Towards sodium combustion modeling with liquid water

Solid and liquid sodium combustion with liquid water occurs through a thin gas layer where exothermic reactions happen with sodium and water vapors. It thus involves multiple interfaces separating liquid and gas in the presence of surface tension, phase transition, heat and mass diffusion as well as surface reactions. The gas phase reaction involves compressible effects resulting in possible shock wave appearance in both gas and liquid phases. To understand and predict the complexity of sodium combustion with water a diffuse interface flow model is built. This formulation enables flow resolution in multidimension in the presence of complex motion, such as for example Leidenfrost-type thermo-chemical flow. More precisely sodium drop autonomous motion on the liquid surface is computed. Various modeling and numerical issues are present and addressed in the present contribution. Explosion phenomenon is addressed in this paper and is reproduced at least qualitatively thanks to additional ingredients such as turbulent mixing of sodium and water vapors in the gas film and delayed ignition modeled through finite rate chemistry. Shock wave emission from the thermo-chemical Leidenfrost-type flow is observed as well as liquid sodium ejection off the water surface, as reported in related experiments.