Yihuan Yan

Effects of passenger thermal plume on the transport and distribution characteristics of airborne particles in an airliner cabin section

Computational fluid dynamics simulations were conducted in this study to investigate the effects of the buoyancy-driven thermal plume on the airflow pattern and transport characteristics of airborne particles in airliner cabins. A cabin section containing three seats and three passengers was built and numerical simulations were conducted using thermal and isothermal conditions, respectively. Airborne particles were assumed to be released by the passengers through coughing. The predicted airflow field was validated using experimental data available in the literature. Comparison of the computational results revealed that the thermal plume significantly changed both the airflow filed and the trajectories of particle transport. In addition, the spatial distribution characteristics of the particles and their residence time in the passengers’ breathing zones were highly sensitive to the location of released particles. Comparatively, the particles released by the passenger seated close to the window may have the highest health risk to other two passengers.

Effects of manikin model simplification on CFD predictions of thermal flow field around human bodies

Simplified computational thermal manikins are beneficial to the computational efficiency of computational fluid dynamics simulations. However, the criterion of how to simplify a computational thermal manikin is still absent. In this study, three simplified computational thermal manikins (CTMs 2, 3 and 4) were rebuilt based on a detailed 3D scanned manikin (CTM 1) using different simplification approaches. Computational fluid dynamics computations of the human thermal plume in a quiescent indoor environment were conducted. The predicted airflow field using CTM 1 agreed well with the experimental observations from the literature. Although the simplified computational thermal manikins did not significantly affect the airflow predictions in the bulk regions, they strongly influenced the predicted airflow patterns near the computational thermal manikins. The predictive error of the computational thermal manikin was strongly related to the simplification approach. The computational thermal manikins generated from the surface-smoothing approach (CTM 2) was very close to CTM 1, while the required mesh elements for a stable numerical solution dropped by over 75%. Comparatively, the predictive errors of CTMs 3 and 4 were considerable in the near-body regions. This study has illustrated the importance of keeping the key body features when simplifying a computational thermal manikin. The surface-smoothing-based simplification method was shown to be a promising approach.

Modelling of evaporation of cough droplets in inhomogeneous humidity fields using the multi-component Eulerian-Lagrangian approach

Abstract This study employed a multi-component Eulerian-Lagrangian approach to model the evaporation and dispersion of cough droplets in quiescent air. The approach is featured with a continuity equation being explicitly solved for water vapor, which allows comprehensively considering the effects of inhomogeneous humidity field on droplets evaporation and movement. The computational fluid dynamics (CFD) computations based on the approach achieved a satisfactory agreement with the theoretical models reported in the literature. The results demonstrated that the evaporation-generated vapor and super-saturated wet air exhaled from the respiratory tracks forms a “vapor plume” in front of the respiratory track opening, which, despite the short life time, significantly impedes the evaporation of the droplets captured in it. The study also revealed that due to the droplet size reduction induced by evaporation, both the number density of airborne droplets and mass concentration of inhalable pathogens remarkably increased, which can result in a higher risk of infection. Parametric studies were finally conducted to evaluate the factors affecting droplet evaporation. Summary The study demonstrated the importance of considering inhomogeneous humidity field when modelling the evaporation and dispersion of cough droplets. The multi-component Eulerian-Lagrangian model presented in this study provides a comprehensive approach to address different influential factors in a wide parametric range, which will enhance the assessment of the health risks associated with droplet exposure.

Effects of cough-jet on airflow and contaminant transport in an airliner cabin section

The goals of this study were to investigate the effect of cough-jet on local airflow and contaminant transport in a typical cabin environment by using computational fluid dynamics. A fully occupied...