A Canonical Biomechanical Vocal Fold Model

The present article aimed at constructing a canonical geometry of the human vocal fold (VF) from subject-specific image slice data. A computer-aided design approach automated the model construction. A subject-specific geometry available in literature, three abstractions (which successively diminished in geometric detail) derived from it, and a widely used quasi two-dimensional VF model geometry were used to create computational models. The first three natural frequencies of the models were used to characterize their mechanical response. These frequencies were determined for a representative range of tissue biomechanical properties, accounting for underlying VF histology. Compared with the subject-specific geometry model (baseline), a higher degree of abstraction was found to always correspond to a larger deviation in model frequency (up to 50% in the relevant range of tissue biomechanical properties). The model we deemed canonical was optimally abstracted, in that it significantly simplified the VF geometry compared with the baseline geometry but can be recalibrated in a consistent manner to match the baseline response. Models providing only a marginally higher degree of abstraction were found to have significant deviation in predicted frequency response. The quasi two-dimensional model presented an extreme situation: it could not be recalibrated for its frequency response to match the subject-specific model. This deficiency was attributed to complex support conditions at anterior-posterior extremities of the VFs, accentuated by further issues introduced through the tissue biomechanical properties. In creating canonical models by leveraging advances in clinical imaging techniques, the automated design procedure makes VF modeling based on subject-specific geometry more realizable

Matematické a fyzikální modelování prouděním vyvolaného kmitání lidských hlasivek

the pressure and velocity fields in coronal plane along the vibrating vocal folds were studied using a finite element mathematical model. The shapes of the vocal folds were specified according to data measured on excised human larynges in phonation position. The mathematical model of the flow is based on 2D incompressible Navier-Stokes equations adapted to deal with the time-variable shape of the domain, caused by vocal fold vibration. The numerical simulations allow to observe closely various flow features related to phonation - flow separation in the glottis, Coanda effect or vortex shedding

Coherent turbulent structures in flow through the human vocal tract

This paper presents experimental and computational data on the coherent turbulent structures in flow through the human vocal tract. The experimental results were obtained using a 4:1 scaled self-oscillating physical model of vocal folds. Flow velocity fields in the coronal plane were visualized and measured using a PIV system phase-synchronized with vocal fold vibration. Computational results originate from finite volume discretizations of viscous incompressible Navier-Stokes equations in 2D and 3D. The results reveal flow separation in the divergent part of glottis and formation of a planar jet. Vortex structures are shed from the shear layer of the jet and convected further downstream. The computational model helps to assess the influence of the ventricular folds on the flow patterns

Interakce tělesa a tekutiny v lidských hlasivkách

Matematicko-fyzikální fakultaFaculty of Mathematics and Physic

Dynamic properties of some physical models of artificial vocal folds

The report presents results from measurements of acoustic and vibratory characteristics of six originally designed artificial vocal fold prototypes made of silicon rubber and based on various aeroelastic principles. During measurements, the dynamic subglottal pressure and output acoustic pressure were recorded. Spectral analysis of the signals was performed, and where the construction permitted, the vibrations were also observed by means of videostroboscopy. For two prototypes a shape and material optimization is possible with the aid of the mathematical models developed in IT AS CR

Matematické modelování interakce tekutiny a tělesa v problematice lidských hlasivek

In the paper numerical results from a mathematical model of human vocal folds are compared with experimental data obtained from measurements on a maquette of vocal folds, which consisted of a silicone element vibrating in a channel conveying air

Evaluation of Interferograms of Unsteady Subsonic Airflow Past a Fluttering Airfoil

The paper reports on time-resolved interferometric measurements of unsteady ow elds around a uttering NACA0015 airfoil. A mechanical model with two degrees of freedom (pitch and plunge) has been designed and tested in a high-speed subsonic wind tunnel. Aeroelastic instability of the classical utter and dynamic stall type has been observed in the Mach number range M = 0.2 - 0.5. The interferograms were recorded using a Mach-Zehnder interferometer and a high-speed camera. An in-house software IFGPro was developed for the postprocessing and evaluation of the interferogram sequences, yielding pressure distribution, lift and drag force on the airfoil