Numerical characterisation of contaminant transport and distribution in airliner cabins
Creators: name: Yan, Yihuan
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 401001
subject: Engineering design
classificationCode: 401101
subject: Air pollution modelling and control
classificationCode: 401204
subject: Computational methods in fluid flow, heat and mass transfer (incl. computational fluid dynamics)
classificationCode: 401706
subject: Numerical modelling and mechanical characterisation

description: The in-flight air quality of commercial airliners has drawn increasing attentions with the rapid annual-growth of air travellers. Contaminants inside airliner cabins could be released from multiple sources (coughing, sneezing, ozone production, etc.) and would suspend inside the cabin as particulate matters (PM). The focus of this project is to comprehensively and effectively assess the transport characteristics of particulate contaminants in airliner cabins and the corresponding infection risks of passengers. <br><br>Computational Fluid Dynamics (CFD) has been proven as a cost-efficient approach to analyse and optimise air quality in airliner cabin environments. However, the holistic simulation of airliner cabin is still absent in existing literature due to the extreme complexity of the cabin environment induced by the multi-scale, multi-coupling and non-linear transport characteristics. Theoretically, existing studies mostly relied on the Lagrangian model to depict particle transport in occupied airliner cabins due to its mechanistic coupling of air-particle interactions. Studies were mostly limited in reduced cabin section due to the factor that the Lagrangian tracking model is very time consuming and costly induced by the individual-tracking strategy. Numerically, due to the extreme complexity of the cabin environment, computational thermal manikin (CTM) models were arbitrarily simplified, causing the deficiency of passenger body features, and the passengers’ thermal effect was also eliminated. This could provide misleading information, particularly in passengers’ breathing zones, when evaluating the infection risks associated with particulate exposure. This research, however, further evaluated these overlooked factors associated with in-depth investigations and optimisation of theoretical and numerical models. By integrating mechanistic multi-phase flow models, novel manikin simplification approach and 3D dynamic characterisation of contaminant transport, a systematic and cost-efficient platform was thereby developed for comprehensive assessment of air quality and particulate contaminant transport in airliner cabins.<br><br>The main body of this thesis was composed of nine chapters. In the first two chapters, research background and comprehensive literature review were summarised in conjunction with the highlighted research gaps found in the existing literature, followed by the research methodology in Chapter 3. The main research contributions were demonstrated from chapters 4 to 8. Chapter 4 evaluated the importance of passengers’ thermal effect in densely occupied cabin environment, which were mostly overlooked in existing studies due to the complexity of cabin environment. In Chapter 5, three mathematical models (Lagrangian, drift-flux and newly proposed Eulerian-Eulerian (E-E) models) were tested and compared in terms of the reliability and efficiency. A particle source in cell (PSI-C) method based program was developed using Matlab to convert particle trajectories into concentrations. The computational thermal manikins (CTMs) were optimised and simplified using various approaches in Chapter 6. The degree/level of applied simplification approaches were found uncontrollable. As a solution, a novel and quantifiable simplification approach based on the mesh decimating algorithm was developed and tested under cabin environment in Chapter 7. Chapter 8 demonstrated a systematic assessment of contaminants transport and infection risks in a large scale cabin environment. All the major components tested in the previous chapters were integrated to achieve comprehensiveness. Unsteady flow behaviour at the aisle region of the cabin was noticed in this study and verified by the collaborator’s experimental measurement. The PSI-C based program was further optimised using Mathematica to provide smooth concentration distributions. A quantifiable approach to assess infection risks was also proposed in this chapter. All the aforementioned contributions are concluded and highlighted in Chapter 9, followed by a list of all published publications during the PhD candidature period. <br><br>This research contributed to the following outcomes: (a) A novel and quantifiable manikin simplification algorithm was developed to reduce the computational costs without sacrificing accuracy. (b) Comprehensive descriptions of inter-phase mechanisms were achieved in a cost-efficient way using E-E model to realise fast predictions of the PM concentration in airliner cabins. (c) An unique technique to convert particle trajectories to concentration was developed and optimised based on the PSI-C method. (d) A quantifiable approach to assess the infection risks in the airliner cabins was proposed. (e) A systematic platform was developed to holistically assess the infection risks in airliner cabin environment. The outcomes of this research laid an important and solid foundation for air quality optimisation and health risks assessment in other densely occupied spaces (high-speed rail, metro, etc.).