Dynamic Wake Inflow Modeling in Ground Effect for Flight Dynamics Applications

Rotor dynamic wake inflow modeling is one of the main issues in the development of efficient and reliable tools for design and flight dynamic simulation of rotorcraft. In general, it is affected by the operating condition (hovering, advancing, steady or maneuvering flight), but the interference with external obstacles might play a crucial role, especially during landing or close-to-ground procedures. The aim of this paper is the presentation of a LTI, finite-state model for the prediction of dynamic wake inflow of helicopter rotors in ground effect. First, two high-fidelity boundary-element aerodynamic formulations capable of taking into account ground effects on wake dynamics are applied, compared and correlated with experimental data. Then, finite-state dynamic inflow models are extracted from a set of responses to kinematic perturbations provided by the high-fidelity aerodynamic tool. The capability of the proposed low-order modeling to capture with good accuracy the time evolution of dynamic wake inflow induced by arbitrary rotor commands perturbations is tested by comparison with the predictions directly provided by the time-marching high-fidelity solver.