Simulation of stratified flows over a ridge using a lattice Boltzmann model
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Simulation of stratified flows over a ridge using a lattice Boltzmann model Yansen Wang1 · Benjamin T. MacCall1 · Christopher M. Hocut1 · Xiping Zeng1 · Harindra J. S. Fernando2
Received: 27 December 2016 / Accepted: 7 May 2018 © The Author(s) 2018
Abstract A three-dimensional thermal lattice Boltzmann model (TLBM) using multirelaxation 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. Keywords Thermal lattice Boltzmann method · Stratified flow over a ridge · Atmospheric boundary layer · Large-eddy simulation
* Yansen Wang [email protected] 1
US Army Research Laboratory, RDRL-CIE-M, US Army Research Laboratory, Adelphi, MD 20783, USA
2
Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
13
Environ Fluid Mech
1 Introduction The Lattice Boltzmann method (LBM) has been developed in recent years as an effective computational fluid dynamics (CFD) tool for fluid flow modeling. Unlike traditional CFD methods, such as finite-volume or finite-element methods, which discretize the Navier–Stokes (NS) equations in a macroscopic continuum, the LBM is a mesoscopic kinetic method based on statistical mechanics [1–4]. The LBM solves the Boltzmann equation for a particle at each grid point by performing collision and propagation calculations of the particle’s probability distribution function (PDF) over a discrete lattice mesh with certain fixed directions. Using the principles of statistical mechanics, the macroscopic flow properties such as mass, velocity, and momentum fluxes are computed from the statistical moments of the particle’s PDF. There are several advantages of the L
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