Bulletin of the American Physical Society
70th Annual Meeting of the APS Division of Fluid Dynamics
Volume 62, Number 14
Sunday–Tuesday, November 19–21, 2017; Denver, Colorado
Session L4: Respiratory: Mucociliary Flows and Respiratory Particle DepositionBio Fluids: Internal
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Chair: Laura Nicolaou, Johns Hopkins University Room: 404 |
Monday, November 20, 2017 4:05PM - 4:18PM |
L4.00001: Metachronal waves in epithelium cilia to transport bronchial mucus in airways Julien Favier, Chateau Sylvain, Umberto D'Ortona, Sébastien Poncet Metachronal waves of beating cilia are an efficient mechanism to transport mucus in human airways. The numerical results we will present will shed new light on the understanding of chronic respiratory diseases, such as Asthma of COPD. A coupled lattice Boltzmann - Immersed Boundary is used to simulate the multiphase environment in which the cilia are immersed : a periciliary layer and the mucus layer. A purely hydrodynamical feedback of the fluids is taken into account, and a coupling parameter α is introduced, allowing the tuning of both the direction of the wave propagation, and the strength of the fluid feedback. The cilia, initially set in a random state, quickly synchronize with their immediate neighbors giving birth to metachronal waves. A comparative study of both antipleptic and sympleptic waves is performed by imposing the metachrony. Antiplectic waves are found to be the most efficient to transport and mix fluids compared to other random or synchronised cilia motions. The numerical results will be discussed and compared to experimental and clinical results obtained by collaborators, to progress on the understanding of the inner mechanisms of chronic respiratory diseases. [Preview Abstract] |
Monday, November 20, 2017 4:18PM - 4:31PM |
L4.00002: Flow Induced by \textit{Ex-Vivo} Nasal Cilia: Developing an Index of Dyskinesis James Grotberg, Mathieu Bottier, Marta Pena-Fernandez, Sylvain Blanchon, Gabriel Pelle, Emilie Bequignon, Daniel Isabey, Andre Coste, Estelle Escudier, Jean-Francois Papon, Marcel Filoche, Bruno Louis Mucociliary clearance is one of the major lines of defense of the respiratory system. The mucus layer coating the pulmonary airways is moved along and out of the lung by the activity of motile cilia, thus expelling the particles trapped in it. Here we compare \textit{ex vivo }measurements of a Newtonian flow induced by cilia beating (using micro-beads as tracers) and a mathematical model of this fluid flow. Samples of nasal epithelial cells placed in water are recorded by high-speed video-microscopy and ciliary beat pattern is inferred. Automatic tracking of micro-beads, used as markers of the flow generated by cilia motion, enables us also to assess the steady velocity profile as a function of the distance above the cilia. This profile is shown to be essentially parabolic. This compares well to a 2D mathematical model for ciliary fluid propulsion using an envelope model. From the model and the experimental measurements, the shear stress exerted by the cilia is deduced. Finally, this shear stress is proposed as a new index for characterizing the efficiency of ciliary beating and diagnosing dyskinesis. [Preview Abstract] |
Monday, November 20, 2017 4:31PM - 4:44PM |
L4.00003: Interfacial distribution of mucus under forced expiration in a double bifurcation model Rahul Rajendran, Arindam Banerjee Mucus is removed from the lung airways by the rhythmic beating of cilia and the mucus interaction with the turbulent core airflow generated during a cough or forced expiration. The quantity and quality of mucus are adversely altered, impairing mucociliary clearance under chronic pulmonary conditions. Existing studies on airflow induced mucus clearance have established a functional relationship between the airflow rate, mucus properties, flow bias, breathing frequency and clearance; however, the impact of airway branching, gravity, and characterization of primary and secondary flows have not been studied. The focus of the current investigation is the detailed understanding of air-mucus two-phase flow mechanism under steady expiratory airflow in a double bifurcation model. The effect of different airflow rates and mucus viscosities on the flow morphology, mucus layer thickness, mucus clearance and pressure drop across the model will be discussed. The impact of in-plane and out-of-plane configurations of the bifurcation model on the primary and secondary flow structures as well as the mucus distribution will be addressed. In addition, a detailed comparison of the flow structures in the mucus-lined airways, and its corresponding dry wall (no mucus lining) case will be presented. [Preview Abstract] |
Monday, November 20, 2017 4:44PM - 4:57PM |
L4.00004: ``Magical'' fluid pathways: inspired airflow corridors for optimal drug delivery to human sinuses Saikat Basu, Zainab Farzal, Julia S. Kimbell Topical delivery methods like nasal sprays are an important therapeutic component for sinusitis (inflammation and clogging of the paranasal sinuses). The sinuses are air-filled sacs, identified as: maxillaries (under the eyes and deep to cheeks bilaterally; largest in volume), frontals (above and medial to the eyes, behind forehead area), ethmoids (between the eyes, inferior to the frontal sinuses), and sphenoids (superior and posterior to ethmoids). We develop anatomic CT-based 3D reconstructions of the human nasal cavity for multiple subjects. Through CFD simulations on Fluent for measured breathing rates, we track inspiratory airflow in all the models and the corresponding sprayed drug transport (for a commercially available sprayer, with experimentally tested particle size distributions). The protocol is implemented for a wide array of spray release points. We make the striking observation that the same release points in each subject provide better particle deposition in all the sinuses, despite the sinuses being located at different portions of the nasal cavity. This leads to the conjecture that the complicated anatomy-based flow physics artifacts in the nasal canal generate certain ``magical'' streamlines, providing passage for improved drug transport to all sinus targets. [Preview Abstract] |
