Abstract

The influence of vocal fold (VF) vibration on perfused flow through VF vasculature is an area of research that has previously received limited attention. The aim of the research presented in this thesis was to contribute towards an improved understanding of the effects vibration on perfusion through vasculature within the VFs. This was done using a series of computational simulations of geometric changes to, and perfusion through, microchannels embedded in VF models. A computational structural model based on synthetic VF models used in previous experimental studies was first developed. The model and its embedded microchannel were initially studied under static pressure loads applied to the inner surfaces of the channel as well as to the VF inferior and medial surfaces. It was shown that the channel volume decreased linearly and the channel length increased quadratically with increasing pressure on the external VF surfaces. Changes in Poisson's ratio and its influence on the embedded channel's maximum deflection, volume, and length were also studied. Across the range of Poisson's ratios that has been studied for silicone used in synthetic VF models (0.4 to 0.495) there was shown to be limited change in microchannel maximum deflection, channel length, and volume for equivalent pressure loads. The model was then modified to include an external oscillating pressure load on the VF surface that caused the model to vibrate. Two separate studies were conducted to determine how frequency and deflection amplitude affected the predicted perfusion flow rate through the embedded microchannel by accounting for the changes in microchannel geometry during vibration. These studies showed that frequency had little effect on predicted flow rate, while increased deflection amplitude led to greater reductions in predicted flow rate. These reductions in flow rate were attributed to channel lengthening and cross section deformation during vibration, with the latter playing a much larger role. Reductions in flow rate results were found to favorably agree with measured experimental flow rate reductions reported previously. Computational fluid dynamics simulations of water flowing through the inflated embedded microchannel during vibration were also conducted. These simulations were used to explore how changes in vibration length, amplitude, and frequency affected the fluid dynamics in the microchannel whilst minimizing geometric changes to the microchannel. The flow rates from each of the simulation cases were compared to determine which of the vibration parameters contributed the most to flow losses. Vibration length and amplitude were shown to be statistically significant. An investigation was undertaken to further elucidate the mechanisms behind the flow losses induced by vibration. The effects of channel elongation, increased channel curvature, pressure rises, and pressure gradients during vibration were analyzed. Changes in channel elongation and pressure were shown to significantly contribute to flow losses and flow rate reduction. The results from these simulations were compared with the structural simulations which analyzed how changes in microchannel geometry affected flow rate reductions. Changes in the microchannel geometry were shown to contribute much more significantly to reductions in perfusion flow rate compared to changes in vibration parameters (i.e., vibration length, amplitude, and frequency).

Degree

College and Department

Ira A. Fulton College of Engineering; Mechanical Engineering

Rights

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