"Correlation Of Unsteady Pressure And Inflow Velocity Fields Of A Pitching Rotor Blade".

Mihir K. Lal, S. G. Liou, G. A. Pierce, N. M. Komerath.

AIAA Paper 93-3082, 24th Fluid Dynamics Conference, Orlando, FL, July 1993. Also, Journal of Aircraft, Vol. 32, No.3, May-June 1995, p. 520 -528.

Abstract: Measurements of unsteady inflow velocity and surface pressure distributions on rotor blades in hover are correlated with predictions from four different analytical methods. A stiff two-bladed teetering rotor is subjected to n-per-rev simple harmonic pitch oscillations. The chordwise distribution of unsteady pressure is correlated with Theodorsen's and Loewy's 2-D incompressible unsteady aerodynamic theories and with Kaladi's pulsating doublet distribution method at three radial locations. Inflow velocity is correlated with Peters' theory. The effect of dynamic inflow on rotor unsteady surface pressure is studied. Excellent agreement is obtained at inboard locations where the 2-D theories are valid. The inflow velocity agrees very well with Peters' theory under steady as well as dynamic pitch. Tip effects and mean pitch angle effects have been demonstrated.