Nonlinear aeroelastic modeling of cycloidal rotor in forward flight
Conference Paper
Overview
Overview
abstract
Copyright 2018 by AHS International, Inc. All rights reserved. In this paper, detailed development of a nonlinear aeroelastic model of a cycloidal rotor in forward flight is presented. Towards this, effect of forward flight on several aerodynamic phenomena such as virtual camber, inflow characteristics as well as effects of several unsteady phenomena such as leading-edge vortices, near and shed wakes are rigorously modeled. It is shown that forward flight velocity changes curvilinear geometry of flow associated with cycloidal rotor, which changes chord-wise variation of incident flow velocity angle on the blade and hence the dynamic virtual camber and incidence. The magnitude and direction of forward velocity along with phasing of cyclic blade pitch is shown to determine induced flow velocity magnitude and direction. The aerodynamic model is validated with in-house experimental data and CFD results. Once validated, the aerodynamic model is coupled with a geometrically exact beam-based blade structural model to develop a fully nonlinear aeroelastic model. Based on a systematic analysis performed using the validated model, it was observed that the dynamic nature of virtual camber and incidence plays an important role in production of net vertical and propulsive force by a cycloidal rotor in forward flight. It is important for a cycloidal rotor to have a backwards rotation with respect to forward speed (blade moving away from the flow in the upper half) for generating an upward vertical force; whereas, the propulsive force is insensitive to the direction of rotation. The vertical force increases with increase in advance ratio, while net propulsive force decreases.
