Abstract
Vegetation in open channels will improve the water quality there and provide favorable space for various lives, but it will reduce the flow carrying capacity of the channel by introducing additional resistance to the flow. A Large Eddy Simulation (LES) model has been developed to study the mean flow and turbulence in open channel with vegetation. In the model the vegetation domain is represented by a drag force layer. One equation model is used for subgrid scale turbulence closure. The length scale of turbulence l is proportional to the grid size and the turbulence energy k is obtained from the solution of the turbulence energy transport equation. The model has been applied to simulate cases of open channel flow with emergent or submerged vegetation. For emergent vegetation occupied in a part of an open channel, transverse shear is produced by vegetation drag. Organized large eddies are developed at the interface between the vegetated and non-vegetated regions and the organized flow structure clearly has a life cycle. At the interface the transverse velocity profile exhibits a steep gradient, which induces significant mass and momentum exchange, acts as a source of vorticity, and generates high Reynolds stresses. For submerged vegetation in open channel, the flow near the top of vegetation is unstable and rolls up into discrete vortices. The turbulent intensity and the Reynolds stresses are the strongest there. Interaction of vortices results in a shear layer above the top of vegetation. The agreement between the numerical results and the available experimental data is satisfactory. The present model is a useful tool for further study of turbulent flow with vegetation, as well as for certain engineering applications.
Original language | English |
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Title of host publication | Proceedings of the 2003 - 17th National Conference on Hydrodynamics and the 16th National Congress on Hydrodynamics |
Pages | 18-28 |
Number of pages | 11 |
Publication status | Published - 1 Dec 2003 |
Event | Proceeding of the 2003 17th National Conference on Hydrodynamics and the 6th National Congress on Hydrodynamics - Hong Kong, Hong Kong Duration: 29 Dec 2003 → 4 Jan 2004 |
Conference
Conference | Proceeding of the 2003 17th National Conference on Hydrodynamics and the 6th National Congress on Hydrodynamics |
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Country/Territory | Hong Kong |
City | Hong Kong |
Period | 29/12/03 → 4/01/04 |
Keywords
- LES
- Open channel
- Turbulent flow
- Vegetation
ASJC Scopus subject areas
- General Engineering