Cylinder-wall junction flow

Semi-confined Flows

Underlying Flow Regime 3-35

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 horizontal oscillations generating turbulent kinetic energy. The vortex is linked to the dynamics of a wall-parallel jet, which exerts highly amplified shear stress to the bottom plate. Due to this shear stress erosion 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 set-up, but were acquired independently and are made accessible at the end of the section Evaluation.

The presented results show the time-averaged flow streamlines visualizing 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.