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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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Numerical experiments for turbulent flows
Trefilík, Jiří ; Kozel, Karel ; Příhoda, J.
The aim of the work is to explorethe possibilities of modelling transonic flowsin the internal and external aerodynamics. Several konfigurationswere analyzed and calculations were performed using both inviscid and viscous models of flow. Viscous turbulent flows have been simulated using either zero equation algebraic Baldwin-Lomax model and two equation k - w model in its basic version and improved TNT variant. The numerical solution was obtained using Lax-Wendroff scheme in the MAcCormack from on structured non-ortogonal grids. Artificial dissipation was added to improve the numerical stability. Achieved results are compared with experimental data.
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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 simulation of 3D flows in atmospheric boundary layer
Šimonek, Jiří ; Kozel, K. ; Jaňour, Zbyněk
The work deals with the numerical solution of 3D turbulent stratified flows in atmospheric boundary layer over the cosine function shaped hill. Mathematical model for the turbulent stratified flows in atmospheric boundary layer is the Boussinesq model - Reynolds averaged Navier-Stokes equations (RANS) for incompressible turbulent flows with addition of the transport equation for density and that is coupled with the RANS system by the source term at the right hand side of the momentum equation. The artificial compressibility method and the finite volume method have been used in all computed cases and Lax-Wendroff scheme (MacCormack form) has been used together with the Cebecci-Smith algebraic turbulence model.
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On using artificial compressibility method for solving turbulent flows
Louda, P. ; Kozel, K. ; Příhoda, Jaromír
The artificial compressibility method is used to solve steady and unsteady flows of viscous incompressible fluid. The method is based on the implicit higher order upwind discretization of the Navier-Stokes equations. The extension for unsteady simulation is considered by increasing artificial compressibility parameter or by using dual time stepping. Both methods are tested on laminar flow around the circular cylinder and used to simulate unsteady turbulent flows by URANS approach. The simulated cases are the synthetic jet flow in a branched channel.
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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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