NUMERICAL INVESTIGATION OF DYNAMIC STALL OF AN OSCILLATING AEROFOIL

The flow structure around an NACA 0012 aerofoil oscillating in pitch a round the quarter-chord is numerically investigated by solving the two -dimensional compressible N-S equations using a special matrix-splitti ng scheme. This scheme is of second-order accuracy in time and space a nd is computationally more efficient than the conventional flux-splitt ing scheme. A 'rigid' C-grid with 149 x 51 points is used for the comp utation of unsteady flow. The freestream Mach number varies from 0.2 t o 0.6 and the Reynolds number from 5000 to 20,000. The reduced frequen cy equals 0.25-0.5. The basic flow structure of dynamic stall is descr ibed and the Reynolds number effect on dynamic stall is briefly discus sed. The influence of the compressibility on dynamic stall is analysed in detail. Numerical results show that there is a significant influen ce of the compressibility on the formation and convection of the dynam ic stall vortex. There is a certain influence of the Reynolds number o n the flow structure. The average convection velocity of the dynamic s tall vortex is approximately 0.348 times the freestream velocity.