EXPERIMENTAL AND NUMERICAL INVESTIGATION OF UNSTEADY AERODYNAMIC LOADS ON THE PITCHING NACA 0012 AIRFOIL WITH OSCILLATING FLAP

摘要

Application of trailing edge flap on helicopter rotor blade is being investigated extensively by various research groups in several research centres. The common expectation is that the trailing edge flap will be useful for helicopter rotor performance improvement, reduction of blade vibrations and diminishing noise level. The numerical simulations and wind tunnel experiments are performed for the concept evaluation. The main difficulty in simulation of dynamics of a blade with a trailing edge flap is modelling of aerodynamic loads. The simplest aerodynamic loads model is strip theory utilising the airfoil with the deflecting flap. In Institute of Aviation (Warsaw, PL) the wind tunnel tests of the oscillating NACA 0012 airfoil with deflecting trailing edge flap were performed in trisonic wind tunnel. The mechanism driving the flap was designed to excite oscillating pitch motion of an airfoil and independent harmonic flap deflections. The tests were performed for the airfoil pitch frequencies 5 and 10 Hz, the amplitudes angle of incidence Δα= 0°, 5°, 10° and the airfoil static incidence α_0 = 0°, 2°, 4°,....., 14°. The frequency of flap deflection was 5 and 10 Hz, the amplitudes of flap deflection angles Δδ= 5°, 10°, 15° for zero mean angle. The experimental results were compared with tlift and moment coefficients. calculated by theoretical method. The correlation was adequate.