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Three‐dimensional flow modelling and sediment transport in the River Klarälven
Author(s) -
Dargahi Bijan
Publication year - 2004
Publication title -
earth surface processes and landforms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.294
H-Index - 127
eISSN - 1096-9837
pISSN - 0197-9337
DOI - 10.1002/esp.1071
Subject(s) - geology , sediment transport , bifurcation , hydrology (agriculture) , closure (psychology) , streamflow , acoustic doppler current profiler , turbulence , flow (mathematics) , calibration , vorticity , current (fluid) , sediment , mechanics , drainage basin , geomorphology , geotechnical engineering , physics , vortex , nonlinear system , oceanography , cartography , quantum mechanics , economics , geography , market economy
A three‐dimensional ow model that uses the RNG k ‐ ε turbulence model and a non‐equilibrium wall function was applied to the River Klarälven in the southwest part of Sweden. The objectives were to study the nature of the ow in the river bifurcation and to investigate the short‐term sediment transport patterns in the river. The effectiveness of three‐dimensional ow models depends upon: (1) how well the river geometry and it surface roughness are modelled; and (2) the choice of the closure model. Improvements were obtained by modelling the river in two parts: the entire river reach, and a selected part. Composite Manning coefcients were used to account for roughness properties. The method requires a calibration process that ensures the water surface proles match the eld data. The k ‐ ε model under‐predicted both the extent of ow separation zones and the number of secondary ow regions having a spiral motion, in comparison with the RNG k ‐ ε model. The 3‐D model could predict with good accuracy both the general and secondary ow elds in the river. The results agreed well with the 3‐D velocity measurements using an acoustic Doppler current proler. A conceptual model was developed that accounts for the development of secondary ows in a river bifurcation having two bends. The main ow feature in the river cross‐sections was the existence of multiple counter‐rotating spiral motions. The number of spiral motions increased as the river bends were approached. The river bends also caused vorticity intensication and increased the vertical velocities. The application of the 3‐D ow model was extended by solving the sediment continuity equation. The sediment transport patterns were related to the secondary ow elds in the river. The sediment transport patterns at the river bifurcations are characterized by the growth of a sandbank. Copyright © 2004 John Wiley & Sons, Ltd.