Flap-lag damping in hover and forward flight with a three-dimensional wakePrediction of lag damping is difficult owing to the delicate balance of drag, induced drag and Coriolis forces in the in-plane direction. Moreover, induced drag is sensitive to dynamic wake, both shed and trailing components, and thus its prediction requires adequate unsteady-wake representation. Accordingly, rigid-blade flap-lag equations are coupled with a three-dimensional finite-state wake model; three isolated rotor configurations with three, four and five blades are treated over a range of thrust levels, Lock numbers, lag frequencies and advance ratios. The investigation includes convergence characteristics of damping with respect to the number of shape functions and harmonics of the wake model for multiblade modes of low frequency (less than 1/rev.) to high frequency (greater than l/rev.). Predicted flap and lag damping levels are then compared with similar predictions with (1) rigid wake (no unsteady induced flow), (2) Loewy lift deficiency, and (3) dynamic inflow.
Document ID
19930051982
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Manjunath, A. R. (Indian Inst. of Science Bangalore, India)
Hagabhushanam, J. (NASA Ames Research Center Moffett Field, CA, United States)
Gaonkar, Gopal H. (Florida Atlantic Univ. Boca Raton, United States)
Peters, David A. (Washington Univ. Saint Louis, MO, United States)