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Computational Modelling of Self- oscillations of the Human Vocal Folds
Hájek, Petr ; Šidlof,, Petr (referee) ; Radolf, Vojtěch (referee) ; Švancara, Pavel (advisor)
The presented dissertation thesis deals with a simulation of the human phonation in terms of latest theories. Phonation is considered here as a bi-directional fluid-structure-acoustic interaction, where the interaction between all three physical domains occurs due to the unsteady viscous compressible Navier-Stokes equations. There is a solid knowledge background in the first part of the thesis. It concerns the latest concepts in computational modeling of the human phonation, the most important and recent theories about the human voice production and some key aspects of the human anatomy, physiology and pathology. Also voice assessment is discussed. The second part of the thesis describes an in-depth analysis of a phonation simulation in a planar computational model. The basic concepts proceed from algorithms developed in the Institute of Solid Mechanics, Mechatronics and Biomechanics. Created models are able to reproduce sounds of all Czech vowels and the most common evaluated parameters very close to physiological ranges. The simulated pathology, Reinke's edema, is demonstrated in order to explore its influence on the vowel sound. The third part focuses on modeling of phonation in a spatial computational model. All Czech vowels are simulated also here and compared to the planar model and to actual measurement. The spatial model serves as the starting point to modeling of a longitudinal pretension incorporated in the vocal folds. In the last part of the thesis, a modeling of the phonation with vocal folds pretension is investigated. Although the models are tuned to a rather soft phonation, the results are in agreement with the relevant physiologic phenomena. While the spatial model is highly computationally expensive, a hybrid planar model with pretension is proposed. A special attention is paid to the analysis of self-sustained oscillation of the vocal folds. It is shown, the planar model cannot reproduce such kind of oscillation in the actual version, albeit time of oscillation was considerably extended. On the other hand, oscillation of the spatial vocal folds are stabilized without effects accompanying subduing of oscillation. It can be supposed that the spatial model is able to reproduce self-sustained oscillation as a basic principle present during the human phonation.
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Study of Inertial Particle Separator in a typical turboprop engine
Skála, Adam ; Doupník, Petr (referee) ; Popela, Robert (advisor)
This thesis focuses on ingestion of foreign objects into standard turboprop engine GE H80 situated in aircraft Let L-410 Turbolet. Aim of this study is to create methodology of numerical simulation of particle movement inside the engine, which could be used during design process of Inertial Particle Separator device. Thesis consists of backward-facing step benchmark study which validates used methodology. Second part describes flow field calculation and numerical setup. The last part is dedicated to particle tracking analysis. Simulated trajectories are visually investigated, and coordinates of particle impacts at 1st rotor of a compressor are correlated to position of real observed damage.
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Computational Modelling of Self- oscillations of the Human Vocal Folds
Hájek, Petr ; Šidlof,, Petr (referee) ; Radolf, Vojtěch (referee) ; Švancara, Pavel (advisor)
The presented dissertation thesis deals with a simulation of the human phonation in terms of latest theories. Phonation is considered here as a bi-directional fluid-structure-acoustic interaction, where the interaction between all three physical domains occurs due to the unsteady viscous compressible Navier-Stokes equations. There is a solid knowledge background in the first part of the thesis. It concerns the latest concepts in computational modeling of the human phonation, the most important and recent theories about the human voice production and some key aspects of the human anatomy, physiology and pathology. Also voice assessment is discussed. The second part of the thesis describes an in-depth analysis of a phonation simulation in a planar computational model. The basic concepts proceed from algorithms developed in the Institute of Solid Mechanics, Mechatronics and Biomechanics. Created models are able to reproduce sounds of all Czech vowels and the most common evaluated parameters very close to physiological ranges. The simulated pathology, Reinke's edema, is demonstrated in order to explore its influence on the vowel sound. The third part focuses on modeling of phonation in a spatial computational model. All Czech vowels are simulated also here and compared to the planar model and to actual measurement. The spatial model serves as the starting point to modeling of a longitudinal pretension incorporated in the vocal folds. In the last part of the thesis, a modeling of the phonation with vocal folds pretension is investigated. Although the models are tuned to a rather soft phonation, the results are in agreement with the relevant physiologic phenomena. While the spatial model is highly computationally expensive, a hybrid planar model with pretension is proposed. A special attention is paid to the analysis of self-sustained oscillation of the vocal folds. It is shown, the planar model cannot reproduce such kind of oscillation in the actual version, albeit time of oscillation was considerably extended. On the other hand, oscillation of the spatial vocal folds are stabilized without effects accompanying subduing of oscillation. It can be supposed that the spatial model is able to reproduce self-sustained oscillation as a basic principle present during the human phonation.
