Author(s): T. Tokyay; G. Constantinescu

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Abstract: The effects of the Reynolds number on the propagation of a lock-exchange Boussinesq compositional gravity current over an array of 2D dunes during the slumping phase are investigated using high-resolution Large Eddy Simulation. The dunes have a height of 0.15H and a wavelength of 3H. Two simulations at a Reynolds number defined with the buoyancy velocity, ub, and the channel depth, H, of 47,800and 1,000,000 are conducted. In the simulation conducted at the higher Reynolds number, the structure of the gravity current approaches the inviscid state that is assumed in most of the analytical models used to describe the evolution of gravity currents in rivers and lakes under realistic conditions. The effect of the Reynolds number on the front velocity, structure of the current and bed shear stress distributions are analyzed. By comparison with the case in which the gravity current propagates over a flat bed, at both Reynolds numbers a strong amplification of the bed shear stress is observed downstream of the region where the gravity current reattaches to the bed, past the crest of each dune.

DOI:

Year: 2009