The effects of Gurney flap on the aerodynamic performance of NACA 0012 airfoil in the rarefied gas flow

In this research, the rarefied gas flow around the NACA 0012 airfoil with attached Gurney flap at Mach number 2 and three different Knudsen numbers (0.026, 0.1 and 0.26) are studied, numerically. The effects of angle of attack and Gurney flap height on the aerodynamic characteristic of airfoil are investigated. At Kn = 0.026 the flow is simulated using Navier-Stokes equations with slip boundary conditions and DSMC method. In two other Kn numbers only the DSMC method is applied. For the clean airfoil, the calculated lift and drag coefficients and surface pressure distribution are compared with previous studies including the experimental and numerical results. This validation reveals that in the case of clean airfoil, there are a good agreement between the results of this study and those presented in literature. Furthermore, the effects of Gurney flap height on the lift and drag coefficients at different Knudsen numbers and angles of attack are studied. The results shows that for angles of attack smaller than 30°, the Gurney flap can improve the aerodynamics characteristics of airfoil. But, for angles of attack larger than 30° the Gurney flap does not have destructive effect on the aerodynamic characteristics.