Bulletin of the American Physical Society
62nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 54, Number 19
Sunday–Tuesday, November 22–24, 2009; Minneapolis, Minnesota
Session LE: Biofluids VII: Phonation/Glottal Flows |
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Chair: Michael Plesniak, George Washington University Room: 101E |
Monday, November 23, 2009 3:35PM - 3:48PM |
LE.00001: Flow Induced Vibration and Glottal Aerodynamics in a Three-Dimensional Laryngeal Model Xudong Zheng, Qian Xue, Rajat Mittal, Steven Bielamowicz Three-dimensional effects associated with phonation remain unclear due to the lack of capability of simulating 3D fluid-tissue interaction in the past. To advance the state-of-the-art in this arena, an immersed-boundary method based flow solver coupled with a finite-element solid dynamics solver is employed to conduct high-fidelity direct-numerical simulations of phonation in a 3D model of the human larynx. Three-dimensional vibration patterns are captured along with turbulence effects and three-dimensional vortex structures in the glottal jet. Results from these simulations are presented. [Preview Abstract] |
Monday, November 23, 2009 3:48PM - 4:01PM |
LE.00002: Computational Modeling and Analysis of Phonation in a Diseased Larynx Qian Xue, Xudong Zheng, Rajat Mittal, Steven Bielamowicz The goal of our current research is to study the fundamental biophysics of phonation in healthy and pathological larynges. We have developed a coupled flow-structure interaction solver to help gain insight into the fundamental biophysics underlying unilateral laryngeal paralysis. The solver models the incompressible Navier-Stokes equations for the glottal aerodynamics and employs the classic two-mass model for the vocal folds. The effect of tension imbalance and subglottal pressure on the vocal fold dynamics is investigated. An analysis of the vibration modes as well as the frequency spectra and sound quality has been conducted. Results from these studies will be presented. [Preview Abstract] |
Monday, November 23, 2009 4:01PM - 4:14PM |
LE.00003: Simulation of Vocal Folds: A Fluid-Induced Self-Oscillating Problem Xingshi Wang, Lucy Zhang The goal of this study is to investigate the process of voice production by simulating the motion and deformation of human vocal folds. The vocal folds are oscillated by a constant lung pressure driven airflow in the throat. The system is modeled in 2-D using the immersed finite element method to simulate and study the fluid-structure interaction mechanism. From our numerical results, the glottal jets are identified. Several parameters such as the Reynolds number, Strouhal number, vocal folds stiffness, density ratio between the fluid and the structure are addressed and compared with experimental results. The frequency of the vocal folds vibration, fluid flow rate and pressure distribution are also investigated. In addition, the energy transfer between the fluid domain and the solid domain are analyzed to assist in explaining the underlying physical mechanism for this fluid-induced self-oscillating vocal folds. [Preview Abstract] |
Monday, November 23, 2009 4:14PM - 4:27PM |
LE.00004: The development of supraglottal flow structures during speech Byron Erath, Michael Plesniak During voiced speech, periodic vocal fold oscillations create a pulsatile jet that emanates from the glottis and is convected through the supraglottal tract. Unsteadiness in the supraglottal jet trajectory (superior to the vocal folds) has been observed in a variety of laryngeal flow investigations, contributing to sound production due to vortex pairing which occurs within the jet as well as the impingement of the deflected jet on physiological structures. However, there is confusion in the literature concerning the mechanisms which contribute to the flow variability. Instabilities in the supraglottal jet include the Kelvin-Helmholtz instability, as well as the hypothesized presence of jet 'flip-flopping', the tendency of the glottal jet to detach from one vocal fold wall and reattach to the opposing wall mid-cycle. The morphology of the supraglottal flow field is investigated using phase-averaged PIV measurements acquired in the anterior-posterior midplane of the superior vocal fold tract of a dynamically controlled 7.5 time life-size vocal fold model. Flow parameters are scaled to match physiological values. The relevant fluid flow phenomena that impact the supraglottal jet trajectory are identified. [Preview Abstract] |
Monday, November 23, 2009 4:27PM - 4:40PM |
