Validation of predicted vibratory loads of a coaxial rotor at high advance ratios with wind tunnel test data
The predictions of a comprehensive analysis based on UMARC are compared to experimental coaxial rotor results. The experiments cover a range of collective pitch angles from 2 to 10 advance ratios from 0:2 to 0:5, and lift offset from 0% to 20% The experimental model rotor system is a pair of hingeless coaxial rotors, with two blades each, and a first flap frequency of approximately 1:6/rev. It was tested in the Glenn L. Martin Wind Tunnel at the University of Maryland as isolated rotors and as a counter rotating coaxial rotor system The simulation is validated against coaxial performance and vibratory loads. The simulation captures increasing rotor efficiency with lift offset and advance ratio and also properly models 2/rev vibratory loads with advance ratio, lift offset, and rotor to rotor phase. The inversion of thrust between upper and lower rotor with advance ratio is identified.