Dynamic stall experiments on the NACA 23012 aerofoil

An experimental investigation was conducted to examine the dynamic stall characteristics of a NACA 23012 aerofoil section at a Reynolds number of 1.5 million. Time-dependent data were obtained from thirty miniature pressure transducers and three hot film gauges situated at the mid-span of the wing. The static stall mechanism of the NACA 23012 was determined to be via abrupt upstream movement of trailing edge separation. Under dynamic conditions, stall was found to occur via leading edge separation, followed by a strong suction wave that moved across the aerofoil. This suction wave is characteristic of a strong moving vortex disturbance. Evidence of strong secondary vortex shedding was also found to occur, and this appears symptomatic of dynamic stall only at low Mach numbers. Some evidence of flow reversals over the trailing edge of the aerofoil were indicated prior to the development of leading edge separation and dynamic stall.List of symbols c aerofoil chord - C _L sectional lift coefficient - C _M sectional pitching moment coefficient measured about the quarter-chord location - C _p pressure-coefficient - k reduced frequency, c/2V - M Mach number - P pressure - R _c Reynolds number based on chordc - t time - V free stream velocity - x distance along chord line - y distance along span - angle of attack - _a oscillation amplitude - _M Mean angle of oscillation - shear stress - circular frequency