<abstract xmlns="http://www.w3.org/1999/xhtml">

<p>In alluvial channel, the non-cohesive bed particles are frequently accelerated by the flows and there has been an inconclusive debate on the deviations of logarithmic law parameters that demonstrate the velocity distributions in flows. Present study aims to elucidate the current knowledge of overwhelming theoretical and experimental evidences in this regard within the scope of near-bed turbulent flow characteristics. The study was conducted in two folds collecting instantaneous velocity of flow over a rigid sand bed under clear water flow conditions and compared to those over mobile sand beds under equilibrium bed-load. Results corroborated additional support to confirm the upward shifting of zero-velocity level in mobile bed flows. Most importantly, the conventional value of von Kármán coefficient significantly deviates in mobile bed flows compared to those in rigid sand bed. Also, the frictional velocity obtained from the bed slope consistently differs to those obtained from the Reynolds shear stress (RSS) distributions owing to transfer of stress aliquot to the bed particles. The mechanism is well demonstrated with the energy-momentum transfer within the framework of energy budget concept which shows near-bed negative pressure energy diffusion rates with increasing turbulence production in mobile bed flows.</p>
</abstract>

In alluvial channel, the non-cohesive bed particles are frequently accelerated by the flows and there has been an inconclusive debate on the deviations of logarithmic law parameters that demonstrate the velocity distributions in flows. Present study aims to elucidate the current knowledge of overwhelming theoretical and experimental evidences in this regard within the scope of near-bed turbulent flow characteristics. The study was conducted in two folds collecting instantaneous velocity of flow over a rigid sand bed under clear water flow conditions and compared to those over mobile sand beds under equilibrium bed-load. Results corroborated additional support to confirm the upward shifting of zero-velocity level in mobile bed flows. Most importantly, the conventional value of von Kármán coefficient significantly deviates in mobile bed flows compared to those in rigid sand bed. Also, the frictional velocity obtained from the bed slope consistently differs to those obtained from the Reynolds shear stress (RSS) distributions owing to transfer of stress aliquot to the bed particles. The mechanism is well demonstrated with the energy-momentum transfer within the framework of energy budget concept which shows near-bed negative pressure energy diffusion rates with increasing turbulence production in mobile bed flows.

Relative role of sediment entrainments on log-law parameters of longitudinal velocity distributions in mobile bed flows

Journal of Hydrology and Hydromechanics

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

In alluvial channel, the non-cohesive bed particles are frequently accelerated by the flows and there has been an inconclusive debate on the deviations of...

Relative role of sediment entrainments on log-law parameters of longitudinal velocity distributions in mobile bed flows

Published Online: Aug 10, 2021

Page range: 243 - 254

Received: Mar 05, 2021

Accepted: Jun 22, 2021

DOI: https://doi.org/10.2478/johh-2021-0017

Keywords
Alluvial channel, Energy budget, Hydrodynamics, Mobile bed, Zero-velocity level

© 2021 Pritam Malakar et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Relative role of sediment entrainments on log-law parameters of longitudinal velocity distributions in mobile bed flows

Published Online: Aug 10, 2021

Page range: 243 - 254

Received: Mar 05, 2021

Accepted: Jun 22, 2021

DOI: https://doi.org/10.2478/johh-2021-0017

KeywordsAlluvial channel, Energy budget, Hydrodynamics, Mobile bed, Zero-velocity level

© 2021 Pritam Malakar et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Keywords
Alluvial channel, Energy budget, Hydrodynamics, Mobile bed, Zero-velocity level