A study on the validity of the Lattice Boltzmann Method as a way to simulate high Reynolds number flows past porous obstacles.

With ever growing levels of urbanisation across the globe, a good understanding of canopy flows is paramount to reduce pollution in major cities and prevent unwanted aerodynamic loading on structures. The multi-scale nature of not only urban construction but that of natural environments requires a more complex modelling system be employed. Fractal geometries have only recently been investigated in turbulent flows, their multi-scale properties make them the logical choice for modelling and simulating flows involving such complex geometries. Additionally, in recent years the usage of Lattice Boltzmann Methods (LBM) vs Computational Fluid Dynamics (CFD) has increased, since LBM offers better computational efficiency and speed over CFD. However, the shortcomings of LBM still need to be benchmarked since macroscopic quantities of the flow are extracted using a probabilistic model of the flow at microscopic scales.
A plan to investigate turbulent flows over a fractal and non-fractal obstacles has been presented by implementing a LBM numerical analysis over a range of Reynolds numbers (100-49410). The suitability of LBM's multiple dynamics models including: Bhatnagar Gross Krook (BGK), Multiple Relaxation Time (MRT) and Regularised Lattice Boltzmann (RLB) have been studied for high reynolds number cases. Results from LBM cases were compared to available experimental data and published literature, although, results of fractal cases were not mesh independent compelling agreement between all three tested obstacles show a significant validation of LBM as tool to investigate high Reynolds number flows.