Session F19: Biological fluid dynamics: Phonation and Speech

Pressure-velocity correlations in a scaled-up vocal fold model – symmetric case

Simultaneous time resolved measurements of pressure, along the centerline, and DPIV, at the mid-plane, were made in a scaled-up vocal fold model.  This allowed for detailed analysis of the fluid-structure interaction associated with the moving vocal folds.  The overarching goal is applying experimental data to the theoretical framework of Krane (2013) in which the principal aeroacoustic source is expressed in terms of vocal fold drag, glottal jet dynamic head, and glottal exit volume flow, reconciling formal theoretical aeroacoustic descriptions of phonation with more traditional lumped-element descriptions.  In this way time resolved velocity field measurements can be used to compute time-resolved estimates of the relevant terms in the integral equations of motion, including phonation aeroacoustic source strength. A simplified 10x scale vocal fold model from Krane, et al. (2007) was used to examine symmetric, i.e. ‘healthy’, oscillatory motion of the vocal folds.  Using water as the working fluid, very high spatial and temporal resolution was achieved.   Experiments were dynamically scaled to examine frequencies corresponding to male and female voice.  Results showing phase relations between pressure and flow are will be presented.   

Pressure-velocity correlations in a scaled-up vocal fold model – divergent cases

This study examines more complex flows in the scaled-up vocal fold model described in Ringenberg, et al (APS-DFD 2018).  Specifically, cases where the vocal fold models do not completely close or only one vocal fold moves are examined.  Simultaneous time resolved measurements of pressure, along the centerline, and DPIV, at the mid-plane, were made for  a range of frequencies and Reynolds numbers characteristic to male and female voice.  For the case where the vocal folds do not close, there are significant differences owing to the fact that the full pressure drop between the upstream and downstream sides of the vocal folds does not develop.  The effects of one stationary and one moving vocal fold are manifest more in asymmetries than differences in fluid forces throughout the oscillation cycle.  Effects on lateral force and the phase relationships between flow and pressure will be examined.   

A Reduced-Order Fluid-Structure Interaction Model for Vocal Fold Vibration

Three-dimensional (3D) accurate modeling of the fluid-structure interaction (FSI) for the vocal fold is useful for medical applications such as patient-specific surgery planning.  However, unknown material properties of the vocal fold tissue for individual patients limit the fidelity of such models.  In addition, high computational cost associated with 3D FSI models hinders their extensive use in the design optimization of surgical implants.  In our work, we aim to develop a reduced-order FSI model that balances between computational cost and accuracy.  Such model will be used for repeated rapid simulations in 1) estimation of unknown modeling parameters and 2) optimization of the implant in the procedure of medialization laryngothyroplasty.  In this model, the 3D anatomy of the vocal fold is retained, and the nonlinear tissue mechanics is solved with a finite-element method.  However, the flow is simplified to a one-dimensional momentum equation based model incorporating the entrance and viscous effects.  The performance of this FSI model will be compared with the 3D FSI simulation, as well as a simple Bernoulli based flow model.   

Aerodynamic, Acoustic, and Vibratory Consequences of Subglottic Stenosis in a Model of the Respiratory Airway Containing Self-Oscillating Vocal Fold Replicas

Subglottic stenosis (SGS) is characterized by a narrowing of the airway below the vocal folds. The extra growth—frequently made of scar tissue—is most commonly caused by prolonged intubation or trauma to the area, although it can develop as a result of disease or be idiopathic. While SGS clearly inhibits respiration, the aerodynamic and acoustic consequences of SGS on voicing remain relatively understudied. It is hypothesized that the jet caused by SGS has the potential to impinge on the vocal folds, causing additional sound production and an altered loading on the vocal folds. For this study, an adjustable, actuated device simulating subglottic stenosis was developed. Synthetic models of the vocal folds in conjunction with upper and lower airway replicas, the latter including regions with geometric changes representative of SGS, and the former including different vowel-vocal tract configurations, were used to explore the influence of SGS on vibratory and acoustic output during voicing. Measurement methods and results are described, including data characterizing the relationships between SGS severity and parameters such as onset pressure, vocal fold model vibratory response, and radiated acoustic spectra.