Design Exploration for Aerodynamic Performance of Hovering Stacked Rotor

Abstract

This study analyzed the aerodynamic performance and the underlying physics of various stacked rotor configurations under hovering conditions using a high-fidelity numerical solver. Three design variables, namely index angle, stacked distance, and pitch angle difference, were adopted to define the stacked rotor configurations. Accordingly, two dominant physical phenomena were captured by high-resolution simulations: the inflow effect and the wake interference effect. In particular, the blade-vortex interaction at the lower blade plays a crucial role in increasing the overall aerodynamic performance by generating upwash that increases the local power loading of the lower blade. Unsteady simulations demonstrated that the blade-vortex interaction of the stacked rotor generates a significantly lower peak-to-peak thrust value compared to the counter-rotating coaxial rotor, which may result in a much lower aeroacoustic noise level. Finally, design optimization to maximize inflow and wake effects was performed leveraging neural networks, successfully extracting design rules that can guide future preliminary design studies.