Conference proceeding
A study of vertical non-uniformity of flow and mass exchange processes in a shallow mixing layer
ICHMT DIGITAL LIBRARY ONLINE
International Symposium On Turbulence Heat and Mass Transfer, 6 (Rome, Italy, 09/14/2009–09/18/2009)
2009
DOI: 10.1615/ICHMT.2009.TurbulHeatMassTransf.110
Abstract
The dynamics of a shallow mixing layer developing between two parallel streams in a long open channel with flat bed is investigated numerically using Detached Eddy Simulation (DES). The simulation captures the expected decrease in the rate of growth of the mixing layer width in the streamwise direction and the shift of its centerline toward the low-speed side observed in laboratory studies of the flow close to the free surface. Simulation results show the rate of growth of the mixing layer decays with increasing distance from the free surface. At large distances from the splitter plate (x>120D, where D is the channel depth), the width of the mixing layer close to the free surface is about 60% larger than the width close to the channel bed. The interface between the mixing layer and the low speed stream is strongly tilted relative to the vertical direction in the downstream part of the mixing layer. Analysis of the concentration flow fields shows that the axes of the large-scale quasi two-dimensional mixing-layer eddies are tilted relative to the vertical direction. Though in the mean flow the values of the bed shear stress beneath the mixing layer are lower than those recorded beneath the high-velocity stream, in the instantaneous flow fields the large-scale eddies convected in the near-bed region induce values of the bed shear stress in the mixing layer region that are significantly higher than those observed beneath the two streams. This means that the scour processes downstream of the confluence between the two streams are driven by the passage of the mixing layer eddies. This is one of the main mechanisms that explain the formation of large scour holes at river confluences.
Details
- Title: Subtitle
- A study of vertical non-uniformity of flow and mass exchange processes in a shallow mixing layer
- Creators
- G. Kirkil - Lawrence Livermore National LaboratoryG. Constantinescu - University of Iowa
- Resource Type
- Conference proceeding
- Publication Details
- ICHMT DIGITAL LIBRARY ONLINE
- Conference
- International Symposium On Turbulence Heat and Mass Transfer, 6 (Rome, Italy, 09/14/2009–09/18/2009)
- DOI
- 10.1615/ICHMT.2009.TurbulHeatMassTransf.110
- ISSN
- 2377-2816
- Language
- English
- Date published
- 2009
- Academic Unit
- Civil and Environmental Engineering
- Record Identifier
- 9984202146802771
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