Study of the sediment transport over flat and wavy bottom using large-eddy simulation

Abstract

In the present paper the sensitivity of the flow and of sediment transport to bottom roughness is studied. First, a thorough numerical investigation of smooth-bottom channel flow at Re _τ = 395 is performed using large-eddy simulations (LESs). A dynamic version of the wall-adapted local eddy-viscosity (WALE) model is used for this study, whereas the subgrid-scale (sgs) diffusion stress is based on a gradient hypothesis. The computed results compare well with direct numerical simulation (DNS) data and experiments. Next, rough-bottom cases, with the bottom having a sinusoidal, wavy shape are considered. It was found that the wavy bottom has a strong influence on the flow field and that the sediment transport is highly sensitive to the bottom waviness, in particular for larger wave heights. It is shown that for light and low-concentrated sediment the Rouse theory is also valid in the case of a wavy bottom, mainly in the outer zone. Finally, it is found that the turbulent-Schmidt-number profiles are not very sensitive to the wave height.

Keywords:

• LES
• sedimentation
• sediment transport
• wavy bottom
• rough bottom

Acknowledgements

This research was partially funded by Flemish Science Foundation (FWO) under contract G.0359.04. This support is gratefully acknowledged.