveness and aerodynamic losses are examined under various blowing ratios. The combined design of the fan-shaped hole with the SPA effectively eliminates the downstream separation spiral node vortices, which typically degrade the film cooling effectiveness. Furthermore, this combined design generates a novel vortex pair that significantly inhibits the formation of the counter rotating vortex pair, a critical factor influencing the jet-crossflow mixing behavior. Consequently, the aerodynamic mixing losses are substantially reduced, and their distribution patterns shift from a single peak to a double peak configuration at low blowing ratio. This double peak pattern is gradually disappeared as the blowing ratio increases, and the entropy generation analysis reveals a 71.6% decrease in irreversible losses attributable to film cooling. Subsequently, the spatiotemporal evolutions of coherent structures, visualized through the total pressure loss coefficient (TPLC), are analyzed. The findings indicate that TPLC values in the vicinity of the horseshoe vortex are positive but are greatly diminished by the implementation of the combined design. In contrast, the TPLC values around the heads of the coherent structures exhibit pronounced negative values, reflecting enhanced mixing between the crossflow and coolant. Furthermore, the combined design significantly reduces the TPLC values associated with these coherent structures, suggesting a weakening of their intensity. This observation is corroborated by analyses of the auto-correlation coefficients and the kinetic energy spectra of velocity fluctuations.