Aerodynamic Load Estimation of Helicopter Rotor in Hovering Flight

Abstract

The aerodynamic characteristics of a helicopter rotor blade are highly dependent on the wake induced flow. The rotor blades, which are rotating wings, shed vortices which trail in helical path along the axis of rotation forming a wake. The velocity field induced by the vortex system influences the blade loading. The free wake model analysis is computationally intensive and numerically unstable in very low speed applications. For the aerodynamic analysis of a hovering rotor, Miller and Reddy have proposed simple wake models in which the spiral vortex wake is replaced by a system of vortex rings or vortex line elements in conjunction with lifting line theory to overcome some of the problems encountered in free-wake models. In the Proposed model of the rotor, the same lifting line model of the rotor is retained, but a further simplification of the vortex wake is proposed. This method requires relatively very small computing time compared to the above models, but without necessarily sacrificing the accuracy in estimating the aerodynamic blade loading.