Fluid dynamics of airfoils with moving surface boundary-layer control

Abstract

Effectiveness of the moving surface boundary-layer control is assessed with reference to a symmetrical Joukowsky airfoil modified with a leading-edge rotating cylinder. Results of the test program and the numerical models suggest the following: 1) The surface singularity method is essential in modeling the complicated flow. With the inclusion of the boundary-layer correction scheme, it becomes an effective tool for obtaining useful information concerning moving surface boundary-layer control. The predicted pressure distributions are in good agreement with experiment almost up to the point of complete separation from the airfoil surface, except in the separation region, where the prediction of separated boundary layers with flow reversal would require the solution of the full Navier-Stokes equations. 2) The concept of moving surface boundary-layer control appears quite promising. The tests showed a significant improvement in maximum lift and stall characteristics. With cylinder rotation, the flow never separated completely from the upper surface for angles of attack as high as 48 deg. The higher rates of rotation (UC/U>1, Uc = cylinder surface velocity, U = freestream velocity) promoted reattachment of the partially separated flow, giving an increase in lift coefficient by as much as 150% for Ue/U = 4.