Wind Tunnel Investigation of A Wing-Propeller Model Performance Degradation Due to Distributed Upper-Surface Roughness and Leading Edge Shape Modification

A wind tunnel investigation has assessed the effects of distributed upper surface roughness, and leading edge ice formation on a powered wing propeller model. In the unpowered state, it was found that roughness reduces the lift slope, and maximum lift by 30 to 50 percent, depending upon particle size and Reynolds number. The leading edge region is especially sensitive to these disturbances, however, removal of the toughness over a small portion of the nose restored the wing to close to its original performance. The application of power to the wing, with an increase of slipstream dynamic pressure increases the lift slope and maximum lift; however, removal of the roughness over a small portion of the nose restored the wing to close to its original performance. The application of power to the wing, with an increase of slipstream dynamic pressure increases the lift slope and maximum lift; however, this benefit is lost if the wing is roughened. Subtraction of the propeller reactions indicated that the slipstream interaction accounted for half the lift increase, and also resulted in reduced drag for the clean surface. This drag reduction was removed when the wing was roughened, indicating that the degradation of wing performance due to roughening is relatively greater when a slipstream is presented, compared to the unpowered wing. Leading edge ice accretion causes similar large losses in lift and increases of form drag although a comparison of the two types of contamination showed that leading edge ice produces a smaller reduction of lift slope prior to flow separation. In both types of contamination, Reynolds number is important, and emphasizes the necessity of testing under near full-scale conditions.