GALCIT Colloquium

Speech production involves unsteady pulsatile flow and turbulent structures that affect the
aeroacoustics and fluid-tissue interaction. Our overarching motivation for studying flow
associated with phonation is to facilitate evaluation and design of treatment interventions and
for surgical planning, i.e. to enable physicians to assess the outcomes of surgical procedures
by using faithful computer simulations. We also seek to inform non-surgical clinical treatment
strategies of voice disorders. The goal of our human phonation research program is to
investigate the dynamics of flow past the vocal folds (VF) and the aerodynamic interaction
with the VF. Silicone-based, self-oscillating synthetic vocal fold (VF) models are fabricated
with material properties representative of the different layers of human VFs and then
evaluated experimentally in a life-size in vitro vocal tract simulator to replicate physiological
conditions. Our experimental investigations utilize high-speed imaging, particle image
velocimetry (PIV), pressure transducers and microphones, and the clinical Rothenberg mask.
Studies are performed under both normal and pathological conditions of speech. Recent
attention has been focused on understanding the role of polyps (growths on the VF) in altering
voice quality. This has led to fundamental studies of 3D flow separation around surface
mounted obstacles in pulsatile flows. We have generalized our studies to various surface
protuberances – hemispheres, cubes and cylinders immersed in highly pulsatile flow. In
addition to experiments we have performed CFD simulations using an in-house Navier-Stokes
code. These investigations are designed to unify the classical instantaneous description of
shed hairpin vortices with the standing arch vortex viewpoint that arises from phase
averaging.