Unsteady aerodynamic characteristics investigation of rotor airfoil under variational freestream velocity

Abstract

Numerical investigations based on CFD method have been accomplished to illustrate the unsteady aerodynamic characteristics of the SC1095 airfoil under conditions of coupled freestream velocity/pitching oscillation. In order to simulate the variational freestream velocity of airfoil, the moving-embedded grid method is employed to calculate the fluctuating velocity. The unsteady RANS equations coupling with the dual time-stepping approach are chosen as the governing equations to predict flowfield of airfoil under variational freestream velocity condition. The implicit Lower–Upper Symmetric Gauss–Seidel scheme and Spalart–Allmaras turbulence model are employed to improve the calculation efficiency and accuracy, respectively. Based on the present CFD method, the unsteady aerodynamic characteristics of the airfoil with variational freestream velocity are simulated under conditions of fixed angle and variational angle. The simulated results indicate that the peaks of lift coefficient, drag coefficient and pitching moment coefficient of airfoil are enlarged with the increasing of fluctuating velocity, and the start of airflow reattachment process on airfoil is delayed with the increasing of fluctuating velocities and reduced frequencies due to the effects of the airflow hysteresis and compressibility. Additionally, it is illustrated in the case of different phase angles that these peaks would be reduced by increasing phase angle.