HR: 17:45h
AN: H54A-08    [Abstracts]
TI: Flow Structure in a Bifurcation: CFD modeling and Validation
AU: * Yu, D
EM: d.yu2@lboro.ac.uk
AF: Departemnt of Geography, Loughborough University, Loughborough, Leicestershire, Loughborough, LE11 3TU, United Kingdom
AU: Lane, S N
EM: s.n.lane@durham.ac.uk
AF: Department of Geography, Durham University, Science Site, South Road, Durham, DH1 3LE, United Kingdom
AU: Hardy, R J
EM: r.j.hardy@durham.ac.uk
AF: Department of Geography, Durham University, Science Site, South Road, Durham, DH1 3LE, United Kingdom
AU: Best, J L
EM: jimbest@uiuc.edu
AF: Departments of Geology and Geography and Ven Te Chow Hydrosystems Laboratory, University of Illinois at Urbana-Champaign, 1301 W Green Street, Urbana, IL 61801, United States
AU: Parsons, D
EM: d.parsons@see.leeds.ac.uk
AF: Institute of Geological Sciences, School of Earth and Environment, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, United Kingdom
AU: Keevil, G
EM: g.keevil@see.leeds.ac.uk
AF: Institute of Geological Sciences, School of Earth and Environment, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, United Kingdom
AU: Thomas, R E
EM: r.thomas@see.leeds.ac.uk
AF: Institute of Geological Sciences, School of Earth and Environment, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, United Kingdom
AB: There has been a recent growth in scientific interest concerning the role of river bifurcations as key nodes within fluvio-deltaic systems and in braided rivers, with the realization that they are critical in the very process of braiding itself. The geometrical characteristics of the bifurcation largely control flow and sediment partitioning between the two distributaries, the inherited downstream flow structure and thus potentially evolution of the subsequent bifurcation morphology. Furthermore, it has been shown that certain geometrical configurations induce flow instabilities that allow formation of a downstream mid-channel bar through symmetric forcing. However, to date, we have a poor process understanding of flow dynamics within such bifurcations and their downstream distributaries. In order to begin to address these issues, here we examine flow structure in a bifurcation through application of a time-averaged Computational Fluid Dynamics model, using an RNG k-å turbulence model, a non-equilibrium wall treatment and a second order accurate numerical solver. The domain was meshed using a multi- (two-) block mesh approach where the inflow channel comprises two connected meshes, which divide at the bifurcation, and become symmetrical in the two distributaries. This thus provides a good boundary representation in the distributaries, as well as a better flow field simulation in the vicinity of the bifurcation, where flow partitioning is sensitive to the mesh design. The numerical experiment replicates concurrent research where a bifurcation has been examined in an identical-geometry physical model that provided the boundary conditions and model validation data. This paper will present details of i) the model and its validation, and ii) subsequent numerical experiments where modifications were made to the distributary channel width, slope and bifurcation angle, that aimed to gain an insight into the dominant geometric characteristics of the bifurcation and their influence on flow structure and potential bifurcation stability.
DE: 1805 Computational hydrology
DE: 1847 Modeling
DE: 1849 Numerical approximations and analysis
DE: 1856 River channels (0483, 0744)
DE: 1860 Streamflow
SC: Hydrology [H]
MN: 2007 Fall Meeting