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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.
a flow around on a flat . The flow horseshoe vortex a turbulent . The vortex is linked to wall shear the . to 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]]
The presented results show the time-averaged flow streamlines visualzing the main flow structure. The distribution of the c- shaped turbulent kinetic energy as well as its budget terms such as mean convection, production, transport, and dissipation are shown. Furthermore, selected profiles of the velocity components and the Reynolds stresses, as well as of the pressure coefficient and the friction coefficient are presented.
the flow . the -, and are . the the of the .
In general, the numerical and experimental results do agree
well with each other. However, slight deviations are visible such as the time-averaged postition of the vortex system. Therefore, we introduced an adjusted horizontal coordinate to account for this deviation and to compare the velocity profiles at the same (relative ) positions in the flow with respect to the position of the vortex.
In general, the numerical and experimental results do agree with each other. However, slight deviations are visible such as the time-averaged of the vortex system. , we introduced an adjusted horizontal coordinatethis and at the same relative to the vortex .
Latest revision as of 15:48, 4 November 2020
Cylinder-wall junction flow
Underlying Flow Regime 3-35
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
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