Computational and Experimental Aeromechanics Analysis of a Coaxial Rotor System in Hover and Forward Flight

The dynamics and aerodynamics of a coaxial rotor model designed for high-advance-ratio forward light were investigated by means of a numerical comprehensive analysis, hover and wind tunnel testing. The focus was on the development of the computational model and its validation using wind tunnel measurements for advance ratios of up to 0.5. Blade structural characteristics were modeled according to the measured elastic properties and reduced-order aerodynamics modeling using a free vortex wake method was used to ensure computational efficiency. Numerical predictions for the coaxial rotors correlated well with the measurements for performance, blade loadings, cyclic controls, and blade clearance for multiple advance ratios and varying lift-offset conditions, and particularly well for medium to high advance ratios (\bm{$\mu=0.3-0.5$}). Differences at high lift-offset conditions may be related to an underprediction in the lateral cyclic controls. Vibratory hub loads correlated well with the measurements in both trends and magnitudes for the isolated rotor. For the coaxial configuration, the same good agreement was found in the axial vibratory loads, while drag and side forces only captured the trends seen in the experiments that also showed significant higher-frequency content. The validated low-order modeling capabilities will be helpful to quickly assess the rotor dynamic response and its aerodynamic sources, including the effects of lift offset and rotor--rotor interactions, and so they will prove instrumental in the understanding of the steady and vibratory loads in the present test article as well as in future coaxial rotor designs.     «

The dynamics and aerodynamics of a coaxial rotor model designed for high-advance-ratio forward light were investigated by means of a numerical comprehensive analysis, hover and wind tunnel testing. The focus was on the development of the computational model and its validation using wind tunnel measurements for advance ratios of up to 0.5. Blade structural characteristics were modeled according to the measured elastic properties and reduced-order aerodynamics modeling using a free vortex wake met...     »