Velocity and turbulence distribution in unsteady open channel flows through an emergent rigid stems

Abstract

Most open channel flows of interest of hydraulic engineers and hydrologists are unsteady. In unsteady flow, some aspects of flow (velocity and depth etc.) are changing in time. But many problems related to unsteady flow have been approximately solved by assuming steady flow or non-uniform flow (for example, constant peak discharges in floodplains without taking the time as a factor). Also, the understanding of vegetated flows under unsteady flow is of primary importance since a new trend on river management consists in restoring rivers and floodplains to their natural form.The present laboratory study focuses on the particular case unsteady flow with combination of highly submerged rigid grass and emergent rigid stems (representing the wood). One hydro-graph is passed repeatedly with 100runs through the rectangular flume using a fixed rigid grass bed with rigid circular stems. Classical hysteresis effect between rising and falling limbs in stage-discharge (h ~ Q) rating curve is illustrated.