Phase-averaged analysis of jet dynamics in a scaled-up vocal fold model with asymmetric motions

This study focuses on the effects of glottal jet dynamics on phonation when one of the vocal folds does not move as much as the other. This can be a pathological condition, such as vocal fold paresis, in which a vocal fold is completely or partially paralyzed. Experiments were conducted using a 10× scaled-up model in a free-surface water tunnel. Two-dimensional vocal fold models with semi-circular ends were computer-driven inside a square duct with constant opening and closing speeds. Four cases were studied in which one vocal fold moved 0%, 50%, 75%, and 100% of the other; the last case being, of course, the nominally “healthy,” symmetric case. Time-resolved Digital Particle Image Velocimetry and pressure measurements along the duct centerline were made at a Reynolds number of 7200 and reduced frequency of 0.0261, corresponding to an equivalent life frequency of 97.5 Hz. Phase-averaged analysis of key contributors to sound production was conducted using terms in the streamwise integral momentum equation. The ultimate goal is understanding how asymmetric gap opening affects the dynamics, specifically vocal fold drag, and therefore, sound production. Results of this experiment show that this nominally simple flow encompasses multiple effects due to varying maximum gap opening, asymmetry due to partial motion of one vocal fold, blockage by the wall boundary layers, and pseudo-frequency effects arising when the two vocal folds move at different speeds. There is indeed a dependence of vocal fold drag on gap opening.