A Diffusion-Inertia Model for the simulation of particulate pollutants dynamics inside a car cabin

Abstract

Simulations of particle pollutants dynamics inside a car cabin were performed using the Diffusion-Inertia Model (DIM) coupled to the RANS (Reynolds-averaged Navier–Stokes equations) k−ω SST turbulence model for single-phase flow. The DIM model has been implemented in a commercial CFD solver and then validated on some reference flow configurations. The validation included particle dispersion in ventilated chambers of one and two compartments, particle deposition in circular 90°bends, and particle-laden jet flow. The DIM model has shown interesting capabilities in taking into account various transport mechanisms such as the transport by the mean flow, gravitational settling, centrifugal effect due to flow streamline curvatures, molecular and turbulent diffusion, and also turbophoresis transport mechanism due to turbulent energy gradients. Moreover, the application of the DIM model to the simulation of solid particles, characterizing particulate pollutants, has revealed characteristic dynamics that is mainly determined by the airflow topology, particularly for ultrafine and fine particles (0.1, 1 and 2.5μm). Inertial effects were found to become significant only for coarse particles (5 and 10μm), as the impact of gravitational and centrifugal effects gradually becomes more noticeable. Furthermore, the risk of exposure to high levels of particulate pollutants has been clearly established when considering the presence of occupants inside the vehicle cabin. These concentration levels are linked in particular to the complex interaction between occupants’ heads and the internal flow, as well as to the tendency of particles to accumulate in the upper part of the cabin and to the rapid homogenization observed throughout the whole interior volume.