Numerical simulation of large scale hydrogen explosions in complex geometries

Large hydrogen air clouds represent a serious hazard during severe accident s in nuclear power plants as well as in facilities of the developing hydrog en technology. The accident scenarios are dominated by large time and lengt h scales with complicated boundary conditions. The combustion can proceed a s an accelerating turbulent flame with possibly transition to detonation. S uch problems require a careful selection of the physical and chemical model s as a fully detailed calculation is not yet feasible. An extension of the well known eddy break-up model together with the k-epsilon -model was calib rated at a large set of experiments on different scales. It was demonstrate d that this model gives good results for a large range of parameters.