The Impact Of Diving Depth On Vibration And Acoustic Radiation Of Cylindrical Shell And Research Of Similarity

In the military field, regardless of naval vessels or submerged submarine, prediction and control of vibration noise is particularly important, especially submarine, stealth performance has become an important factor in defeating the enemy submarine, so the research of vibration and acoustic radiation characteristic has become an important task in the military field. The vibration and acoustic radiation characteristic of submarine is affected by the water surface and water bottom, also by hydrostatic pressure that related to immersion depth. Submarine as a typical elastic cylindrical shell structure, so the paper is based on the cylindrical shell as the research object, analyzing that immersion depth has influence on vibration and acoustic radiation characteristic of submerged cylindrical shell, as well as the similarity of underwater cylindrical shell’s vibration and acoustic radiation is studied, the main accomplished tasks as follows:Firstly, modal analysis is carried out on submerged cylindrical shell by finite element software ANSYS, and compared with the results of the analytical solution in the literature, the both results are very consistent, explaining that submerged cylindrical shell’s modal analysis using ANSYS is accurate, that is prepared for numerical simulation and calculation of the research of the ensuing chapters. Immersion depth bas influence on vibration and acoustic radiation characteristic of submerged cylindrical shell, it reflects that hydrostatic pressure related to immersion depth as a prestressed load, and the vibration characteristic is changed by the load. When making use of ANSYS for simulation and calculation, the hydrostatic pressure gradient load is applied to the finite element model of the cylindrical shell, the static analysis is carried out on submerged cylindrical shell firstly, then the modal analysis of being hydrostatic pressure is carried out, the vibration displacement response results is calculated by ANSYS as velocity boundary conditions, and combined with acoustic BEM software for acoustic analysis. The paper also discusses that water surface and bottom surface and different position of excited force have influence on vibration and acoustic radiation characteristic of submerged cylindrical shell. The research results show as follow:when the ratio of diving depth and the cylindrical shell radius reaches more than20times, the impact of diving depth on vibration and acoustic radiation characteristic of submerged cylindrical shell can’t be neglected. The impact of water surface, bottom surface and the different positions of excitation force on vibration and acoustic radiation characteristic of submerged cylindrical shell also can’t be neglected.The paper establishes the similarity theory of cylindrical shell vibration and acoustic radiation characteristic by finite element and boundary element method. Using ANSYS to create the model and prototype of cylindrical shell with geometric similarity, and combined with acoustic BEM software for numerical analysis, the results show that vibration and acoustic radiation characteristic of submerged cylindrical shell meets similarity theory.