Underwater explosive loading resulting from rapid phase transitions (RPT's) is one example of a fast transient dynamic event. The leakage of substances such as LPG or LNG when stored underwater can cause an RPT. These substances are often stored in a combination of very low temperatures and high pressures with respect to the surrounding fluid (seawater) and their leakage can cause the equivalent of an underwater explosion. Such containers are usually found to be part of a much larger 'storage field' of containers. An RPT occurring in one container will cause underwater explosive loading on neighbouring containers. By simulating an RPT using explosive charges experiments were initially designed using theoretical and empirical techniques. The fluid and structural response of a prototype container subject to symmetric and axisymmetric underwater explosive (UNDEX) loading was then examined experimentally. Theoretical predictions using the finite element hydrocode LS-DYNA and boundary element code USA-DYNA3D were undertaken and compared with experimental observations. Several non-destructive techniques were employed to estimate dynamic collapse buckling criteria from both experimental and theoretical results. The experimental work concluded that the critical regions of the prototype container were the apex and the base under both forms of loading. The quality of the numerical predictions varied dependent on the form of the loading. In some cases the fluid and structural responses were overpredicted, and in others underpredicted. Within the limitations of these numerical procedures it was possible to predict a conservative estimate of a critical charge size under axisymmetric UNDEX loading using LS-DYNA. The critical stand off distance was also estimated from experimental results under symmetric UNDEX loading. The use of numerical approaches to predict fluid-structure interaction as successful for the shock phase of an underwater loading and both LS-DYNA and USA-DYnA3D have been validated for shock loading. Bubble loading simulations proved unsuccessful. Suggested improvements are proposed to increase the application of, and enhance the reliability of, the techniques used in this work.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:641839 |
| Date | January 1999 |
| Creators | Boyd, Alistair Richard |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/10835 |
Page generated in 0.0137 seconds