APPLICATION OF LOW-ORDER WAKE INFLOW MODELS TO ROTORCRAFT AEROMECHANICS

摘要

The effect of dynamic inflow modeling on helicopter aeromechanic simulation for stability, response and control purposes is investigated. Two different linear time-invariant inflow models, extracted from high-fidelity aerodynamic simulations, are presented and applied. One provides the wake inflow as a function of rotor kinematic variables, while the second one gives the wake inflow dynamics forced by rotor loads. In both cases, first the involved transfer functions are identified through time-marching aerodynamic simulations, and then a rational-matrix formula is applied for their finite-state approximation. The resulting state-space dynamic inflow models are applied to helicopter response and stability analyses, showing that the aeromechanic transfer functions and poles predicted by kinematic-based and loads-based models are somewhat different, with those related to the loads-based inflow depending on the kinematic perturbation considered to synthesize the model. Both simulations present discrepancies with respect to those obtained by the widely-used Pitt-Peters dynamic inflow model.