2018/01/31 by Yanbiao Gan, Aiguo Xu, Guangcai Zhang +2 · 1 citation
Physics and Astronomy · #physics.flu-dyn #physics.comp-ph
paper · pdf · doi:10.1103/physreve.97.053312
published as Phys. Rev. E 97, 053312 (2018) · Accepted for publication in Physical Review E
arxiv created 2018/05/11 · arxiv updated 2018/06/06
We present a general framework for constructing trans-scale discrete Boltzmann models (DBMs) for high-speed compressible flows ranging from continuum to transition regime. This is achieved by designing a higher-order discrete equilibrium distribution function which satisfies additional nonhydrodynamic kinetic moments. In order to characterize the % thermodynamic non-equilibrium (TNE) effects and estimate the condition under which the DBMs at various levels should be used, two novel measures are presented: (i) the relative TNE strength, describing the relative strength of the (N+1)-th order TNE effects to the N-th order one; (ii) the TNE discrepancy between DBM simulation and relevant theoretical analysis. Whether or not the higher-order TNE effects should be taken into account in the modeling and which level of DBM should be adopted, is best described by the relative TNE intensity and/or the discrepancy, rather than by the value of the Knudsen number. As a model example, a two-dimensional DBM with 26 discrete velocities at Burnett level is formulated, verified, and validated.