The Effect Of Linked Material On The Sound Radiation From Double Cylindrical Shell

It is very important to hide itself for the submarine in modern war and finite cylindrical shells with stiffened ribs are major structure of cabin on the submerged or underwater vehicles. Finite cylindrical shell with stiffened ribs is the standard structure of underwater vehicles. Double shell mainly coupled by transverse structures such as braces and frame. Because of its intensive layout and directly being connected with the double shell, when the inner shell is excited, the vibration waves transmit to outer shell quickly. Therefore, it is of great importance to research the effect of the connection forms (stiffeners or flow field) to the double shell acoustic properties. This means much for underwater vehicle's vibration control and noise reduction.Based on elastics wave theory and theory of plate vibration, the stiffened double cylindrical shell with different linked materials is studied. The Flügge theory of thin shell and helmholtz wave equation are applied to describe shell motion. The effects of stiffeners are induced into vibration equation by treating it as reverse forces on the shell. Splint is simplified as pole, which is treated as the radial forces acting on the inner shell and outer shell. Get the stiffeners reaction equation and the couple equation of acoustics-fluid-structure of double shell. The effects of connection types between the inner shell and outer shell on radiated power and radial quadratic velocity are discussed.Based on FEM and BEM, the vibration and sound radiation of double cylindrical shell connected with stiffeners and solid floor is compared studied by emulation. Get the influence of different connection types on the structure's vibration and sound radiation.The double shell acoustic response of different parameters is developed studied by emulation. The influences of different frame spaces of double cylindrical shell and the thickness variation of inner and outer shell on acoustic characteristics are compared.Based on the above analysis, develop the optimum design of vibration control and noise reduction. In main path for the transmission of vibration and noise, design vibration isolation. Thereby, reduce efficiently the transmission of the principle component of vibration. This thesis introduces a kind of composite brace which contains damping layer. Combined FEM and BEM , the underwater vibration and sound radiation of double cylindrical shell with the braces coated with damping layer is numerically experimented.