High-performance airfoil with moving surface boundary-layer control

All airfoils are known to stall at high angles of attack as a result of dow separation, resulting in a sudden loss of the lift force. To avoid now separation, it is necessary to introduce some form of boundary-layer control. The present study focuses on the performance of an airfoil with moving surface boundary-layer control (MSBC). Effects of the angles of attack, rate of momentum injection, as well as rotating cylinder surface condition on the surface pressure distribution and aerodynamic coefficients are assessed. A comprehensive study involving wind-tunnel investigation, numerical simulation, and now visualization clearly demonstrates that the momentum injection through MSBC results in a significant delay in the stall angle (from 10 to 50 deg) and an increase in the lift coefficient by more than 200% at high angles of attack (alpha approximate to 30 deg). The results show that a multielement panel method, modeling the flow separation using free vortex lines, predicts the overall aerodynamics of an airfoil with the MSBC quite accurately. The airfoil performance can be improved further by judicious selection of the rotating cylinder surface condition. Among the three different surface roughness conditions studied, the cylinder with axial splines was found to be the mast effective.