A dissertation submitted to the Faculty of Engineering and the Built Environment, University
of the Witwatersrand, Johannesburg, in ful lment of the requirements for the degree of Master
of Science in Engineering.
Johannesburg, April 2016 / An explosive event in an industrial gas transmission pipe stresses the pipe and can result in
pipe rupture and separation at weak points. A shock wave results propagating from the
high pressure section of the pipe, through the gap and to the low pressure section. The
present study simulates numerically and experimentally the resulting
ow eld at the
position of pipe separation and propagation conditions in both pipe sections. The e ects of
gap width, gap geometry and shock Mach number variation are investigated. Shock Mach
numbers of 1.34, 1.45,1.60 and 2.2, gap widths of 40mm to 310mm were used. All variations
of boundary conditions were found to have an e ect on the propagation conditions as well
as the development of the
ow features within the gap. The variation of the gap geometry
was done for a pipe gap and a
anged gap experimentally. Extended geometries were
simulated numerically. For the pipe gap, the incident shock wave accelerated the gas in the
upstream pipe to high subsonic speeds and continued in the downstream pipe at a much
reduced strength. A strong expansion propagated into the
ow in the upstream pipe
causing a signi cant pressure drop from the initial post-shock pressure. Expansion waves at
the out
ow 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 downstream
pipe. In addition to the standing shock, shock cells of alternating shocks and expansions
developed within the gap essentially controlling the propagation conditions in the
downstream 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. The
propagation conditions in the downstream pipe showed that the pressure is initially
unsteady 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 hence
produced much more intense and complex
ow feature interactions and an earlier transition
of the
ow to turbulence. Numerical investigations for a burst pipe gap, for a gap with a
di erent diameter downstream pipe and a gap with a 90-degree bend downstream pipe
produced peculiar
ow features. / MT2016
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/21159 |
| Date | 11 October 2016 |
| Creators | Kapfudzaruwa, Simbarashe |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf, application/pdf |
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