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O validaci numerického modelu pro simulaci turbulentního proudění s volnou hladinou
Bodnár, T. ; Kozel, K. ; Příhoda, Jaromír
The numerical solution of averaged Navier-Stokes equations with the two-equation SST turbulence model is carried out by means of the VOF method. This approach is based on the assumptions for variable-density incompressible flow with discontinuity in density profile at the free-surface. Numerical solution by means of the finite-volume method utilises the cell-centered scheme on a structured mesh. Numerical results were compared with experimental data for subcritical flow over ribs in an open channel.
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Vyšetřování turbulentního proudění v otevřeném kanálu s příčnými prahy
Příhoda, Jaromír ; Šulc, J. ; Sedlář, M. ; Zubík, P.
The contribution deals with the experimental and numerical modelling of turbulent supercritical flow over one and/or two transversal ribs with the cross-section 30x30 mm placed at the bottom of an open channel. Numerical simulation was carried out using the VOF (Volume-of-Fluid) method by means of the commercial software ANSYS CFX-11.0 for supercritical flow characterised by the Froudé number Fr = 2.2. The effect of the rib spacing on the extent of the separation region, the deformation of free surface and on the drag of individual ribs was primarily investigated. Numerical results were compared with experiments accomplished in the water channel with the cross-section 200x200 mm by means of PIV and LDA measuring methods. Optical methods were completed by the measurement of pressure distribution on rib surface in the channel centreline.
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Experimentální a numerické modelování turbulentního obtékání příčných prahů v otevřeném kanálu
Příhoda, Jaromír ; Šulc, J. ; Sedlář, M. ; Zubík, P.
Modelling of turbulent flow in an open channel with transversal ribs on its bottom was concentrated particularly on the development of flow separation behind ribs and on the corresponding changes of free surface. Further, the pressure drag of individual ribs was investigated including their dependence on the rib spacing, as well as the origin of secondary flow near the side walls of the channel behind ribs. Numerical results obtained by the software ANSYS CFX 11.0 were compared with experiments carried out by means of LDA and PIV techniques in free-surface water channel 200x200 mm with one and/or two transversal ribs 10xl0 mm with various spacing.
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Modelling of flow over two transversal ribs in a channel with free surface
Sládek, A. ; Příhoda, Jaromír ; Stanislav, Jiří
Numerical simulation of turbulent flow over two transversal ribs on the bottom of a channel with free surface was carried out. The VOF (Volume-of-Fluid) method implemented in the commercial software FLUENT 6.3 was used for the solution of supercritical flow in a channel with free surface. The two-equation turbulence model according to Shih et al. was applied. The simulation was realised for ribs with the relative spacing t/b = 6; 10 and 20. Profiles of mean velocity and velocity fluctuation obtained by numerical simulation were compared with experimental data from LDA and PIV measurements. The behaviour of free surface over ribs was compared with experiments as well.
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Modelling of flow over one transversal rib in a channel with free surface
Sládek, Aleš ; Příhoda, Jaromír
Numerical simulation of flow over one transversal rib on the bottom of a channel with free surface was carried out. The VOF (Volume-of-Fluid) method implemented in the commercial software FLUENT 6.3 was used for the solution of supercritical flow in a channel with free surface. The two-equation turbulence model according to Shih et al. was applied. Profiles of mean velocity and velocity fluctuation obtained by numerical simulation were compared with experimental data from PIV measurements. Secondary flow and the length of separated region behind the rib were compared with experimental data as well.
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Porovnání kritérií pro určení zkráceného přechodu
Příhoda, Jaromír ; Popelka, Lukáš
Empirical relations for the bypass transition were compared with experimental data and with numerical results obtained by the Xfoil code for the flat-plate flow. Relations for the transition onset and the length of the transitional region were tested for the effect free-stream turbulence. The effect of wall roughness was considered as well.
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