Multi-phase simulation of ammonium nitrate emulsion detonations

Ammonium-nitrate-based explosives used by the mining industry exhibit strong non-ideal detonation behaviour. Detonation velocities in rate-sticks with radii close to the failure radius, can be as low as one third of the ideal detonation velocity, which poses a significant challenge for their accurate predictive computational modelling. Given that these emulsions are highly heterogeneous, multi-phase formulations are well suited for their representation in numerical hydrocodes. To this end, a single-pressure, single-velocity multi-phase model is employed for the simulation of an explosive emulsion widely used by the mining industry. The model is modified to rectify a problem related to the calculation of a unique detonation state, and is evaluated using a high-resolution, shock-capturing Riemann problem-based scheme. In order to perform high-resolution numerical simulations at a reduced cost, a shock-following method is implemented and validated against the full-domain solutions. An improved iterative fitting procedure for steady-state detonation kinetics is also presented. Validation against experimental evidence shows that the model can reproduce confined VOD experimental data, solely by adjusting the reaction kinetics to match unconfined experimental VOD data. Furthermore, the model can match experimental front curvature measurement without further adjustments.