A dissertation submitted to the Faculty of Faculty of Engineering and the Built Environment,
University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the
degree of Master of Science in Engineering.
Johannesburg, February 2018The design, construction and validation of a non-explosively driven blast tube was
undertaken in order to reduce the cost and time of blast wave experimentation as well as to
enable the study of blast waves in the test laboratory environment. The design of the blast
tube was performed numerically using commercially available CFD software. Numerous
di erent driver shapes and con gurations were analysed during the design process including
linearly diverging drivers, straight drivers and polynomial drivers.
Based on the results and analysis performed in it was deduced that a driver section required
a few key features in order to generate a blast wave with a realistic Friedlander pressure
pro le namely, the driver section must end in a sharp corner in order to enable expansion
focusing to occur, the walls of the driver section must be divergent to cause the expansion
waves to re
ect downstream almost immediately after the diaphragm bursts as well to drive
the expansion focusing, the walls of the driver section must transition smoothly, that is
without a corner, into the expansion section walls and the walls of the driver section must
be curved in order to induce smooth and continuous expansion wave re
ection and focusing.
After some tests were carried out on a few iterations of driver section shapes, three shapes
were settled on, namely a concave driver, a linear driver and a convex driver.
Once the nal design of the blast tube was settled upon, a working prototype was
manufactured and assembled in the North West Engineering Laboratories and the prototype
was tested. During testing of the blast tube it was found that, despite issues arising due to
choice of mechanism employed to pressurise the driver being
awed, there being notches
and steps at the joints along the tube length and the downstream end of the test section
being closed, the blast tube did in fact generate blast waves with realistic pressure decay
pro les and good visual quality. After being validated the blast tube was used to examine
the di raction of the blast wave around a 90 corner and the re
ection of the blast wave
induced upon impinging wedges having angles of 15 , 30 and 45 . The blast wave
di raction and re
ection experimentation were carried out in the 1:2 < Ms < 1:4 range.MT 201
