Aerodynamic and Dynamic Interactions with Coaxial Rotor Systems

To investigate the dynamic and aerodynamic interactions associated with coaxial rotor systems, a model rotor designed for high-advance-ratio forward flight was investigated by means of a numerical comprehensive analysis, hover and wind tunnel testing. Flight tests with a different, full-scale, teetering coaxial rotor system were performed, of which the flight test instrumentation and data acquisition procedures are also discussed in this paper. The focus of the current work was on the development of a computational aeromechanics 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. Tip vortex dynamics and blade–vortex interactions were investigated. Numerical predictions for the rigid coaxial rotors correlated well with the measurements for performance, blade loadings, cyclic controls, and blade clearance for multiple advance ratios and varying lift offsets. 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. The validated low-order modeling capabilities will be helpful to quickly assess the interactional aerodynamics of coaxial rotor systems and the rotor dynamic response. Therefore, these modeling capabilities will prove instrumental in the understanding of the steady and vibratory loads in the present test article, and they will also help define future wind tunnel and flight test requirements with coaxial rotors.     «

To investigate the dynamic and aerodynamic interactions associated with coaxial rotor systems, a model rotor designed for high-advance-ratio forward flight was investigated by means of a numerical comprehensive analysis, hover and wind tunnel testing. Flight tests with a different, full-scale, teetering coaxial rotor system were performed, of which the flight test instrumentation and data acquisition procedures are also discussed in this paper. The focus of the current work was on the developmen...     »