Monday, November 20, 2017 4:57PM - 5:10PM |
L4.00005: Turbulence in the trachea and its effect on micro-particle deposition Taylor Geisler, Eric Shaqfeh, Gianluca Iaccarino The health effects of inhaled aerosols are often predicted by extrapolating experimental data taken using nonhuman primate animal studies to humans. While the existence of a laminar-to-turbulent flow transition in the human larynx is widely reported in the literature, it was previously unknown, to our knowledge, whether a similar flow behavior exists in the airways of rhesus monkeys. By using Large Eddy Simulation (LES) in the CT-based airway models of rhesus monkeys we demonstrate the existence of such a flow transition at elevated inspiratory flow rates. The geometries comprise the nasal cavity, larynx, and trachea. We observe turbulence intensity values that peak after the larynx and decay throughout the trachea similar to that of humans. Deposition of inhaled micro-particles is also computed and validated using experiments in 3D-printed model airways with excellent agreement. Deposition in the turbulent regions of the airway (larynx and trachea) is shown to be substantial at elevated flow rates and to depend on the flow unsteadiness. These results provide insight into the fate of inhaled particles in rhesus monkey animal experiments and their connection to human inhalation. [Preview Abstract] |
Monday, November 20, 2017 5:10PM - 5:23PM |
L4.00006: Flow recirculation in cartilaginous ring cavities of a human trachea model Jose Montoya Segnini, Humberto Bocanegra Evans, Luciano Castillo Most flow studies of the human respiratory tract assume that the trachea and bronchi have smooth walls despite the fact that the walls in both of these airway generations are lined with cartilaginous rings. Recent studies demonstrate that the rings do have an impact in the flow behavior and particle deposition, but there is still a lack of detailed knowledge of the effect the rings have on the flow evolution. To uncover the flow dynamics near the rings, we employed particle image velocimetry (PIV) and particle tracking velocimetry (PTV) measurements in a Refractive Index-matched facility at a flow rate comparable to a resting state; with a trachea-based Reynolds number Re $=$ 2800. We have carried out high-resolution experiments to capture the velocity field inside the cavity created by the rings in the trachea model. Our data indicate that a small recirculation is created inside the cavities. The recirculation is found in the upstream side of the cavities throughout the trachea. This recirculation will affect the dispersion and collision of particles with the wall. This observation is consistent with previous studies, which have shown an increase in the collision of particles within the ring cavity. [Preview Abstract] |
Monday, November 20, 2017 5:23PM - 5:36PM |
L4.00007: Particle sedimentation and impaction in the respiratory airways Laura Nicolaou, Tamer Zaki Impaction is the dominant deposition mechanism for micron-sized particles in the upper airways. However, sedimentation becomes significant as the flowrate decreases and particle size increases. In order to assess the relative importance of impaction and sedimentation, we examine particle transport and deposition under different inhalation conditions, and for different particle sizes. Two important dimensionless parameters are (i) the Stokes number, $Stk$, and (ii) the ratio of the gravitational settling velocity to the fluid velocity, $V_{g}$. Their ratio is the Froude number, which measures the relative importance of inertial to gravitational forces. Instantaneous definitions of the Stokes and Froude numbers are derived, based on the local flow properties, in order to obtain a more accurate representation of the particle trajectories. The instantaneous Froude number can be 3-4 orders of magnitude smaller than the reference value in regions of the flow. Therefore, gravitational effects should not be neglected. In addition, deposition is shown to correlate with high values of $StkV_{g}$. Particles with high $V_{g}$ deposit primarily in the mouth, via sedimentation, while particles with high $Stk$ deposit mainly in the larynx and trachea, via impaction. [Preview Abstract] |
Monday, November 20, 2017 5:36PM - 5:49PM |
L4.00008: Transient Particle Deposition Simulations in a Human Whole-Lung Model Kamran Poorbahrami, Jessica Oakes Efficiency of aerosol therapeutic delivery to treat pulmonary disease is correlated to particle characteristics, respiration waveforms, and delivery method. Targeted delivery may enable delivery of medications directly to areas in need, while alleviating adverse side effects. In this work, we performed CFD and particle transport simulations in an image-based human 3D lung model by employing multi-domain methods. The particle trajectories were calculated by coupling Maxey-Riley and advection-diffusion equations. Near wall transport effects were included within the framework. The influence of respiration parameters (e.g. steady, sinusoidal and realistic respiration waveforms) coupled with particle diameters (1, 3, and 5micron) on regional deposition was studied. To identify times of enhanced deposition efficiency, we recorded regional particle deposition over time and correlated with the particle bolus injection time. Simulation results highlight the link between boundary conditions, particle size, and particle release time with regional particle deposition concentrations. [Preview Abstract] |
