Global Pressure and Temperature Surface Measurements on a NACA 0012 Airfoil in Oscillatory Compressible Flow at Low Reduced Frequencies.

摘要

A co-axial contra-rotating helicopter in forward flight has stall mechanisms that are intrinsically different from those on a traditional helicopter. Traditional helicopters need a cyclic pitch mechanism to balance the rotor lift about each rotation, which leads to dynamic stall from the rapid oscillations in pitch. Co-axial contra-rotating helicopters, which have a fixed pitch about each cycle, encounter a sinusoidal oscillation in Mach number with the mean velocity seen as the rotational velocity while the half amplitude is equal to the forward flight speed. The fluid dynamic mechanism limiting the forward flight speed is entirely different from that of traditional dynamic stall studies. This work sets out to design, create, and study the application of an oscillatory compressible flow field on a NACA 0012 airfoil in order to experimentally model this flow situation.