An Actuator Disc Theory for the Shed Wake at Low Tip Speed Ratios 650089
A model of flow through a helicopter rotor, suitable for estimating effects of shed wake in hovering and at low tip speed ratios, is described. With this method, the result for aerodynamic damping of blade bending oscillations is in agreement with more elaborate theories. It is shown that damping of small natural oscillations is to a first order unaffected by tip speed ratio. Interharmonic couplings, which are neglected in more elaborate theories, prove to be quite important, especially if resonance occurs. Also, in the presence of strong interharmonic coupling, the effective lift curve slope cannot be considered independent of blade motion.