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Flow Characteristics over Equilibrium and Non-Equilibrium Dunes

Author(s): Kenneth Lockwood; Patrick Grover; Ana Maria Ferreira Da Silva; Mareen A. Lenz

Linked Author(s): Ana Maria Ferreira da Silva, Patrick Grover

Keywords: Dunes; Morphological changes; Laboratory study; Flow; Sediment transport

Abstract: This paper concerns the coupling between flow, sediment transport and morphological changes of dunes. Its objective is to investigate intrinsic differences between the flow over equilibrium and non-equilibrium dunes that might explain their different behavior. The study is based on a dune development experiment previously carri ed out at Queen’s University, in which equilibrium dunes were subjected to a sudden decrease in flow depth. For the present purposes, the equilibrium dunes in the experiment under consideration were recreated and immobilized, to enable the study of the flo w field at equilibrium state, and just after the flow depth was suddenly decreased. It was found that the near bed time-averaged flow characteristics, as well as the near bed streamwise Reynolds stresses do not correlate well with the observed dune morphological changes. This study further suggests that the local bed-load rates and the local bed shear stress are not as strongly correlated as in the case of uniform flows.


Year: 2015

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