Numerical simulation of unsteady flow through the rigid glottis

The present study is intended as an investigation of speech dynamics, particularly the unsteady motion of glottal flow in the larynx. In order to focus on only fluid motion, the vocal cords are assumed to be non-vibrating rigid bodies, although the glottal sound source is described as the interaction between the flow and the vibrating vocal cords. The glottal flow based on the two-dimensional rigid body model is simulated by solving basic equations in a compressible viscous fluid that is subject to appropriate initial and boundary conditions. The obtained results demonstrate that the initial glottal flow was a simple symmetric jet and that the flow became an unsteady complicated flow with vortices distributed in two-dimensional space. Furthermore, the structure of the complicated flow changed with time. These results indicate that simple assumptions, such as linearization of the fluid equations or one-dimensional models, are inappropriate for analysis of the speech production process.