Study On Water Flow Noise Calculation Using Viscous Acoustic Splitting Method

Flow noise of submarine at high speed is one of the most important aspects on the concealment performance. Accurate prediction and evaluation of flow noise is one of the vital segments in further submarine design.The objects of this study are the theory, calculation method of Computational Hydro-Acoustic(CHA) and their application in computing water flow noise. Taking the distinct differences between the physical properties of water and air into consideration, the theory and algorithm of Computational Aero-Acoustic(CAA) are adjusted into the field of Computational Hydro-Acoustic. Firstly, based on the state equation of water, the governing equations and discretization method of Viscous Acoustic Splitting Method(VASM) for water flow noise are derived in the Cartesian coordinates and the curvilinear coordinates. Secondly, the established VASM for water medium and the corresponding acoustic field program are verified by the numerical results of three typical cases: noise generated by a pair of spinning vortex, sound reflected by a cylinder and vortex-sound interaction with a cylinder. At last, taking flow around a cylinder and cavity flow as computing models, the hybrid method of Large Eddy Simulation/Viscous Acoustic Splitting Method(LES/VASM) is realized to simulate the generation and propagation of flow noise and the generation mechanism and propagation characteristics of flow noise are investigated.Analysis results show that VASM for water medium is efficient for analyzing how flow noise generates and propagates. After an assessment of the effects of mesh size, time step and damping coefficient on the numerical results, reasonable and credible results are worked out using VASM for water medium and the corresponding acoustic field program.Aiming at the properties of water such as extreme weak compressibility, big density and small kinematic viscosity and the characteristics of water flow such as low Mach number and high Reynolds number, theory and methods of CAA are studied to establish a novel calculation strategy for water flow noise with the help of advanced numerical computing technology. The study is able to provide an essential technical foundation for hydrodynamic noise estimation software, submarine overall optimization design and further research on hydrodynamic noise.