Investigation of inhalation and exhalation flow pattern in a realistic human upper airway model by PIV experiments and C
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ORIGINAL PAPER
Investigation of inhalation and exhalation flow pattern in a realistic human upper airway model by PIV experiments and CFD simulations Xiaoyu Xu1,2 · Jialin Wu1,2 · Wenguo Weng1,2 · Ming Fu3 Received: 24 September 2019 / Accepted: 21 January 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In this study, flow field characteristics in the trachea region in a realistic human upper airway model were firstly measured by particle image velocimetry (PIV) in the air under three constant inhalation and exhalation conditions: 36 L/min, 64 L/ min and 90 L/min, representing flow rates of 18 L/min, 32 L/min and 45 L/min in real human airway (the model was twice the size of a human airway). Computational fluid dynamics (CFD) analyses were performed on four turbulence models, with boundary conditions corresponding to the PIV experiments. The effects of flow rates and breathing modes on the airflow patterns were investigated. The CFD prediction results were compared with the PIV measurements and showed relatively good agreement in all cases. During inhalation, the higher the flow rates, the less significant the “glottal jet” phenomenon, and the smaller the area of the separation zone. The air in the nasal inhalation condition accelerated more dramatically after glottis. The SST-Transition model was the best choice for predicting inhalation velocity profiles. For exhalation condition, the maximum velocity was much smaller than that during inhalation due to the more uniform flow field. The exhalation flow rates and breathing modes had little effect on the flow characteristics in the trachea region. The RNG k − ε model and SST k − ω model were recommended to simulate the flow field in the respiratory tract during exhalation. Keywords Human upper airway model · Flow field distribution · PIV · CFD
1 Introduction Inhalation exposure of airborne particles is associated with high respiratory disease, cardiovascular diseases and lung cancer morbidity and mortality (Guarnieri and Balmes 2014; Kim et al. 2015; Morris 2001). It is of great importance to study the transport and fate of inhaled particles in the respiratory tract. Understanding the flow pattern in the respiratory tract can aid in treatment for respiratory diseases. A research about the changes in aerodynamics during vocal cord dysfunction found evidence of abrupt laryngeal * Wenguo Weng [email protected] 1
Institute of Public Safety Research, Department of Engineering Physics, Tsinghua University, Beijing 100084, People’s Republic of China
2
Beijing Key Laboratory of City Integrated Emergency Response Science, Tsinghua University, Beijing 100084, China
3
Hefei Institute for Public Safety Research, Tsinghua University, Hefei 320601, Anhui Province, China
pressure gradient, chaotic airflow and high concentration of shear stresses in the glottal region (Frank-Ito et al. 2015). The impact of laryngotracheal stenosis (LTS) on inspiratory airflow and resistance was investigated,demonstrating that LTS increases resistanc
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