The effect of sulcus vocalis on vocal folds function is investigated. A type II sulcus vocalis is defined, parameterized and incorporated into a three-dimensional, fully coupled finite element model of vocal folds and laryngeal airway. The proposed Fluid-Structure Interaction (FSI) model is utilized in computational fluid dynamics, Arbitrary Lagrangian-Eulerian (ALE), incompressible continuity and Navier-Stokes equations and in a structure range of a three-layer elastic linear model. Flow parameters, vibration behavior and glottal jet aerodynamics of healthy and patient vocal folds models are compared with each other. Flow visualization is utilized to characterize Coanda effect and three dimensionality of flow patterns. The vibration frequency of vocal folds having sulcus vocalis decreases in comparison with that of healthy ones. Upon increasing the volume flux in the sulcus vocalis model, the non-periodic and disordered behavior of it is visible for patient vocal folds. Underlying mechanisms for the observed changes, possible implications for treatments of sulcus vocalis and human perfect voice production are also discussed.

Speaking is a very complex process resulting from the interaction between the air flow along the larynx and the vibrating structure of the vocal folds. Sulcus is a disease missing layers in the vocal folds result in cracks resulting in some disorders in producing sounds. Sulcus and its effects on the vocal cord vibrations are numerically studied for the first time in this paper. An ideal model of healthy vocal folds and Sulcus vocalis has been two-dimensionally defined and the finite element model of vocal folds is solved in a fully coupled form. The proposed calculative model was used in a fluid range of the computational fluid dynamics, arbitrary Lagrangian-Eulerian (ALE), incompressible continuity and Navier-Stokes equations and in a structure range of a three-layer elastic linear model. Self-excited oscillations were presented for vocal folds among type II patients and compared with healthy models. Responses were qualitatively and quantitatively studied. The healthy model was compared with numerical and empirical results. In addition, the effects of the disease on the flow parameters and the vibration frequency of the vocal folds were studied. According to the simulated model, the oscillation frequency decreased 25% and the average and instantaneous volume flux significantly increased compared to healthy samples. Results may help present a guideline for surgery and subsequently evaluate patients’ improvement.