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(An)Isotropy Analysis of Turbulence
Uruba, Václav
Basic ideas of (an)isotropy analysis and rating of turbulent flows are presented oriented on point velocity data analysis. Two types of anisotropy invariant maps are proposed. Practical example is shown.
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IMPLEMENTATION OF k-k(L)-omega TURBULENCE MODEL FOR COMPRESSIBLE TRANSITIONAL FLOW INTO OPENFOAM
Kožíšek, Martin ; Martinez, J. ; Fürst, J. ; Příhoda, Jaromír ; Doerffer, P.
This paper deals with the results of implementation of k-kL-ω RANS turbulence model for compressible transitional flow into OpenFOAM. This model was firstly proposed by Walters and Leylek (2005) and utilizes the approach of laminar kinetic energy in order to predict transition between laminar and turbulent flows. The capability of laminar/turbulent transition modelling is tested for the basic flat plate test cases and for the VKI turbine cascade. The comparison between new implementation, k-kL-ω for incompressible flow supplied in OpenFOAM and g−Req model from commercial CFD package FINE/Turbo distributed by NUMECA Int. are shown. The properties of the implementation of k-kL-ω model for compressible flow simulations into OpenFOAM are discussed.
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TOWARDS PRESSURE GRADIENT SENSITIVE TRANSITIONAL k-kL-omega MODEL: THE NATURAL TRANSITION FOR LOW RE AIRFOILS
Fürst, J. ; Islam, M. ; Příhoda, Jaromír ; Wood, D.
The work deals with the development of a pressure gradient sensitive variant of a three-equation RANS model for turbulent and transitional flows. The model is based on the laminar kinetic energy approach by Walters and Cokljat. The revisited model was successfully validated for zero or mild pressure gradient flows with the so-called bypass transition. In the case of natural transition in adverse pressure gradient flows the model usually tends to predict the transition too late, see. The aim of present work is to improve the model for the case of flows with very low free-stream turbulence levels with adverse pressure gradient. As a first step we focus the attention to the onset of linear instability.
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On numerical approximation of fluid-structure interactions of air flow with a model of vocal folds
Valášek, J. ; Horáček, Jaromír ; Sváček, P.
This paper deals with flow driven vibration of an elastic body. Our goal is to develop and mathematically describe a simplified model of the human vocal fold. The developed numerical schemes for viscous incompressible fluid flow in ALE formulation and the elastic body are implemented by two solvers, specific for each domain. The studied problem is coupled by Dirichlet-Neumann boundary conditions. Both solvers are based on the finite element method. Particularly, for the fluid model the crossgrid elements are used. Numerical results focus on the verification of the developed program.
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Large eddy simulation of airflow in human vocal folds
Šidlof, Petr
Human phonation is a complex physiological process involving flow-induced oscillations of the vocal folds and aeroacoustic sound generation. The flow fields encountered in phonation are highly unsteady, feature massive flow separation and recirculation in the supraglottal spaces and generation of coherent vortex structures from the shear layer of the jet. For the sake of computational aeroacoustic modeling of human voice generation, an accurate resolution of the airflow through the vocal folds is essential. The Reynolds-averaged Navier-Stokes turbulence modeling is inappropriate, since it provides only the averaged flow field. The paper presents the first results obtained with a large-eddy simulation of flow through a model of human vocal folds using a second-order finite volume discretization of incompressible Navier-Stokes equations. In the first step, the flow field was resolved on a fine 2D mesh covering a short subglottal region, the glottis and a part of the supraglottal channel. The simulation was parallelized using domain decomposition method and run in parallel on a shared-memory supercomputer. The results compare two large eddy simulations using the algebraic Smagorinsky and one-equation sub-grid scale models against a simulation without turbulence model.
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On application of finite element method for approximation of 3D flow problems
Sváček, P. ; Horáček, Jaromír
This paper is interested to the interactions of the incompressible flow with a flexibly supported airfoil. The bending and the torsion modes are considered. The problem is mathematically described. The numerical method is based on the finite element method. A combination of the streamline-upwind/Petrov-Galerkin and pressure stabilizing/Petrov-Galerkin method is used for the stabilization of the finite element method. The numerical results for a three-dimensional problem of flow over an airfoil are shown.
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