Monday, November 20, 2017 5:49PM - 6:02PM |
L4.00009: Cluster-guided imaging-based CFD analysis of airflow and particle deposition in asthmatic human lungs. Jiwoong Choi, Lawrence LeBlanc, Sanghun Choi, Babak Haghighi, Eric Hoffman, Ching-Long Lin The goal of this study is to assess inter-subject variability in delivery of orally inhaled drug products to small airways in asthmatic lungs. A recent multiscale imaging-based cluster analysis (MICA) of computed tomography (CT) lung images in an asthmatic cohort identified four clusters with statistically distinct structural and functional phenotypes associating with unique clinical biomarkers. Thus, we aimed to address inter-subject variability via inter-cluster variability. We selected a representative subject from each of the 4 asthma clusters as well as 1 male and 1 female healthy controls, and performed computational fluid and particle simulations on CT-based airway models of these subjects. The results from one severe and one non-severe asthmatic cluster subjects characterized by segmental airway constriction had increased particle deposition efficiency, as compared with the other two cluster subjects (one non-severe and one severe asthmatics) without airway constriction. Constriction-induced jets impinging on distal bifurcations led to excessive particle deposition. The results emphasize the impact of airway constriction on regional particle deposition rather than disease severity, demonstrating the potential of using cluster membership to tailor drug delivery. [Preview Abstract] |
Monday, November 20, 2017 6:02PM - 6:15PM |
L4.00010: Characteristics of airflow and particle deposition in COPD current smokers Chunrui Zou, Jiwoong Choi, Babak Haghighi, Sanghun Choi, Eric A. Hoffman, Ching-Long Lin A recent imaging-based cluster analysis of computed tomography (CT) lung images in a chronic obstructive pulmonary disease (COPD) cohort identified four clusters, viz. disease sub-populations. Cluster 1 had relatively normal airway structures; Cluster 2 had wall thickening; Cluster 3 exhibited decreased wall thickness and luminal narrowing; Cluster 4 had a significant decrease of luminal diameter and a significant reduction of lung deformation, thus having relatively low pulmonary functions. To better understand the characteristics of airflow and particle deposition in these clusters, we performed computational fluid and particle dynamics analyses on representative cluster patients and healthy controls using CT-based airway models and subject-specific 3D-1D coupled boundary conditions. The results show that particle deposition in central airways of cluster 4 patients was noticeably increased especially with increasing particle size despite reduced vital capacity as compared to other clusters and healthy controls. This may be attributable in part to significant airway constriction in cluster 4. This study demonstrates the potential application of cluster-guided CFD analysis in disease populations. [Preview Abstract] |
Monday, November 20, 2017 6:15PM - 6:28PM |
L4.00011: Cluster-specific small airway modeling for imaging-based CFD analysis of pulmonary air flow and particle deposition in COPD smokers Babak Haghighi, Jiwoong Choi, Sanghun Choi, Eric A Hoffman, Ching-Long Lin Accurate modeling of small airway diameters in patients with chronic obstructive pulmonary disease (COPD) is a crucial step toward patient-specific CFD simulations of regional airflow and particle transport. We proposed to use computed tomography (CT) imaging-based cluster membership to identify structural characteristics of airways in each cluster and use them to develop cluster-specific airway diameter models. We analyzed 284 COPD smokers with airflow limitation, and 69 healthy controls. We used multiscale imaging-based cluster analysis (MICA) to classify smokers into 4 clusters. With representative cluster patients and healthy controls, we performed multiple regressions to quantify variation of airway diameters by generation as well as by cluster. The cluster 2 and 4 showed more diameter decrease as generation increases than other clusters. The cluster 4 had more rapid decreases of airway diameters in the upper lobes, while cluster 2 in the lower lobes. We then used these regression models to estimate airway diameters in CT unresolved regions to obtain pressure-volume hysteresis curves using a 1D resistance model. These 1D flow solutions can be used to provide the patient-specific boundary conditions for 3D CFD simulations in COPD patients. [Preview Abstract] |
Monday, November 20, 2017 6:28PM - 6:41PM |
L4.00012: The pressure is all in your head: A cilia-driven high-pressure pump in the head of a deep-sea animal Janna Nawroth, Kakani Katija, Michael Shelley, Eva Kanso Motile cilia are microscopic, hair-like structures on the cell surface that can sense and propel the extracellular fluid environment. In many ciliated systems found in nature, such as the mammalian airways and marine sponges, the organization and collective behavior of the cilia favors the pumping of fluids at low pressures and high volumes. We recently discovered an alternate design located in the head of a deep-sea animal called Larvacean. Here, cilia morphology, kinematics and flow indicate a role in maintaining the hydrostatic skeleton of the animal by generating a high-pressure flow. We describe our empirical and computational approaches toward understanding the design principles and dynamic range of this newly discovered pumping mechanism. In ongoing work, we further explore the fluid dynamic constraints on the morphological diversity of cilia and the resulting categories of fluid transport functions.~ [Preview Abstract] |
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