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| Titel |
Development and stability of bed forms: a numerical analysis of dune pattern coarsening and giant dunes |
| VerfasserIn |
Xin Gao, Clement Narteau, Olivier Rozier |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250104733
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| Publikation (Nr.) |
 EGU/EGU2015-4164.pdf |
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| Zusammenfassung |
| We investigate the development and stability of transverse dunes for ranges of flow
depths and velocities using a cellular automaton dune model. Subsequent to the
initial bed instability, dune pattern coarsening is driven by bed form interactions.
Collisions lead to two types of coalescence associated with upstream or downstream
dominant dunes. In addition, a single collision-ejection mechanism enhances the
exchange of mass between two consecutive bed forms (through-passing dunes). The
power-law increases in wavelength and amplitude exhibit the same exponents, which are
independent of flow properties. Contrary to the wavelength, dune height is not only
limited by flow depth but also by the strength of the flow. Superimposed bedforms
may propagate and continuously destabilize the largest dunes. Then, we identify
three classes of steady-state transverse dune fields according to the periodicity in
crest-to-crest spacing and the mechanism of size limitation. In all cases, the steady
state is reached when the bed shear stress in the dune trough regions is close to its
critical value for motion inception. Such a critical shear stress value is reached and
maintained through the dynamic equilibrium between flow strength and dune aspect ratio.
Comparisons with natural dune fields show that many of them may have reached
such a steady state. Finally, we infer that the sedimentary patterns in the model
may be used to bring new constraints on the stability of modern and ancient dune
fields. |
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