Authors : Olatunji Peter Folorunso and James Olugbenga Aribisala
Abstract: Most open channels are not comprised of uniform boundary roughness but instead in any given cross section consist of different roughness with varying frictional surface resistance, this heterogeneous bed roughness is ubiquitous in natural rivers and often influence and control the mean and turbulent flow structures in open channels thereby impacting on the conveyance capacity. This study describes the interaction of flexible vegetation and gravel bed on the mean and turbulent flow characteristics of an idealized heterogeneous open channel modelled using Astroturf (as grass vegetation) and gravel, the bed interaction is established alternately at both sides of the flume to form a partly vegetated open channel in a checkerboard pattern under a fully submerged condition. Mean velocities and turbulent properties are measured using the Acoustic Doppler Velocimeter (ADV). From the measured data, the cross sectional distribution of velocity and turbulent properties are obtained. The study shows flow concentration at the free surface and a reduced mean flow near bed over the grass bed. Estimated pattern of secondary flow reveals the interaction between the two bed roughness. The primary source of velocity shear as the dominant cause of the increased Reynolds shear stresses and turbulent activities occurred over the grass bed.
Olatunji Peter Folorunso and James Olugbenga Aribisala, 2020. Lateral Behaviour of Velocity and Turbulence Characteristics in Open Channels with Submerged Heterogeneous Bed. Research Journal of Applied Sciences, 15: 122-129.