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Simulace proudění špičkovým řezem turbinové mříže při různých vstupních podmínkách
Straka, P. ; Příhoda, Jaromír
Příspěvek se zabývá numerickou simulací 2D stlačitelného proudění špičkovým řezem turbinové lopatkové mříže pomocí EARSM modelu turbulence doplněného algebraickým modelem přechodu. Výpočty byly provedeny při Reynoldsově čísle Re2is = 1.85E+06 pro Machova čísla M2is = 1.77 a 1.92. Simulace byla zaměřena na vliv malých změn vstupního úhlu proudu a změn turbulence vnějšího proudu na strukturu proudění v lopatkové mříži, zejména na interakci rázových vln s mezní vrstvou.
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Modelling of the Laminar/Turbulenttransition on a Heated Flat Plate Using the k-kL-w Model
Kožíšek, Martin ; Fürst, J. ; Příhoda, Jaromír
The contribution deals with the numerical simulation of the transition to turbulence on a heated flat plate by means of the k-kL-k-kL-w model of Walters and Cokljat (2008). The revised version of the three-equation model was implemented into the OpenFOAM code for the incompressible and compressible flows. Numerical simulations of the boundary-layer development were carried out according to measurements of Sohn and Reshotko (1991). The transition model was tested by means of the skin friction and the Stanton number distributions for various free-stream turbulence levels. Results were compared with empirical correlations expressing the Reynolds analogy according to Kays and Crawford (1993) and with experimental data of Pinson and Wang (2000).
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CFD Calculations in Turbomachinery and their Validation
Váchová, J. ; Louda, P. ; Příhoda, Jaromír ; Luxa, Martin ; Šimurda, David
Numerical data obtained by 2D compressible flow CFD simulation were validated by the comparison with experimental results. The investigation was made on the mid-section of the 48" long rotor blade and it was focused on the effect of shock-wave interactions with shear layers. This interaction results in the laminar/turbulent transition where separated flow occurs and it has impacts on flow structure and the blade cascade losses. Numerical simulations were carried out by two different codes: the commercial code NUMECA based on the gamma-Re transition model connected with the SST k-epsilon/k-omega turbulence model and in-house code of the Dept. of Technical mathematics, CTU Prague/ Institute of Thermodynamics in Prague. Simulations of the laminar and the fully turbulent flows were accomplished for comparison using the same numerical approach.
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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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Modelování proudění ve špičkové turbinové lopatkové mříži se supersonickým vstupem
Straka, P. ; Stodůlka, J. ; Příhoda, Jaromír
Příspěvek se zabývá numerickou simulací stlačitelného proudění ve špičkové turbinové lopatkové mříži TGR-U-4 se supersonickými vstupními podmínkami. Výpočet je proveden jednak pomocí vlastního numerického programu s explicitním algebraickým modelem Reynoldsových napětí doplněným algebraickým modelem zkráceného přechodu a jednak pomocí SST modelu turbulence s gama-Re modelu přechodu implementovaného v komerčním programu Fluent. Získané výsledky jsou porovnány a diskutovány.
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