Abstract
An experimental investigation, conducted in two different flows Reynolds number, was carried out to study the structure of the flow field upstream of a cylindrical obstacle. An Acoustic Doppler Velocity Profiler (ADVP) was used to obtain instantaneously the three directions of the mean velocity. Results of the experiments show the longitudinal velocities, , decrease approaching the cylinder, their distribution becomes more uniform and close to the bed a reverse flow is noticeable with increasing importance. The downward velocity component is clearly shown, continuing with the return flow near the bed, forming a vortex. At positions where the vortex appears upstream from the cylinder, a large increase of the three components of the turbulence intensities is remarked. Approaching the cylinder, one observes the shear stress decreases, having the opposite direction at positions close to the cylinder. A zero value of shear stress should be at the separation point.
Highlights
IntroductionThe flow upstream will undergo a separation of the turbulent boundary layer and rolls up to form the well-known horseshoevortex system
A complex flow fields is established if flow is disturbed by an obstacle
This study investigates flow fields upstream a cylinder by using experiment data conducted in open channel
Summary
The flow upstream will undergo a separation of the turbulent boundary layer and rolls up to form the well-known horseshoevortex system. This type of flow occurs in a variety of situations, such as flow around bridge piers, around buildings and structures, and at different types of junctions. Similar experiment measurements were conducted for flow around a vertical semicircular cylinder attached to the sidewall [8] and at a wingwall abutment installed at a rectangular channel [9]. This study investigates flow fields upstream a cylinder by using experiment data conducted in open channel
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