Application of turbulent diffusivity models to point-source dispersion in outdoor and indoor flows

The modelling and prediction of scalar transport in turbulent flows is crucial for many environmental and industrial flows. We discuss the key findings of our experimental campaigns which focus on two relevant applications: the scalar dispersion of a ground-level point-source in (1) a smooth-wall turbulent boundary layer flow and (2) a supply-ventilated empty room model. For flows dominated by mean advection, including many outdoor flows, we show how the Gaussian Plume Model provides a good framework to describe the mean scalar field and discuss its limitations in assuming an isotropic and homogeneous turbulent diffusivity. For indoor flows, we explore the balance of the advective and turbulent fluxes and their dependence on the near-source flow field. We use our improved understanding on the scalar transport mechanism in these applications to assess the application of the Eddy Diffusion Model to predict indoor scalar dispersion, and highlight the importance of carefully defining what the turbulent diffusivity coefficient encompasses in different approaches.