Fluid–structure interaction analysis of lesion size and elasticity effects in vocal folds

Abstract Benign vocal fold (VF) lesions introduce localized geometric and mechanical heterogeneity that alters phonatory dynamics, yet their relative contributions to vibration behavior remain unclear. In this study, a three-dimensional fluid–structure interaction (FSI) model of the VFs is developed to investigate how lesion geometry and lesion material stiffness influence VF vibration and glottal aerodynamics during phonation. A unilateral lesion is introduced in the cover layer of a single fold, and a parametric study is conducted in which lesion length and material stiffness are varied across physiologically plausible ranges. These ranges represent clinically observed lesion sizes and variability in material properties associated with different benign pathologies and age-related tissue changes. Transient FSI simulations are performed to compute the coupled airflow and tissue motion. Vibration behavior is quantified using displacement time histories and maximum deformation of the fold’s tissue, while aerodynamic effects are characterized by peak glottal jet velocity and intraglottal pressure, and AC glottal volume flow. The peak VF contact pressure is additionally evaluated to characterize localized contact loading. The results show that increasing lesion length produces pronounced changes in vibration amplitude and asymmetry between the folds, whereas variations in lesion stiffness result in minor changes in overall vibration patterns. Aerodynamic analysis demonstrates that geometric obstruction due to the lesion presence alters airflow velocity and pressure within the glottal constriction, which contributes to the observed vibration differences. The AC glottal flow rate changes moderately with lesion length and stiffness, whereas peak contact pressure increases consistently with lesion stiffness, indicating greater stiffness effects on localized contact mechanics than on global vibratory and aerodynamic measures. Overall, within the investigated parameter ranges, lesion geometry has a more pronounced influence than lesion material stiffness in determining global VF vibration and glottal aerodynamic behavior, while lesion stiffness has a stronger influence on contact pressure. These findings link lesion-induced changes in glottal aerodynamics to vibration asymmetry while demonstrating the distinct response of localized contact mechanics.