A Eulerian-Lagrangian approach for the non-isothermal and transient CFD analysis of the aerosol airborne dispersion in a car cabin

Car cabin micro-environment represents a potential hotspot for transmission of respiratory infections related to possible high concentration levels of viruses and bacteria and to reduced social distance between occupants. Since Heating, Ventilation and Air Conditioning (HVAC) system in a vehicle influences velocity and temperature fields, the position of inlet air vents, the air flow rate entering the car cabin, the air recirculation, the passenger number and location etc. highly influence the thermal comfort and potential health risks for occupants. In this paper, a Eulerian-Lagrangian model is adopted to numerically analyse transient non-isothermal aerosol airborne dispersion in a passenger car cabin. Numerical results are validated against PIV measurements and the performances of different turbulence models are analysed. The validated numerical model is applied to the simulation of aerosol droplets emitted by a contagious subject in a car cabin during a 15-min journey. Two occupants are present in the car cabin and different scenarios for the ventilation system and the occupant position are investigated. The aim of the present paper is to provide a properly validated numerical tool that can be applied on one side to the assessment of thermal comfort of occupants and, on the other side, to the analysis of potential infection risk with aerosol transmissible pathogens (e.g. SARS-CoV-2 virus) during short journeys.