Turbulence Study Around Bar in a Braided River Model

Resumo

Turbulent flow is a flow regime which is described by the anarchic property changes. This includes the rapid variation of pressure, high momentum convection and flow velocity in time and space. A turbulent phenomenon in a braided river is much more complex as compared to the straight and meandering rivers. Turbulent flow characteristics around the braid bar are not thoroughly studied till now. In the current paper, the quadrant method is used to analyze the turbulence characteristics of flow around the island in a braided river model using 2-D burstingevents technique. Three velocity fluctuation components (u′, v′, w′), were measured with Acoustic Doppler Velocimetry. Although many advances have been made within recent years in interpreting the mechanics of flow, transport of sediment and sedimentary architecture of braided rivers, many key issues remains to be addressed, in particular, the underlying processes of braid bar initiation. An attempt has been made herein to relate the depositional characteristics around the island in the braided river model to the sweep and ejection events. The concept of the hole is used in order to isolate the extreme events that contribute to the turbulent burst. The angle of sweep and ejection events are calculated at points around the island. The angle of events at these points depict the pattern similar to scouring/ deposition at points around the island in the braided river model.