Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session B29: Biological Fluid Dynamics : Respiratory Flows II |
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Chair: James B. Grotberg, University of Michigan Room: 611 |
Saturday, November 23, 2019 4:40PM - 4:53PM |
B29.00001: A dynamical systems approach to particle transport in lung airways Ali Farghadan, Filippo Coletti, Amirhossein Arzani Computer modeling of respiratory flows and particle transport are of both physiological and toxicological interests. In this talk, we present hidden dynamical systems features that control transport in human conducting airways. High-resolution computational fluid dynamics (CFD) simulation is carried out for an image-based tracheobronchial model under sinusoidal respiration flow. The destination map, which synchronizes the particle destination on the release point is found after performing Lagrangian particle tracking for microparticles. Finite-time Lyapunov exponent (FTLE) is calculated and inertial Lagrangian coherent structures (ILCS) are tracked during the breathing cycle. The results show that these dynamical systems features control the spatiotemporal evolution of the destination map at the trachea. Finally, slow manifolds are used as an efficient technique to identify the source of any arbitrary particle with backward integration of the Maxey-Riley equation. The novel dynamical systems techniques presented have important implications for drug delivery in respiratory disease. [Preview Abstract] |
Saturday, November 23, 2019 4:53PM - 5:06PM |
B29.00002: Can we use CFD to improve targeted drug delivery in throat? Saikat Basu, Rupali Shah, Andrew Pappa, Jihong Wu, Alyssa Burke, William Bennett, Wanda Bodnar, Julia Kimbell Numerical simulations of respiratory airflow and particle transport, along with synergistic physical experiments, can be used to identify the nebulized particle sizes that are most effective in enhancing targeted deposition at the laryngeal vocal fold granulomas in human throats. Narrow tracheal geometry results in high-speed inhaled airflow, leading to transitional and turbulent flow features. To account for short time-scale effects such as vortices, which can affect particle transport, our computational modeling scheme implements Large Eddy Simulations (LES) in three CT-derived anatomic mouth-nose-trachea reconstructions. To validate the numerical predictions, two distinct in vitro techniques, namely gamma scintigraphy and mass spectrophotometry, are used for measuring topical deposition in one CT-based solid model. Findings suggest a specific range $\approx$ 8 -- 10 $\mu$m of particle sizes with laryngeal granulomas and glottis as the specific deposition sites. The study considers three granuloma sizes (small, 3 mm; medium, 4.5 mm; large, 6 mm diameter) positioned at three distinct locations along the tissue lining of the vocal folds. The results have the potential to come up with novel personalized therapy protocol. [Preview Abstract] |
Saturday, November 23, 2019 5:06PM - 5:19PM |
B29.00003: Role of two-phase air-mucus interaction on aerosolized drug delivery in idealized lung models Rahul Rajendran, Arindam Banerjee Aerosolized drug delivery to the lung airways depends on the particle size, breathing pattern, and the airway geometry. The influence of the two-phase flow morphology and the local airflow structures developed in the mucus-lined airways of obstructive airway diseases, on the deposition of inhaled drugs is investigated. The Lagrangian particle tracking model is coupled with the multiphase Eulerian-Eulerian model to investigate the gas-liquid-solid flow in 3D idealized airway geometries. Mucus is modeled as a non-Newtonian fluid using the power-law equation, and flow turbulence is modeling using the low-Re k-$\omega $ SST model, including the eddy interaction model (EIM) for the particles. The results from the study are validated with experimental results from the literature and comparisons with constricted dry-wall airways are presented. The role of mucus rheology, airflow rate, particle size, airway geometry and gravity are discussed. A quantitative assessment on the global and regional deposition fractions of the particles, sites of deposition, clearance rates, pressure drop across the airway, and airway resistance in mucus-lined airways will be presented. [Preview Abstract] |
Saturday, November 23, 2019 5:19PM - 5:32PM |
B29.00004: Effect of viscoelasticity and surfactant on an airway closure model Francesco Romano', Hideki Fujioka, Metin Muradoglu, James B. Grotberg A liquid made out of mucus and serous layers lines the human lung airways. Several different flow regimes are observed depending on the generation of the bifurcation and when small airways are considered (9th or 10th generation of the airway tree), surface tension effects dominate and they can induce a Plateau-Rayleigh instability. The airway is modeled as a rigid pipe coated with a single-layer fluid and the effects of surfactant and non-Newtonian properties of mucus are investigated using numerical simulations. The viscoelasticity of mucus is taken into account by means of the Oldroyd-B model, whereas surfactant is considered for a Newtonian lining liquid. The evolution equations of the interfacial and bulk surfactant concentrations are solved coupled with the incompressible Navier--Stokes equations. The viscoelastic behavior of mucus strongly increases post-coalescence wall shear stresses (about 50\% in their peak value) when the Laplace number is high, whereas pre-coalescence stresses are almost insensitive to the Weissenberg number. Surfactant has a negligible effect on the closure-induced shear stress, except when the elasticity parameter or the surfactant concentration is high enough. Our parametric study covers both, healthy and pathological conditions. [Preview Abstract] |
