Study of an oct-tree based Monte Carlo algorithm for gas radiative transfer in complex geometries

International audienceIn this work, we study quantitatively the efficiency of a Monte Carlo technique using a space partitioning recursive oct-tree algorithm applied to radiative transfer calculations. The obstacles are embedded in finer parallelepipedic volumes than the free space left for photon propagation. This enables faster propagation of the photons inside the obstacle-free space but, for absorbing media, this does not allow the progressive deposit of the absorbed energy in each crossed cell. Three algorithms have been implemented for general geometries together with fast intersection methods. Comparisons for a complex geometry are made first for hypothetical gray media to assess clearly the effects of optical thickness and then for an electric discharge-like air plasma at local chemical and thermal equilibrium using a global spectral model. When compared to standard forward and energy partitioning approach, the oct-tree algorithm is shown to reduce the CPU time for wall flux calculations but not for radiative volumetric powers at equivalent statistical convergence