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Published in: Meccanica 12/2023

14-11-2023

Spatial-averaged turbulence characteristics over staggered pattern roughness

Authors: Jayanta Shounda, Krishnendu Barman, Koustuv Debnath

Published in: Meccanica | Issue 12/2023

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Abstract

This present study reports the turbulent flow characteristics under the framework of double-averaged (time and spatial domains) Navier–Stokes equations over hemispherical bottom roughness arranged in staggered order based on laboratory flume experiments. Under uniform flow conditions, the instantaneous velocity data was collected by using an acoustic Doppler velocimeter to capture the detailed rough bed flow structures over different pitch ratios of bottom roughness p/r = 4, 6, and 8 (p = pitch distance and r = height of hemisphere). The results reveal that the local velocity fluctuations are strongly modulated in the near-bed region for the roughness spacing p/r = 4 and this case is marked by the lowest spatial-averaged (SA) values among the cases studied herein. Results reveal that the SA velocity profile follows a logarithmic distribution for the entire flow depth. The form-induced intensity and relative turbulence intensity profiles show their maximum peak within the interfacial sub-layer of roughness for all three coordinate directions. Third-order moments of turbulent velocity fluctuations were evaluated to check the strength of shear stress flux and efficiency of energy transportation along the stream-wise and bottom-normal directions. Results portray that the production and dissipation rates of turbulent kinetic energy reach their maximum values above the bottom edge of the form-induced sub-layer. The double-averaging technique of rough-bed flow representation is important for modelling of natural rough-bed flows that partition the scale of roughness geometry and flow.

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Literature
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Metadata
Title
Spatial-averaged turbulence characteristics over staggered pattern roughness
Authors
Jayanta Shounda
Krishnendu Barman
Koustuv Debnath
Publication date
14-11-2023
Publisher
Springer Netherlands
Published in
Meccanica / Issue 12/2023
Print ISSN: 0025-6455
Electronic ISSN: 1572-9648
DOI
https://doi.org/10.1007/s11012-023-01728-4

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