EXPERIMENTS ON FLOW AROUND A CYLINDER IN A SCOURED CRANNEL BED

1 INTRODUCTION'LOcal scour around a pier is a result of the interatiOn amongst the pier, the aPproach flow and theerodible bed. The Presence of a pier results in a stagnation pressure build-up in front of the pier and athree-dimensional tUrbulent flow echaracterized by the downward flow ahead of the pier and the so-called horseshoe vortex along the base of the Pier forms itself The flow modifies the erothe bed inthe vicinity of the pier when local scour takes place (Graf and AJhnakar l…

EXPERIMENTS ON FLOW AROUND A CYLINDER IN A SCOURED CRANNEL BED

The flow pattern around a cylinder, installed in a scourd channel bed, was experimentally investigated. Detailed measurements of the instantaneous 3D velocities were performed by using an Acoustic Doppler Velocity Profiler (ADVP), from which the profiles of the time~averaged velocities and turbulence stresses were obtained. It is shown that the influence of thC cylinder and of the scour hole alters the approach flow; this is essentially confined to the viciulty of the cylinder and to the inside of the scour hole. The horseshoe vortex is measured as a flow reversal inside the scour hole, formed by the downward flow along the cylinder face and the reversed flow at the scour bed.