Numerical investigation of thermal hazards from under-expanded hydrogen jet fires using a new scheme for the angular discretization of radiative intensity

In the context of a numerical investigation of thermal hazards from two under-expanded hydrogen jet fires, results from a newly-developed thermal radiation module of the ADREA-HF computational fluid dynamics (CFD) code were validated against two physical experiments. The first experiment was a vertical under-expanded hydrogen jet fire at 170 bar, with the objective of the numerical investigation being to capture the spatial distribution of the radial radiative heat flux at a given time instant. In the second case, a horizontal under-expanded hydrogen jet fire at 340 bar was considered. Here, the objective was to capture the temporal evolution of the radial radiative heat flux at selected fixed points in space. The numerical study employs the eddy dissipation model for combustion and the finite volume method (FVM) for the calculation of the radiative intensity. The FVM was implemented using a novel angular discretization scheme. By dividing the unit sphere into an arbitrary number of exactly equal angular control volumes, this new scheme allows for more flexibility and efficiency. A demonstration of numerical convergence as a function the number of both spatial and angular control volumes was performed.