The influence factors of near water effect of rotor

Cross-media vehicles, or hybrid aerial underwater vehicles (HAUV) are capable of operating in air and water and performing continuous and uninterrupted high-quality observation and sampling. However, the mixed air-water flows generated by the rotor near the water surface always resulting the near water effect. To understand the potential risks caused by the near water effect in the cross-media process, near water and ground tests were conducted to obtain the aerodynamic characteristics of carbon fiber rotor blades with different diameters under the conditions of out of ground effect, ground effect and near water effect. The study identified the key factors influencing the near water effect, and explained the significant changes in thrust, torque, power, and other factors when the rotor operates close to the water surface. The study also revealed the physics of near water effect, including the impact of droplets on the blades. For blades with a diameter of 0.56 m, when operating at high throttle and low distance off the water surface, the near water effect leads to a nonlinear increase in thrust, torque, required power, and a decrease in rotor speed. Under low throttle and high distance conditions, the near water effect is similar to the ground effect, resulting in increased thrust and reduced torque; additionally, the rotor size, blade type, and rotor speed have significant consequences on the near water effect. For blades with a diameter of 0.25 m, the near water effect leads to a increase in thrust and decrease in torque. It is evident that comprehending the near water effect of the rotor is advantageous for the layout design and dynamic modeling of cross-media vehicles.