Cylinder-wall junction flow
Underlying Flow Regime 3-35
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. 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.
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.
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.
Contributed by: Ulrich Jenssen, Wolfgang Schanderl, Michael Manhart — Technical University Munich
© copyright ERCOFTAC 2019