Modeling of the human larynx with application to the influence of false vocal folds on the glottal flow

Hosnieh Farahani, Mehrdad. "Modeling of the human larynx with application to the influence of false vocal folds on the glottal flow. ii To my parents iii ACKNOWLEDGMENTS I would like to thank my adviser Dr. Sarah Vigmostad for introducing me to this interesting research project. I am also grateful for her guidance and support. In addition, I am thankful to my committee members for their suggestions. Especially, I am sincerely thankful of Dr. Fariborz Alipour for his kind suggestions and advice in the course of this journey. He generously allowed me to use his laboratory for the experimental investigations. I would also like to express my gratitude to Dr. Udaykumar for his suggestions and advise for the computational part of my dissertation. My greatest appreciation goes to my colleague John Mousel for his friendship, patience, support, valuable comments, and constructive suggestions. Sitting next to me in our lab with his immense computational knowledge, he was always willing to help. I am thankful to Seth Dillard for image segmentation of medical images. I would also like to acknowledge my friendly and fun atmosphere. Last but not least, I am grateful of my family for their continued love and support. iv ABSTRACT Human phonation is a complex phenomenon produced by multiphysics interaction of the fluid, tissue and acoustics fields. Despite recent advancement, little is known about the effect of false vocal folds on the fluid dynamics of the glottal flow. Recent investigations have hypothesized that this pair of tissue can affect the laryngeal flow during phonation. This hypothesis is tested both computationally and experimentally in this dissertation. The computations were performed using an incompressible solver developed on fixed Cartesian grid with a second order sharp immersed-boundary formulation while the experiments were carried out in a low-speed wind tunnel with physiologic speeds and dimensions. A parametric study was performed to understand the effect of false vocal folds geometry on the glottal flow dynamics and the flow structures in the laryngeal ventricle. The investigation focused on three geometric features: the size of the false vocal fold gap, the height between the true and false vocal folds, and the width of the laryngeal ventricle. It was found that the size of the false vocal fold gap has a significant effect on glottal flow aerodynamics; whereas the height between the true and false vocal folds and the width of the laryngeal ventricle were of lesser importance. …