Low-dimensional models of the glottal flow incorporating viscous-inviscid interaction.

The behavior of glottal flow can, to a large extent, be characterized by development and separation of the boundary layer. The point of flow separation is known to vary during the phonatory cycle due to change in channel configuration. To take the movable nature of the separation point into account, the boundary-layer equation is solved numerically, and the values of the characteristic quantities are determined as well as the point of separation. Development of the boundary layer in general reduces the effective size of the channel, and, therefore, increases the core flow velocity, which, in turn provides the boundary condition of the boundary-layer equation. The interaction between the viscous (boundary layer) and inviscid (core flow) parts of the glottal flow is, therefore, strongly indicated. To apply this viscous-inviscid interaction, the expression of the core flow is derived for a two-dimensional flow field, and is solved jointly with the boundary-layer equation. Numerical results are shown to examine the effect of the Reynolds number and glottal configuration, with special emphasis on the comparison of flow models developed for one- and two-dimensional flow fields. Numerical results are also quantitatively compared with data obtained from flow measurement experiments.