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Open Channel Flow Over and Through a Porous Bed

Narendra Kumar Patel, University of Nebraska - Lincoln

Abstract

The main objectives of this research were to describe the velocity profile for flow over and through a porous bed and to examine flow characteristics like TKE and turbulence dissipation at the region near the interface between free flow and flow through the porous bed. Three approaches were used to study the research problem: theoretical, experimental, and numerical. In our theoretical research, velocity profiles for flow over and through the submerged vegetation (Guo et al. 2016) were used, assuming that the porous media behaves similar to flow through submerged vegetation and can be modeled using similar equations. The fitting parameter in the theoretical velocity profile was adjusted to match experimental and numerical velocity profiles. ANSYS Fluent software was used to numerically simulate the flow field both within and above the porous bed. In Fluent, the volume of fluid (VOF) and zero velocity gradient at free surface methods were used to generate flow field. Turbulence was modeled using a realizable k-e model. Uniform flow fields were generated for different porosities and bed slopes. In the experiments, velocity profiles were measured above and within a porous bed. Data were collected in a 15.0 m long x 0.38 m wide x 0.5 m deep flume that contained a 12.6 cm thick bed of coarse sand. A fiber optics-based sensor was developed to detect the presence of dye by measuring the water opacity. Three arrays of nine vertically distributed optical sensors were installed in the bed. The arrays were located at three equidistant positions along the streamwise direction. During experiments, dye was injected into the bed and the resulting dye cloud was tracked using the sensor arrays. The speed of the dye cloud within the bed was then assessed using the tracking data. Above the bed, an Acoustic Doppler Velocimeter (ADV) was used to measure velocity profiles.

Subject Area

Civil engineering|Fluid mechanics|Physics

Recommended Citation

Patel, Narendra Kumar, "Open Channel Flow Over and Through a Porous Bed" (2020). ETD collection for University of Nebraska - Lincoln. AAI28086416.
https://digitalcommons.unl.edu/dissertations/AAI28086416

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