Thermal Effects on Dispersion about Structures

Computational fluid dynamics (CFD) models are being increasingly used to predict fine scale features of dispersion in an urban environment. It is well known that thermal effects can impact the flow around and within structures. This study examines the impact of including thermal effects in flow calculations about a building. The modeling couples thermal radiation, conduction, and convection effects with a CFD model of both the interior and exterior of a building. The emphasis here is on the exterior flow about the building and its effect on dispersion of a contaminant released in the vicinity.

The thermal modeling includes a diurnal cycle of solar radiation and includes view factors to compute shading of portions of the building. Conduction varies with material properties. The building modeled is complicated and includes passive solar Trombe walls. There is coupling between convective cooling of surfaces and thermally induced convection within and around the building. Careful comparisons of computations with and without heating demonstrate the differences that would be expected in dispersion computations that arise due to the influence of heat transfer. The technology developed here could be used to delineate differences due to heat transfer effects on dispersion within an urban setting.