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= Abstract =
 
= Abstract =
We applied a Large Eddy Simulation as well as Particle Image Velocity experiments at the flow around a vertical cylinder on a flat rigid bed. The occurring flow structure (horseshoe vortex) reveals a high dynamic pattern with horzintal oscillations generating turbulent kinetic energy. The vortex is linked to the dynamic of a wall-parallel jet, which exters highly amplified shear stress to the bottom plate. Due to this shear stress erosoin can take place in case of sand-embedded bridge piers leading to scour.
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Cylinder-wall junction flow is an example for a flow around bluff bodies mounted on a flat plate. Such flows appear in various technical applications, e.g. wing-body junctions, or environmental flows, e.g. flow around a bridge pier. The flow dynamics in such situations are often dominated by a so-called horseshoe vortex system establishing in front of the obstacle and wrapping around it. It has been demonstrated that this system undergoes a complicated dynamics including bi-modal velocity distributions and large levels of turbulent fluctuations around the horseshoe vortex center. The horseshoe vortex is linked to strongly enhanced wall shear stresses in front and around the cylinder which e.g. can give rise to scouring of bridge piers.  
This study followed a bilateral apporach by studying this flow configuration numerically as well as experimentally. Both data sets refer to the same flow configuration, but were acquired independently and are made accessible at the end of the section [[Evaluation|Evaluation]].
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This study follows a dual approach using a numerical as well as an experimental approach. We applied a highly resolved large eddy simulation as well as a particle image velocity experiment to the flow around a cylinder mounted vertically on a flat rigid plate. Both data sets refer to the same set-up, but were acquired independently and are made accessible in files at the end of the [[UFR 3-35 Evaluation|Evaluation]] section of this document. The data for the inflow condition can be found at the end of the [[UFR 3-35 Test Case|Test Case Studies]] section of this document, too.
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The results presented show the time-averaged streamlines visualizing the main flow structure. The distribution of the c-shaped turbulent kinetic energy and its budget terms such as mean convection, production, diffusive transport and dissipation are shown as well. Furthermore, selected profiles of the velocity components and the Reynolds stresses, the pressure coefficient and the friction coefficient are presented.
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In general, the numerical and experimental results do agree with each other. However, slight deviations are visible such as for the time-averaged position of the vortex system. To ease the comparison of the velocity profiles at the same positions relative to the vortex system, we introduced an adjusted horizontal coordinate. The data presented below were evaluated at distinct horizontal positions in this adjusted coordinate system and are thus located at the same positions relative to the vortex center in both numerical and experimental datasets.
  
  

Latest revision as of 15:48, 4 November 2020

Cylinder-wall junction flow

Front Page

Description

Test Case Studies

Evaluation

Best Practice Advice

References

Semi-confined Flows

Underlying Flow Regime 3-35

Abstract

Cylinder-wall junction flow is an example for a flow around bluff bodies mounted on a flat plate. Such flows appear in various technical applications, e.g. wing-body junctions, or environmental flows, e.g. flow around a bridge pier. The flow dynamics in such situations are often dominated by a so-called horseshoe vortex system establishing in front of the obstacle and wrapping around it. It has been demonstrated that this system undergoes a complicated dynamics including bi-modal velocity distributions and large levels of turbulent fluctuations around the horseshoe vortex center. The horseshoe vortex is linked to strongly enhanced wall shear stresses in front and around the cylinder which e.g. can give rise to scouring of bridge piers.

This study follows a dual approach using a numerical as well as an experimental approach. We applied a highly resolved large eddy simulation as well as a particle image velocity experiment to the flow around a cylinder mounted vertically on a flat rigid plate. Both data sets refer to the same set-up, but were acquired independently and are made accessible in files at the end of the Evaluation section of this document. The data for the inflow condition can be found at the end of the Test Case Studies section of this document, too.

The results presented show the time-averaged streamlines visualizing the main flow structure. The distribution of the c-shaped turbulent kinetic energy and its budget terms such as mean convection, production, diffusive transport and dissipation are shown as well. Furthermore, selected profiles of the velocity components and the Reynolds stresses, the pressure coefficient and the friction coefficient are presented.

In general, the numerical and experimental results do agree with each other. However, slight deviations are visible such as for the time-averaged position of the vortex system. To ease the comparison of the velocity profiles at the same positions relative to the vortex system, we introduced an adjusted horizontal coordinate. The data presented below were evaluated at distinct horizontal positions in this adjusted coordinate system and are thus located at the same positions relative to the vortex center in both numerical and experimental datasets.




Contributed by: Ulrich Jenssen, Wolfgang Schanderl, Michael Manhart — Technical University Munich

Front Page

Description

Test Case Studies

Evaluation

Best Practice Advice

References


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