Separation control using quasi-radial wall jets

In this paper, flow separation control over a NACA 4415 wing section using arrays of discrete quasi-radial wall jets is numerically investigated. This novel flow control method is studied under conditions which the wing section angle of attack is α=18 degrees and Reynolds number based on chord length is Rec=550000. Contours of mean streamwise velocity indicated that quasi-radial wall jets cover wing surface rapidly. Therefore, arranging them in a spanwise row can be an effective way in adding momentum to the near wall fluid particles. According to the results, if blowing parameters of the jets be chosen correctly, arrays of quasi-radial wall jets would lead to considerable decrease in wake region extent and would bring enhancement of wing aerodynamic performance (up to 46% increment of lift coefficient). Moreover, investigation of streamlines and velocity vectors reveals the presence of two helical vortices on both edges of quasi-radial wall jets. These vortices, which form due to interactions between external stream and spanwise velocity component of jets, generate mixing in the surrounding fluid. It could be said that besides momentum addition, quasi-radial wall jets in an external stream act like vortex generators.