Transfer Pattern And Defense Structure Of Explosive Shock Wave For Sea Pipeline System

Pipeline system mainly refers to the combination of pipelines that transfer fluid media and their accessories, such as the mechanical parts, pumps, monitor instruments and valves. The system serves as the maintenance for the vessels, just like the blood vascular system for human beings. It is thus necessary and significant to consider the anti-explosive shock loads abilities under water for the system in the structural design.By using the explicit non-linear dynamic finite element analysis software MSC.DYTRAN and constructing the FE models including pipe system, fluid inside the pipe system and fluid outside the pipe system, this thesis mainly concerns with the study of the shock wave transfer pattern in the sea pipeline system generated by the close-range non-contact underwater explosive, and subsequently two defense structural forms are suggested based on the above study.Firstly, the complex pipeline system model is simplified as the combination of three classical forms: straight pipe, bent pipe and T-branch pipe. Pressure at the pipe orifice, the fluid velocities and their distributions with different relative positions between the explosive and pipe orifice are calculated respectively. Subsequently the shock wave transfer patterns for these three typical forms and the influence of different pipe diameters for the shock wave pressure distribution are discussed in detail, when the shock wave was entering the pipe in normal incidence and oblique incidence. According to the computation, the shock wave could be considered as plane wave after a certain distance traveling.As there are also lots of important equipments in the pipeline system, their ability of resisting the explosive shock have to be considered. In the thesis, the most common equipments in the pipeline system, including valves and cylindrical liquid-filled equipments are modeled and analyzed. It seems from the calculation that the valves will increase the shock wave pressure while the cylindrical liquid-filled instruments will reduce the pressure. Based on the computation above, two shock wave defense structures, gradually changed pipes and energy accumulator are suggested. In particular, defense effects for these two structures with different diameters and length (or height) are analyzed and compared, which can provide with useful suggestions for the selection of the proper defense structure in pipeline system.