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| Titel |
Hydro- and morphodynamics in curved river reaches - recent results and directions for future research |
| VerfasserIn |
K. Blanckaert, G. Constantinescu, W. Uijttewaal, Q. Chen |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7340
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| Digitales Dokument |
URL |
| Erschienen |
In: Sediment Transport and Landscape Dynamics (SALADYN) Workshop 2012 ; Nr. 37 (2013-12-17), S.19-25 |
| Datensatznummer |
250086182
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| Publikation (Nr.) |
 copernicus.org/adgeo-37-19-2013.pdf |
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| Zusammenfassung |
| Curved river reaches were investigated as an example of river configurations
where three-dimensional processes prevail. Similar processes occur, for
example, in confluences and bifurcations, or near hydraulic structures such
as bridge piers and abutments. Some important processes were investigated in
detail in the laboratory, simulated numerically by means of eddy-resolving
techniques, and finally parameterized in long-term and large-scale
morphodynamic models. Investigated flow processes include secondary flow,
large-scale coherent turbulence structures, shear layers and flow separation
at the convex inner bank. Secondary flow causes a redistribution of the flow
and a transverse inclination of the riverbed, which favour erosion of the
outer bank and meander migration. Secondary flow generates vertical
velocities that impinge on the riverbed, and are known to increase the
erosive capacity of the flow. Large-scale turbulent coherent structures also
increase the sediment entrainment and transport capacity. Both processes are
not accounted for in sediment transport formulae, which leads to an
underestimation of the bend scour and the erosion of the outer bank.
Eddy-resolving numerical models are computationally too expensive to be
implemented in long-term and large-scale morphodynamic models. But they
provide insight in the flow processes and broaden the investigated parameter
space. Results from laboratory experiments and eddy-resolving numerical
models were at the basis of the development of a new parameterization
without curvature restrictions of secondary flow effects, which is
applicable in long-term and large-scale morphodynamic models. It also led to
the development of a new engineering technique to modify the flow and the
bed morphology by means of an air-bubble screen. The rising air bubbles
generate secondary flow, which redistributes the patterns of flow, boundary
shear stress and sediment transport. |
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