Coupling of a scalar dispersion and an urban canyon energy budget model

The development of SCAM, a three-dimensional numerical model for the prediction of airflow and scalar dispersion in urban canyons, has been described [3]. The first application of SCAM [4] was to study the dispersion of carbon monoxide emanating from car exhausts, but the long term aim has been to develop an urban canyon energy exchange model. In this quest, SCAM represents a facility which is capable of simulating the advection and turbulent diffusion of any scalar and hence can be applied to the convective transfer of heat, provided buoyancy is ignored. In order to achieve the long term aim, SCAM must be coupled with an energy budget model which simulates the heating and cooling of the urban fabric under the full range of atmospheric environments experienced during any 24 hour period at any given location. A building facet energy budget model for an idealised building group already exists [2]. This model is based on a radiation budget model [I] which has been used by the climatological research community. This paper reports on the work achieved thus far in linking the two models. The initial formulation is two-dimensional, for clear skies and for a dry system. The crucial linkage between the models occurs at surface boundaries and the heat fluxes at these points are checked with respect to physical plausibility.