The Blast Wave Produced by Bursting Spheres With Simultaneous or Delayed Explosion or Implosion of The Contents
Shimpi, Shirish Ambadas
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https://hdl.handle.net/2142/67473
Description
Title
The Blast Wave Produced by Bursting Spheres With Simultaneous or Delayed Explosion or Implosion of The Contents
Author(s)
Shimpi, Shirish Ambadas
Issue Date
1980
Department of Study
Aeronautical and Astronautical Engineering
Discipline
Aeronautical and Astronautical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Aerospace
Language
eng
Abstract
This dissertation consists of a systematic study to determine the structure of blast waves generated by a variety of non-ideal energy sources. The energy sources considered included bursting spheres, centrally initiated spherical explosions, edge initiated spherical implosions and combinations of the above with and without ignition delays. Although the combustion process was modeled after methane combustion, the technique for generalizing to other fuels was presented. The Oppenheim CLOUD computer program with appropriate energy source terms was used to perform all the calculations. The bursting sphere energy density was systematically varied with the energy density of methane being included in the energy densities considered. This enabled the comparison between the blast waves generated by a bursting sphere and other energy sources. The effective normal burning velocity for the explosion and implosion cases was varied to include a range of velocities from very low flame velocities up to detonation causing velocities. Flame acceleration processes were also carefully simulated. Details of the blast structure for all the cases considered was provided.
The following conclusions were reached from this study. High effective normal burning velocities are required to produce damaging blast waves. Constant velocity explosions have much higher peak overpressures than constant velocity implosions except near the center of the source where the reflected waves from an implosion cause high peak overpressures. A bursting sphere with immediate explosion of the contents produces a lead wave which is totally bursting sphere related with a secondary combustion wave which always trails the lead wave for low flame velocities. However, for the corresponding implosion case with sphere burst, the implosion process contributes to the peak overpressures even for relatively low flame velocities. It was noted that accelerating flames whether implosive or explosive, show that the maximum overpressure generated by such flames is no higher than that generated by a constant velocity flame which travels through the entire source region at the maximum velocity reached when the acceleration process ceases. The energy scaled impulse versus energy scaled radius show far field equivalency for all the cases considered. The peak overpressure versus energy scaled radius show good far field equivalency with Baker's Pentolite (high explosive) for all except the very low velocity cases.
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