Investigating the three-dimensional flow separation induced by a model vocal fold polyp

Area of Science:

• Fluid dynamics
• Acoustic phonetics
• Biomedical engineering

Background:

• Normal speech fluid-structure energy exchange is understood, but not for pathological conditions like vocal fold polyps.
• Polyps are geometric abnormalities on vocal folds, disrupting dynamics and communication.
• Previous particle image velocimetry (PIV) showed polyps disrupt glottal jet behavior.

Purpose of the Study:

• Investigate 3D flow separation induced by a model vocal fold polyp.
• Understand the impact of flow separation on aerodynamic loadings.
• Advance treatment for vocal fold polyp pathological conditions.

Main Methods:

• Used a wall-mounted prolate hemispheroid (2:1 aspect ratio) as a model vocal fold polyp in cross-flow.
• Employed an oil-film visualization technique.
• Examined unsteady, 3D flow separation and wall pressure loading using skin friction line visualization and pressure measurements.

Main Results:

• Observed considerable disruption of glottal jet behavior by the model polyp.
• Identified unsteady, three-dimensional flow separation.
• Quantified the impact of flow separation on wall pressure loading.

Conclusions:

• Geometric abnormalities like polyps significantly alter vocal fold airflow dynamics.
• Understanding flow separation is crucial for diagnosing and treating voice pathologies.
• This research provides insights into aerodynamic forces influencing vocal fold vibration in pathological conditions.