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Characterization of Surface and Hyporheic Flows Associated With a Gravel Bar

Author(s): Mohammad Saeid Ahadi, Seyed Hessam Seyed Mirzaei, Ana Maria Ferreira Da Silva

Linked Author(s): Ana Maria Ferreira da Silva

Keywords: Gravel bar, hyporheic flow, surface flow, mean flow, turbulence characteristics

Abstract: An experimental and numerical study of the turbulent hyporheic and free surface flows associated with a gravel bar is presented. The hyporheic flow is visualized and quantified with the aid of dye injections; and further resolved with the aid of a numerical model. The mean and turbulence characteristics of the free surface flow are analyzed on the basis of flow velocity measurements using a 2-D ADV. It is found that 14% of the streamflow is entrained into the gravel bar and its substrate. The bar shifts the bulk of the flow towards the upper flow layers, resulting in large velocities towards the free surface for a considerable distance downstream of the bar top, and leading to a region rather protected from the flow action towards the bed after the bar. Two regions of higher turbulence activity are identified downstream of the bar top. In comparison to flow over an impervious gravel bar and bed, differences are found in both the free surface profile and velocities near the bed, especially immediately downstream of the bar top


Year: 2017

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