Explosively driven particle fields imaged using a high speed framing camera and particle image velocimetry

Jenkins, Charles M.; Horie, Y.; Ripley, Robert C.; Wilson, William H.

doi:10.1016/j.ijmultiphaseflow.2012.08.008

Cited by 16 publications

(9 citation statements)

References 24 publications

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“…Alternative approaches use pressurised glass spheres [19] or detonation transmission tubing [20] in place of the explosive. In the near-field, however, the detonation product fireball is still rapidly expanding and remains attached to the surrounding layer of compressed air [21]. Thus, in the early stages of fireball expansion, measurement of the velocity of the outer surface of the detonation product fireball equates to measurement of the shock velocity, as is assumed in this article.…”

Section: Introductionmentioning

confidence: 90%

“…10 are compiled in Table 1 along with incident (measured) and reflected (calculated) Mach numbers. As previously, y, x, and r are stand-off distance, distance from the plate centre, and slant distance to the measurement point, which is assumed to be exactly equal to the fireball radius at the moment of impingement after [21]. Maximum and mean HPB peak pressures are provided for comparative purposes.…”

Section: Comparison To Directly Measured Peak Pressuresmentioning

confidence: 99%

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Reflected Near-field Blast Pressure Measurements Using High Speed Video

et al. 2020

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Background: The design and analysis of protective systems requires a detailed understanding of, and the ability to accurately predict, the distribution of pressure loads acting on an obstacle following an explosive detonation. In particular, there is a pressing need for accurate characterisation of blast loads in the region very close to a detonation, where even small improvised devices can produce serious structural or material damage. Objective: Accurate experimental measurement of these near-field blast events, using intrusive methods, is demanding owing to the high magnitudes (> 100 MPa) and short durations (< 1 ms) of loading. The objective of this article is to develop a non-intrusive method for measuring reflected blast pressure distributions using image analysis. Methods: This article presents results from high speed video analysis of nearfield spherical PE4 explosive blasts. The Canny edge detection algorithm is used to track the outer surface of the explosive fireball, with the results used to derive a velocity-radius relationship. Reflected pressure distributions are calculated using this velocity-radius relationship in conjunction with the Rankine-Hugoniot jump conditions. Results: The indirectly measured pressure distributions from high speed video are compared with directly measured pressure distributions and are shown to be in good qualitative agreement with respect to distribution of reflected pressures, and in good quantitative agreement with peak reflected pressures (within 10% of the maximum recorded value). Conclusions: The results indicate that it is possible to accurately measure blast loads in the order of 100s MPa using techniques which do not require sensitive recording equipment to be located close to the source of the explosion.

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Section: Introductionmentioning

confidence: 90%

Section: Comparison To Directly Measured Peak Pressuresmentioning

confidence: 99%

Reflected Near-field Blast Pressure Measurements Using High Speed Video

et al. 2020

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“…When polar angle ϕ is varied within the range from 0 to 5π, the results of the computations by formulas (11) and (12) for the particles with density = 3900 kg/m 3 differ by no more than 10% compared to the compu tations by formulas (9) and (10) for A < 0.125.…”

Section: Particle Motion Simulationmentioning

confidence: 95%

“…High values of the dynamic slip of the particles were observed in [12] during the experimental study of pecu liarities of explosive scattering of aluminum (13.4 µm and 113 µm) and tungsten particles (34.5 µm) in the pro cess of their interaction with the shock wave.…”

Section: Introductionmentioning

confidence: 99%

About choice of particle parameters for visualization and diagnostics of free concentrated air vortices

2014

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The problem of the choice of parameters (density, size) of particle inertia for visualization and diagnostics of free vortices of various intensities (characteristic velocity, vortex funnel diameter) is considered. The dimensionless criterion (Stokes number) is used, which determines the peculiarities of solid particles behavior in concentrated vortex structures. An example of the choice of particle parameters for visualization of a laboratory simulated air vortex funnel and debris cloud is described.

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“…Furthermore, the sudden increase in pressure at the vicinity of a detonation will cause an increase in temperature (few thousand kelvins). Finally, the transfer of momentum between the shock front and solid particles will also cause these solid particles to accelerate spherically away from the center [23][24][25]. The combined effect will result in the creation of an optically thick visible fireball.…”

Section: Introductionmentioning

confidence: 99%

Beirut explosion: TNT equivalence from the fireball evolution in the first 170 milliseconds

et al. 2021

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The evolution of the fireball resulting from the August 2020 Beirut explosion is traced using amateur videos taken during the first 400 ms after the detonation. Thirty-nine frames separated by 16.66–33.33 ms are extracted from six different videos located precisely on the map. Time evolution of the shock wave radius is traced by the fireball at consecutive time moments until about $$ t \approx 170$$ t ≈ 170 ms and a distance $$ d \approx 128$$ d ≈ 128 m. Pixel scales for the videos are calibrated by de-projecting the existing grain silos building, for which accurate as-built drawings are available, using the length, the width, and the height and by defining the line-of-sight incident angles. In the distance range $$ d \approx $$ d ≈ 60–128 m from the explosion center, the evolution of the fireball follows the Sedov–Taylor model with spherical geometry and an almost instantaneous energy release. This model is used to derive the energy available to drive the shock front at early times. Additionally, a drag model is fitted to the fireball evolution until its stopping at a time $$ t \approx 500$$ t ≈ 500 ms at a distance $$d \approx 145\pm 5$$ d ≈ 145 ± 5 m. Using the derived TNT equivalent yield, the scaled stopping distance reached by the fireball and the shock wave-fireball detachment epoch within which the fireball is used to measure the shock wave are in excellent agreement with other experimental data. A total TNT equivalence of $$ 200\pm 80\,\mathrm{t}$$ 200 ± 80 t at a distance $$ d \approx 130$$ d ≈ 130 m is found. Finally, the dimensions of the crater size taken from a hydrographic survey conducted 6 days after the explosion are scaled with the known correlation equations yielding a close range of results. A recent published article by Dewey (Shock Waves 31:95–99, 2021) shows that the Beirut explosion TNT equivalence is an increasing function of distance. The results of the current paper are quantitatively in excellent agreement with this finding. These results present an argument that the actual mass of ammonium nitrate that contributed to the detonation is much less than the quantity that was officially claimed available.

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Explosively driven particle fields imaged using a high speed framing camera and particle image velocimetry

Cited by 16 publications

References 24 publications

Reflected Near-field Blast Pressure Measurements Using High Speed Video

Reflected Near-field Blast Pressure Measurements Using High Speed Video

About choice of particle parameters for visualization and diagnostics of free concentrated air vortices

Beirut explosion: TNT equivalence from the fireball evolution in the first 170 milliseconds

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