3 years ago

Discrete Boltzmann trans-scale modeling of high-speed compressible flows.

Guangcai Zhang, Sauro Succi, Yudong Zhang, Yanbiao Gan, Aiguo Xu

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 nonequilibrium effects (TNE) and estimate the condition under which the DBMs at various levles should be used, two novel measures are presented: (i) the relative TNE strength, describing the relative strength of the (N + 1)-th order TNE to the N-th order one; (ii) the TNE discrepancy between DBM simulation and relevant theoretical analysis. Whether or not the higher-order TNE 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 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.

Publisher URL: http://arxiv.org/abs/1801.04522

DOI: arXiv:1801.04522v1

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