Simulation of the Effects of an Air Blast Wave - ELSA - Europa

lengthExplosiveopeningxd pyrad ex,in d ex,endd air,ind air,endFigure 19: 3D simplified model with hexahedrons or tetrahedronsAlternatively four tetrahedral elements can be used instead of one hexahedral element. This resultsin a higher number of elements. The meshing can be done with scripts that convert the hexahedronsin tetrahedrons. These scripts are presented in [7]. The script pxhex2te converts the hexahedrons intetrahedrons; the script pxqua2tr converts the quadrangles to triangles (necessary for the surfaces).For the simulation a model is used which has in most cases a TNT charge of a volume of 8000 cm 3 ,accordingly a cube of 20 x 20 x 20 cm or a sphere with radius of 12.4 cm. The mass of this chargeis 12.8 kg. An ALE-calculation is used for all further investigations. The explosive is build as anEulerian mesh, the air is build as an ALE mesh.The symmetry at the surfaces can be considered by defining symmetry planes with the CONTSPLA AUTO command. This command defines symmetry conditions orthogonal to the surface ofthe defined nodes. Another possibility is the definition with the FSR-command as a sliding surface.Both methods give the same results.The calculations performed with the conical model are summarized in Table 4 and shortly describedhereafter.30