Defense Date

3-12-2025

Graduation Date

Spring 5-10-2025

Availability

One-year Embargo

Submission Type

thesis

Degree Name

MS

Department

Biomedical Engineering

School

School of Science and Engineering

Committee Chair

Rana Zakerzadeh

Committee Member

Melikhan Tanyeri

Committee Member

Lauren Sugden

Committee Member

David S. Ford

Keywords

Fluid-Structure Interaction, Vocal Folds, VF Lesion

Abstract

The biomechanical and aerodynamic behaviors of the vocal folds (VFs) during phonation are heavily influenced by their structural composition and pathological changes. These conditions can induce localized stiffening that disrupts vibratory symmetry and alters airflow resistance. Previous research has lacked the integration of VF lesions in computational simulations using anatomically accurate models, limiting the understanding of their effects in phonation and potential contribution to voice disorders. Addressing this gap, this thesis develops a fluid-structure interaction (FSI) model of a realistic two-layered VF structure with lesions, comparing airflow patterns, structural deformations, and vibration profiles in both healthy and diseased cases.

The modeling leverages ANSYS software to couple fluid dynamics and solid mechanics, simulating the interaction between airflow and VF tissue deformation. The Navier-Stokes and continuity equations govern fluid flow, while the momentum conservation equation for balance of total forces is solved for soft tissues. Material properties such as Young’s modulus and Poisson’s ratio are defined, and boundary conditions are applied. The realistic geometry is constructed, and a cover layer is added in an attempt of more accurately representing the VF structure. A lesion representing a blood clot is added to the double-layered model, fully embedded in the cover layer. A final case also simulates permeable lesion tissue, introducing the geometry of a dilated blood vessel.

The results proved the layered geometry to be a more physiologically accurate way of representing the VFs than the one-layered model, with a focus on the achievement of full closure of the glottal gap during closing phases of the oscillation cycle. The introduction of the lesion caused noticeable asymmetric structural variations, not only in the diseased fold, but also in its healthy counterpart. These variations impacted the frequency and amplitude of the tissue’s deformation, both of which are known to affect vocal function, particularly pitch and intensity.

This research offers valuable insights into how VF layers and lesions influence structural and airflow changes that can impair phonation and contribute to voice disorders. The FSI modeling was crucial for the analysis and interpretation of the results, as magnitude values alone were not significant without visualized contours. By establishing a computational framework to understand the physiological effects of VF pathologies, these findings emphasize FSI modeling as a valuable tool for studying VF pathologies and developing targeted interventions for laryngeal diseases.

Language

English

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