Airflow analysis in the alveolar region using the lattice-Boltzmann method

Abstract

A validated lattice-Boltzmann code has been developed based on the Bhatnagar-Gross-Krook formulation to simulate and analyze transient laminar two-dimensional airflow in alveoli and bifurcating alveolated ducts with moving walls, representative of the human respiratory zone. A physically more realistic pressure boundary condition has been implemented, considering a physiological Reynolds number range, i.e., 0 < Re < 11, which covers the inhalation scenarios from resting mode to moderate exercise. Axial velocity contours, vortex propagation, and streamlines as well as mid-plane pressure variations in different alveolar geometries and shapes are illustrated and discussed. The results show that the influence of the geometric structure on the airflow fields in the human alveolar region is very important. Furthermore, the effect of a moving alveolus wall is significant, i.e., the vortices in the duct or alveolar sacs may change in size. In summary, for a given set of realistic inlet conditions, the airflow velocity and vortical flows are greatly dependent on the different alveolar sac shapes, local geometric structures, and sac expansion rates. The pressure distributions are less influenced by the alveolus shape and wall movement. The present results provide new physical insight and are important for the simulation of particle transport/deposition in the deep lung region.

Effect of Laryngopharyngeal Anatomy on Expiratory Airflow and Submicrometer Particle Deposition in Human Extrathoracic Airways

“…Other factors that limit the physiological realism of the current study include the assumptions of steady flow, simplified inlet conditions, a smooth and rigid airway surface, no humidity, and a constant glottal aperture and nasal valve for various breathing conditions. Other studies have highlighted the physical significance of transient breathing [13,48], inlet velocity profiles [49,50], nasal wall motion [51], glottal aperture variation [2], and nasal valve change during respiratory maneuvers [52,53]. Moreover, the nasal cavity model in this study is based on images of a single subject, which does not account for intersubject [54] variability.…”

Fluid-structure interaction analysis of air flow in pulmonary alveoli during normal breathing in healthy humans

“…Recently, Li and Kleinstreuer [12] used a space lling polygon shaped alveolar model and investigated the air ow for di erent wall motions.…”

Airflow patterns in a 3D model of the human acinus

“…Harington et al [10] also modeled a bifurcation and studied the particle deposition. Unlike other studies, which used Navier-Stokes equations or Monte Carlo method to study the acinar ow, Li and Kleinstreuer [12] employed the Lattice-Boltzmann method for numerical investigation of air ow patterns in this region. Using 2D alveolar geometries and imposing pressure inlet condition, they analyzed vortex propagation as well as the impact of alveolus expansion on air ow patterns, and pressure distributions for low inlet Reynolds number ranges.…”