Shock-induced flow through a pipe gap

[摘要] An explosive event in an industrial gas transmission pipe stresses the pipe and can result inpipe rupture and separation at weak points. A shock wave results propagating from thehigh pressure section of the pipe, through the gap and to the low pressure section. Thepresent study simulates numerically and experimentally the resulting oweld at theposition of pipe separation and propagation conditions in both pipe sections. The e ects ofgap width, gap geometry and shock Mach number variation are investigated. Shock Machnumbers of 1.34, 1.45,1.60 and 2.2, gap widths of 40mm to 310mm were used. All variationsof boundary conditions were found to have an e ect on the propagation conditions as wellas the development of the ow features within the gap. The variation of the gap geometrywas done for a pipe gap and a anged gap experimentally. Extended geometries weresimulated numerically. For the pipe gap, the incident shock wave accelerated the gas in theupstream pipe to high subsonic speeds and continued in the downstream pipe at a muchreduced strength. A strong expansion propagated into the ow in the upstream pipecausing a signi cant pressure drop from the initial post-shock pressure. Expansion waves atthe outow resulted in supersonic speeds as the ow entered the gap for Mach 1.45 and 1.6.A notable feature was the formation of a standing shock at the inlet to the downstreampipe. In addition to the standing shock, shock cells of alternating shocks and expansionsdeveloped within the gap essentially controlling the propagation conditions in thedownstream pipe. For the lower Mach number of 1.3, no sharp discontinuities were noticed.The e ect of the gap width was found on the nature of the shock cells within the gap. Thepropagation conditions in the downstream pipe showed that the pressure is initiallyunsteady but becomes more uniform, controlled by the developed wave system in the gap.For the anged gap case, the ow within the gap is con ned for much longer and henceproduced much more intense and complex ow feature interactions and an earlier transitionof the ow to turbulence. Numerical investigations for a burst pipe gap, for a gap with adi erent diameter downstream pipe and a gap with a 90-degree bend downstream pipeproduced peculiar ow features.

[发布机构] University of the Witwatersrand