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 advection-dominated outdoor flows, we show how a Gaussian Plume Model provides a good framework to describe the mean scalar field and discuss its limitations in (wrongly) assuming a constant turbulent diffusivity. For indoor flows, we explore the balance of the advective and turbulent fluxes and their dependence on the room geometry and source position. We use our improved understanding on the scalar transport mechanism in these applications to assess the application of turbulent diffusivity models to predict scalar dispersion, highlighting the importance of carefully defining what the eddy diffusivity coefficient encompasses in different approaches.