On the viscous-inviscid interaction of the flow passing through the glottis

Abstract

A model of flow passing through the glottis is presented, that assumes a boundary layer. The fluid dynamic theory implies that a thin boundary layer formed in the vicinity of the glottal wall characterizes the flow behavior, including the flow separation, jet formation, and pressure loss across the channel. To analyze the boundary layer accurately, methods have been developed for solving the integral momentum relation on the basis of the similarity of the velocity profiles inside the layer, by assuming that the core flow velocity is known. On the other hand, development of the boundary layer reduces the effective size of the channel and increases the core flow velocity, thus causing the problem of viscous-inviscid interaction of the boundary layer. In this paper, the interactive boundary-layer problem is solved for glottal flow, and numerical results are compared with a conventional noninteractive model. In addition, the effects of the Reynolds number and glottal configuration on the flow behavior have been examined to validate the usefulness of the proposed flow analysis method.

Effect of channel asymmetry on the behavior of flow passing through the glottis

“…By extending our previous flow analysis studies [10,11], this paper presents a method for analyzing the two-dimensional flow in asymmetrical glottal channels. In addition to the boundary-layer approximation, our method considers the coupling between the main flow, which is assumed to be inviscid, and the boundary layer, which is a viscous flow.…”

“…In regular phonation, the glottal shape is convergent during the opening phase of the glottal cycle and divergent during the closing phase [2]. The aerodynamic pressure of glottal flow then becomes both positive and negative according to the convergentdivergent change in the glottal shape, supporting the maintenance of the vocal fold oscillation [9][10][11]. As such, precise analysis of flow behavior will increase our knowledge about the mechanism of voice production for both the regular case and irregular pathological case.…”

“…By assuming that the flow is steady and incompressible, Bernoulli's law is applied to determine the relationship between the flow velocity and the pressure distribution along the glottal wall. This analysis method is reliable if the friction loss due to the air viscosity and estimation of the flow separation point are incorporated [9,10]. In the case of the pathological voice, however, the glottal channel is asymmetrical because of unbalanced motion of the left and right vocal folds.…”

“…A similar computational fluid dynamics approach was used for both symmetrical and asymmetrical glottal channels [13,14]. On the other hand, it has been revealed that the analysis methods based on the boundary-layer approximation are highly accurate and computationally efficient [9][10][11]15]. Lagrée et al [16] applied a method called interactive boundary-layer (IBL) analysis to investigate the asymmetrical effects, and they calculated the distribution of the characteristic quantities of glottal flow along the channel.…”

“…The effect of flow asymmetry is examined for a large number of channel shapes. Numerical results are also compared with those obtained by one-dimensional IBL analysis [10] to quantitatively evaluate the applicability of the conventional one-dimensional assumption.…”