Abstract
A three-dimensional thermal lattice Boltzmann model (TLBM) using multi-relaxation time method was used to simulate stratified atmospheric flows over a ridge. The main objective was to study the efficacy of this method for turbulent flows in the atmospheric boundary layer, complex terrain flows in particular. The simulation results were compared with results obtained using a traditional finite difference method based on the Navier–Stokes equations and with previous laboratory results on stably stratified flows over an isolated ridge. The initial density profile is neutral stratification in the boundary layer, topped with a stable cap and stable stratification aloft. The TLBM simulations produced waves, rotors, and hydraulic jumps in the lee side of the ridge for stably stratified flows, depending on the governing stability parameters. The Smagorinsky turbulence parameterization produced typical turbulence spectra for the velocity components at the lee side of the ridge, and the turbulent flow characteristics of varied stratifications were also analyzed. The comparison of TLBM simulations with other numerical simulations and laboratory studies indicated that TLBM is a viable method for numerical modeling of stratified atmospheric flows. To our knowledge, this is the first TLBM simulation of stratified atmospheric flow over a ridge. The details of the TLBM, its implementation of complex boundaries and the subgrid turbulence parameterizations used in this study are also described in this article.
Highlights
The Lattice Boltzmann method (LBM) has been developed in recent years as an effective computational fluid dynamics (CFD) tool for fluid flow modeling
As in any other atmospheric numerical model, the thermal lattice Boltzmann model (TLBM) simulation results and the actual flow have to go through a scale transformation
A novel large-eddy simulation model is being developed at the Army Research Laboratory for simulating atmospheric flows based on the lattice Boltzmann method
Summary
The Lattice Boltzmann method (LBM) has been developed in recent years as an effective computational fluid dynamics (CFD) tool for fluid flow modeling. There are several advantages of the LBM over traditional CFD (finite-volume and finite-difference) methods that solve NS equations, including the simplicities in code development, in implementation of complex boundary conditions, and intrinsic parallelism [1,2,3,4]. There are many publications that detail further developments of LBM such as the reduction of compressibility effects [11,12,13,14], the implementation of boundary conditions [15,16,17,18], turbulent flow simulations [19,20,21,22], energy and mass transport, multiphase flow [23,24,25,26], and in parallel computation using graphical processing unit (GPU) [27, 28]. A detailed review of the literature, including historical and recent developments in LBM, can be found in [1,2,3,4], with abundant citations
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