Research on the underwater noise radiation of high pressure water jet propulsion

Abstract High pressure water jet propulsion is a new type of propulsion, which has the characteristics of simple system structure, small energy loss in the water inlet duct, easy vectored control, without additional drag force and so on. Underwater jet noise radiation of high pressure waterjet propulsion is an important factor that would directly determine the stealth performance of underwater vehicles. A co-simulation method combining the CFD (Computational Fluid Dynamics) and CAA (Computational Aeroacoustics) was used in this paper to study and analyze the underwater jet noise radiation characteristics of high pressure water jet propulsion. The Realizable k-e turbulence model was used to numerically simulate the flow field of waterjet. And the FFT processing of the flow field results were implemented by use of the Actran iCFD module in order to obtain the sound source of the waterjet radiation. Then, the Lighthill acoustic analogy theory was utilized to achieve the underwater jet noise radiation characteristic. Consequently, the effects of inlet velocity on the underwater jet noise radiation characteristics of high pressure waterjet propulsion were researched. The results indicated that the underwater jet noise radiation of high pressure water jet propulsion mainly comes from the mixing area where is the 8–10 times diameter away from the nozzle outlet, and the increase of the inlet flow velocity would enlarge the sound pressure level of the underwater jet noise radiation. In addition, the underwater noise jet radiation is directional and mainly propagates in the axial direction. However, the inlet velocity has little influence on the frequency domain characteristics of underwater jet noise radiation and the underwater jet noise radiation has high energy below the frequency 200 Hz. The research provides theoretical guidance for reducing the underwater jet noise radiation of high pressure waterjet propulsion and improving the stealth performance of underwater vehicles.