Evaluation of aircraft cabin ventilation through inlet/outlet modifications: a computational study of airflow and contaminant dispersion in a generic scaled-down empty aircraft cabin

The safety of air quality inside aircraft cabins, despite modern ventilation systems, remains ambiguous. This has increased uncertainty regarding personal safety among aircraft passengers, especially in the context of airborne contaminant transmission. To better understand and manage this issue, Computational Fluid Dynamics (CFD) is applied as it is a powerful tool for analysing complex airflow behaviours and predicting contaminant transport in enclosed spaces such as aircraft cabins. However, there are still critical gaps in the understanding of how different ventilation parameters affect airflow and contaminant dispersion. Therefore, this study addresses these critical gaps in understanding aircraft cabin ventilation systems through CFD to evaluate the performance of an aircraft cabin ventilation system. Specifically, the aim is to investigate the accuracy of turbulence models, the effect of the ratio of the inlet to outlet height on the air distribution and characteristics of the flow, the ventilation performance and contaminant dispersion mechanisms of the different types of mixing ventilation systems in a scaled-down generic empty aircraft cabin. The simulation is performed in Open Field Operation and Manipulation (OpenFOAM) version 2106, while the computational domain presents a commercial single-aisle aircraft cabin on a 1:11 scale. It was found that the Launder Sharma Low Reynolds Number turbulence model gives the best flow prediction. By examining different inlet-outlet configurations and ventilation systems, the inlet size significantly influences velocity distribution and flow characteristics. The sidewall mixing ventilation system (SV) performed best in delivering fresh air to the aircraft cabin, followed by ceiling mixing (CV) and combined ceiling-sidewall (CSV) configurations. The study revealed that among the CSV configurations, the ceiling-sidewall configurations with a volume flow rate of 40% ceiling and 60% sidewall inlets, CSV1, are the most effective in delivering fresh air across the cabin. The air change effectiveness (ACE) also shows that SV exhibits superior performance. The location of the contaminant source significantly influences dispersion patterns, with CSV1 showing the best containment for Case 1 (passenger standing in the aisle) and SV for Case 2 (seated passenger). Quantitative analysis of contaminant removal effectiveness (CRE) reveals higher CRE in Case 1, which is 1.15–1.79 with CSV1 at 1.79, while Case 2 has a lower CRE value of 0.65–1.0, with SV performing relatively better due to younger local air ages. Local air age directly correlates with a spatial distribution, which would affect passenger exposure risks. The SV ventilation system is a suitable configuration to remove the contaminants effectively for both cases. This research enhances the CFD method through comprehensive validation of turbulence models and evaluation of the ventilation system performance. The research provides validated simulation guidelines for OpenFOAM, enhances the understanding of mechanisms of airflow in aircraft cabins, and contributes to the safety of passengers by improving contaminant transport analysis. These findings are applicable not only to aircraft but also to other high-density transportation environments.