Clustering and combustion of dilute aluminum particle clouds in a post-detonation flow field K. Balakrishnan, S. Ukai, S. Menon ⇑ School of Aerospace Engineering, Georgia Institute of Technology, 270 Ferst Drive, Atlanta, GA 30332-0150, USA Available online 24 September 2010 Abstract A hybrid two-phase numerical methodology is used to investigate the flow-field subsequent to the det- onation of a spherical charge of TNT with an ambient distribution of a dilute cloud of aluminum particles. The interaction of the particle cloud with the contact surface results in Rayleigh–Taylor instability, which grows in time and gives rise to a mixing layer where the detonation products mix with the air and afterburn. At early times, the ambient particles get engulfed into the detonation products and ignite. Subsequently, they catch up with the Rayleigh–Taylor structures, and the vortex rings around the hydrodynamic struc- tures cause transverse dispersion that results in the clustering of particles. Then, the particles leave the mix- ing layer and quench, yet preserve their hydrodynamic foot print. Preferential heating and combustion of particles occurs due to clustering. A higher initial mass loading in the ambient cloud results in larger clus- ters due to stronger/larger vortex rings around the hydrodynamic structures. A larger particle size results in the formation of fewer and degenerate clusters when the initial width of the cloud is larger. A theoretical model is used to predict the bubble amplitudes, and are in good accordance with the simulation results. Overall, this study has provided some useful insights on the explosive dispersal of dilute aluminum particle clouds and the gas dynamics of the flow field in the mixing layer. Ó 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved. Keywords: Explosive; Blast wave; Ignition; Clustering; Hydrodynamic instability 1. Introduction The study of the interaction of a high explosive generated flow field with reactive solid particles has been undertaken recently [1–3], and is a field of research gaining interest. Computational simulations have shown that hydrodynamic instabilities such as Rayleigh–Taylor [4] and Richtmyer–Meshkov [5] occur in the flow field behind blast waves [6–8], thereby resulting in a turbulent mixing layer where the inner detonation products mix with the outer air and burn, accom- panied by an exothermic energy release. Subse- quent to the detonation, as the contact surface overtakes the particles and engulfs them into the detonation products, the particles introduce per- turbations on the contact surface due to momen- tum and energy absorption, which subsequently grow into Rayleigh–Taylor instability [4]. Then, the particles pick up significant momentum and energy from the gas, are set into motion, and catch up with the hydrodynamic structures. The hydrodynamic instabilities on the contact surface grow as bubbles of lighter fluid rising into the heavier fluid, and spikes of heavier fluid falling 1540-7489/$ - see front matter Ó 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved. doi:10.1016/j.proci.2010.07.064 ⇑ Corresponding author. Fax: +1 404 894 2760. E-mail address: suresh.menon@aerospace.gatech.edu (S. Menon). Available online at www.sciencedirect.com Proceedings of the Combustion Institute 33 (2011) 2255–2263 www.elsevier.com/locate/proci Proceedings of the Combustion Institute