Numerical studies of indoor particulate and gaseous micropollutant transport and its impact on human health in densely-occupied spaces.

Micropollutants (MPs) have increasingly become a matter of concern owing to potential health risks associated with human inhalation exposure, particularly in densely-occupied indoor environments. This study employed numerical simulations in a traditional built indoor workspace and a public transport cabin to elucidate the transport dynamics and health impacts of particulate and gaseous type of indoor MPs on varying groups of occupants. The risk of infection from pathogen-bearing MPs was evaluated in the workspace using the integrated Eulerian-Lagrangian and modified Wells-Riley model.

Semi-surrogate modelling of droplets evaporation process via XGBoost integrated CFD simulations.

The applications of machine learning (ML) based approach are emerging as possible tools to accelerate CFD simulations. This study proposed a semi-surrogate model for CFD with integration of the cutting-edge ML algorithm, eXtreme Gradient Boosting (XGB), which enlightened a possible pathway to effectively and efficiently solve and predict those costly but highly repetitive fluid dynamics-related problems. Droplet evaporation, a complex but essential phenomenon in respiratory droplets transport, was studied as the practical case using the proposed model.

A spatiotemporal assessment of occupants' infection risks in a multi-occupants space using modified Wells-Riley model.

Escalating demands of assessing airborne disease infection risks had been awakened from ongoing pandemics. An inhalation index linked to biomedical characteristics of pathogens (e.g.

Analysis of occupants' exposure risk of cough-expelled droplets in the workspace with various mixing ventilation layouts.

This study numerically investigated the transport characteristics of the cough-expelled droplets and their corresponding exposure risk of each occupant under various mixing ventilation layouts. Transient simulations were conducted in a conference room, while pathogen-bearing droplets were released by a standing speaker. The results showed that droplet residues (< 40 μm) had a high potential to reach occupant's breathing zone, among which the number fraction of aerosol residues (< 10 μm) could be nearly doubled compared with that of the rest droplet residues in the breathing zone.

Evaluation of cough-jet effects on the transport characteristics of respiratory-induced contaminants in airline passengers' local environments.

Urgent demands of assessing respiratory disease transmission in airliner cabins had awakened from the COVID-19 pandemics. This study numerically investigated the cough flow and its time-dependent jet-effects on the transport characteristics of respiratory-induced contaminants in passengers' local environments. Transient simulations were conducted in a three-row Boeing 737 cabin section, while respiratory contaminants (2 μm-1000 μm) were released by different passengers with and without coughing and were tracked by the Lagrangian approach.

Numerical investigation of indoor particulate contaminant transport using the Eulerian-Eulerian and Eulerian-Lagrangian two-phase flow models.

Transport of micron particles in a displacement ventilated room was simulated using both the Eulerian-Eulerian model and the Eulerian-Lagrangian model. The same inter-phase action mechanisms were included in both models. The models were compared against each other in the aspects of air velocity, particle concentration, and particle-wall interactions.

Characterisation and analysis of indoor tornado for contaminant removal and emergency ventilation.

As an essential emergency management strategy, innovative emergency ventilation schemes that can quickly remove infectious and fatal contaminants without further spreading are highly demanded for public and commercial buildings. This study numerically investigated a vortex flow driven ventilation in a model room to explore the dynamic characteristics and 3D visualisation of vortex-driven indoor tornados. Four approaches to identify the core region of the indoor tornado were developed and compared against each other.

Thermal effect of human body on cough droplets evaporation and dispersion in an enclosed space.

This study numerically investigated the thermal effect of human body on the time-dependent dispersion of cough droplets with evaporation process. The thermal flow of human body was imitated using a 3D thermal manikin with real body features, while a recent developed multi-component Eulerian-Lagrangian approach was used to address the effects of inhomogeneous temperature and humidity fields on droplet evaporation. By comparing the results yielded without and with the human body heat, the outcomes demonstrated strong impact of human body heat on the droplets mass fraction and local air velocity distributions.

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

Unlabelled: 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.

Evaluation of airborne disease infection risks in an airliner cabin using the Lagrangian-based Wells-Riley approach.

An urgent demand of assessing passengers' exposure risks in airliner cabins was raised as commercial airliners are one of the major media that carrying and transmitting infectious disease worldwide. In this study, simulations were conducted using a Boeing 737 cabin model to study the transport characteristics of airborne droplets and the associated infection risks of passengers. The numerical results of the airflow field were firstly compared against the experimental data in the literature to validate the reliability of the simulations.