Hybrid suction/blowing actuator to control flow separation on the ramp and energy cost analysis

Abstract

The flow separation control on an adverse-pressure-gradient ramp model is studied using various flow control strategies. Using a steady turbulent flow, the effects of utilizing an active hybrid control (suction and blowing) on the separation bubble behind a ramp are investigated numerically. A parametric analysis is conducted in which the actuators' pitch angle, diameter, and streamwise position are varied. The results are compared to determine the most effective method for compensating adverse pressure gradients and managing the separated flows on a ramp model. The best results for the blowing scenario correspond to a blowing actuator with a dimensionless distance of Lx/L1=−1/70 from the top of the ramp, a dimensionless diameter of d/L1=1/70, and a dimensionless angle of θ/θ0=2/6. The actuator is found to be able to wipe out the separation zone entirely at a velocity ratio of 3. The best results for the suction approach belong to a suction actuator with Lx/L1=1+1/70 from the top of the ramp, d/L1=3/70, and θ/θ0=−4/6. The modeling shows that the actuator removes the separation zone at a lower velocity ratio, namely, at 1.5. Nonetheless, a recirculation zone forms behind the suction point. Using a combined system, with a velocity ratio of 0.5 for a diameter of 3 and 2 for a diameter of 1, eliminates the separation zones on the ramp and after the suction actuator while lowering energy consumption. The blowing actuator consumed 3.2 times as much power as the combined actuator, whereas the suction actuator consumed 1.2 times as much power. Therefore, analyzing the present results as a prerequisite makes it possible to reduce flow separation and its adverse effects in more practical environments such as airfoils with an optimal cost.