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You are here : eLibrary : IAHR World Congress Proceedings : 32nd Congress - Venice (2007) : THEME C: Fluid Mechanics and Hydraulics : Estimating parameters for conveyance in 1d models of open channel flow from large eddy simulation
Estimating parameters for conveyance in 1d models of open channel flow from large eddy simulation
Author : Faye Beaman, Hervé Morvan and Nigel Wright
This paper describes Large Eddy Simulation (LES) of steady uniform flow in a series of in-bank channels at Reynolds numbers ~50,000-100,000. The simulation results are used to investigate the behaviour of three empirical constants f , λ andΓ associated with a conveyance estimation system; the Shiono & Knight Method (SKM) (Shiono and Knight 1988; Shiono and Knight 1991). The SKM offers an approach to calculating the lateral distributions of depth-averaged velocity and boundary shear stress for in-bank and over-bank channel flows and has recently been adopted by the Environment Agency (EA) for England and Wales as part of its new Conveyance Estimation System (CES) (McGahey and Samuels 2003). The SKM is a function of three parameters f , λ andΓ , which account for bed shear, lateral shear and secondary flow effects respectively and which require careful calibration. Initial investigation has been undertaken into the behaviour of f , λ and Γ from experimental results (Shiono and Knight 1991) and also from a process of optimisation (Chlebek and Knight 2006). This research intends to extend that investigation; firstly comparing the LES derived parameters with published values and then further investigating the physical behaviour of f , λ andΓ . Initial results showed that LES derived f andλ are in good agreement with published results and from initial investigation they seem relatively well defined. The secondary flow term,Γ , is shown to be the most difficult to predict and it is also shown that to prescribe an averageΓ value over the cross-section is an inaccurate description of the flow physics.
File Size : 445,177 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 32nd Congress - Venice (2007)
Article : THEME C: Fluid Mechanics and Hydraulics
Date Published : 01/07/2007
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