Study of the flow unsteadiness in the human airway using large eddy simulation

Bernate, Jorge A.; Geisler, Taylor S.; Padhy, Sourav; Shaqfeh, Eric S. G.; Iaccarino, Gianluca

doi:10.1103/physrevfluids.2.083101

Cited by 23 publications

(10 citation statements)

References 31 publications

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“…The narrow larynx and resulting unsteady jet formation contribute to the biased flow distribution on the cross‐sectional planes while the curved airway structure is most likely responsible for the secondary flow generation . The current CFD simulations and MRI measurements enabled us to confirm the appearance of complex tracheal flow characteristics induced by the upper airway such as the laryngeal jet, biased cross‐sectional airway flow distribution, secondary flow, and dynamic velocity profiles, which have been illustrated in previous modelling studies . Those complex flow behaviours are highly dependent on the airway geometry as well as the flow rate.…”

Section: Discussionsupporting

confidence: 69%

“…The turbulent flow behaviour induced by the upper airway was gradually attenuated as the flow moves towards the distal branches. However, unsteady flow fluctuation was still discernible not only in the trachea but also in the primary and secondary bronchi . While the local flow dynamics caused by the upper airway is well described in literature, the potential influence of the upper airways affecting ventilation distribution in the lung has not been fully discussed yet.…”

Section: Introductionmentioning

confidence: 97%

See 1 more Smart Citation

Effect of upper airway on tracheobronchial fluid dynamics

Kim

Collier

Wild

et al. 2018

Numer Methods Biomed Eng

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The upper airways play a significant role in the tracheal flow dynamics. Despite many previous studies, however, the effect of the upper airways on the ventilation distribution in distal airways has remained a challenge. The aim of this study is to experimentally and computationally investigate the dynamic behaviour in the intratracheal flow induced by the upper respiratory tract and to assess its influence on the subsequent tributaries. Patient-specific images from 2 different modalities (magnetic resonance imaging of the upper airways and computed tomography of the lower airways) were segmented and combined. An experimental phantom of patient-specific airways (including the oral cavity, larynx, trachea, down to generations 6-8) was generated using 3D printing. The flow velocities in this phantom model were measured by the flow-sensitised phase contrast magnetic resonance imaging technique and compared with the computational fluid dynamics simulations. Both experimental and computational results show a good agreement in the time-averaged velocity fields as well as fluctuating velocity. The flows in the proximal trachea were complex and unsteady under both lower- and higher-flow rate conditions. Computational fluid dynamics simulations were also performed with an airways model without the upper airways. Although the flow near the carina remained unstable only when the inflow rate was high, the influence of the upper airways caused notable changes in distal flow distributions when the 2 airways models were compared with and without the upper airways. The results suggest that the influence of the upper airways should be included in the respiratory flow assessment as the upper airways extensively affect the flows in distal airways and consequent ventilation distribution in the lungs.

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Section: Discussionsupporting

confidence: 69%

Section: Introductionmentioning

confidence: 97%

Effect of upper airway on tracheobronchial fluid dynamics

Kim

Collier

Wild

et al. 2018

Numer Methods Biomed Eng

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“…Chen, Feng, Zhong and Kleinstreuer [56] reported that air flow becomes turbulent near the mouth cavity at 15-45 L/min flow rate. Different turbulent models, Reynolds-averaged Navier-Stokes (RANS) [57]; [58,59], k- [60,61], k-ω [39,62], Large Eddy Simulation (LES) [63][64][65][66] have been used for airflow characterization in the oral airways of the lung. RANS turbulence model solves the time-averaged equations of motion which is computationally less expensive.…”

Section: Extrathoracic Regionmentioning

confidence: 99%

A Review of Respiratory Anatomical Development, Air Flow Characterization and Particle Deposition

Islam

Paul

Ong

et al. 2020

IJERPH

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The understanding of complex inhalation and transport processes of pollutant particles through the human respiratory system is important for investigations into dosimetry and respiratory health effects in various settings, such as environmental or occupational health. The studies over the last few decades for micro- and nanoparticle transport and deposition have advanced the understanding of drug-aerosol impacts in the mouth-throat and the upper airways. However, most of the Lagrangian and Eulerian studies have utilized the non-realistic symmetric anatomical model for airflow and particle deposition predictions. Recent improvements to visualization techniques using high-resolution computed tomography (CT) data and the resultant development of three dimensional (3-D) anatomical models support the realistic representation of lung geometry. Yet, the selection of different modelling approaches to analyze the transitional flow behavior and the use of different inlet and outlet conditions provide a dissimilar prediction of particle deposition in the human lung. Moreover, incorporation of relevant physical and appropriate boundary conditions are important factors to consider for the more accurate prediction of transitional flow and particle transport in human lung. This review critically appraises currently available literature on airflow and particle transport mechanism in the lungs, as well as numerical simulations with the aim to explore processes involved. Numerical studies found that both the Euler–Lagrange (E-L) and Euler–Euler methods do not influence nanoparticle (particle diameter ≤50 nm) deposition patterns at a flow rate ≤25 L/min. Furthermore, numerical studies demonstrated that turbulence dispersion does not significantly affect nanoparticle deposition patterns. This critical review aims to develop the field and increase the state-of-the-art in human lung modelling.

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“…It was assumed that the differences between average flow fields in steady and unsteady conditions are negligible. More recently, the experimental results were compared to CFD simulations performed with the same geometry as the model, showing good agreement . The same group extended experimental flow measurement to 4D PCV‐MRI with 3D measurement of the three velocity components in the same airway model during oscillatory flow …”

mentioning

confidence: 96%

“…More recently, the experimental results were compared to CFD simulations performed with the same geometry as the model, showing good agreement. 32 The same group extended experimental flow measurement to 4D PCV-MRI with 3D measurement of the three velocity components in the same airway model during oscillatory flow. 33 In this work, we aim to demonstrate that MRI-based methods can be used as an investigative tool to study airflow pattern in vitro and as a validation tool for CFD simulation.…”

mentioning

confidence: 99%