National Repository of Grey Literature 209 records found  previous11 - 20nextend  jump to record: Search took 0.01 seconds. 
Incompressible and compressible viscous flow with low Mach numbers
Balázsová, M. ; Feistauer, M. ; Sváček, Petr ; Horáček, Jaromír
In this paper we compare incompressible flow and low Mach number compressible viscous flow. Incompressible Navier-Stokes equations were treated with the aid of discontinuous Galerkin method in space and backward difference method in time. We present numerical results for a flow in a channel which represents a simplified model of the human vocal tract. Presented numerical results give a good correspondence between the incompressible flow and the compressible flow with low Mach numbers.
2D finite element formulation of elastic string vibrations with large displacements
Michálek, Jakub ; Horáček, Jaromír (advisor) ; Matyska, Ctirad (referee)
The thesis addresses the numerical solution of the oscillation of the vocal fold at finite strain, whereas the literature has so far been concerned with infinitesimal strain only. The geometry concerned corresponds to the easiest situation of falsetto, since we observe an isolated vocal fold. The vocal fold is treated as non-linear and non-isotropic continuum in 2D space. To demonstrate the function of the model, we simulate the behaviour of the vocal fold with the linear constitutive equation numerically. The vocal fold is modelled by the finite element method with quadratic elements for static and dynamic surface load. We show that a proper simulation of vocal fold tissue deformation requires the equations with finite strain term. Numerical simulation of the vocal fold can be used e.g. for the construction of artificial vocal folds, and for the optimization of their function. Understanding the phonatory mechanism is also essential for discovering the causes of the disorders such as the vocal nodules and for the scientific foundation of phoniatrics and education of singers. The thesis is interdisciplinary and synthesises the facts from mechanics of continuum, anatomy and education of singers.
Influence of the velopharyngeal opening on human voice quality
Vampola, T. ; Horáček, Jaromír
The 3D FE models of the nasal cavities and adult female vocal tract were developed from computer tomography (CT) images for vowels /a:/ and /i:/. The interconnections between the oral and nasal cavities were created according to the anatomical literature. The acoustic frequency - modal characteristics of the FE models were studied by the modal analysis considering zero pressure at the lips and nose and the influence of velopharyngeal insufficiency on the first ten formants was evaluated.
Effect of a soft tissue on vocal tract acoustic resonance properties in vocal exercises using phonation into tubes
Radolf, Vojtěch ; Horáček, Jaromír ; Laukkanen, A. M.
Mathematical model is introduced to clarify the influence of the vocal tract soft tissues on the acoustic resonance (formant) frequencies. The influence is studied in the context of voice therapy technique that uses phonation into tubes. Strong acoustc-structural interaction is demonstrated to take place in the vocal tract when it is prolonged by a tube with the distal end in air or submerged 2 cm and 10 cm in water. The numerical results from the model are compared with the resonance frequencies measured in humans.
Experimental investigation of phonation using artificial models of human vocal folds and vocal tract
Horáček, Jaromír ; Radolf, Vojtěch ; Bula, Vítězslav ; Košina, Jan ; Vampola, T. ; Dušková, Miroslava
The contribution presents results of in vitro measurements of voicing performed on originally developed models of the human vocal folds and vocal tract. The designed models are based on CT and MRI measurements of human subject during phonation. The measured phonation (aerodynamic, vibration and acoustic) chacteristics are comparable with values found in humans.
FE modelling of the influence of the lamina propria properties on the vocal folds vibration and produced sound for specific Czech vowels
Hájek, P. ; Švancara, P. ; Horáček, Jaromír ; Švec, J.G.
The developed two-dimensional finite element model of the flow-induced self-oscillation of the human vocal folds is used for solving fluid-structure-acoustic interaction occurring during phonation. The aim is to nalyze the influence of stiffness of superficial lamina propria on vocal folds vibration considering vocal tracts shaped for the vowels [i:] and [u:].
Computation of aerodynamic damping in aeroelastic system based on analytical and numerical approach
Chládek, Štěpán ; Horáček, Jaromír ; Zolotarev, Igor
The paper describes computation of aerodynamic damping and natural frequencies of aeroelastic systems. The damping is a critical parameter for the stability analysis of aeroelastic systems. Structural damping of the system is important for very low fluid flow velocities, however by increasing the flow velocity, the aerodynamic damping dominates in the instability search. The damping can be evaluated in time or in frequency domain. The presented computation of aerodynamic damping consists of two analytical and one numerical approach. The analytical approaches are represented by the well-known pk method and the unsteady panel method. The pk method is based on Theodorsen unsteady aerodynamics and on the computation of complex eigenvalues of the system as functions of the flow velocity. The unsteady panel method enables the computation of the interaction between aeroelastic system and fluid flow. The aerodynamic damping is evaluated in time domain from the system response to given initial conditions. The numerical approach is based on the finite volume method (FVM) modelling the complete fluid-structure interaction (FSI) coupled problem. The aerodynamic damping is also computed from the system response to a given initial condition. The results of the mentioned methods are compared for the profile NACA 0012 with two degrees of freedom (2-DOF) for plunge and pitch motion around an elastic axis.
Using the proper orthogonal decomposition analysis for detecting pathologic vocal fold vibration
Štorkán, J. ; Vampola, T. ; Horáček, Jaromír
A three-dimensional (3D) finite element (FE) fully parametric model of the human larynx based on computer tomography (CT) measurements was developed and specially adapted for numerical simulation of vocal folds vibrations with collisions. The complex model consists of the vocal folds, arytenoids, thyroid and cricoid cartilages. The vocal fold tissue is modeled as a four layered material where part of the cover was substituted by a liquid layer modelling the superficial layer of lamina propria. The proper orthogonal decomposition (POD) analysis of the excited modes of vibration was used for detecting changes in vibration properties of the vocal folds caused by pathologic changes of vocal fold structure (vocal nodule).
Numerical simulation of the effect of stiffness of lamina propria on the self-sustained oscillation of the vocal folds
Hájek, P. ; Švancara, P. ; Horáček, Jaromír ; Švec, J. G.
A two-dimensional (2D) finite element (FE) model of the fluid-structure-acoustic interaction during selfsustained oscillation of the human vocal folds (VF) is presented in this paper. The aim is to analyze the effect of stiffness of lamina propria on VF vibrations. Such stiffness change can be caused by some VF pathologies. The developed FE model consists of the FE models of the VF, trachea and a simplified human vocal tract. The vocal tract model shaped for simulation of phonation of Czech vowel [a:] was created by converting data from the magnetic resonance images (MRI). The developed FE model includes VF contact, large deformations of the VF tissue, fluid-structure interaction (FSI), moving boundary of the fluid mesh (Arbitrary Lagrangian-Eulerian (ALE) approach), airflow separation during the glottis closure and solution of unsteady viscous compressible airflow described by the Navier-Stokes equations. The numerical simulations showed that higher values of lamina propria Young's modulus (stiffer lamina propria) result in a decrease of the maximum glottis opening. Stiffer lamina propria also requires the use of higher subglottal pressure to initiate self-sustained vibration of the VF.

National Repository of Grey Literature : 209 records found   previous11 - 20nextend  jump to record:
See also: similar author names
6 HORÁČEK, Jakub
1 Horáček, J.
6 Horáček, Jakub
13 Horáček, Jan
6 Horáček, Jaroslav
23 Horáček, Jiří
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