Experimental study of the effect of turbulence on a section model blade oscillating in stall

This article highlights part of the recent static and dynamic section model tests performed on a NACA 634_421 aerofoil for Reynolds numbers close to 106 and three flow turbulence levels, 1·1%, 4·5% and 7·5%. These tests were conducted in the 5 m × 3 m S4 wind tunnel at the Institut AéroTechnique, using an experimental rig which forces the section model to oscillate in pitch. An upwind grid was used to generate the higher turbulence intensities characterized by turbulence length scales smaller than the chord of the aerofoil. The aerofoil's static characteristics were measured at angles of attack ranging from 0° to 30°. In the dynamic tests the aerofoil was made to oscillate in pitch around its fore quarter‐chord line at different values of mean angle of attack (below, in and beyond the static stall region), reduced frequency (ranging from 0·0183 to 0·183) and amplitude of motion (from 2° to 8°). For all tests the aerodynamic loads were obtained through unsteady surface pressure measurements. The unsteady lift, pitching moment and pressure distributions are analysed and the effects of both the motion characteristics and the turbulence level of the incident flow are highlighted.