<abstract xml:lang="en" xmlns="http://www.w3.org/1999/xhtml"><p>The friction conditions at the top of a mobile bed are discussed for flows in the upper-plane-bed regime, i.e. for the flows with values of the bed Shields parameter larger than approximately 0.6. A special attention is devoted to flows of the bed Shields parameter bigger than 2. Experimental data for flows at high bed shear are collected from literature and new data are added from own measurements of flows of a 1.36-mm sand slurry in the 100-mm pipe loop of the Institute of Hydrodynamics. The database represents flows of very different solids and covers friction conditions within a broad range of Shields parameters up to the maximum value of about 23. The paper analyses the data in order to evaluate a relationship among the equivalent roughness of the top of the bed and other relevant parameters. A semi-empirical formula is proposed that relates the equivalent roughness to the bed Shields parameter, the ratio of flow velocity and particle settling velocity, and the ratio of flow hydraulic radius and particle diameter. The formula is applicable primarily to flows of combined load (contact- and suspended loads together).</p></abstract>

The friction conditions at the top of a mobile bed are discussed for flows in the upper-plane-bed regime, i.e. for the flows with values of the bed Shields parameter larger than approximately 0.6. A special attention is devoted to flows of the bed Shields parameter bigger than 2. Experimental data for flows at high bed shear are collected from literature and new data are added from own measurements of flows of a 1.36-mm sand slurry in the 100-mm pipe loop of the Institute of Hydrodynamics. The database represents flows of very different solids and covers friction conditions within a broad range of Shields parameters up to the maximum value of about 23. The paper analyses the data in order to evaluate a relationship among the equivalent roughness of the top of the bed and other relevant parameters. A semi-empirical formula is proposed that relates the equivalent roughness to the bed Shields parameter, the ratio of flow velocity and particle settling velocity, and the ratio of flow hydraulic radius and particle diameter. The formula is applicable primarily to flows of combined load (contact- and suspended loads together).

On equivalent roughness of mobile bed at high shear stress

Institute of Hydrodynamics, Academy of Sciences of the Czech Republic, Pod Paťankou 30/5, 166 12 Prague 6, Czech Republic

Journal of Hydrology and Hydromechanics

{"article-title":"On equivalent roughness of mobile bed at high shear stress"}

The friction conditions at the top of a mobile bed are discussed for flows in the upper-plane-bed regime, i.e. for the flows with values of the bed Shields...

On equivalent roughness of mobile bed at high shear stress

Publié en ligne: 10 août 2009

Pages: 191 - 199

DOI: https://doi.org/10.2478/v10098-009-0018-9

Mots clés
tření o dno, experiment, hydraulická doprava, pohyb splavenin

This content is open access.

On equivalent roughness of mobile bed at high shear stress

Publié en ligne: 10 août 2009

Pages: 191 - 199

DOI: https://doi.org/10.2478/v10098-009-0018-9

Mots cléstření o dno, experiment, hydraulická doprava, pohyb splavenin

This content is open access.

Mots clés
tření o dno, experiment, hydraulická doprava, pohyb splavenin