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Incompressible fiscous flow at viscous velocities in interaction with a vibrating profile NACA 0012
Honzátko, R. ; Horáček, Jaromír ; Kozel, Karel
The work presents numerical solution of the interaction of 2D incompressible viscous flow and a freely vibrating profile NACA 0012 with large amplitudes. The upstream flow velocities are consider in the range 5-40 m/s. The profile has two degrees of freedom. It can rotate around an elastic axis and oscillate in the vertical direction. Its motion is described by two nonlinear ordinary differential equations. Fourth-order Runge-Kutta method is used to solve these equations numerically. The incompressible Navier-Stokes equations represent the mathematical model of the laminar viscous flow. Numerical schemes of the FVM are applied on a structured Quadrilateral C-mesh. The method of artificial compressibility and dual-time stepping method is employed for numerical simulations. Deformations of the computational domain are treated using the ALE method. Numerical simulations of the profile motion are performed for the case solved earlier by the FE method, and the results are in good agreement.
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Napěťová analýza lidských hlasivek
Vampola, T. ; Horáček, Jaromír
A three-dimensional (3D) finite element (FE) fully parametric model of the human larynx was developed and used for numerical simulation of stresses during vibrating vocal folds the collisions. The complex model consists of the vocal folds, arytenoids, thyroid and cricoid cartilages. The vocal fold tissue is modelled as a three layered orthotropic material. The results of numerical simulation of the vocal folds oscillations excited by a prescribed intraglottal aerodynamic pressure are presented. The FE contact elements are used modelling the vocal folds collisions and the principal and shear stresses are computed in time domain on the surface and inside the vocal fold tissue. The results show significant dynamic stresses in all there directions and comparable maxima of Von Mises stresses were obtained for closed and open phases of the vocal folds motion.
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Numerical simulation of unsteady low-Mach number viscous flow in a channel
Punčochářová, P. ; Kozel, Karel ; Horáček, Jaromír ; Fürst, J.
This study deals with a numerical solution of a 2D unsteady flow of a compressible viscous fluid in a channel for low inlet airflow velocity. The unsteadiness of the flow is caused by a prescribed periodic motion of a part of the channel wall with large amplitudes, nearly closing the channel during oscillations. The channel is a simplified model of the glottal space in the human vocal and the flow can represent a model of airflow coming from the trachea, through the glottal region with periodically vibrating vocal folds to the human vocal tract. The flow is described by a system of Navier-Stokes equations for laminar flows. The numerical solution is implemented using a grid of quadrilateral cells. Due the motion of the grid, the basic equations are considered in the Arbitrary Lagrangian-Eulerian form. Numerical results are presented for Mach number 0,012m, Reynolds number 5000 and vibration frequency 100 Hz.
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Zviditelnění nestacionárního proudění kolem vibrujícího profilu: Experimentální uspořádání a předběžné testy
Vlček, Václav ; Horáček, Jaromír ; Luxa, Martin ; Veselý, Jan ; Bula, Vítězslav
The contribution presents the designed aeroelastic model, experimental set-up and preliminary tests of optical measurements of flow field around a vibrating NACA 0017 profile elastically supported in the measurement section of the wind tunnel. The profile can vibrate with two degrees of freedom for translation and rotation. The interferometry method combined with the high speed filming was used for flow visualization of in different phases of the profile motion. The measurements were performed in a subsonic wind tunnel above the airflow velocity for loss of the system stability by flutter, thus the vibration amplitudes were relatively large up to about 7 mm for vertical translation and 16.5 degrees for angle of rotation around the elastic axis. The 52 images of the flow field were recorded during one oscillation period of the profile from which the pressure and velocity can be evaluated in the given time instants.
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DEVICE FOR EXPERIMENTAL RESEARCH OF INTERACTION OF ENERGY SOURCE WITH VIBRATING SYSTEM
Půst, Ladislav
For improvement and complementation of theoretical studies of interaction between a non-ideal source of exciting energy and vibrating mechanical system, a simple experimental equipment has been designed, produced and putt into testing service in IT – AS CR. This equipment consist of 1 DOF mechanical subsystem, connected by a crank mechanism with DC electromotor, fed by a prescribed voltage function. Measuring and recording apparatuses are prepared for evaluation of dynamical properties of various system modifications.
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Two-mass dynamical system with singular stiffnes matrix
Kozánek, Jan
In this paper the solution of two-mass symmetric dynamical system with singular stiffnes matrix via the state space formulation is given. The coefficient matrix is non-diagonalizable. The terminology problems concerning eigenvectors and latent vectors are discussed, too. Finally the resolvent of this symmetric system was expressed in symmetric form.
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