Implementation and Linearization of a Rotor Simulation with a State-Space Free-Vortex Wake Model

This paper describes the implementation and linearization of a free-vortex wake model in state-variable form as applied to a helicopter rotor. Following a detailed mathematical description, the wake model is implemented for a UH-60 rotor and tested in forward flight and for simple control inputs. A periodic solution to the wake model is found by time marching the coupled rotor and vortex wake dynamics. Next, linearized harmonic decomposition models are obtained and validated against nonlinear simulations. Order reduction methods are explored to guide the development of linearized wake models that provide increased runtime performance compared to the nonlinear and linearized harmonic decomposition wake models while guaranteeing satisfactory prediction of the periodic response of the wake.