Mixing in an explosion is largely affected by the reshock process and corresponding Rayleigh-Taylor and Richtmyer-Meshkov instabilities (RMI). The conventional understanding of RMI stems from a laboratory-scale channel. However, the reshock process in an explosion is different due to combustion, implosion, and reshock generation from the core. This numerical study quantifies mixing layer growth, mixedness, and turbulence, first within the fireball of a free-field TNT explosion and then within an SF6 curtain placed near the charge. The results show that the postreshock mixing within the fireball is consistent with the conventional understanding of RMI, showing a linear mixing layer growth and a rapid rise in the mixedness within the time frame of the shock passage through the mixing layer. However, the early-time mixing shows a strong effect of implosion and deviation from the conventional understanding of RMI. The SF6 mixing is strongly dependent on curtain placement due to two reasons: (a) stronger shocks near the charge cause a more violent RMI and mixing and (b) implosion and fireball cause a deviation in the mixing behavior from the conventional understanding of RMI if the SF6 placement is within the fireball radius. The curtain thickness is shown to have minimal effects on the mixing behavior, except for interactions between the inner and the outer boundaries of the curtain that lead to a more complex mixing for thinner curtains. The differences in mixing layer growth rates are explained using correlations for shock overpressure decay, Rankine-Hugoniot equations, and mixing models.

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• Richtmyer-Meshkov instability
• Shock waves
• Turbulent mixing