Conditional Statistics of Turbulent Open Channel Flow in Upstream, Interior and Downstream Regions of Emergent and Sparse Vegetation Patch

Emergent and rigid vegetated open channel flow has a significant influence on the flow hydrodynamics and protects the channel bed from erosion as it gives strength and stability to the channel bed. Therefore, investigation of flow characteristics inside the emergent vegetation patch is a topic of importance for the scientific community. In this direction, the main aim of this study is to investigate the conditional statistics of streamwise and vertical velocities, in the upstream, interior and downstream region of the vegetation patch. Seventy numbers of acrylic cylinders were used to make the emergent vegetation array in the middle of a laboratory flume. A Nortek Vectrinoplus Acoustic Doppler Velocimeter (ADV) was used to measure the point velocity data throughout the depth along the centreline of the vegetation patch in the upstream, interior and downstream regions. In this study, flows with two different Reynolds numbers and two different aspect ratios were investigated. The results indicate that the strength of velocity fluctuations and quadrant events in the interior of the vegetation is increasing with the aspect ratio and Reynolds number. Further, the experimental investigation reveals that the quadrant events are strongest in the vicinity of the trailing edge of the vegetation patch.

Keywords: Turbulent flow, Open channel flow, quadrant analysis, conditional statistics, emergent vegetation patch.