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[FAQ]

You can model explosives in AUTODYN in two ways, JWL EOS or Ideal Gas EOS. If the detonation of explosives is one of the key factors that affect the simulation results, for example, shaped charge simulations or EFP simulations, JWL EOS is usually used to model the explosives. You need to define a detonation point/line/surface to initiate the explosives, usually in Euler-Multi-Material solver. When the propagation of explosive detonation wave is not very important, Euler-Ideal Gas solver can be used to model the explosives. You need to fill the space that the explosive takes with the explosive’s density and specific internal energy. For the typical explosive: TNT, the density is 1.63g/cm3 and energy is 3681000J/Kg in the system of units “mm/mg/ms”. When the explosive gas product has undergone substantial expansion in volume, Euler-Ideal Gas solver can be used to model the expansion of the explosive gas product. Euler-Multi-material solver is used to simulate the initial detonation and expansion of explosive in axial-symmetric analyses and then remapping is used to remap the blast field to 3D Euler-Ideal Gas space to simulate the subsequent expansion. Euler-Ideal Gas solver runs faster than Euler-Multi-Material solver. Unlike Euler-Multi-Material solver, Euler-Ideal Gas solver can be decomposed into many subdomains so parallel processing can be done more efficiently. The typical application when Euler-Ideal Gas solver is used to model explosives is blast/structure interaction. To have consistent results between JWL and Ideal Gas EOS, the total mass and total internal energy of the explosive have to be exactly the same in both JWL and Ideal Gas models. To find the mass, volume, momentum, and energy summary per material or per part, you can run your models for one cycle and then open the print file “ident.prt” to view the material or part summary. The .prt file is in the same data directory as the model files (.ad files). The following papers show the comparsion of the explosive pressure field between AUTODYN Euler-Ideal Gas solver and analytical and experimental results. They are in good agreement. This should justify the approach of AUTODYN Euler-Ideal Gas EOS for explosives. There are more papers in our web site to download if you want to see more applications on this topic. Greg E Fairlie, Efficient Analysis of High Explosive Air Blast in Complex Urban Geometries Using the AUTODYN-2D & 3D Hydrocodes, Analytical and Experimental Methods. 15th Int. Symposium on the Military Aspects of Blast and Shock, 14-19 September 1997, Banff, Canada. TC Chapman, TA Rose, and PD Smith, Blast wave simulation using AUTODYN 2D: a parametric study. International Journal of Impact Engineering, vol 16, no 5/6, pp 777-787, 1995.