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Numerical simulations of turbulent flow through DCA 8% cascade
Trefilík, Jiří ; Kozel, K. ; Příhoda, Jaromír
The work deals with further development of numerical methods for simulation of transonic turbulent flows through the DCA 8% cascade. Results of numerical experiments modelling the viscous and inviscid flows in a cascade with various inlet Mach numbers are compared and discussed. For turbulence modelling the algebraic Baldwin-Lomax model and two- equation standard k-ω and TNT k-omega models were employed.
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Unsteady flows in convergent channel with stationary walls
Pořízková, P. ; Kozel, Karel ; Horáček, Jaromír
A current challenging question is a mathematical and physical description of the mechanism for transforming the airflow energy in human vocal tract (convergent channel) into the acoustic energy representing the voice source in humans. Goal of this work is to describe mathematical model of flow in 2D convergent channel which involves attributes of real flow as is “Coanda phenomenon”, vortex convection and diffusion, jet flapping etc. along with lower call on computer time, due to later extension in 3D channel flow.
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Numerical comparison of unsteady compressible viscous flow in convergent channel
Pořízková, P. ; Kozel, Karel ; Horáček, Jaromír
This study deals with a numerical solution of a 2D flows a compressible viscous fluids in a convergent channel for low inlet airflow velocity. Three governing systems – Full system, Adiabatic system, Iso-energetic system based on the Navier-Stokes equations for laminar flow are tested. The numerical solution is realized by finite volume method and the predictor-corrector MacCormack scheme with Jameson artificial viscosity using a gird of quadrilateral cells. This unsteady grid of quadrilateral cells is considered in the form of conservation laws using Arbitrary Lagrangian-Eulerian method. The numerical results, acquired from a developed program. Are presented for inlet velocity ûĄ = 4,12ms-1 and Reynolds number Re = 4 x 103.
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Numerical experiment of compressible flow in convergent channel- pressure spectral analysis
Pořízková, P. ; Kozel, Karel ; Horáček, Jaromír
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 flow is described by the system of Navier-Stokes equations for laminar flows. The numerical solution is implemented using the finite volume method (FVM) and the predictor-corrector MacCormack scheme with Jameson artificial viscosity using a gird of quadrilateral cells. The numerical results of unsteady flows in the channel are presented for inlet velocity uĄ = 4.12m/s, inlet Reynolds number ReĄ = 4481 and wall motion frequency 100Hz.
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Numerical computation and comparison of low Mach number flow in a channel
Pořízková, P. ; Kozel, K. ; Horáček, Jaromír
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 tract. The authors present unsteady numerical solutions of flow in two similar computational domains. The numerical results are presented for inlet Mach number MĄ = 0.012, Reynolds number Re = 4481 and the wall motion frequency 100 Hz.
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Computation of inviscid and viscous turbulent subsonic and transonic flows
Trefilík, J. ; Kozel, K. ; Příhoda, Jaromír
The work deals with the developement of numerical methods for simulation of subsonic and transonic turbulent flows in the GAMM channel and through the DCA 8% cascade. Results of numerical modelling of viscous and inviscid flows with the inlet Mach numbers M = 0.6, 0.675 and 0.85 are compared and discussed. For turbulence modelling one equation algebraic Baldwin-Lomax model and two equations k-omega model were applied and their numerical results were compared.
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On the thermally stratified atmospheric flow modeling
Sládek, Ivo ; Kozel, K. ; Jaňour, Zbyněk
The paper deals with a numerical study devoted to thermally /indifferently stratified atmospheric boundary layer flow. The main objective is related to definition of the model and flow conditions as well as to presentation of some first numerical results concerning the flow over selected hill configuration under the indifferent thermal conditions. The mathematical model is based on the system of Reynolds-averaged Navier Stokes (RANS)equations closed by two-equation k-e turbulence model together with wall functions.The thermal stratification is modeled using transport equation for the potential temperature. The finite volume method and the explicit Runge-Kutta time integration method are utilized for the numerics. A 2D-hill test case with a rough wall has been chosen to perform numerical test.
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On the validation study devoted to stratified atmospheric flow over an isolated hill
Sládek, Ivo ; Kozel, Karel ; Jaňour, Zbyněk
The paper deals with description of the validation model, °ow conditions and mainly it presents some numerical results. Reference and input data for the validation study are based on work of Eidsvik [3]. The mathematical model is based on the system of RANS-equations closed by two-equation k ¡ " turbulence model together with wall functions. The thermal strati¯cation is modeled using transport equation for the potential temperature. The ¯nite volume method and the explicit Runge{Kutta time integration method are utilized for the numerics.
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Numerical tests of flow in human vocal tract
Pořízková, P. ; Kozel, K. ; Horáček, Jaromír
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 tract. The authors present several numerical tests of computational domain, of modified numerical scheme and types of mesh for the wall motion frequency 100 Hz.
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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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