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

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

3. 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

4. SPH
Interpolation theory
Kernel function

5. 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.

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

7. Free field 1kg of TNT

8. 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

9. Density and pressure

10. Density animation

11. Pressure and velocity sensors measurements

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

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

14. Empirical formulas
Skjeltorp et al.
Helseth
Kingery and Gion

15. Exterior pressure distribution

16. 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.

17. 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.