Unsteady Airloads on Oscillating Wings in Post-Stall Condition

摘要

Wind tunnel tests were performed on two wing configurations; a basic trapezoidal half-wing model and the same basic wing equipped with a strake. The tests were executed under incompressible flow conditions in a low-speed wind tunnel at a mach number less than 0.2 and a maximum Reynolds number of 2,000,000. The steady mean angles of attack covered the range 0 to 40 deg. The wings could be excited to forced oscillations with angular amplitudes up to 4 deg and in the frequency range 0 to 12 Hz corresponding to a range of reduced frequencies 0 omega* 0.9. The steady mean pressures are found to be strongly dependent on the geometry of the wing as well as on the angle of attack. The dependence on the latter is quite nonlinear as a consequence of the complex vortex systems. The unsteady pressure fluctuations due to the flow separation from the stationary wing can be explained rather well by means of the steady mean pressure distributions. At very high incidence the possibility of periodic vortex shedding can be shown. From coherence functions it becomes evident that the correlation lengths in the chordwise direction are considerable.