Evaporation Boundary Conditions for the R13 Equations of Rarefied Gas Dynamics




Struchtrup, Henning
Beckmann, Alexander
Rana, Anirudh Singh
Frezzotti, Aldo

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Physics of Fluids


The regularized 13 moment equations (R13) are a macroscopic model for the description of rarefied gas flows in the transition regime. The equations have been shown to give meaningful results for Knudsen numbers up to about 0.5. Here, their range of applicability is extended by deriving and testing boundary conditions for evaporating and condensing interfaces. The macroscopic interface conditions are derived from the microscopic interface conditions of kinetic theory. Tests include evaporation into a half-space, and evaporation/condensation of a vapor between two liquid surfaces of different temperatures. Comparison indicates that overall the R13 equations agree better with microscopic solutions than classical hydrodynamics.




Henning Struchtrup, Alexander Beckmann, Anirudh Singh Rana, and Aldo Frezzotti. Evaporation boundary conditions for the R13 equations of rarefied gas dynamics. Physics of Fluids 29 092004 (2017).