AEROMECHANICS OF A COAXIAL MARS HELICOPTER USING HIGH-FIDELITY CFD/CA

摘要

A high-fidelity coupled computational fluid dynamics (CFD) and comprehensive analysis (CA) solver is developed for application on the Mars helicopter. Accurate aeromechanical understanding of a coaxial rotor on Mars is necessary in order to make proper design decisions for future aircraft with longer range and greater payload. The objectives are to understand the performance, structural loads, control loads (pitch link), wake interaction, and blade strike for hingeless and articulated coaxial rotors, so that an informed decision between the two rotor hubs can be made. This will become more important as the vehicle size and payload grows. Lower fidelity tools are not capable of capturing the complex flow phenomena (blade vortex interaction, roll-up and core growth, and 3D unsteady pitching moments at low Re), and therefore this problem requires coupled CFD/CA. Some of the key conclusions specific to Mars are: (1) an articulated rotor in fact benefits from greater rotor separation because pitch angles, not flapping motion dictates separation (2) a hingeless rotor experiences only marginally greater (6 - 7%) flap bending moments compared to an articulated rotor, (3) the oscillatory pitch link loads on an articulated rotor are nominally 15.5% greater than on a hingeless rotor and (4) the steady pitch link loads of a hingeless rotor are in fact 8 times greater than an articulated rotor. For these reasons, larger future Mars helicopter it appears an articulated rotor might be more desirable over a hingeless rotor, for considerations of structural and control loads.