WER-26: Additional reflection plane tests of control devices on an NACA 23024 airfoil

Abstract

Reflection plane tests of the NACA 23024 airfoil were conducted in the 7 x 10 ft wind tunnel to determine the effects of various aileron hingeline positions and auxiliary leading-edge and tip cap on effectiveness of ailerons used as aerodynamic control of horizontal axis wind turbines. Primary purpose of control is to slow or to stop the turning of a wind turbine rotor, requiring negative torque. Negative torque of a zero-pitch untwisted rotor requires negative chordwise suction force over a wide range of angles of attack. Tests of 30% chord aileron at -90 degrees angle of deflection and with 10 and 20 percent chord deflector plates were conducted at hingeline positions of XH = 75%, ZH = 10% and XH = 80%, ZH = 14% chord. Tests were conducted with gaps between the airfoil and the aileron at fully-open, half-open and fully-closed positions. The auxiliary leading edge "Sharp 4" and the wingtip cap were also examined. Wind tunnel tests were conducted at Reynolds numbers of 0.6 and 0.9 million which correspond to Mach numbers of 0.1 and 0.175, respectively. Results of the studies show that the aileron with a 20% deflector plate at hingeline position of XH = 80%, ZH = 14% chord produced largest negative chordwise suction force for all angles of attack from -10 to 90 degrees. It is recommended that ailerons of this type be tested on a rotating blade.