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Proposing Institution

Institut für Hydromechanik
Project Manager

Prof. Markus Uhlmann
Kaiserstr. 12
76131 Karlsruhe
Under certain circumstances, a small perturbation of an initially flat subaqueous sediment bed will be amplified and give rise to wave-like patterns in the form of ripples or dunes which are commonly observed in rivers and coastal waters. Providing fundamental understanding of the mechanisms involved in the formation of these patterns is highly desirable. However, the complex interaction between the sediment particles and the driving turbulent shear flow as well as the dependence on multiple governing parameters has made this task very challenging to the present date.Recently, we have performed simulations of the formation of subaqueous patterns in a statistically unidirectional channel flow configuration, in both the laminar and turbulent regimes, by means of high-fidelity numerical simulations which resolve all the relevant length and time scales of the turbulent flow, even the near-field around the individual particles (Kidanemariam & Uhlmann, J. Fluid Mech., 2014, 750, R2). Our results have successfully addressed important open questions on sedimentary patterns such as the initial pattern wavelength and it is believed that it will greatly contribute to the elucidation of the mechanisms of pattern formation.The present project is an extension of our previous work with the objective of simulating the evolution (beyond the initial formation) of these patterns in domains which are much larger in size than the anticipated initial wavelength of the bed patterns. A thorough analysis of the generated numerical data will allow us to address the following fundamental questions: How can the driving turbulent flow field over the time-dependent bedform be characterized? How do particles respond, individually or collectively, to the turbulent coherent structures? At what characteristic wavelength does the flat bed initially destabilize to form the ripple/dune patterns as a function of the governing parameters? How does the bedform evolve during the subsequent phases of the initiation of pattern formation? Moreover, we will be in a position to verify/falsify various existing theories for pattern formation based upon our data. The results of the proposed research are also expected to contribute to the establishment of an improved model of subaqueous pattern formation.

Impressum, Conny Wendler