On the dispersion of contaminants released far upwind of a cubical building for different turbulent inflows

Abstract

The effect of turbulent inflows on the transport of contaminants around a cubical building model is investigated using large-eddy simulation with the dynamic subgrid-scale eddy viscosity and eddy diffusivity models for the subgrid stress and scalar flux, respectively. Two different turbulent inflows, i.e. the synthetic turbulent inflow and the fully developed turbulent inflow, are examined in the simulations. The same concentration field is applied at the inlet for both velocity inflows. Two cases with and without the building are simulated for each inflow to examine the building effect on the dispersion of contaminants. While the simulated velocity fields from the two inflows are similar with each other upwind of the building, the concentration fields exhibit significant variations with the contaminants from the fully developed turbulent inflow case being distributed across a wider region and having significantly lower concentration compared with the synthetic turbulent inflow case. In the wake of the building the two velocity inflows result in insignificant differences among the two computed velocity fields but are shown to have a profound effect on the resulting concentration fields both in so far as mean values and statistics are concerned. The different building effects on the contaminant dispersion are caused by the different concentration fields approaching the building as a result of the different velocity inflows applied at the inlet. This work demonstrates the importance of applying proper velocity inflows at the inlet for simulating the contaminant transport in urban environments.