Aerodynamic transfer of energy to the vocal folds

Abstract

The aerodynamic transfer of energy from glottal airflow to vocal fold tissue during phonation was explored using complementary synthetic and numerical vocal fold models. The synthetic model was fabricated using a flexible polyurethane rubber compound. The model size, shape, and material properties were generally similar to corresponding human vocal fold characteristics. Regular, self-sustained oscillations were achieved at a frequency of approximately 120 Hz. The onset pressure was approximately 1.2 kPa. A corresponding two-dimensional finite element model was developed using geometry definitions and material properties based on the synthetic model. The finite element model upstream and downstream pressure boundary conditions were based on experimental values acquired using the synthetic model. An analysis of the fully coupled fluid and solid numerical domains included flow separation and unsteady effects. The numerical results provided detailed flow data that was used to investigate aerodynamic energy transfer mechanisms. The results support the hypothesis that a cyclic variation of the orifice profile from a convergent to a divergent shape leads to a temporal asymmetry in the average wall pressure, which is the key factor for the achievement of self-sustained vocal fold oscillations. me rica.

Computational modeling of phonatory dynamics in a tubular three-dimensional model of the human larynx

“…The largest velocity always occurs at the superior tip of the VFs. This convergent-divergent glottis shape has been proved to be the essential mechanism for the continuous transfer of mechanical energy from the airflow to the VF (Titze, 1988;Thomson et al, 2005).…”

A Flow Perfusion Bioreactor System for Vocal Fold Tissue Engineering Applications

“…38 The present bioreactor design evolved through several generations of physical replicas of the human larynx built over the past 20 years to mimic phonation, particularly the fold collisions, in vitro. 34,39,40 The oscillation frequency, onset phonatory characteristics, and pressure-versus-flow characteristics of synthetic replicas without inner cavities were previously shown to be in the range of those of human phonation. 22,41 The concept of physical replicas was modified by the introduction of an inner cavity to host the CSM.…”

“…The model was evolved from previously developed models, which have been verified and used to study VF vibrations. [31][32][33][34] The fluid domain was governed by using the viscous, unsteady Navier-Stokes equations. The flow was assumed to be laminar and slightly compressible, with the latter allowing for acoustical effects to be modeled.…”

Computational aeroacoustics of human phonation

“…These include studies with fixed vocal folds (e.g. [12,13,14,15]), forced vocal fold oscillation [16,17,6,18,19,20,21,22,23] and models with the airflow fully coupled to elastic tissue oscillations [24,25,26,27,28,29,30]. Only a few of these computational studies [24,12,14,15,22] solve the flow field in 3D, and most of them on a static geometry.…”

“…Some recent papers [37,14,15] claim that RANS approach for modeling of human phonation is inadequate and employ Large Eddy Simulations (LES). However, still many authors [16,24,18,25,19,20,13,28,21,30] use a "laminar" model, actually a Direct Numerical Simulation…”