CFD Simulation of Aerosol and Odor Gas Transport Dynamics in Shipboard Underwater Lavatories

The underwater lavatories aboard ships are compact and suffer from inadequate ventilation, thereby increasing the likelihood of infection and odor issues. The crew will endure discomfort from the poor air quality within the lavatories, especially following prolonged travel. This study establishes a three-dimensional numerical model of an underwater lavatory unit, employing computational fluid dynamics (CFD) to assess ventilation performance and contaminant distributions. The concentration of odor gas and the fate of particles within the lavatory were evaluated for a duration of 3 min subsequent to flushing, considering two scenarios: occupants using either the toilet or the urinal. Additionally, the exhaust air volume and the layouts of the lavatory vents were optimized. The results indicate that the individual using the toilet has a lower concentration of ammonia inhalation, and both scenarios remain unaffected by odors within 60 s after flushing. In contrast to the scenario of using the toilet, the case of using the urinal poses notably fewer risks of human contact, with 65.7% of the deposited particles residing on the urinal surfaces and a mere 8.9% adhering to the manikin surfaces. Enhancing the exhaust air volume can facilitate odor removal in the urinal scenario while slightly improving odor control in the case of using the toilet. An airflow rate of 250 m3/h resulted in a 40% increase in particle deposition within the urinal and a roughly 70% decrease on the manikin during the toileting scenario. The existing ship lavatory ventilation is insufficient to manage the risk of aerosol exposure and sense of smell in the breathing zone of standing crew. The air quality within a lavatory can be significantly improved by employing upper air-supply and lower air-exhaust ventilation.