Experimental Investigation of Heavy Rainfall Effect on A 2-D High Lift Airfoil

The effects of simulated heavy rainfall on a 2D high lift airfoil were studied in a wind tunnel program. The experiment was carried out in the 2D test section of the 1.5 m x 1.5 m blowdown wind tunnel of the High Speed Aerodynamics Laboratory. The model used in the investigation was a modified NACA 65(sub 2)215 multi-element airfoil with a basic chord of 254 mm. The Mach number was fixed at M = 0.2, typical of the landing speed of transport type aircraft. The chord Reynolds number range was 1.7 to 8.8 x 10(exp 6). Measurements included lift, drag, and pitching moment of the airfoil obtained by side wall balances and the flow rate from a water spray manifold. The effects of the simulated rainfall to the airfoil performances are very significant. The loss in maximum lift coefficient ranged from 6 percent to a high of 16 percent. The drag levels at constant lift are up to 43 percent higher under wet conditions. A smaller performance degradation was noted when the model was stripped of the smooth epoxy paint with which it was originally finished.