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