Numerical investigation of airborne transmission in low-ceiling rooms under displacement ventilation

Abstract

This study employs computational fluid dynamics (CFD) simulations to evaluate the risk of airborne transmission of COVID-19 in low-ceiling rooms, such as elevator cabins, under mechanical displacement ventilation. The simulations take into account the effects of the human body's thermal environment and respiratory jet dynamics on the transmission of pathogens. The results of the study are used to propose a potential mitigation strategy based on ventilation thermal control to reduce the risk of airborne transmission in these types of enclosed indoor spaces. Our findings demonstrate that show that as the ventilation rate ( Qv) increases, the efficiency of removing airborne particles ( εp) initially increases rapidly, reaches a plateau at a critical ventilation rate ( Qc), and subsequently increases at a slower rate beyond Qc. Further analysis of the flow and temperature fields reveals that εp is closely linked to the thermal stratification fields, as characterized by the thermal interface height ( hti), the height of the temperature isosurface at T=20.7 ℃ ( hT,20.7), and temperature gradient. The simulations also indicate that the location of infector relative to ventilation inlet/outlet affects Qc and εp,c with higher Qc and lower εp,c observed when infector is in a corner due to potential formation of a local hot spot of high infection risk when infector is near the ventilation inlet. Our findings indicate that the thermal environment, including the temperature difference among the occupants, ventilation, and ambient environment plays a critical role in the transmission of airborne diseases confined spaces.

Comparative Analysis of Indoor Air Quality and Thermal Comfort Standards in School Buildings across New Zealand with Other OECD Countries

“…Likewise, previous studies have quantified the direct correlation between aeration rates and the percentage of aerial disease spread [11,12] in indoor spaces. For example, Wang and Hong [13] emphasise that lower ventilation rates in confined spaces contribute to transmitting airborne diseases like tuberculosis and SARS. Wei et al [14] note that an elevated risk of airborne disease transmission is pronounced in higher-occupancy spaces, making school classrooms susceptible to hotspots.…”

Hydrodynamics Matters: Unravelling the Gas Transfer Law for the Energy Dissipation Process in a High-energy Stream

“…Following established physical modeling practices, we simulated the flow until it reached a stable state, typically around 45 s, to ensure proper analysis of the hydraulic jump oscillations around its mean position. The detailed model configuration, mesh sensitivity analysis and model validation against physical data are not presented for the sake of conciseness, but similar model setup and treatment are reported inWang et al (2023).Utilizing optical flow (OF) techniques, Wüthrich et al (2021) estimated the dimensionless surface turbulence energy dissipation rate on breaking bores characterized by strong free-surface turbulence and significant air entrainment (Fr 1 = 2.45, Re = 1.86 × 10 5 ). The magnitude and trend observed in their findings align closely with the outcomes derived from our numerical simulations.…”