Computational aeroacoustics of flow through static model of human vocal tract

Abstract

Computational aeroacoustics studies of flow through the human vocal tract, here modeled as a planar channel with an orifice, hence referred to as the glottis, were conducted using large-eddy simulation (LES). Comparisons were made between LES predictions and experimental wall pressure measurements and particle-imaging-velocimetry flow fields. Rigid models of both converging and diverging glottal passages, each featuring a 20-deg included angle and a minimal glottal width of 0.04 cm with transglottal pressure of 15 cm H2O, were studied. The compressible Navier-Stokes equations were accurately and efficiently integrated for the low Mach number flow through the use of an additive semi-implicit Runge-Kutta method and high-order compact finite-difference schemes for spatial discretization. Characteristic-based nonreflecting boundary conditions were used together with an exit zone in the context of a multiblock approach. Asymmetry of the flow due to a Coanda effect, and transition to turbulence were observed. An acoustic analogy based on the Ffowcs Williams-Hawkings equation was applied to decompose the near-field acoustic source into its monopole, dipole, and quadrupole contributions to assess glottal geometry effects on far-field sound. The results showed that dipole sources due to the unsteady forces exerted on the duct wall are dominant. [Work funded by NIH Grant RO1 DC03577.]