Lattice-Boltzmann Modelling of Supercritical Flows
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Autonomous access to space has been identified as a keystone need for the European Union to keep its industrial, technological and economical competitiveness in the next decades. In that sense, Europe needs to keep modernizing its space launch ecosystem, notably Vega and Ariane launchers. To do so, powerful CFD tools need to be developed in order to quickly and precisely model the most expensive part of these launchers, namely their engines. Lattice-Boltzmann Methods (LBM) have been identified as excellent candidates to overcome such a challenge, and recent developments at M2P2 prove their relevancy and competitiveness to model complex industrial reactive flows. However, given the high pressures taking place in a rocket launch system, the ideal gas Equation Of State (EOS), often used for reactive flows, is deemed inadequate. To model the non-ideal behaviour of such high-pressure fluids, Cubic EOS (CEOS) are known to be suitable. The stability of the LBM-CEOS system was therefore proved in a 2D double shear layer set-up, where conditions match the transcritical Nitrogen jet studied by Mayer et al. Furthermore, peculiar behaviours have been identified for such super- and transcritical flows, such as a pseudo-phase change. The characteristic length of this phenomenon has been reported to be smaller than the smallest turbulence scales, hence calling for the development of sub-grid thermodynamic models. Our recent progresses in the development of such models will be presented. Finally, results of Mayer’s jet configuration will be presented, the main outline being that the LBM method developed is stable and accurate for the modeling of trans- and supercritical flows.
