Bulk scaling of flow characteristics in the interior of sparse, emergent and rigid vegetation patch

Abstract

Vegetation has an important role on erosion and sedimentation of rivers, river bank and marshy lands, etc. This effect depends on type of flow characteristics present in a vegetation patch. However, it’s a great challenge to find out the flow characteristics in the interior of vegetation patch. The objective of this study is to determine the appropriate scaling of flow characteristics throughout the interior of an emergent and sparse vegetation patch for a given flowrate and depth, which can be used to predict the flow field in a similar vegetation conditions. In this study uniform acrylic cylinders were planted in a structured array to create a vegetation patch. Two different flow conditions by varying aspect ratio for a given Reynolds number were used in this laboratory study. Nortek ADV was used for measuring point velocities in the interior of the vegetation patch. Mean flow and turbulence quantities at all the measuring locations in the interior of the patch were scaled appropriately so that they collapse on a single curve. The local maximum velocity is found to be an appropriate scaling parameter for normalizing the streamwise velocity profiles, further the scaled velocity in the interior of the patch found to be following a power law. Lateral and vertical velocities in the interior of the patch are appropriately scaled by velocity vector across the section. Average bulk lateral velocity and scaled shear stress in a sparse and emergent vegetation patch can be described by linear equations in terms of scaled depth.