FURTHER EXPERIMENTS ON VORTEX FORMATION AROUND AN OSCILLATING AND TRANSLATING AIRFOIL AT LARGE INCIDENCES

The starting flows past a two-dimensional NACA 0012 airfoil translating and oscillating at large incidences are investigated by visualization experiments and numerical calculations. The airfoil model is set in motion impulsively and subjected simultaneously to a constant translation and harmonic oscillation in pitch. The evolution of the vortex wake is followed in a sequence of streamline visualizations and the wake pattern generated is analysed. The parameters varied in the visualization experiment are the Reynolds number ranging from 1500 to 10 000, the reduced frequency from 0.1 to 1.0, the mean incidence 30-degrees or 15-degrees and the angular amplitude 15-degrees or 7-degrees. There are also two additional parameters of special interest: the airfoil cross-section and the pitching axis. The effects of these parameters are discussed in relation to the resultant wake patterns. Some comparison is made with the results of earlier experiments.