Research On The Acoustic Design And Application Of Ship-base Connection Form

The stealth of ship is an importance critical performance indicator and it is particularly significant in terms of submarines. Structure of typical cabin on submarines, torpedoes and other underwater vehicles are the finite stiffened double cylindrical shell. Inside the submarine structure, mechanical equipment is generally installed in a certain base. And the base structure is equivalent to the series and parallel of variety connections. As the mechanical equipment acting on the base panel, vibration wave energy will follow the connection structure transmission to other structures, leading to vibration of the hull structure, and then radiating noise to the ocean. Therefore, the investigation of the base in the shell structure has a very practical significance to the submarine noise and vibration reduction.When the stationary structure mutation (mass, stiffness, etc.), structural changes will result in resistance changes, leading to impedance mismatch between the structure, making the vibration wave reflect or transmission in the mutant cross-section. The purpose of reducing vibration and noise is achieved by reducing the wave propagation efficiency and holding up the energy of vibration wave passes downstream structural. Firstly, based on wave theory, the phenomenon of wave-type conversion and impedance mismatch was analyzed when the structural broken. Vibration wave propagation characteristics in combination of several typical joint board structure (typical connection structure including linear, "L "-shaped, "T"-shaped, "+"-shaped, "(?) "-shaped, "(?)"-shaped,) were studied. Efficiency of reflection and transmission coefficients in different forms of the structure connecting was discussed, which provided a theoretical basis for the numerical simulation and experimental study.Firstly the finite element/boundary element (FEM/BEM) coupling method was used to analyzed the effect of vibration and sound radiation of the base in double cylindrical shell in low frequency. Based on wave theory in Chapter II, the high transmission loss base was designed by replacing the "T"-shaped connection base to "(?)"-shaped connection base. Vibration and noise reduction effect in low-frequency was proved by the numerical method.Due to the deficiency of FEM/BEM and statistical energy analysis (SEA), sound radiation characteristics of the double cylindrical shell in the band were solved by the hybrid FE-SEA method, verifying the high frequency vibration and noise reduction effect of the high transmission loss base that designed.Finally, model experimental was carried and the two kinds of base form were respectively placed on two side of shell. Contrasting with experiment, damping effect at the typical measuring point can be obtained when respectively using "T"-shaped connection and "(?)"-shaped. The experimental results and numerical simulation results were compared to verify the accuracy of numerical simulation methods, and it can provide guidance for the next step numerical simulation.