M. Omang, S. Børve, and J. Trulsen Numerical simulations of blast wave propagation in underground facilities M. Omang, S. Børve, and J. Trulsen

Outline Numerical method HE modeling Free-field explosion Detonation in underground facility Conclusions Future work

Numerical method Smoothed Particle Hydrodynamics; SPH A Lagrangian particle method, where particles are used to simulate gas flow Regularized Smoothed Particle Hydrodynamics (RSPH)- extension to SPH Step-wise variable resolution Particle redistribution Symmetry assumptions

SPH Interpolation theory Kernel function

HE source model The High Explosive model is based on a Constant Volume Model Complete explosion; no after-burning of rest products. Constant gamma reaction Symmetry assumptions: Axis-symmetry: 3D computed in 2D. Spherical symmetry: 3Dcomputed in 1D.

HE data Data Free-field test Chamber-tunnel test Density [kg/m3] 1630 Charge weight [kg] 1.0 157.08 Loading density - 25

Free field 1kg of TNT

Accidental explosions in underground facilities Data Free-field test Chamber length [m] 2.0 Chamber diameter [m] Tunnel diameter [m] 1.0 Tunnel length [m] 5.0

Density and pressure

Density animation

Pressure and velocity sensors measurements

Maximum pressure Maximum pressure is recorded for each pressure sensor The plot illustrate the overall maximum pressure for the exterior tunnel area.

Tunnel exit pressure -comparison to empirical data Skjeltorp Helseth Results from Exit pressure, kPa Skjeltorp et al 4886 Helseth 5144 RSPH 4730

Empirical formulas Skjeltorp et al. Helseth Kingery and Gion

Exterior pressure distribution

Conclusions The constant volume model has been used to simulate free-field detonation of 1kg of TNT. The agreement is good, when results are compared against empirical data. Simulations of complex underground facilities is a challenge, since high resolution combined with large computational domains are required. In RSPH the problem is solved by stepwise increasing the computational domain. When exterior pressure results from RSPH is compared to results from empirical formulas, fairly good agreement is achieved. The discrepancy observed may indicate that the description of the exterior pressure as a linear relation in a log-log scale may be incorrect. Similar results have been observed previously for empirical data plotted against the given formulas.

Future work After-burning of rest products are not taken into account in the current simulations, work is however, in progress to implement a relative simple after-burning model. In the current simulations a single phase simulation was used. Plans are maid to implement and upgrade the code to handle multiphase flow.