Wind tunnel test of the RISØ-1 airfoil

Wind tunnel tests with approximately 2d flow were carried out for the RISØ-1 airfoil in the VELUX open jet wind tunnel. The airfoil section was mounted in a test stand equipped with end plates to retain 2d flow conditions. The stand was then inserted into the tunnel test section. The Reynolds number was 1.6 million, the chord of the airfoil model 0.6 m and the span 1.9 m.

Pressure distribution measurements provided the aerodynamic load coefficients and wake rake pressure measurements provided the total drag coefficient. Wind tunnel corrections were applied for streamline curvature and down-wash. Steady inflow measurements showed that the airfoil behaved well with a well defined maximum lift coefficient of 1.3, a minimum drag of 0.0075, and a smooth stall region.

Comparisons with numerical predictions from the EllipSys2D Navier-Stokes code showed good agreement among the calculated and measured lift and drag coefficients. Leading edge roughness devices were found to reduce the maximum lift coefficient by 15% to 1.1 and to increase the drag coefficient at low incidence.

Dynamic inflow measurements with the airfoil in pitching motion were carried out to study the hysteresis effects on the aerodynamic coefficients. The lift coefficient hysteresis loops at high incidence had smooth shapes and did not show leading edge separation. Steady inflow measurements at high angles of attack showed that the airfoil flow was stationary and did not indicate double stall. (au).