Simulations of flow around a cubical building: comparison with towing-tankdata and assessment of radiatively induced thermal effects

A three-dimensional (3-D) computational fluid dynamics (CFD) model, coupled with a meteorological radiation and surface physics package, is used to mo del the mean flow field and tracer dispersion in the vicinity of an idealiz ed cubical building. We first compare the simulations with earlier numerica l studies as well as towing-tank laboratory experiments, where radiation ef fects were not included. Our simulations capture most of the features revea led by the towing-tank data, including the variation of the flow reattachme nt point as a function of Froude number and the induction of a prominent le e wave in the low Froude number regime. The simulated tracer concentration also compares very favorably with the data. We then assess the thermal effects due to radiative heating on the ground a nd building including shading by the building, on the mean flow and tracer dispersion. Our simulations show that convergence within and beyond the cav ity zone causes a substantial lofting of the air mass downstream from the b uilding. This lofting results from the combination of thermal heating of th e ground and building roof, and vortex circulation associated with the hors eshoe eddy along the lateral sides of the building. The specific effect of shading on the flow field is isolated by comparing simulations for which th e radiative heating and shading patterns are kept constant, but the environ mental wind direction is altered. It is found that the shading exerts local cooling, which can be combined into the overall thermodynamic interaction, described above, to effectively alter the circulation downstream from the building. (C) 2001 Elsevier Science Ltd. All rights reserved.