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 J04: Phonation |
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Chair: Timothy Wei, Northwestern University Room: Ballroom D |
Sunday, November 24, 2024 5:50PM - 6:03PM |
J04.00001: Fluid structure interaction simulations to investigate asymmetrical vocal fold vibration Guofeng He, Lea Sayce, Haoxiang Luo, Zheng Li Human phonation is the result of the interaction between a pair of vocal folds and the airflow flowing through the glottis. The airflow is responsible for activating and maintaining vocal fold vibration, and the vibration of the vocal folds in turn regulates the airflow flow pattern. Many voice disorders are caused by the significantly asymmetrical vocal folds, such as unilateral vocal fold paralysis and muscle atrophy. In this work, we develop a Multiphysics model tool to simulate the fluid structure interaction (FSI) process of vocal fold vibration using COMSOL Multiphysics, while a two-dimensional simplified vocal fold model will be utilized. FSI simulations have been performed on the symmetrical vocal fold model first, while asymmetrical vibration can also be found in this condition. It could be caused by the flow separation after leaving the glottis. After that, the FSI simulations have been performed for the asymmetrical vocal folds to mimic the disease condition, while asymmetrical vibration have been achieved as expected. The results are informative for the future treatment of voice disorder. |
Sunday, November 24, 2024 6:03PM - 6:16PM |
J04.00002: Improved definitions of voice efficiency Michael H Krane Novel measures of voice efficiency are presented. Separate measures which distinguish acoustic production and transmission are defined. The analysis uses the integral equation for fluid mechanical energy, applied to a control volume encompassing the human airway system and its component parts. The physiological work inputs and acoustic work outputs are identified, along with the interplay of these with the work performed by other mechanisms present in the vocal system, such a viscous dissipation and work done by the airflow on the vocal folds. Non-linear interaction between acoustic production and transmission is also explicitly accounted for by this analysis. Reduced-order modeling of human phonation is presented to provide a comparison with previous definitions of voice efficiency. |
Sunday, November 24, 2024 6:16PM - 6:29PM |
J04.00003: A comprehensive fluid structure acoustic modeling tool development for vocal vibration simulation Qilin Liu, Guofeng He, Lea Sayce, Haoxiang Luo, Zheng Li Voice production is a fluid structure interaction (FSI) process between glottal airflow and vocal fold tissue, which is a two-way coupling. Regarding the low Mach number for human phonation, we can simplify it into flow induce sound, which is a one-way couple. We aim to develop a comprehensive fluid structure acoustic interaction modeling tool for vocal fold vibrations, which can be applied to various disease related voice disorders. In this work, we aim to use the retro 3D FSI results and animal experiments to test the flow induced sound solver. Linearized perturbed compressible equation (LPCE) is employed to predict sound propagation. The LPCE is discretized by low-dissipation and low-dispersion finite difference stencils, with careful treatments on the near wall region and the non-reflection boundaries. The source terms of the LPCE are extracted from the three-dimensional incompressible simulation results of the flow in rabbit larynges. The acoustic fields in the simplified vocal fold model, subject specific models with healthy phonation and voice disorder will be simulated respectively. The relations between vocal fold vibration patterns and acoustic performance will be discussed. |
Sunday, November 24, 2024 6:29PM - 6:42PM |
J04.00004: Droplet Formation inside the Human Larynx: In Vivo Observations and Ex Vivo Models William D Ristenpart, Amir Heidarzadeh, Samantha J Yan, Daniel J Cates, Harishankar Manikantan Phonation during human speech involves saliva-coated vocal folds opening and closing about 200 times per second. This process is known to produce large quantities of micron-scale expiratory droplets that are believed to be responsible for transmitting infectious pathogens into the air, leading to millions of deaths, but little is known about the formation of these salivary droplets. Here we present two sets of video evidence elucidating the nature of droplet formation during phonation. (1) In collaboration with an otolaryngologist, we inserted a laryngoscope (i.e., camera fed in through the nose) to directly visualize vocal folds during phonation. We observe that salivary filaments or ‘strings’ often stretch between the vocal folds and pinch off during each cycle, and occasionally exhibit the ‘beads-on-a-string’ instability that occurs with viscoelastic fluids. (2) We used a monster-truck subwoofer to construct artificial vocal folds that oscillate up to 200 Hz with multi-millimeter amplitudes. High speed video of saliva in the apparatus exhibits behavior like that observed in vivo, affording an opportunity to systematically test droplet formation under controlled conditions. We interpret both sets of observed behavior in terms of a balance between capillary, elastic, and inertial forces, and we discuss the implications for understanding unresolved questions about human-to-human variability in rates of expiratory aerosol emission. |
Sunday, November 24, 2024 6:42PM - 6:55PM |
J04.00005: Unravelling jet dynamics associated with incomplete glottal opening Timothy Wei, Abigail Haworth, Nathaniel J Wei, Hunter Ringenberg, Michael H Krane This study focuses on the effects of glottal jet dynamics on phonation when one of the vocal folds does not move as much as the other. This can be a pathological condition in which a vocal fold is partially/completely paralyzed, parysis, but also occurs naturally particularly with aging. Physiological effects include hoarseness, pain, or fatigue in speaking. Data were collected from a scaled-up (10x), 2-D vocal-fold model with semi-circular ends that were computer driven inside a square duct with constant opening and closing speeds. The working fluid was water. Cases in which one vocal fold moved 0%, 50%, 75%, and 100% of the other were examined; the last case being, of course, the nominally 'healthy', symmetric case. Time resolved DPIV and pressure measurements along the duct centerline made at Re = 7200 and reduced frequency of 0.0261 (corresponding to an equivalent life frequency of 97.5 Hz) were used to generate time traces of terms in the integral streamwise momentum equal. Examination of these traces revealed that differences in glottal opening speed, dh/dt, boundary layer blockage, and asymmetry are all factors in the glottal jet dynamics. The focus of this presentation will be on identifying and unravelling these different effects. |
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