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Dynamics of Flow-Field behind Backward-Facing Step in the Plane of Symmetry
Uruba, Václav
Dynamics of the flow-field behind a backward-facing step in a narrow channel is studied experimentally using time-resolved PIV technique in the measuring plane being the plane of symmetry in the streamwise direction. The channel width is 4 step heights, Reynolds number based on the step height was about 7 200. Instability of the free shear layer of Kelvin-Helmholtz type is observed. Dynamics of the flow is studied using the Bi-Orthogonal Decomposition (BOD) and Oscillation Pattern Decomposition (OPD) techniques. Typical time-mean structures of velocity statistics as well as dynamical structures are to be presented.
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3D Structure of the Flow-Field behind Backward-Facing Step in a Narrow Channel
Uruba, Václav
Time-mean flow-field structure behind the backward facing step in a narrow channel was studied in details using the PIV technique. The measuring cuboid was covered by systems of measuring planes in various orientations. The channel width to the step height ratio was 4, Reynolds number based on the step height was 34 400. Special attention has been paid to the region just behind the step forming the back-flow region.
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Dynamics of Recirculation Region Behind Backward-Facing Step
Uruba, Václav
Dynamics of the flow-field behind a backward-facing step in a narrow channel is studied experimentally using time-resolved PIV technique. Instability of the free shear layer of Kelvin-Helmholtz type is studied using simple averaging and Oscillation Pattern Decomposition (OPD) methods. Mean picture suggests existence of the classical recirculation zone. The OPD method reveals the structure of the instability consisting of a system of traveling vortical structures.
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Dynamics of flow behind backward-facing step in a narrow channel
Uruba, Václav
The results and their analysis from experiments obtained by TR-PIV are presented on the model of backward-facing step in a narrow channel. The recirculation zone is studied in details. Mean structures are evaluated from fluctuating velocity fields. Then dynamics of the flow is characterized with help of POD (BOD) technique. Substantial differences in high energy dynamical structures behaviour within the back-flow region and further downstream behind the flow reattachment have been found.
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Vliv pulzací nátoku na strukturu toku v kanále za náhlým rozšířením.
Pěnkavová, Věra ; Tihon, Jaroslav
The wall shear rate profiles were measured along the bottom and roof walls of rectangular channel with backward-facing step. The profiles were measured by two-strip electrodiffusion probes. It is possible to see the strong effect of the inlet flow pulsations on the flow structure. The influence of the inlet flow pulsation was studied for various frequence and amplitude for water when the Reynolds number was ranging from 100 to 1500 and expansion ratio of the channel was 2.
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Diagnostika toku v kanále za náhlým rozšířením
Tihon, Jaroslav
A backward-facing step flow is studied by measuring the instantaneous wall shear rate along the channel certenline. A two-step electrodiffusion probe is applied to provide information on the flow direction in the near-wall region. The wall shear rate profiles behind the step are measured and the position of reattachment point detected. The Reynolds numbers examined cover the laminar, transient and beginning of turbulent flow regime. The results are found to be in a good agreement with the experimental and numerical data previously published for the same channel geometry.
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Modelling of flow over a backward-facing step in streams with various turbulence level
Příhoda, Jaromír ; Sedlář, M.
Turbulent flow over a backward-facing step in streams with a various turbulence level was numerically simulated using software ANSYS CFX-5. Numerical solution carried on with the two-equation SST model and/or with a k-omega based Reynolds stress model was compared with experimental data obtained for three different values of free-stream turbulence level. The predicted length of the recirculation region corresponds well with experimental data but the dependence of the ratio xr/h on free-stream turbulence level is smaller.
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