Formulation of a Computational Aeroelastic Model to Predict Trim and Response of a Helicopter Rotor System

Abstract

Comparison of theoretical and experimental data (flight test data) reveals that still there is a gap between theory and experiment. Some of the observed phenomenon in flight test may be due to the nonlinearities associated with the aeroelastic problems and this paper attempts to develop a theoretical formulation including the geometrical nonlinearities associated with structural modeling and the aerodynamic nonlinearities associated with dynamic stall. In this paper, the consolidated set of equations representing blade dynamics, rotor inflow and sectional aerodynamics are presented. The iterative computational solution technique developed for trim and response analysis is described and a systematic study is undertaken to analyse the influence of various aerodynamic models, representing rotor inflow and sectional loads, on the helicopter trim and aeroelastic response of the rotor blades. It is also shown that the structural coupling due to blade pretwist significantly influences the rotor blade response and loads compared to an untwisted rotor blade.