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Three-dimensional numerical analysis of Czech vowel production
Hájek, P. ; Švancara, P. ; Horáček, Jaromír ; Švec, J. G.
Spatial air pressures generated in human vocal tract by vibrating vocal folds present sound sources of vowel production. This paper simulates phonation phenomena by using fluid-structure-acoustic scheme in a three-dimensional (3D) finite element model of a Czech vowel [o:]. The computational model was composed of four-layered M5-shaped vocal folds together with an idealized trachea and vocal tract. Spatial fluid flow in the trachea and in the vocal tract was obtained by unsteady viscous compressible Navier-Stokes equations. The oscillating vocal folds were modelled by a momentum equation. Large deformations were allowed. Transient analysis was performed based on separate structure and fluid solvers, which were exchanging loads acting on the vocal folds boundaries in each time iteration. The deformation of the fluid mesh during the vocal fold oscillation was realized by the arbitrary Lagrangian-Eulerian approach and by interpolation of fluid results on the deformed fluid mesh. Preliminary results show vibration characteristics of the vocal folds, which correspond to those obtained from human phonation at higher pitch. The vocal folds were self-oscillating at a reasonable frequency of 180 Hz. The vocal tract eigenfrequencies were in the ranges of the formant frequencies of Czech vowel [o:] measured on humans, during self-oscillations the formants shifted to lower frequencies.
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Study of Inertial Particle Separator in a typical turboprop engine
Skála, Adam ; Doupník, Petr (referee) ; Popela, Robert (advisor)
This thesis focuses on ingestion of foreign objects into standard turboprop engine GE H80 situated in aircraft Let L-410 Turbolet. Aim of this study is to create methodology of numerical simulation of particle movement inside the engine, which could be used during design process of Inertial Particle Separator device. Thesis consists of backward-facing step benchmark study which validates used methodology. Second part describes flow field calculation and numerical setup. The last part is dedicated to particle tracking analysis. Simulated trajectories are visually investigated, and coordinates of particle impacts at 1st rotor of a compressor are correlated to position of real observed damage.
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Numerical simulation of turbulent compressible flows
Trefilík, J. ; Kozel, Karel ; Příhoda, Jaromír
The work deals with the development of numerical methods for simulation of subsonic and transonic turbulent flow over the DCA 20% profile in a cascade configuration with a zero stagger angle. Numerical results for compressible subsonic flow for Mach numbers M1 = 0.35 and 0.5 are compared with respekt to two different used turbulence models. A special attention was paid to modelling of the separation region near the trailing edge of profile.
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Numerické řešení dvoufázového proudění při interakci statoru a rotoru
Halama, Jan ; Fořt, Jaroslav
This work deals with a numerical solution of 2D unsteady compressible flow of mixture of vapor and condensed droplets in axial turbine stage. Governing equations consist of the Euler equations for the mixture and the transport equations for integral parameters of droplet spectra (Hill's approximation). The computational domain is created by several stator and rotor blade passages in order to get simple periodicity condition. The stator and the rotor parts are connected by 'interface cells', proposed originally by Giles. Numerical method is based on the Strang splitting method, convection part is solved by the finite volume cell-vertex method based on the Lax-Wendroff scheme with artificial viscosity term and condensation part is solved by two-stage explicit Runge-Kutta method. The first numerical results are discussed.
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