Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session T05: Respiratory Flows I |
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Chair: Francesco Romano', AMValor, Arts et Métiers Institute of Technology Room: Ballroom E |
Monday, November 25, 2024 4:45PM - 4:58PM |
T05.00001: Integrations of numerical and experimental investigations to compare the effectiveness of drug delivery among three intranasal sprays Guiliang N Liu, Bingkai Chen, Rui Ni, Adam Kimple, Zheng Li Intranasal sprays play a crucial role in treating allergies and sinus disease. Both conditions decrease the quality of life and contribute to a substantial economic burden. There are various intranasal sprays available at pharmacies, which result in different effectiveness of drug delivery. In this work, we integrate computational fluid dynamics (CFD) and particle image velocimetry (PIV) investigations to compare the effectiveness of drug delivery among three over-the-counter (OTC) intranasal corticosteroid sprays (INCS). Firstly, the flow field near the nozzle exit in the drug spray was measured using PIV to serve as the initial condition for the CFD modeling. Secondly, a subject-specific model of the nasal cavity was reconstructed based on CT scans. Thirdly, drug depositions in the subject-specific nasal cavity for the three OTC INCS were simulated with CFD using the initial conditions from PIV. The CFD results show significant discrepancies among the three OTC INCS. A more detailed comparison can be expected after considering more subject-specific samples from diverse groups. |
Monday, November 25, 2024 4:58PM - 5:11PM |
T05.00002: Exploring statistical laws governing inhalation-induced upper airway deposition Emma Louwagie, Saikat Basu Inhalation directs air through a defined pathway, initiating from nostrils, moving through the main nasal cavity, past the pharynx and trachea, and culminating in the lungs. Inhaled particles, of a range of sizes, are ferried by this incoming air but are filtered and trapped by upper airway structures to protect the delicate lower respiratory system. From an energetics perspective, the airflow physics along this convoluted tract is characterized by turbulence. The system approaches a critical stationary state over the time scales during which particles enter the airway and deposit. This stasis can be conjectured to correspond with the emergence of criticality in the complex flow domain. For such systemic criticality (i.e., sensitivity to perturbations), inhaled particle deposition impacted by the surrounding flow processes can act as signature 'avalanche'-like events. Based on the principles of organized criticality, we have explored the emergence of power law trends in particle deposition levels at the nasopharynx, a key initial infection site for airborne pathogens. These trends are derived from numerical data from five anatomic airway geometries for 15-85 L/min inhalation rates, modeled using high-fidelity Large Eddy Simulations. |
Monday, November 25, 2024 5:11PM - 5:24PM |
T05.00003: Effects of Injection Size Distribution on the Aerosol Deposition within Human Airways Jacob Pratt, Reetesh Ranjan, Jin Wang Aerosolized drug delivery within the human airways using metered-dose inhalers (MDI) is an effective strategy for treating pulmonary diseases. The particle size distribution from MDI is usually polydisperse, which exhibits differences in aerosol deposition compared to a monodisperse distribution. In this study, we examine the effects of injection size distribution on the local and global deposition within a realistic human airway model based on the SimInhale benchmark case, comprising the extrathoracic and intrathoracic airways. We employ the well-established Eulerian-Lagrangian framework to perform large-eddy simulation (LES) under a one-way coupled regime. First, the LES results from the monodisperse injection with the particle size of 4.3 μm at the inlet bulk Reynolds number of 3745 are compared with reference results. Afterward, we compare the monodisperse and polydisperse distributions with the same mean particle size and different values of geometric standard deviation representative of MDI. For the polydisperse injection, we consider Rosin-Rammler, Gaussian, and uniform types of distribution models. Lastly, we perform uncertainty quantification (UQ) of the aerosol deposition under the polydisperse injection scenario by employing a non-intrusive framework relying on the polynomial chaos expansion-based surrogate modeling technique. For the UQ study, the particle size is considered as the uncertain parameter, and the aerosol deposition is regarded as the quantity of interest. |
Monday, November 25, 2024 5:24PM - 5:37PM |
T05.00004: Quantifying inter-subject variability in Pulmonary Drug Delivery using Monte Carlo simulations DEBJIT KUNDU, Mahesh V Panchagnula The trajectories of inhaled particles in the distal lung depend on the unique geometry of each person's respiratory tract. Therefore, variation in lung anatomy is a major reason why different people respond to inhaled medications differently. To quantify the extents of inter-subject variability in large and diverse populations, we perform Monte-Carlo simulations (for 6000 realizations) of a stochastic asymmetric multi-path model of the human airways. We introduce stochasticity in the branching asymmetry to generate biologically realistic and representative models of the lung geometry. We report the statistical variations of regional particle deposition as a function of several key parameters - branching asymmetry, particle size, breathing period, bronchoconstriction, etc. We show how particles of specific sizes preferentially deposit in the deep lung and others in the upper airways, how asymmetry can decrease deposition in the upper airways and how bronchoconstriction can alter the distribution of particle deposition across the lung. These insights will be valuable for determining drug dosages as well as design and choice of delivery devices (inhalers/nebulizers). |
Monday, November 25, 2024 5:37PM - 5:50PM |
