多旋翼近水面效应气动特性实验OA

When the cross-medium vehicle approach the water surface,the interaction between its downwash flow and the water surface generates mixed air-water flows.In this flow field,the rotor exhibits aerodynamic characteristics distinctly different from in-ground effect,a phenomenon known as the near-water effect.Compared to the near-water effect of single-rotor,the near-water effect of multi-rotor becomes more complex due to the aerodynamic interference be-tween rotors and the coupling of their respective induced mixed air-water flows.Given the current lack of understanding of the near-water effect of multi-rotor,experiments are conducted to investigate the aerodynamic characteristics of multi-rotors near the water surface,measuring the aerodynamic forces and rotational speeds under different blade tip clear-ances and hovering heights.Combining the existing research on the near-ground wake structure of multi-rotor and the observed morphology of the mixed air-water flows,a preliminary cognitive framework of the near-water effect of multi-rotor is established,categorized as"merging,contacting and separating".Under different mixed air-water flows condi-tions,the merging mode with the closest blade tip clearance exhibits the best aerodynamic performance.As the blade tip clearance increases,the contacting mode at a relatively higher distance from the water surface shows no significant thrust loss,whereas the contacting mode closer to the water surface results in a notable reduction in the rotor thrust coef-ficient.Additionally,in the separating mode with the largest blade tip clearance,the strong interaction between the water droplets generated by the rotor-water interaction and the rotor leads to a sharp increase in rotor torque.