Bulletin of the American Physical Society
60th Annual Meeting of the Divison of Fluid Dynamics
Volume 52, Number 12
Sunday–Tuesday, November 18–20, 2007; Salt Lake City, Utah
Session ED: Biofluids III: Voice |
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Chair: Michael Krane, Pennsylvania State University Room: Salt Palace Convention Center 151 A-C |
Sunday, November 18, 2007 4:10PM - 4:23PM |
ED.00001: High-Fidelity Modeling of the Biophysics of Phonation using a Coupled IBM-FEM method Xudong Zheng, Rajat Mittal, Haoxiang Luo A coupled 3-D IBM-FEM method has been developed to investigate the biophysics of phonation. Phonation is a complex biological phenomenon which results from a highly coupled biomechanical interaction between glottal aerodynamics and vocal fold tissue. An accurate sharp interface immersed boundary method (IBM) is employed to simulate the glottal flow and this is coupled with a finite-element method which is designed to solve the elastodynamic equations for the vocal folds. The vocal fold structure is based on high-resolution CT scans. A three-layer finite-element anisotropic vocal fold tissue model is used for the vocal folds and a penalty-coefficient method has been employed in order to model the vocal fold collision. Self-sustained vibrations in the vocal fold are achieved and we analyze the computational results to gain insights into the the glottal jet aerodynamics as well as the dynamics and deformation of the vocal folds. [Preview Abstract] |
Sunday, November 18, 2007 4:23PM - 4:36PM |
ED.00002: Coupled Aero-Structural Dynamics in the Human Larynx During Phonation Haoxiang Luo, Xudong Zheng, Rajat Mittal, Steven Bielamowicz We simulate the nonlinear flow--structure interaction during the phonation process in the human larynx by coupling an incompressible flow solver and a linear viscoelasticity solver. In both solvers, computations are done efficiently on Cartesian grids, and boundary conditions for both flow and solid are treated using the immersed-boundary methods. The airflow is driven by the constant subglottal pressure, and the vocal folds are modeled by a simplified three-layer structure. A pair of false vocal folds are included to better approximate the geometry. In addition, we have incorporated a simple contact model to deal with the vocal fold collision. Several salient features of phonation are captured, and the statistical quantities of the glottal waveform are consistent with the clinical data. Supported by NIDCD Grant R01 DC007125-01A1. [Preview Abstract] |
Sunday, November 18, 2007 4:36PM - 4:49PM |
ED.00003: Fluid-Structure Interactions in a Scaled-Up Human Vocal Fold Model. Keith Peterson, Michael Krane, Timothy Wei Experiments using a simplified, self-oscillating, scale model of the human vocal folds are presented. The vocal fold models were thin sheets of flexible stainless steel with pliable PVC ends. The mass and spring constants could be tuned to match Strouhal and Reynolds numbers characteristic of human phonation; dynamic similarity to life scale motions was maintained. DPIV and DPIA (Digital Particle Image Accelerometry) measurements were taken conducted in the RPI free surface water tunnel to record the motion of both the fluid motion and the model vocal folds. The mechanical vibration behavior of the model vocal folds was also measured independently. This fully-coupled fluid-structure-interaction experiment has a dynamic richness surpassing stationary or forced vibration experiments. Cycle-to-cycle variations and flow asymmetries will be presented and discussed. The use of these measurements to estimate the energy budget of the fluid-structure interaction will also be discussed. * \textit{supported by the NIH} [Preview Abstract] |
Sunday, November 18, 2007 4:49PM - 5:02PM |
ED.00004: Impact of wall motion on flow through a model glottis Michael Krane The dynamic importance of unsteady displacement of vocal fold walls on glottal flow aerodynamics was studied using measurements of flow through a scaled-up model glottis (Krane, et al. JASA, 2007). Scaling laws developed by Krane and Wei (JASA, 2006) to describe glottal aerodynamics are used to collapse data and show the relevant flow physics. Particular focus is given to the relative importance of wall motion, relative to both glottal jet inertia and convective acceleration. How these relationships vary with vibration frequency is also addressed. (Supported by NIH grant 5R01 DC00564245.) [Preview Abstract] |
Sunday, November 18, 2007 5:02PM - 5:15PM |
ED.00005: Computational study of flow through a model glottis L. Joel Peltier, Michael Krane A computational study to determine the dominant dynamic mechanisms in glottal airflow is presented.~ Computations of the flow through a scaled-up model of the human glottis were performed for f* = 0.035, 0.040, and 0.080, and a Reynolds number of 8000.~ Choice of boundary conditions is discussed. Comparison to available data (Krane, et al., JASA, 2007) is presented.~ Computed results are used to calculate dynamic relevance of momentum equation terms, and how this relevance varies with vibration frequency.~ The energy budget of the flow is also computed to show the dominant terms. (Supported by NIH grant 5R01 DC00564245.) [Preview Abstract] |
Sunday, November 18, 2007 5:15PM - 5:28PM |
ED.00006: Aeroacoustics of unvoiced human speech sound production Daniel Leonard, Michael Krane Measurements of airflow and sound were performed in an idealized model of the human vocal tract in order to determine the aeroacoustic sources which give rise to unvoiced consonant speech sounds. The turbulent jet formed at a narrow constriction interacts with another constriction further downstream. The unsteady aerodynamic forces on these constrictions produce broadband sound, which is modulated by the acoustic response of the vocal tract. Sound source characteristics are determined by estimating the force on the constrictions, and how the temporal behavior of these forces correlates to the spatial and temporal structure of the jet. (Supported by NIH grant 5R01 DC00564245.) [Preview Abstract] |
Sunday, November 18, 2007 5:28PM - 5:41PM |
ED.00007: Aerodynamics of Vocal Fold Movement: A Novel Fluid-Structure Interaction Model Comer Duncan, Todd Harman, James Guilkey The present study applies a tightly coupled fluid-structure interaction algorithm to the modeling of the material dynamics and aerodynamics of phonation. The Material Point Method (MPM) is used to model the material and the Implicit Continuous-fluid Eulerian (ICE) method is used to model the aerodynamics. We focus on a two-dimensional model with specified transglottal pressure and simulate the aerodyanmics which results from the intrinsic coupling between the material and the air. The emergent properties of the system result from the close interplay between the two subsystems. We report visualizations of several cases showing the pressure field and vorticity field which results. The results demonstrate the promise of this approach to the modeling of the relation between material properties, aerodynamics, and eventual acoustical output of the model vocal folds. [Preview Abstract] |
Sunday, November 18, 2007 5:41PM - 5:54PM |
ED.00008: Glottal jet measurements in synthetic, MRI-based human vocal fold models Scott Thomson, Brian Pickup, Paul Gollnick Human vocal fold vibration generates a time-varying elliptically-shaped glottal jet that produces sound in speech. Improved understanding of glottal jet dynamics can yield insight into voice production mechanisms and improve the diagnosis and treatment of voice disorders. Experiments using recently developed life-sized synthetic models of the vocal folds are presented. The fabrication process of converting MRI images to synthetic models is described. The process allows for varying the Young's modulus of the models, allowing for asymmetric conditions to be created by casting opposing vocal folds using materials of different stiffness. The models are shown to oscillate at frequencies, pressures, and flow rates typical of human speech. Phase-locked particle image velocimetry (PIV) results are presented which characterize the glottal jet, including jet direction, vortical structures, and turbulence levels. Results are shown for symmetric and asymmetric vocal fold models. The degree of material asymmetry required to cause significant asymmetry in the glottal jet is reported. [Preview Abstract] |
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