Transmission of aerosols inside a moving auto rickshaw: a computational fluid dynamic study

We report a 3D Euler-Lagrangian CFD model to quantify the dispersion and transport of aerosols in a moving, semi-open auto rickshaw. The vehicle has a driver at the front, with two passengers seated behind in the rear section. This mode of transport is commonly seen in developing countries across Asia and Africa. Aerosol particles are generated due to the continuous, unmasked speaking of a passenger inside the auto rickshaw. The Eulerian portion of the model has been validated against reported experimental data on flow fields in enclosures with and without obstacles. Three RANS-based turbulence models-standard k-ε, realizable k-ε, and SST k-ω-are compared with experimental data, and the standard k-ε model is found to be the most suitable. Since the sides of the auto rickshaw are open, there is significant air exchange with the surroundings, which greatly affects the spread of aerosol particles. The presence of a partition between the driver and the passenger compartment reduces the probability of infection transmission from 1 to 0. A decrease in the auto rickshaw's speed from 60 to 20 km/h also reduces the probability of spread from 1 to 0. Additionally, a lateral wind (perpendicular or oblique to the direction of travel) further decreases the probability of transmission from 1 to 0. For all cases, the face velocity for all passengers is computed. The state of dispersion is significantly influenced by the location of aerosol generation. The relative importance of the different scenarios studied is quantified. Finally, a set of recommendations is outlined and compared with those reported for other modes of public transport.