Lattice-Boltzmann modeling of buoyancy-driven turbulent flows

Abstract

The pressure-based hybrid lattice-Boltzmann method presented by Farag & al (Phys. Fluids 2020) is assessed for the simulation of buoyancy driven flows. The model is first validated on Rayleigh-Benard and Rayleigh-Taylor two-dimensional cases. A large-eddy simulation of a turbulent forced plume is then carried out, and results are validated against experiments. A good overall agreement is obtained, both for mean and fluctuations quantities, as well as global entertainment. The self-similarity character of the plume in the far-field is also recovered.

Large eddy simulation of fire-induced flows using Lattice-Boltzmann methods

“…A rise of the cross-stream velocity indicates an increased entrainment from the surrounding fluid which will result in a surge in the streamwise velocity following the conservation of mass. So accurate predictions of the cross-stream velocities is crucial, as in these type of flows, entertainment controls the mixing (as elaborated in a previous work [40]), which is a fundamental parameter in pool fires where the combustion process is mainly controlled by mixing (i.e., diffusion flame) as will be seen in Sec. 4.…”

“…On the other hand, Lattice Boltzmann Methods (LBM) appear as an attractive alternative to the classical Navier-Stokes solvers due to their lower computational cost, their capacities for massively parallel computing and the ease to deal with complex geometries using multi-level Cartesian grids [24]. These methods have been successfully applied to different classes of problems, including compressible flows [25][26][27][28][29][30], atmospheric flows [31][32][33][34][35], reactive flows [36][37][38][39] and, recently, to buoyancydriven flows encountered in the far field of plumes [40].…”

Energetics of buoyancy-generated turbulent flows with active scalar: pure buoyant plume

“…Such trends are reasonable as budget analysis will later reveal that buoyancy is a dominant mechanism in the Reynolds stress and dissipation is a counterpart. For species plumes, the difference can be realized through the Atwood number as high At is associated with increasing mixing in buoyancy-driven flows (Luo et al 2020;Taha et al 2022).…”