Spherical combustion clouds in explosions

Kuhl, A. L.; Bell, John B.; Beckner, Vince; Balakrishnan, Kaushik; Aspden, A. J.

doi:10.1007/s00193-012-0410-y

Cited by 30 publications

(21 citation statements)

References 26 publications

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“…Nevertheless, it gives some confidence to the analysis of postdetonation turbulent mixing using numerical simulations. The phenomenology captured by the simulation is consistent with other simulations found in the literature [11,28], even the ones concerning HE fireballs. It shows that the compressed balloon analogy, which was known to be well representative of the blast-related characteristics of the flow produced by the detonation of a HE, can also be applied to study mixing inside fireballs.…”

Section: Conclusion Of the 2d Studysupporting

confidence: 81%

“…About half of the turbulent kinetic energy is produced during the strong blast wave phase and the second half is produced during the implosion phase, i.e., while the interface is strongly decelerated. The initial exponential increase is, for example, consistent with simulations of HE fireballs performed by Kuhl et al [11,28]. Figure 6d shows the evolution of the ratio between the actual area of the mixing layer internal boundary (i.e., the isosurface Y O 2 = 0.1Y O 2 ,0 ) and the area of the sphere whose radius is equal to the internal boundary mean radius.…”

Section: Global Phenomenologysupporting

confidence: 67%

“…Previous studies have shown that the combustion process inside fireballs is mainly driven by the turbulent mixing of detonation products with air [1]. Rayleigh-Taylor (RT) instabilities [2,3] and, then, Richtmyer-Meshkov (RM) instabilities [4,5] allow the growth of a turbulent mixing layer at their edge.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of mixing in high-explosive fireballs using small-scale pressurised spheres

et al. 2018

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OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in : http://oatao.univ-toulouse.fr/ Eprints ID : 19758To link to this article : DOI : 10.1007/s00193-018-0814-4 URL : http://dx.doi.org/10.1007/s00193-018-0814-4Any correspondence concerning this service should be sent to the repository administrator: staff-oatao@listes-diff.inp-toulouse.fr AbstractAfter the detonation of an oxygen-deficient homogeneous high explosive, a phase of turbulent combustion, called afterburning, takes place at the interface between the rich detonation products and air. Its modelling is instrumental for the accurate prediction of the performance of these explosives. Because of the high temperature of detonation products, the chemical reactions are mixing-driven. Modelling afterburning thus relies on the precise description of the mixing process inside fireballs. This work presents a joint numerical and experimental study of a non-reacting reduced-scale set-up, which uses the compressed balloon analogy and does not involve the detonation of a high explosive. The set-up produces a flow similar to the one caused by a spherical detonation and allows focusing on the mixing process. The numerical work is composed of 2D and 3D LES simulations of the set-up. It is shown that grid independence can be reached by imposing perturbations at the edge of the fireball. The results compare well with the existing literature and give new insights on the mixing process inside fireballs. In particular, they highlight the fact that the mixing layer development follows an energetic scaling law but remains sensitive to the density ratio between the detonation products and air.

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Section: Conclusion Of the 2d Studysupporting

confidence: 81%

Section: Global Phenomenologysupporting

confidence: 67%

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Analysis of mixing in high-explosive fireballs using small-scale pressurised spheres

et al. 2018

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“…In the past, we have studied turbulent combustion effects in both confined [1,2] and unconfined [3] explosions. And we have proposed gasdynamic models [4] and heterogeneous continuum models [5] for the turbulent combustion fields.…”

Section: Introductionmentioning

confidence: 99%

Turbulent combustion in aluminum-air clouds for different scale explosion fields

Kuhl

Balakrishnan

Bell

et al. 2017

AIP Conference Proceedings

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Abstract. This paper explores "scaling issues" associated with Al particle combustion in explosions. The basic idea is the following: in this non-premixed combustion system, the global burning rate is controlled by rate of turbulent mixing of fuel (Al particles) with air. From similarity considerations, the turbulent mixing rates should scale with the explosion length and time scales. However, the induction time for ignition of Al particles depends on an Arrhenius function, which is independent of the explosion length and time. To study this, we have performed numerical simulations of turbulent combustion in unconfined Al-SDF (shock-dispersed-fuel) explosion fields at different scales. Three different charge masses were assumed: 1-g, 1-kg and 1-T Al-powder charges. We found that there are two combustion regimes: an ignition regime-where the burning rate decays as a power-law function of time, and a turbulent combustion regimewhere the burning rate decays exponentially with time. This exponential dependence is typical of first order reactions and the more general concept of Life Functions that control the dynamics of evolutionary systems. Details of the combustion model are described. Results, including mean and rms profiles in combustion cloud and fuel consumption histories, are presented.

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“…Such explosives are primarily designed to enhance the afterburn in the post-detonation flow field. Past studies of afterburn [1,2,3,4,5] have attempted to quantify the evolution of the blast wave and the mixing zone behind it, but these studies are mostly limited to explosives with a low volume fraction of solid particles, i.e., < 0.01. However, experimental and realistic high energy heterogeneous explosives contain a large number of particles with the range of volume fraction of particles between 0.01 to 0.65.…”

Section: Introductionmentioning

confidence: 99%

Turbulent mixing and afterburn in post-detonation flow with dense particle clouds

Gottiparthi¹,

Menon²

2017

AIP Conference Proceedings

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Abstract. Augmentation of the impact of an explosive is routinely achieved by packing metal particles in the explosive charge. When detonated, the particles in the charge are ejected and dispersed. The ejecta influences the post-detonation combustion processes that bolster the blast wave and determines the total impact of the explosive. While the classical Eulerian-Lagrangian (EL) methods can accurately handle the post-detonation mixing zone in the dilute regime, the Eulerian-Eulerian (EE) method is preferred for the initial dense clustering. Here, we summarize the results obtained using both EL and EE methods as well as demonstrate a new hybrid EE-EL approach. The EL method, which is also developed to handle both dense and dilute flows using the discrete equation method, is used initially to study the dispersion of a relatively dense particle shell by blast waves. The results show distinct clustering of particles that later leads to the formation of jet-like structures as seen in experiments. Then, the hybrid EE-EL method is used to study the dispersion of dense clouds from explosives packed with aluminum (reactive) or steel (inert) particles. A transitioning criterion is used to smoothly transfer the initially dense Eulerian mass to Lagrangian particles when dilute. Results are presented to demonstrate that the approach is computationally efficient and accurate for certain ranges of particle sizes and loading. It is shown that mixing between the ambient and post-detonation products can be enhanced when particles are present in the flow. Furthermore, the afterburn of aluminum particles increases in the average gas-phase temperature by 100 K -200 K when compared to a case with non-reacting particles. More studies are still needed to establish a robust strategy for wider applications.

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Spherical combustion clouds in explosions

Cited by 30 publications

References 26 publications

Analysis of mixing in high-explosive fireballs using small-scale pressurised spheres

Analysis of mixing in high-explosive fireballs using small-scale pressurised spheres

Turbulent combustion in aluminum-air clouds for different scale explosion fields

Turbulent mixing and afterburn in post-detonation flow with dense particle clouds

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