NACA 0012 Oscillatory and Transient Pitching

Abstract : These results are extracted from tabulations of wing pressures resulting from the 3rd series of pitching tests about O.25c axis made in the ARA 2-dimensional tunnel, using the pitching and heaving rig, Ref 1. The main purpose of these tests was to examine the conditions of dynamic stall and recovery at sealed time rates similar to those of a typical helicopter application. Dynamic similarity was maintained also in Reynolds number, the approximately quarter scale blade section was therefore run, for all the cases reported here, at a tunnel stagnation pressure of 4 bar to match low altitude flight of the helicopter. Consequently, no artificial boundary layer transition trips were applied to the test wing. The output of dynamic pressure transducers was sampled at fixed intervals, the instantaneous pressures and reference conditions having a matched and filtered response within 3 dB up to 460 Hz. The results represent one specific cycle, and are not averaged over a number of cycles. The data bank at ARA contains at least 4 cycles of each dynamic condition. Ramp motions have only a single transient. Up to 6 increments of mean incidence and amplitude singly or in combination, could be ran: the present programme called for 3 increments (called programme steps or PSTEP) of mean incidence am. The time-dependent results arc presented without harmonic or spectral analysis. Note that the harmonic content of the pitching motion is relatively high, due to the intrusion of other modes of the drive system: