Tracing the origin of large respiratory droplets by their deposition characteristics inside the respiratory tract during speech  

作　　者：Yihan Wang Jianjian Wei Caroline X.Gao Tao Jin Li Liu 

机构地区：[1]Institute of Refrigeration and Cryogenics,Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province,Zhejiang University,Hangzhou 310000,China [2]Public Health and Preventive Medicine,Monash University,Melbourne,VIC,3004,Australia [3]Department of Building Science,Tsinghua University,Beijing 100084,China

出　　处：《Building Simulation》2023年第5期781-794,共14页建筑模拟（英文）

基　　金：supported by the National Natural Science Foundation of China(No.51808488,No.52178092)。

摘　　要：Origin of differently sized respiratory droplets is fundamental for clarifying their viral loads and the sequential transmission mechanism of SARS-CoV-2 in indoor environments.Transient talking activities characterized by low(0.2 L/s),medium(0.9 L/s),and high(1.6 L/s)airflow rates of monosyllabic and successive syllabic vocalizations were investigated by computational fluid dynamics(CFD)simulations based on a real human airway model.SST k-ωmodel was chosen to predict the airflow field,and the discrete phase model(DPM)was used to calculate the trajectories of droplets within the respiratory tract.The results showed that flow field in the respiratory tract during speech is characterized by a significant laryngeal jet,and bronchi,larynx,and pharynx-larynx junction were main deposition sites for droplets released from the lower respiratory tract or around the vocal cords,and among which,over 90%of droplets over 5μm released from vocal cords deposited at the larynx and pharynx-larynx junction.Generally,droplets’deposition fraction increased with their size,and the maximum size of droplets that were able to escape into external environment decreased with the airflow rate.This threshold size for droplets released from the vocal folds was 10-20μm,while that for droplets released from the bronchi was 5-20μm under various airflow rates.Besides,successive syllables pronounced at low airflow rates promoted the escape of small droplets,but do not significantly affect the droplet threshold diameter.This study indicates that droplets larger than 20μm may entirely originate from the oral cavity,where viral loads are lower;it provides a reference for evaluating the relative importance of large-droplet spray and airborne transmission route of COVID-19 and other respiratory infections.

关 键 词：respiratory droplets deposition viral load airborne transmission COVID-19 

分 类 号：R563[医药卫生—呼吸系统]