| In this thesis,the finite-depth cylindrical shell is taken as the research object.Based on fluid-structure interaction analysis,the vibration and noise characteristics of the cylindrical shell under the action of flow field and internal excitation force are studied.Subsequently,the flow-induced noise and radiation noise of the cylindrical shell under the action of flow field are analyzed.The coupling effect of the flow-induced noise and the radiation noise of the cylindrical shell is further studied,and the flow-induced noise and the radiation noise are compared and synthesized.The research results of this thesis can provide reference for optimization of structural strength and suppression of vibration noise in cylindrical shells.(1)The fluid-solid coupling analysis of the cylindrical shell model with finite depth is carried out.First,the boundary conditions of the basin are set,the calculation parameters are set,and an excitation force is applied in the cylindrical shell.Second,the flow field characteristics of the cylindrical shell and the vibration response spectrum under the dual action of the flow field and excitation force in the cylindrical shell are then studied.The results show that the placing stiffeners in the cylindrical shell can effectively improve its structural strength.(2)Based on the calculation results of the flow field,the acoustic boundary element method and acoustic finite element method are used to perform calculations of underwater flow-induced noise of the cylindrical shell by using LMS Virtual Lab acoustic simulation software.The calculation results of the two methods are compared,and it can be seen that the sound pressure levels obtained by the two methods are in good agreement.(3)Based on the surface displacement vector of the cylindrical shell structure calculated by Workbench,the radiated sound power of the cylindrical shell is calculated by the acoustic finite element method using LMS Virtual Lab acoustic simulation software.The results give the indication that the flow rate has little to no effect on the gross radiated acoustic power of the cylindrical shell.However,increasing shell thickness tends to decrease the total radiated acoustic power.The gross radiated acoustic power of cylindrical shell can be lowered by placing stiffeners inside the cylindrical shell,especially in the low frequency band(20 Hz to 50 Hz).(4)The acoustic boundary element method and acoustic finite element method are used to calculate the level of underwater radiated noise in the cylindrical shell.By comparing the calculation results of the two methods,it is established that the radiated sound pressure levels obtained by the two methods are in good agreement.(5)The comprehensive noise level of a cylindrical shell with limited depth is analyzed and evaluated.The analysis reveals that the flow-induced noise dominates in the range of 20-100 Hz,while the radiation noise dominates in the range of 160 Hz-200 Hz. |
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