Saturday, November 23, 2019 5:32PM - 5:45PM |
B29.00005: Effect of viscoelasticity and surfactant on the propagation and rupture of a liquid plug in an airway Metin Muradoglu, Francesco Romano', Hideki Fujioka, James B. Grotberg The propagation and rupture of a liquid plug in a distal airway are studied using numerical simulations. The simulations are carried out using a finite-difference/front-tracking method, previously validated for airway reopening with Newtonian fluids. The airway walls are considered rigid and the plug is driven by a pressure gradient enforced between the extrema of the pipe. The effect of interfacial and bulk surfactant is considered, together with the viscoelasticity of mucus, which is here taken into account using the FENE-P model. Our parametric study shows that the presence of surfactant can efficiently reduce the wall stresses along the airway wall, hence surfactant helps to reduce the damage on the epithelial cells distributed along the internal surface of an airway. Moreover, the effect of several viscoelastic parameters is considered, such as the Weissenberg number, the length of the polymer and the polymer-to-solvent viscosity ratio. Particular attention is paid to the distribution of extra stresses due to the non-Newtonian behavior of mucus since interesting elastic dynamics are triggered by the liquid plug rupture over the liquid-gas interface. [Preview Abstract] |
Saturday, November 23, 2019 5:45PM - 5:58PM |
B29.00006: Computational investigation of plug flow dynamics and splitting through 3D multi-branching bifurcating lung airway models Cory Hoi, Ashish Pathak, Mehdi Raessi Liquid plug flow in capillary tubes has applications in medical procedures, including surfactant replacement therapy (SRT), which is used to treat respiratory distress syndrome in preterm infants by delivering surfactant plugs to their lungs. Current SRT procedures have a 35\% non-response rate, which has been attributed to the complex fluid dynamics of liquid plug propagation through the lung airway network. Previous computational works performed 2D investigation of plug splitting in a single bifurcating airway geometry and mathematical models have been developed to calculate the plug split ratio at each independent airway bifurcation. In contrast, we present 3D CFD simulations of surfactant plug transport through multi-branching bifurcating lung airway models with three generations, in which upstream plugs show a strong dependence on the downstream flow behavior of previously instilled plugs in subsequent airway generations, a phenomenon not captured in previous computational studies. Our simulations investigate the effects of plug instillation frequency, downstream plug blockages and plug rupture on plug split ratio and distribution, improving our understanding of SRT and helping to increase its effectiveness. [Preview Abstract] |
Saturday, November 23, 2019 5:58PM - 6:11PM |
B29.00007: Multi-scale spatial heterogeneity enhances particle clearance in airway ciliary arrays Guillermina Ramirez-San Juan, Arnold Mathijssen, Mu He, Lily Jan, Wallace Marshall, Manu Prakash Mucus clearance is the primary defense of the respiratory system. This transport across the airway emerges from the integrated activity of thousands of cilia, which coordinate their spatial arrangement, alignment and motility. The mechanisms of fluid transport by cilia have been studied extensively at the level of the individual cilium and metachronal waves. However, how the topology of ciliary arrays is optimized to generate organ-scale directed flows is largely unexplored. Here, we image the mouse airway to map the geometry of its ciliary carpet, from the sub-cellular ($10^{-9}$m) to the organ scales ($10^{-3}$m), characterizing quantitatively its ciliary arrangement and the generated flows. Locally we measure heterogeneity in both cilia organization and flow structure, but across the trachea fluid transport is coherent. To examine this result, we develop a hydrodynamic model to explore systematically different tissue architectures. Surprisingly, we find that disorder enhances particle clearance, whether it originates from fluctuations, heterogeneity in multiciliated cell arrangement or ciliary misalignment. Together, our results shed light on how the microstructure of an active carpet determines its emergent dynamics and are applicable to understand airway pathologies. [Preview Abstract] |
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