ROTORCRAFT AEROELASTIC ANALYSIS USING DYNAMIC WAKE/DYNAMIC STALL MODELS AND ITS VALIDATION

Accurate prediction of helicopter loads and response requires the development of a multi-disciplinary comprehensive analysis program. Helicopter loads and response is an aeroelastic problem as it involves interaction of the structural, inertia and aerodynamic operators. The objective of this paper is to describe the development of a comprehensive analysis code for helicopter aeroelastic analysis and present some of the validation studies. The helicopter modeled is a conventional one with a hingeless single main rotor and single tail rotor. The blade undergoes flap, lag, torsion and axial deformations and is modeled using beam finite elements. Tip sweep, pretwist, precone, predroop, torque offset and root offset are included in the model. Aerodynamic model includes Peters-He dynamic wake theory for inflow and the modified ONERA dynamic stall theory for airloads calculations. The complete 6-dof nonlinear equilibrium equations are solved for analyzing general flight conditions including steady maneuver. Validation studies presented in this paper include comparison of experimental data with the analysis results pertaining to (i) structural dynamics of swept-tip blades, (ii) whirl tower test and (iii) steady forward flight trim state of a helicopter. Results of a study showing the effects of the blade geometric parameters on the performance, response and loads of the rotor are also given.

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