Effect of Surface Roughness on Laminar Separation Bubble over a Wing at a Low-Reynolds Number

Abstract

Laminar separation bubbles (LSBs) are often found over the wing of micro air vehicles (MAV) at low Reynolds numbers, and strongly influence the lift, drag and other aerodynamic performance parameters. A numerical investigation of a passive LSB control techniques by using roughness bumps on a low-Reynolds number wing is conducted in this paper. A high-order spectral difference unstructured grid Navier-Stokes solver is employed in the simulations. The study of surface roughness on laminar separation and turbulent transition can provide insights into the design of future passive control devices on wings. The transitional flow with LSB past a SD7003 rectangular wing with Reynolds number of 60,000 is used as the basic (uncontrolled) case. In the controlled cases, roughness bumps are strategically located near the leading edge of the wing for the purpose of improving aerodynamic performance. The location, bump size, the number of bumps and the angle-ofattacke (AoA) are varied to study the effects. The pressure drag forces in the controlled cases are found to be reduced when the LSB are diminished or avoided, resulting in much improved lift over drag ratio