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The Chaotic Voice: Nonlinear Fluid-Structure Interaction in Abnormal Phonation

University of Registration: University of Birmingham

BBSRC Research Themes:

• Integrated Understanding of Health (Ageing, Diet and Health)

Project Outline

Human voice production emerges from the complex interaction between airflow from the lungs, the nonlinear vibrations of the vocal folds, and acoustic resonances of the vocal tract. In normal phonation, this interaction yields nearly periodic oscillations that produce a stable and harmonic sound. However, in pathological cases such as vocal fold paralysis, nodules, or asymmetry, this delicate balance is disrupted, leading to irregular, noisy, and often chaotic vibrations. Such abnormal phonation manifests clinically through measures such as jitter, shimmer, and increased spectral noise; however, the mechanistic origins of these phenomena remain insufficiently understood. Capturing the chaotic dynamics of phonation requires resolving the strongly coupled, nonlinear fluid-structure interaction (FSI) between glottal airflow and deformable vocal fold tissue at a fidelity beyond the reach of traditional reduced-order models.

This project addresses this gap by developing high-fidelity, GPU-accelerated simulations of abnormal phonation. A three-dimensional computational framework will couple an incompressible Navier鈥揝tokes fluid solver with a nonlinear finite element model of vocal fold tissue, represented as a multi-layered, anisotropic, hyperelastic structure. Immersed boundary or sharp-interface methods will be employed to resolve large deformations and the intricate vortex-structure interactions that drive irregular vocal fold motion. Systematic parameter studies will explore the influence of tissue stiffness, asymmetry, geometry, and subglottal pressure on the transition from periodic oscillations to chaotic phonation. By linking biomechanical changes to observed voice instabilities, the research will provide a mechanistic understanding of how pathology alters phonatory dynamics. Ultimately, the work will deliver predictive tools for diagnosing and treating vocal disorders, inform surgical planning, and inspire the design of next-generation voice prostheses.

Computational and Mechanistic Modelling of Porosity Effects in Eye Fluid Mechanics - Implications for Glaucoma

Secondary Supervisor(s): Prof Lisa Hill

University of Registration: University of Birmingham

BBSRC Research Themes:

• Integrated Understanding of Health (Ageing, Diet and Health)

Project Outline

The human eye relies on tightly regulated fluid dynamics to maintain intraocular pressure (IOP), nutrient transport, and tissue health. While aqueous humour flow and conventional outflow pathways, such as the trabecular meshwork and Schlemm鈥檚 canal, are well studied, the role of microscale tissue porosity in controlling fluid transport and biomechanical stresses remains poorly understood. Ocular tissues, including the sclera, cornea, and optic nerve head, display porous structures that facilitate interstitial flow and influence deformation under both physiological and pathological conditions. Dysregulation of these pathways can elevate IOP, a significant risk factor for glaucoma, leading to optic nerve damage. Mechanistic understanding of how porosity affects fluid flow and tissue stresses is therefore critical for elucidating glaucoma progression and informing potential interventions.

This research aims to quantify the impact of tissue porosity on ocular fluid mechanics and glaucoma risk through high-fidelity GPU-accelerated CFD simulations. Objectives include characterising how porosity and permeability govern aqueous humour outflow and interstitial fluid movement, developing a coupled fluid-structure framework integrating Navier-Stokes flow with poroelastic tissue mechanics, and investigating the interplay between fluid transport and structural stresses under elevated IOP. Methodology combines experimental tissue characterisation, mechanistic modelling, and high-resolution GPU-accelerated CFD simulations. Fluid flow in the anterior chamber will follow Navier-Stokes equations, while porous tissue transport will use Darcy鈥檚 law. Parametric studies of porosity, permeability, and pressure will identify critical factors affecting ocular mechanics. Model validation will use clinical and experimental data on IOP, outflow facility, and tissue deformation, establishing a robust framework for understanding glaucoma mechanics.