Investigation of Loose and Tight Aeroelastic Coupling for High Speed and High Thrust Flight Conditions

Coupled computational fluid dynamics and structural dynamics methods offer the potential to significantly improve the prediction capabilities for aeromechanical loading of helicopter rotors. Accurate unsteady loads prediction is necessary for the optimal design of the rotor dynamic components and blades. High-thrust and extreme maneuvering conditions, which are important for design, are especially challenging for the analysis tools to predict accurately due to dynamic stall and its coupling with the structural dynamics. Evaluation of complex features such as highly 3D tip shapes, composite structures, and active devices, further increases the need for accurate analysis tools. To date, these aeroelastic calculations are typically performed in a loosely-coupled manner, which is computationally efficient, but may compromise accuracy for highly unsteady cases, such as those with significant dynamic stall. In this paper, results from loosely and tightly coupled methods for steady-level flight conditions are compared, and the tightly coupled procedure is applied to the UTTAS pull-up maneuver.