Dynamic modeling of plasma effects during multi-phase detonations near a surface and/or in a magnetic field
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A multi-physics model has been developed to simulate detonations and condensed-phase explosions in the presence of an external electromagnetic field. To simulate these effects, models for high-temperature gas physics, plasma-production, dispersed-phase mixing, and turbulence have been implemented within the framework of a numerical method capable of simulating magnetohydrodynamic (MHD) flows. This research has leveraged past work in MHD flows, detonations, and turbulence-chemistry interactions to study multi-scale detonation-plasma-field interactions, and has furthered the understanding of many key physical processes of these flows. This work targeted three main basic science objectives: the study of plasma-production by detonations and condensed-phase explosions, the study of MHD instabilities and turbulence relevant to post-detonation flows, and the study of how a detonation is affected by the presence of a magnetic field. Simulations indicate that gaseous detonation waves generate a weakly ionized plasma in the post-detonation region. The average electrical conductivity in the post-detonation flow, however, is of the order of 10-3 S/m, and practical engineering applications involving the use of MHD forces to manipulate the flow for generation of electrical power, propulsive thrust, etc., require higher levels of electrical conductivity. Simulations of mixtures seeded with particles of a low ionization potential show a substantial increase the flow's electrical conductivity. The presence of these particles can adversely affect the detonation propagation. The physics of how an electromagnetic field interacts with the conducting products of a detonation, and how that interaction might affect the stability and propagation of the detonation wave is systematically studied. The magnetic field applied in the direction of detonation propagation affects the detonation through a combined effect of Joule heating and Lorentz force, in some cases altering the cellular structure of the detonation completely by reducing the half-reaction zone thickness. Basic studies of the Richtmyer-Meshkov instability, an important mechanism for the transition to turbulence in explosions, are used to elucidate several salient features of these types of MHD flows. Namely, simulations show that the presence of a dispersed phase alters the mixing growth-rates of the instability, and furthermore, an applied magnetic field is shown to either suppress or enhance fluid mixing.