Low Reynolds Number Laminar Separation Bubble Control Using a Backward Facing Step

The problem of a laminar separation bubble on the upper surface of a 9.5% thick airfoil operated at low Reynolds number (RN = 380,000) was investigated experimentally. An unmodified LRN-010 airfoil and a modified LRN-010 airfoil with a backward facing step on its upper surface were built and tested in the ERAU wind tunnel in order to obtain pressure distributions and drag for different angles of attack. Results were found to be in good agreement with the results obtained from the XFOIL CFD code. It was concluded that the step cutout modification improves the airfoil’s lift-to-drag ratio at low angles of attack by tripping the boundary layer and decreasing the size of the laminar separation bubble. For higher angles of attack, the step cutout degraded the performance of the airfoil