Abstract: The starting flows past a pitching oscillation Karmam-Trafftz airfoil with 0.12 relative thickness are investigated by numerical calculations for the unsteady N-S equations at Reynolds number 1 000. The emphasis of this study is put on the relation between the complicated vortex structure and the pressure distribution on the body. It is shown that in the present numerical investigations, the trailing edge shape and the reduced frequency have an important influence on the vortex evolution. A high suction peak is induced by the stall vortex as the trailing edge vortex sheds downstream smoothly. Once the trailing edge vortex stays at the trailing edge the interaction of complex vortex structures occurs and no longer has a beneficial effect on the suction peak induced by the stall vortex.

Key words: dynamic stall, vortex motion, separation flow, unsteady N-S equations, finite difference solution