Temporal flow evolution of sediment embedded circular bridge piers

Abstract

Bridge hydraulics has become an important issue in river engineering given the importance ofbridges as a basic infrastructure. Many of the current research works investigate empirically the temporal advanceof scour depth. In contrast, this paper presents some major results on the flow characteristics around a circularcylindrical bridge pier mounted in a mobile sediment bed resulting from an experimental study conducted atVersuchsanstalt für Wasserbau, Hydrologie und Glaziologie VAW during the past four years. The internal flowfeatures were investigated by a newly developedParticle Image Velocimetrysetup. This installation allows for aquasi 3-dimensional visualization of the velocity field around a bridge pier by means of horizontal and verticalplanes. The main characteristics of the down-flow, the horseshoe vortex system and the tailwater vorticity fieldwere detected from the non-intrusive and instantaneously measured velocity fields; additionally the bed-shearstresses were calculated in the scour region. This work, therefore, provides novel insight into the complex andfascinating two-phase flow around circular bridge.