Lattice-Boltzmann Large Eddy Simulation Solver for Atmospheric Transport and Dispersion Applications

Abstract

Accurate prediction of metropolitan climate conditions is essential for public health

and national security, directly influencing commercial, environmental, social, and political activity. High-fidelity dispersion modelling therefore has broad utility, including risk assessment, urban planning, emergency response, and sustainable city management. However, urban morphologies are highly heterogeneous, producing inherently unsteady wind fields with turbulent processes spanning wide spatial and temporal scales. Consequently, industrial-scale simulations involve many degrees of freedom, making prognostic modelling demanding.

This thesis presents a wall-modelled large eddy simulation solver for

atmospheric transport and dispersion in urban environments at grid resolutions of 1–10m. A hybrid method is considered, wherein the hydrodynamics are modelled using a D3Q27 cumulant lattice Boltzmann method (LBM), while passive scalar transport is modelled via the MUSCL-Hancock finite volume scheme.

Following a brief literature review and introduction of the numerical methods, this work systematically the spectral bandwidth of various cumulant LBM-LES formulations, and wall-modelling techniques. The fully integrated solver is then applied to validation cases in both idealised urban environments using the Mock Urban Setting Test database and real-world geometries using the Joint URBAN 2003 database for downtown Oklahoma City.

Results show that the WMLES solver predictions are in good agreement with experimental data, exceeding industry-standard performance criteria. In the idealised urban canopy, velocity predictions achieve FAC1.3 accuracy. Concentration statistics exhibit larger deviations but remain within experimental uncertainty. For downtown Oklahoma City, the solver retains strong predictive capability in real urban conditions; although formal accuracy is slightly below FAC1.3 despite minor geometric discrepancies, it remains above the industry-standard FAC2 threshold.