Fluid-membrane interaction of nano rotor based on dynamic mode decomposition

As the size decreases, the flight Reynolds number of nano rotors decreases, reaching approximately 104 in magnitude, leading to a sharp decline in their aerodynamic efficiency. Therefore, it becomes crucial to improve the aerodynamic performance of nano rotors at low Reynolds numbers through flow control methods. Existing studies have shown that flexible membranes can improve aerodynamic performance of nano rotors, yet the mechanisms behind this improvement remain unclear. This study uses a dynamic mode decomposition (DMD) framework for analyzing the fluid-structure interactions of flexible membrane rotors, enabling simultaneous examination of fluid and structural variables. Results show that the aerodynamic efficiency of flexible membrane rotors has increased by approximately 7.5% compared to non-membrane rotors. DMD analysis reveals that both membrane and non-membrane rotors are dominated by static modes, which contribute over 65% to the flow field, indicating that the primary mechanism driving the improvement in aerodynamic efficiency is attributed to the static deformation of the membrane. Regarding vibration characteristics, differences in rotor structural properties result in distinct forms of vibration, which excite higher-order aerodynamic modes when coupled with the flow field. This effect becomes more pronounced with increasing collective angles, with higher-order modes contributing up to approximately 35% to the flow field. Research shows that the static deformation of flexible membranes improves aerodynamic performance of nano rotors, while their vibration has a significant impact on flight stability.