Computational modeling and analysis of fluid-structure interaction during phonation in healthy and diseased larynges

The motivation of the current study is to explore the use of computational biomechanics tools for analysis of phonation in healthy and diseased larynges and assess the viability of using such tools for planning medialization laryngoplasty, which is one of the most common surgeries for treatment of laryngeal paralysis.;A flow-structure interaction computational solver, which explicitly couples an immersed boundary method based Navier-Stokes solver and a finite-element method based solid dynamics solver, is developed to model the biomechanical interaction between glottal aerodynamics and vocal fold tissue vibrations.;A parametric eigen-analysis is first carried out to address the uncertainty associated with the internal structure of the vocal folds for simulation based surgery planning. The overall conclusion regarding the feasibility of accurate computational modeling of phonation in the face of relatively high levels of uncertainty regarding the inner structure is generally positive. However, significant changes in ligament and cover thickness can potentially produce different dynamics.;A high-fidelity three-dimensional simulation has been performed to study the glottal flow and vocal fold vibrations during phonation. The laryngeal model was designed with a high level realism with respect to the anatomical details. The resulting glottal waveform, glottal jet evolution and vocal fold vibration pattern are found to be well corresponding to in-vivo and in-vitro observations. Detailed analysis about glottal jet evolution, jet deflection and the energy transfer between glottal flow and vocal folds has been provided. The effect of the false vocal folds on phonation has also been examined. The presence of false vocal folds is found to suppress the large-scale deflection of the glottal jet, which in turn reduces the viscous losses associated with flow-mixing. Meanwhile, the glottal vibration and sound intensity is also reduced by the addition of the false vocal folds.;Finally, two as well as three-dimensional laryngeal models have been used to study the effect of tension imbalance on vocal fold vibrations and glottal aerodynamics, as well as its implication on phonation. The results indicate that tension imbalance influences phonation onset, intensity, the fundamental phonation frequency as well as the energy transfer between glottal flow and vocal folds.