Hybrid lattice Boltzmann model for atmospheric flows under anelastic approximation

Abstract

Lattice Boltzmann (LB) method for atmospheric dynamics is developed by considering the characteristics of the anelastic approximation. After introducing reference base state values in atmospheric flows, an LB model, with an external force term, has been constructed in anelastic framework. In the proposed anelastic LB model, mass and momentum conservation equations are solved by the LB method with a regularization procedure, and temperature field or scalar transport is simulated by finite volume method. The derived macroscopic governing equations from the anelastic model are analyzed and discussed in Chapman–Enskog asymptotic expansion. The anelastic LB model is assessed considering three benchmarks including a non-hydrostatic atmospheric inviscid convection, two-dimensional density currents, and inertia-gravity waves in stably stratified atmospheric layer. The validations demonstrate that the anelastic extension of the LB method can simulate atmospheric flows effectively and accurately. Besides, the proposed model offers a unified framework for both Boussinesq approximation and anelastic approximation, which is largely free of characteristic depth of atmospheric flows.