Preliminary Study of a Test Procedure for Obtaining Step Wave Loadings on Structures at Deep Submergence

摘要

This investigation is concerned with the development of a possible technique for obtaining step wave loading on deeply submerged structures. In this technique, a fluid-filled cylinder would be used as the test device and the cylinder itself submerged. A structural model would be placed inside the cylinder and the internal fluid brought to the required test pressure. A charge designed to produce a step wave would be placed in the water outside the test device. The shock wave from the charge would thus produce a loading in the pressurized cylinder and hence on the test mode. One of the first questions that arises is what is the form of the pressure wave that is produced within the cylinder. This report presents a preliminary study of this problem by considering the response of a submerged fluid-filled ring subjected to a transverse step wave. The external fluid is represented by using the plane wave approximation. The ring and internal fluid equations are replaced by finite difference approximations using central differences in space and time. Details of the numerical method, and the results of six calculations are given. In these six calculations, water is used as the internal and external fluids, and the ring which has the properties of either steel or aluminum, has two different radii and two or three different thicknesses. The primary reason for these calculaitons is to determine whether the ring is 'transparent'. That is, does the internal pressure time history look nearly the same as the external pressure.