Mechanism analysis of the bionic rudders on the operating performances of the high-speed autonomous underwater vehicle

As the core hydraulic model to absorb the fluid into the propulsion system and guide the operating direction of the navigating underwater vehicle, the rudder plays an important role in determining the flow stability of the underwater vehicle. Installed with an independently developed high-speed water-jet pump with a rotating speed of 17 500 r/min, a hydraulic model of a high-speed autonomous underwater vehicle (AUV) with a cruising speed of 50 kn was constructed, and the operational performances for the high-speed underwater vehicle under different bionic rudders were analyzed. A comparative analysis leads to the following conclusions: (1) The bionic leading edge, the bionic trailing edge, and the bionic leading–trailing edge can all improve the underwater vehicle operating performances at different cruising speeds. At the design speed of 50 kn, the underwater vehicle with the bionic leading–trailing edge achieves head increase in 0.81 m, power reduction of 1.81 kW, efficiency increase in 0.31%, and thrust increase in 65.74 N; (2) in relative to the bionic leading edge, the bionic trailing edge can greatly decrease the flow losses in the propulsion system with the entropy production theory, reducing the entropy generation rate of the inlet channel and impeller by 1.48 and 2.04 W/K, respectively; (3) the external sound field analysis reveals that the three bionic rudders all can reduce the noise, and the bionic trailing edge and the bionic leading and trailing edges have the better noise reduction effects at the near field, reducing noise by 0.68 and 0.72 dB, respectively; (4) via the bionic mechanism analysis with pressure pulsation and mode decomposition, it was found out that the bionic trailing edge of the rudder body significantly improves the pressure pulsations at the inlet of the water-jet propulsion channel, so that operating performances of the propulsion system as well as the underwater vehicle can be improved. In summary, the design of the bionic rudder enhances flow stability in the AUV propulsion system, boosts the overall performance of the AUV, reduces energy consumption, and contributes to the efficient operation of the AUV.