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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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Affine Correlation Method for Direct Vorticity, Skew and Displacement Estimation
Gronát, Petr
In this paper, a correlation method for direct vorticity computation of the fluid velocity field is introduced. The correlation method considering the affine transformation of a correlation window is presented. It is shown, that Lagrangian field of displacements, con- sidering the linear terms only, satis- fyes the requirements for affine transfor- mation. Using the Normalized–Cross– Correlation together with affine trans- formation and Newton-Raphson itera- tive method, six parameters defining the transformation can be estimated. Subse- quently, both displacement and vorticity can be computed using the above men- tioned parameters, hence, the vorticty is being obtained for every single point di- rectly during the correlation procedure.
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Modification of an algebraic bypass-transition model for internal flows
Straka, P. ; Příhoda, Jaromír
The contribution deals with testing of an algebraic bypass-transition model for shear flows characteristic for turbomachinery. The transition model based on the algebraic equation for the intermittency coefficient is added to the averaged Navier-Stokes equations with the SST turbulence model. The transition onset and length are given by empirical relations. The modified model considers different intermittency coefficient in the transitional boundary layer and in the outer turbulent stream. The model was verified by means of test cases ERCOFTAC covering boundary-layer flow with various free-stream turbulence and pressure gradient.
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Numerical solution of flow over 2D backward facing step with different inclination angle
Louda, P. ; Sváček, P. ; Kozel, K. ; Příhoda, Jaromír
The finite-volume and finite-element techniques are used for the numerical simulation of the incompressible turbulent flows in a closed channel with a backward-facing step and with an inclined step under the angle 45 degree. A comparison of the finite-volume method based on the averaged Navier-Stokes equations closed by the explicit algebraic Reynolds stress model and the finite-element method using the Navier-Stokes equations with the two-equation k-eps model is presented. Numerical results are compared with experimental data of Makiola (1992).
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Numerical simulation of turbulent compressible flows
Trefilík, J. ; Kozel, Karel ; Příhoda, Jaromír
The work deals with the development of numerical methods for simulation of subsonic and transonic turbulent flow over the DCA 20% profile in a cascade configuration with a zero stagger angle. Numerical results for compressible subsonic flow for Mach numbers M1 = 0.35 and 0.5 are compared with respekt to two different used turbulence models. A special attention was paid to modelling of the separation region near the trailing edge of profile.
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