Quantifying the effect of natural ventilation on post-occupancy aerosol exposure in a cruise ship cabin

Most studies on airborne transmission in transportation systems have focused on exposure during the simultaneous presence of infectors and susceptible occupants, whereas the transport mechanisms of residual aerosols after the infector departs remain insufficiently understood. This study employed validated computational fluid dynamics (CFD) simulations to investigate the temporal evolution of aerosol concentrations in a cruise ship cabin during and after the presence of an infector, under varying ambient wind directions and natural ventilation configurations. Results show that ambient pressure distribution governs aerosol removal by reorganizing cabin airflow. Under recirculating air-conditioning ventilation, a closed longitudinal circulation continuously redistributes aerosols without forming an effective exhaust pathway, resulting in rapid aerosol accumulation to 4381 ppm after 10 min. In contrast, natural ventilation establishes pressure-driven through-flow transport. Against-wind conditions produce a longitudinal transport pathway, whereas side wind generates a transverse cross-cabin pathway that accelerates aerosol removal. Accordingly, the air change rate increases from 23.39–104.38 h−1 under against-wind conditions to 61.78–333.65 h−1 under side-wind conditions. Furthermore, ventilation effectiveness is governed primarily by the organization of transport pathways rather than the area of ventilation openings. The frontal opening may disrupt the pressure-driven transport pathway by introducing an opposing inflow. These findings reveal how natural ventilation controls aerosol transport in moving enclosures and provide a generalized framework for ventilation design.