Numerical simulation of flow over a rough bed
Numerical simulation of flow over a rough bed
This paper presents results of a direct numerical simulation (DNS) of turbulent flow over the rough bed of an open channel. We consider a hexagonal arrangement of spheres on the channel bed. The depth of flow has been taken as four times the diameter of the spheres and the Reynolds number has been chosen so that the roughness Reynolds number is greater than 70, thus ensuring a fully rough flow. A parallel code based on finite difference, domain decomposition, and multigrid methods has been used for the DNS. Computed results are compared with available experimental data. We report the first- and second-order statistics, variation of lift/drag and exchange coefficients. Good agreement with experimental results is seen for the mean velocity, turbulence intensities, and Reynolds stress. Further, the DNS results provide accurate quantitative statistics for rough bed flow. Detailed analysis of the DNS data confirms the streaky nature of the flow near the effective bed and the existence of a hierarchy of vortices aligned with the streamwise direction, and supports the wall similarity hypothesis. The computed exchange coefficients indicate a large degree of mixing between the fluid trapped below the midplane of the roughness elements and that above it.
386-398
Singh, K.M.
a7066f26-f08e-481b-94ca-f67a1ba73429
Sandham, N.D.
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Williams, J.J.R.
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April 2007
Singh, K.M.
a7066f26-f08e-481b-94ca-f67a1ba73429
Sandham, N.D.
0024d8cd-c788-4811-a470-57934fbdcf97
Williams, J.J.R.
00bddc69-411c-4267-98d9-0503b837ccda
Abstract
This paper presents results of a direct numerical simulation (DNS) of turbulent flow over the rough bed of an open channel. We consider a hexagonal arrangement of spheres on the channel bed. The depth of flow has been taken as four times the diameter of the spheres and the Reynolds number has been chosen so that the roughness Reynolds number is greater than 70, thus ensuring a fully rough flow. A parallel code based on finite difference, domain decomposition, and multigrid methods has been used for the DNS. Computed results are compared with available experimental data. We report the first- and second-order statistics, variation of lift/drag and exchange coefficients. Good agreement with experimental results is seen for the mean velocity, turbulence intensities, and Reynolds stress. Further, the DNS results provide accurate quantitative statistics for rough bed flow. Detailed analysis of the DNS data confirms the streaky nature of the flow near the effective bed and the existence of a hierarchy of vortices aligned with the streamwise direction, and supports the wall similarity hypothesis. The computed exchange coefficients indicate a large degree of mixing between the fluid trapped below the midplane of the roughness elements and that above it.
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SinghSandhamWilliamsJHE2007.pdf
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Published date: April 2007
Organisations:
Aerodynamics & Flight Mechanics
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Local EPrints ID: 48560
URI: http://eprints.soton.ac.uk/id/eprint/48560
PURE UUID: ae5f27fd-7b5e-4c86-bd33-2429863b0429
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Date deposited: 01 Oct 2007
Last modified: 16 Mar 2024 03:03
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Author:
K.M. Singh
Author:
N.D. Sandham
Author:
J.J.R. Williams
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