Dynamic of Submerged Reinforced Cylindrical Shells

An approximate analytic technique is developed for the determination of the dynamic transient elastic response of circular cylindrical shells which are immersed in acoustic media. For a simple example, a comparison is made between the approximate technique developed and the exact analytic response. Comparison is also made between the proposed approximate technique and the existing approximate techniques, i.e., the plane wave and cylindrical wave approximations. The proposed approximate technique compares quite favorably with the exact solution and is superior to the existing approximate techniques. Making use of the proposed approximate technique the dynamic elastic response of a reinforced circular cylindrical shell to a moving pressure pulse applied through a surrounding acoustic medium is investigated. The pressure pulse is assumed to have its wave front parallel to the axis of the shell. The shell is assumed to be reinforced with periodically spaced rigid septa or stiffening rings. The response of each mode of a steel shell having typical geometry is calculated for a pressure pulse applied through an acoustic medium of water. This response is compared to the modal response of the shell in a vacuum but subjected to the same pressure pulse. It is found that in general the presence of an acoustic medium such as water reduces the amplitude in each mode and reduces the free vibration frequency.