LE.00005: Three-dimensional flow patterns in a scaled, physical vocal fold model with a unilateral polyp Angela Seawright, Byron Erath, Michael Plesniak Trauma to the vocal folds often causes the formation of polyps; affecting the efficiency of speech and making voice rough and breathy. The change in flow characteristics due to a unilateral polyp positioned on the medial surface of a 7.5 times life-size physical vocal fold model was investigated. Previously reported phase-averaged intraglottal particle image velocimetry (PIV) investigations in a coronal plane indicated significant variations in the flow behavior on different anterior offset planes relative to the polyp. Flow three-dimensionality was investigated by resolving the temporal evolution of the flow with laser Doppler velocimetry (LDV). Data were acquired superior to the glottal exit. Physiological values of Reynolds, Strouhal, and Euler numbers were matched. Results were compared to velocity fields generated by healthy vocal fold motion. The glottal jet trajectory, flow separation points, and the velocity distribution along the vocal fold walls were influenced. Thus, a polyp significantly disturbs and modifies the airflow through the vocal folds, which has implications on both the fluid-structure energy exchange and the sound production. [Preview Abstract] |
Monday, November 23, 2009 4:40PM - 4:53PM |
LE.00006: Measurement of Glottal Flow across Scaled Up Dynamic Vocal Fold Motion Erica Sherman, Michael Krane, Lucy Zhang, Timothy Wei An experiment to provide DPIV measurements of dynamic human vocal folds motion is presented. The experiment is run in a free-stream water tunnel using a 10x scaled-up model of the human vocal folds and vocal tract. The vocal fold model is a new design that incorporates both the rocking as well as the oscillatory open/close motions characteristic of vocal fold motions The Reynolds number and Strouhal number have been matched to human physiologic conditions. Flow measurements show the start-up jet, vortex dynamics and ultimate jet pinch-off as the model progresses through a cycle. The effects of asymmetries associated with disease will be discussed. [Preview Abstract] |
Monday, November 23, 2009 4:53PM - 5:06PM |
LE.00007: Aeroelastic-aeroacoustic measurements in a self-oscillating physical model of the human vocal folds Michael Krane, Zachary Cates Measurements are presented characterizing the relationship between the structure of physical models of the human vocal folds and the sound produced by their vibration by airflow from the lungs. The model vocal folds are fabricated by molding two layers of silicone rubber of specified stiffness, approximating the body/cover structure. These are mounted in a model vocal tract, where the prephonatory gap adjusted using micropositioners. Measurements conducted in an anechoic chamber include radiated sound pressure, and high-speed video of the vibrating model vocal folds, using prephonatory separation, body stiffness, and subglottal pressure as input parameters.. Essential behavior of the vocal fold models is presented. Vibration fundamental frequency and radiated sound pressure level outside the model vocal tract as a function of subglottal pressure and prephonatory gap are presented for the cases of two identical vocal folds and one vocal fold with lower stiffness, approximating vocal fold paralysis. [Preview Abstract] |
Monday, November 23, 2009 5:06PM - 5:19PM |
LE.00008: Direct measurement of aeroacoustic source spectrum due to a jet/wall interaction Shane Lani, Michael Krane The aeroacoustic source spectrum due to a turbulent jet passing over an obstruction is found experimentally. The model consists of a constriction and planar obstacle in a duct with dimensions commensurate with the those of a human vocal tract. An unsteady jet formed at a constriction interacts with a planar obstruction downstream with the jet normal to the planar surface. The aeroacoustic source spectrum is found both by measuring the unsteady force imparted on the planar obstruction as well as measuring radiated sound outside the duct. A comparison of the force spectrum to the inverse-filtered radiated sound measurements will be presented. [Preview Abstract] |
Monday, November 23, 2009 5:19PM - 5:32PM |
LE.00009: Comparison of measured aeroacoustic source spectra to predictions using a jet model Daniel Leonard, Michael Krane Sound radiated from a turbulent jet-wall interaction in a duct is measured for several jet-wall interaction geometries, for which the acoustic response of the duct was identical at low frequencies. This sound production mechanism is identical to that of unvoiced speech sounds. Traditionally in these cases, the speech science community has stressed the acoustic filter's role in determining the radiated sound, and has neglected the importance of the aeroacoustic source. When the local source region aerodynamics, such as the mean jet path relative to the wall and the jet speed are varied, but the acoustic filter held constant, distinct differences due to the aeroacoustic source are observable in the radiated sound. The source spectra are determined and qualitatively compared to an analytical model, and the distinct differences in the source spectra are described theoretically, whereas the classical approach would not have been able to theoretically describe these results. It is concluded that the turbulent jet's path makes a crucial contribution to the `shape' of the source spectrum and that unvoiced speech sound production depends as much on the local details of the source region aerodynamics and geometry as it does on the acoustic filter. [Preview Abstract] |
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