TRANSIENT RESPONSES OF SUBMERGED CYLINDRICAL SHELL ATTACKED BY UNDERWATER SHOCK WAVE

Abstract

To evaluate the transient responses of submerged structures subjected to underwater shock wave, a recently developed approximate method, the "Reflected-After-flow Virtual Source" (RAVS) method, has been employed. Using this methodology, the fluid-structure interaction is studied and the transient responses of elastic cylindrical shell, two-layered cylindrical shell and orthotropic cylindrical shell are examined.

After formulating the governing equation of ela tic cylindrical shell under the Love­ Timoshenko' s approximation, a model for calculating the structural transient responses has been derived by means of RAVS method. Numerical results are compared to exact solution as well as the results determined by using NASTRAN/USA and they are in good agreement. The effects of Young's modulus and time-decaying constant on the responses are also studied.

Similar developments are pursued for a two-layered cylindrical shell. Numerical results compared to those determined by using USA/LSDYNA3D code are in good agreement. In addition, the effects of different Young's modulus of the two layers on the radial velocity, radial displacement and the starting nondimensional time for the elastic disturbance to arrive at the points ? = ?/2 , ?= ? of the structure are studied.

In order to calculate the transient responses of a submerged orthotropic shell subjected to underwater shock wave, the governing equations have been derived by using classical laminate theory (CLT). The RAVS model and the finite difference method are then applied to study the transient responses of the structure. The numerical results are compared with those determined by using USA/LSDYNA3D code and the agreement is acceptable. The effects of fiber orientation, curvatures of the structures and thickness-radius ratio are investigated.