Impacts of solid wall boundary conditions in the lattice Boltzmann method on turbulent outdoor flow: A case study of a single 1:1:2 building model

Abstract

Solid wall boundary condition is an important topic in outdoor wind environment simulation represented by single building based on lattice Boltzmann method (LBM), but there is a lack of quantitative comparative analysis of simulation results under these boundary conditions. This paper conducted LBM-based large-eddy simulation (LBM-LES) of turbulent flow around a 1:1:2 single building, applying both half-way bounce-back and interpolation-based bounce-back (the Bouzidi–Firdaouss–Lallemand scheme, BFL) to solid wall boundaries. The simulation accuracy of different solid wall boundary conditions was examed with consideration of grid resolutions and relative positions between grid points and solid boundaries. Data obtained via experiments and the finite volume method-based large-eddy simulation (FVM-LES) technique were used to examine the flow structure and distribution of the time-averaged velocity and turbulent kinetic energy (TKE). The computational costs were also discussed. Results demonstrated that when the all the boundaries fell on the grid and orthogonal to the grid, the half-way bounce-back scheme attained a high accuracy. On the contrary, the BFL scheme achieved a higher accuracy if the solid wall boundaries did not fall on the grid. Under both boundary schemes, the grid resolutions of b/32 and b/16 (b: building width) could satisfy the acceptable range, but the b/32 grid resolution facilitated a better performance near the wall. The BFL scheme was more sensitive to the grid resolution and the accuracy improved faster with increasing grid resolution than half-way. As for the calculation costs, the calculation time of BFL is more than twice that of half-way bounce-back. However, BFL is still recommended if the wall boundaries are curved and complex in the actual built environment.