Separation and Unsteady Vortex Shedding from Leading Edge Surface

The properties of isolated and distributed surface roughness, as well as their effects on transition, separation and overall airfoil performance, are reviewed for steady and unsteady flows. Ongoing research aimed at developing Direct Numerical Simulation tools for the study of leading edge roughness is discussed, and representative calculations are presented for steady and unsteady flows past two and three-dimensional isolated and distributed roughness on airfoil leading edges. Preliminary two-dimensional computations of the suppression of flow separation using dynamic surface roughness are also presented. 1.0 LEADING EDGE ROUGHNESS AND AIRCRAFT PERFORMANCE The lift and drag performance of an aerodynamic surface, such as an airfoil or a wing, is highly dependent on the state of the boundary layer. The performance specifications of such surfaces typically assume that the wing is smooth and has no imperfections. However, when the wing becomes exposed to the environment, dirt, insect debris, frost formation and other imperfections can lead to the presence of small roughness on th