Session

Session 2 2022

Start Date

10-26-2022 12:00 AM

Abstract

Block ramps are ecofriendly drop structures, which ensure stable downstream river bed, peculiar to flows over macro roughness elements. It uniquely serves an essential paradigm in riverine management, to encounter deliveries in an ecologically sound manner. It permits safe fish passage, stabilizes stream banks and bed profiles and creates habitat diversity. Study of flows over block ramps are quite extensive and are associated with many intricacies. In this paper, flume experiments were conducted in the hydraulic laboratory of National Institute of Technology Patna. The particle densimetric Froude number (F*) was calculated for the mobile bed and chosen to predict the hydraulic conditions for incipient sediment motion in the uniform beds and it is compared with the established literature formulations to estimate the stability of the beds under large-scale roughness conditions. Scour volumes from each experimental run is quantified and the intensity of sediment motion was determined. Experimental data analysis allowed describing the mechanism of incipient motion of the mobile bed in the stilling basin, energy dissipation, flow resistance and in the interstitial flow over rock ramps and intensity of block movement for various flow regimes. It was found that the dimensionless shields stress increases with ramp slope and the intensity of ramp motion decreases with the shear stress. The results indicated that friction resistance increases with relative submergence for the tested range of experiments. A comparison with previous literature with uniform sediment transport indicates that relative roughness of block is responsible for increasing the dimensionless Shields stress. The results of physical testing can be used to assess and predict the effective dissipation of energy and its impact on the stability of rock structures.

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Oct 26th, 12:00 AM

Investigation of Energy Attenuation, Flow Resistance and Impending Motion of Downstream Bed Material in Rock Ramps

Block ramps are ecofriendly drop structures, which ensure stable downstream river bed, peculiar to flows over macro roughness elements. It uniquely serves an essential paradigm in riverine management, to encounter deliveries in an ecologically sound manner. It permits safe fish passage, stabilizes stream banks and bed profiles and creates habitat diversity. Study of flows over block ramps are quite extensive and are associated with many intricacies. In this paper, flume experiments were conducted in the hydraulic laboratory of National Institute of Technology Patna. The particle densimetric Froude number (F*) was calculated for the mobile bed and chosen to predict the hydraulic conditions for incipient sediment motion in the uniform beds and it is compared with the established literature formulations to estimate the stability of the beds under large-scale roughness conditions. Scour volumes from each experimental run is quantified and the intensity of sediment motion was determined. Experimental data analysis allowed describing the mechanism of incipient motion of the mobile bed in the stilling basin, energy dissipation, flow resistance and in the interstitial flow over rock ramps and intensity of block movement for various flow regimes. It was found that the dimensionless shields stress increases with ramp slope and the intensity of ramp motion decreases with the shear stress. The results indicated that friction resistance increases with relative submergence for the tested range of experiments. A comparison with previous literature with uniform sediment transport indicates that relative roughness of block is responsible for increasing the dimensionless Shields stress. The results of physical testing can be used to assess and predict the effective dissipation of energy and its impact on the stability of rock structures.