Surface suction on aerofoil aerodynamic characteristics at transonic speeds

This paper presents a numerical study of the effects of an active flow cont rol through surface suction on shock boundary layer interactions over trans onic aerofoils. Two different aerofoils were studied. Firstly, for the purp ose of validation, an NACA64A010 aerofoil with a trailing edge flap was inv estigated and the numerical results were compared with experimental data wi th and without suction for surface pressure distributions and lift and drag coefficients. Grid sensitivity has also been studied regarding the numeric al accuracy. The second geometry was an RAE9647 aerofoil, which was designe d for superior aerodynamic performance when applied to a helicopter rotor b lade. An active surface was used to prevent or alleviate shock-induced sepa ration. The suction strength and location were varied to determine the effe ct on aerodynamic performance and to provide an effective means of suppress ing undesirable flow features. In both cases, increases in both lift and dr ag were observed when surface suction was applied. However, the benefit of suction appeared in the form of a substantial increase in the lift-drag rat io. It was also found that the shock location and strength are very sensiti ve to the suction location and strength. Two different mechanisms for activ e flow control over transonic aerofoils are discussed.