Actively Reduced Airfoil Drag by Transversal Surface Waves

The flow over a DRA2303 wing section at a Reynolds number of Re =400,000 is actively controlled by spanwise traveling transversal surface waves. The actuated low-Mach number flow is investigated by a high-resolution large-eddy simulation. Approximately 74% of the solid surface on both sides of the wing section is deflected by a sinusoidal space- and time-dependent function in the wall-normal direction. The turbulence intensitites and wall-normal vorticity fluctuations are significantly reduced and a shift from one-dimensional turbulence to two-dimensional turbulence is observed. Besides a viscous drag reduction by 8.6% with a strong decrease of skin-friction in the favorable pressure gradient region and an overall drag decrease by 7.5%, a slight increase in lift is achieved for an external flow over a realistic geometry.