T05.00005: Elastoviscoplastic effects on liquid plug propagation and rupture in an airway model Renjie Hao, Daulet Izbassarov, Metin Muradoglu, James Bernard Grotberg, Tom Lacassagne, Amir Bahrani, Francesco Romano' Non-Newtonian effects on liquid plug propagation and rupture occurring in distal airways are studied computationally using the volume-of-fluid solver Basilisk. The plug is driven by an applied constant pressure in a rigid axisymmetric tube whose inner surface is coated by a thin non-Newtonian liquid film. Extensive simulations are performed to investigate the effects of viscoelasticity on the plug and film dynamics, revealing an elastic instability for sufficiently large Weissenberg numbers. Under unstable conditions, we also identify a resonance that amplifies the stresses created by the elastic instability. A corresponding mechanical analog is proposed to explain the occurrence of the resonance in terms of the ratio between the Laplace number and the Weissenberg number. The robustness of our analysis to viscoplastic effects is finally tested using the Saramito-Herschel-Bulkley rheological model. |
Monday, November 25, 2024 5:50PM - 6:03PM |
T05.00006: A Versatile Simulator for Accurate Replication and Analysis of Human Cough Jet Profiles Zackary Foss Van Zante, Tanya Purwar, Soohyeon Kang, Jhon J Quinones, Leonardo Chamorro, Luciano Castillo The rise of the COVID-19 pandemic has highlighted the critical need for detailed studies of respiratory diseases, particularly focusing on human coughs, which are a primary transmission route. Traditional experimental methods often involve a limited number of human subjects or concentrate on isolated aspects, such as droplets or airflow. Droplet studies frequently overlook the interrupted jet flow characteristics of a cough, while airflow studies often lack variability in flow patterns. This study introduces a versatile simulator designed to replicate human cough jet profiles and analyze their flow dynamics comprehensively. The system employs a synthetic jet actuator (speaker) driven by signals derived from human cough parameters. This speaker, paired with an aerosol chamber and an interchangeable mouthpiece, effectively simulates the respiratory tract. The analysis of the flow field was done utilizing particle image velocimetry and flow visualization techniques. The results have demonstrated that the cough jets generated by the system accurately replicate the velocity profiles observed in previous human studies. Additionally, the system's versatility and repeatability were thoroughly tested and confirmed. |
Monday, November 25, 2024 6:03PM - 6:16PM |
T05.00007: Human Respiration Complications from Limitations of Mass Transport in Microgravity Som Dutta, Anton Kadomtsev, Aditya Parik, Yicheng Chen, Marshall Porterfield, Aaron Berliner A major requirement for humans is a breathable atmosphere. In microgravity, despite environmental life support systems regulating air exchange, astronauts complain about air quality, with elevated CO2-levels resulting in detrimental health and performance effects. We extend extant accounts of human respiration to include the role of gravity and buoyancy. Using computational fluid dynamics, we demonstrate that the absence of bio-thermal convection in microgravity reduces airflow around the human body. This impairs gas exchange by creating an environmental breathing deadspace in front of the face, leading to significant CO2-rebreathing, with implications for astronaut health and countermeasures. We also show that in 1g, increasing ambient air temperature can also reduce buoyancy required for efficient respiratory exchange, resulting in breathing conditions equivalent to those in microgravity, with implications for treating respiratory disease on Earth. The simulations were conducted in 2D and 3D. 2D direct numerical simulations (DNS) were conducted using high-order spectral element methods (SEM). 2D and 3D RANS simulations were conducted to validate the 2D DNS simulations. |
Monday, November 25, 2024 6:16PM - 6:29PM |
T05.00008: Interdisciplinary Study to Understand Ventilator-mediated Pulmonary Ventilation Anas M Nawafleh, Rodrigo Padilla, Tao Xing, Vibhav Durgesh Globally, 4 million people per year die prematurely from chronic respiratory disease. When respiratory diseases are severe, intubation and mechanical ventilation are deemed necessary but with high mortality rates. The development of effective and safe mechanical ventilation to treat respiratory disease is greatly hampered by a lack of understanding of the gas transportation and exchange and fluid-structure (gas-tissue) interaction (FSI) in lungs. As a result, the operation of conventional mechanical ventilators (CMV) and high-frequency percussive ventilators (HFPV) often relies significantly on respiratory therapists' clinical judgment and expertise. There is an urgent need to develop more unified and quantitative guidelines and protocols for using mechanical ventilators in treating lung diseases. The goal of this project is to increase the understanding of ventilator-mediated pulmonary ventilation significantly by evaluating the difference in key clinically useful variables between natural breathing and ventilation (both CMV and HFPV) using FSI simulations and in-vitro experiments. The FSI models were validated with the experimental results. The results clearly showed that lung compliance plays a significant role in flow behavior in different generations of the lungs and lung tissue stress. This will help develop new unified and quantitative guidelines and protocols for using CMV and HFPV to provide desired respiratory support while minimizing ventilator-induced lung injury. |
Monday, November 25, 2024 6:29PM - 6:42PM |
T05.00009: Quantitative analysis of airflow dynamics with masks during breathing using particle image velocimetry Vijaya Esther Veeravalli, Marc Buckley Detailed quantitative airflow measurements in the vicinity of a person's face while breathing are important for the optimization of mask usage and respiratory protection in diverse settings. |
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