November 2, 2021 @ 3:00 pm - 4:00 pm
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“Enhanced Blast Pressure, Temperature, and Impulse from Metalized Explosive Fireballs”
David Frost, Department of Mechanical Engineering, McGill University
Please contact Rachel Wise for connection information.
Fireballs generated by metalized explosives are highly heterogenous, with large spatial variations in gas and particle density and temperature, and exhibit multiple internal wave interactions driven by particle jetting. For fuel-rich systems with high solid particle mass loading, there is insufficient oxidizing species in the detonation products, and the particles continue to burn as they move into the shocked air. For fuel-lean systems, early-time enhancement of the blast pressure suggests that a substantial fraction of the metal particles release their energy on the timescale of the detonation propagation (10s of microseconds), consistent with the early-time enhancement of metal acceleration in plate-push experiments using the same metalized explosive. Surprisingly, the blast augmentation due to particle energy release is not a systematic function of particle size, indicating that we need to completely rethink how the particles release their energy in the extreme conditions behind the detonation wave and within the detonation products. Other interesting effects result from the interaction of shock waves with the metalized fireball, particle collision and fragmentation, relative motion between the particles and gas, and the particular mode of combustion of different metals. I will illustrate some of the features of this complex multiphase reacting environment using a variety of experimental techniques, and highlight some of the outstanding issues that need to be resolved.
David Frost is currently a Professor in the Mechanical Engineering Department of McGill University in Montreal. This year he will be happy to finish his term as Associate Dean and reduce his Zoom-fatigue from innumerable Covid-related meetings. His research interests are in the areas of metal combustion, multiphase combustion processes and shock wave physics. He joined McGill after completing his PhD at Caltech where he studied the dynamics of explosive boiling at the superheat limit. Past projects have involved steam explosions due to molten metal/water interactions, bubble detonations, shock interactions with compressible materials, and the synthesis of ballistic ceramics. For the last few decades he has been studying the combustion of dust clouds and blast waves from metalized explosives. Everything he knows about metal combustion and optical diagnostics he learned from discussions with his great colleagues, including Sam Goroshin, Jeff Bergthorson, Nick Glumac, Mike Soo, among others, frequently over beer.