Meshing effects on CFD modelling of atmospheric flow over buildings situated on ground with high terrain

Abstract

A Computational Fluid Dynamics (CFD) study was carried out on the wind environment and vehicle pollution dispersion from a newly built by-pass adjacent to the Whatman International site in Maidstone, UK. The site buildings are sited on ground incorporating an area of high terrain, accordingly they were modelled using Geographical Information System (GIS). The site contains a substantial number of trees of differing species which were extensively surveyed and modeled using a simple 2D momentum sink dependent on the tree Leaf Area Density (LAD). One of the important factors which has a significant effect on CFD results is the computational mesh. The purpose of this paper is to investigate the effects of using different mesh approaches for both easterly and southerly wind scenarios and the results are compared with that of field measurements taken at the site which include the CO concentration and wind velocity. The CFD results showed that the hexahedral mesh delivers a higher level of agreement with field measurements than the tetrahedral dominant mesh and this is mainly due to the higher truncation error in the tetrahedral cell type. It was also found that the tetrahedral dominant mesh can be significantly improved by applying different numerical solving techniques such as the Node-based gradient solver.