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Numerické řešení nestacionárního proudění stlačitelné viskozní tekutiny v kanále
Punčochářová, Petra ; Kozel, Karel ; Fürst, J. ; Horáček, Jaromír
This work deals with numerical solutin of viscous laminar flows in a channel with time-changing wall. MacCormack scheme and Jameson artificial viscosity are used for numerical solution in the form of finite volume method with grid of quadrilateral cells. Mathematical model is unsteady system of 2D laminar Navier-Stokes equations. Unsteady behavior is caused by time dependent-boundary of lower. The channel represents a simple case of vocal tract. an unsteady domain is presented using Arbitrary Lagrangian-Eulerian method. In the work several numerical results of flows in two different channels are presented.
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Computational acoustic modal analysis of selected parts of a steam pipe system
Zolotarev, Igor ; Horáček, Jaromír ; Pešek, Luděk
The repart deals with frite element modelling and computations of the frequency-modal acoustic characteristics of selected parts of complicated pipe systems conveying water steam. In all cases studied, first 10 acoustic natural frequencies were in the frequency range up to 150 Hz. No lateral acoustic natural mode of vibration appeared in this frequency range and all modes were longitu-dinal, that can be approximately described by 1D theory for acoustic wave propagation in cylondrical ducts.
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Numerical simulation of interaction of a vibrating airfoil with turbulent flax
Dubcová, L. ; Feistauer, M. ; Horáček, Jaromír ; Sváček, Petr
The report deals with numerical simulations of 2D viscous incompressible flow around a rotationaly vibrating profile. The flow is described by continuity and Navier-Stokes equations. Solution of the partial differential equations is based on finite element method. Because the Reynolds numbers higher than 10 000 are considered the solution is stabilized by SUPG method. Alge-braic turbulence model is taken into account and for simulations of the flow on moving grids the ALE method is used. the method was applied on harmonie vibrations of the profil NACA 0012 and the results are in good agreement with the experimental data obtained in ARTI.
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PIV měření proudění kolem samobuzeně kmitajícího modelu hlasivek
Šidlof, Petr ; Doaré, O. ; Cherfa, L. ; Lahcene, Ch. ; Chaigne, A. ; Horáček, Jaromír
A new mechanical model of vocal folds was developed in cooperation with Ecole Nationale Supérieure de Techniques Avancées, Paris. Under specific conditions, the model exhibits flow-induced vibrations, where the vocal folds collide in each cycle. The model was designed to allow dynamic, acoustic and PIV measurements synchronized with the vocal fold oscillations. The results provide interesting information about the vocal fold dynamics and about the nonstationary flow structures, developing downstream the glottis, which closes periodically.
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Zpětná vazba v proudění nestlačitelné tekutiny a pohybujícího se tělesa
Růžička, M. ; Feistauer, M. ; Sváček, P. ; Horáček, Jaromír
the subject of this article is the numerical simulation of the interaction of two-dimensional incompressible viscous fluid and a vibrating airfoil. A solid airfoil with two degrees of freedom, which can rotate around the elastic axis and oscillate in the vertical direction, is considered. The numerical simulation sonsists of the finite element solutin of the Navier-Stokes equations coupled with a system of ordinary differential equations describing the airfoil motion. The time-dependent computational domain and a moving grid are taken into account with the aid of the Arbitrary Lagrangian-Eulerian (ALE) formulation of the Navier-Stokes equations. High Reynolds numbers up to 1 000 000 require the application of a suitable stabilization of the finite element discretization. Numerical tests prove that the developed method is sufficiently accurate and robust.
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Physical Model of the Vocal Folds
Kryštůfek, Jan ; Bula, Vítězslav ; Horáček, Jaromír
Assuming symmetry of self-oscillations, a half physical model of the vocal folds was made. Working principle of the model is based on self-induced oscillations occurring when a critical air flow rate is crossed. Air flow rate of 0,6 l/s was used for generation of flow-induced oscillations of elastic part of the model with fundamental frequency 117 Hz. Used elastic element made of polyurethane rubber was designed and manufactured by Thomson from Purdue University (Indiana) [1], [2]. The introductory measurements were performed by using a high speed digital camera. We propose to use the model as a source of acoustic pressure for excitation of physical models of the human vocal tract.
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Computational and Experimental analysis of Effect of Tonillectomy on Production of Czech Vowels
Švancara, P. ; Vokřál, J. ; Horáček, Jaromír
The effect of tonsillectomy on production of Czech vowels is numerically and experimentally examined. Experimental results show statistically significant shift down to lower frequencies of 3rd formant frequency for vowels /a/, /e/ and /o/. The finite element (FE) models of the acoustic spaces corresponding to the human vocal tracts and acoustic space around the human head are used in numerical simulations of phonation. Computed results show that tonsillectomy causes frequency shifts of some formant frequencies mostly down to lower frequencies. The frequency shifts of the formants are significantly dependent on position and size of th tonsils. Experimental and computational results are consistent.
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Numerické modelování nestacionárního proudění viskozní tekutiny ve 2D kanále pro nízká Machova čísla
Punčochářová, Petra ; Kozel, Karel ; Fürst, J. ; Horáček, Jaromír
The work presents an unsteady viscous flow for low upstream Mach number (M =0.012) in a 2D channel. Unsteady flow is caused by a moving part of the channel wall as a given function of time. The problem is described by the system of Navier-Stokes equations for compressible leminar flows. It is numerically solved by the explicit central finite volume version of MacCormack scheme on a grid of quadrilateral cells. Moved grid of quadrilateral cells is considered in the form of conservation laws using Arbitrary Lagrangian-Eulerian method. Physically the flow in the symmetrical channel can present some very simple model of flow in a human vocal tract. The aim is to compare two different cases of this problem of the flowfield.
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