The effect of non-equilibrium condensation on the coefficients of force with the angle of attack in the transonic airfoil flow of NACA0012

Abstract

A transonic flow with a non-equilibrium condensation past NACA0012 profile whose aspect ratio AR is 1.0 with the angle of attack was analyzed by numerical analysis using a TVD scheme, and investigated using an intermittent indraft type supersonic wind tunnel. Transonic flows of 0.70–0.90 in free stream Mach number with variations of Φ0 and α were tested. For the same M∞ and α, the increase in stagnation relative humidity Φ0 caused a decrease in the drag coefficient of profile (that is total) which is composed of the components of form, viscous, wave and condensation; however, the lift coefficient up to Φ0 = 50% increased in the opposite direction. As an example, in the case of M∞ = 0.83, Φ0 = 50%, α = 3○ and T0 = 298 K, the decreasing rate of the coefficient of profile drag and the increasing rate of the lift coefficient compared to the case of Φ0 = 0% caused by non-equilibrium condensation amounted to 65% and 52%, respectively. In addition, for the same Φ0 and α, as the free stream Mach number M∞ increased, at first, the lift coefficient increased slightly, and then suddenly severely dropped, and finally remained nearly constant. The suddenly dropped free stream Mach number in CL became larger with an increase of Φ0. It turned out that the drag coefficients of form and viscous were almost independent of Φ0. The contribution of wave drag to the coefficient of profile drag for M∞ = 0.83, Φ0 = 30%, α = 3° and T0 = 298 K amounted to approximately 79%, and in the case of Φ0 = 60%, the contribution of the non-equilibrium condensation to the reduction in the coefficient of the profile drag compared to the case without condensation amounted to 75%. Especially, for the case of Φ0 = 0% and α = 0°, there was an oscillatory flow region around M∞ = 0.87.