Impact of Bed Surface Roughness on Flow Turbulence and Sediment Grains Transport: A Preliminary Laboratory Flume Study

Abstract

This study examines how sediment bed characteristics can influence flow turbulence that may modulate the initiation of sediment grain movement and suspension during transport. A series of laboratory flume experiments was carried out to investigate near-bed flow turbulence under varying flow conditions using fixed sand and gravelly beds respectively. Flow velocity fluctuation was used to determine the magnitude of turbulence which was measured using a 3-C Vectrino ADV profiler. The findings demonstrated that turbulence was greater on flows over rough gravelly bed surface than on sandy bed surface. Also, with the same flow thickness, the mean flow velocity for flows under sand bed ranged between 0.306 -0.333m/s, while that of flows under gravel bed was 0.551–0617m/s. Thus, an increase in bed roughness leads to an increase in turbulence which controls sediment grain motion and its suspension during transport.