Characteristics of the pulsating jet flow through a dynamic glottal model with a lens-like constriction

Phase-averaged and cycle-to-cycle analysis of jet dynamics in a scaled up vocal-fold model

Phase-averaged and cycle-to-cycle analysis of key contributors to sound production in phonation is examined in a scaled-up vocal-fold model. Simultaneous temporally and spatially resolved pressure and velocity measurements permitted examination of each term in the streamwise integral momentum equation. The relative sizes of these terms were used to address the issue of whether transglottal pressure is a surrogate for vocal-fold drag, a quantity directly related to sound production. Further, time traces of transglottal pressure and volume flow rate provided insight into the role of cycle-to-cycle variations in voiced sound production which affect voice quality. Experiments were conducted using a 10× scaled-up model in a free-surface water tunnel. Two-dimensional vocal-fold models with semi-circular ends inside a square duct were driven with constant opening and closing speeds. The time from opening to closed, T_o , was half the oscillation period. Time-resolved digital particle image velocimetry (DPIV) and pressure measurements along the duct centreline were made for 3650 ≤ Re ≤ 8100 and equivalent life frequencies from 52.5 to 97.5 Hz. Results showed that transglottal pressure does serve as a surrogate for the vocal-fold drag. However, smaller but non-negligible momentum flux and inertia terms, caused by the jet and vocal-fold motions, may also contribute to vocal-fold drag. Further, cycle-to-cycle variations including jet switching and modulation are inherent in flows of this type despite their high degrees of symmetry and repeatability. The origins of these variations and their potential role in sound production and voice quality are discussed.

Cycle-to-cycle flow variations in a square duct with a symmetrically oscillating constriction

Spatially and temporally resolved Digital Particle Image Velocimetry (DPIV) measurements are presented of flow complexities in a nominally two-dimensional, symmetric, duct with an oscillating constriction. The motivation for this research lies in advancing the state-of-the-art in applying integral control volume analysis to modeling unsteady internal flows. The specific target is acoustic modeling of human phonation. The integral mass and momentum equations are directly coupled to the acoustic equations and provide quantitative insight into acoustic source strengths in addition to the dynamics of the fluid-structure interactions in the glottis. In this study, a square cross-section duct was constructed with symmetric, computer controlled, oscillating constrictions that incorporate both rocking as well as oscillatory open/close motions. Experiments were run in a free-surface water tunnel over a Strouhal number range, based on maximum jet speed and model length, of 0.012 - 0.048, for a fixed Reynolds number, based on maximum gap opening and maximum jet speed, of 8000. In this study, the constriction motions were continuous with one open-close cycle immediately following another. While the model and its motions were nominally two-dimensional and symmetric, flow asymmetries and oscillation frequency dependent cycle-to-cycle variations were observed. These are examined in the context of terms in the integral conservation equations.