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Effect of bottom stress formulation on modelled flow and turbidity maxima in cross-sections of tide-dominated estuaries |
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| Authors: | George P Schramkowski Huib E de Swart Henk M Schuttelaars |
| Institution: | 1. Flanders Hydraulic Research, Berchemlei 115, 2140, Antwerp, Belgium 2. Institute for Marine and Atmospheric research Utrecht, University of Utrecht, PO Box 80000, Utrecht, The Netherlands 3. Delft Institute of Applied Mathematics, Delft University of Technology, Mekelweg 4, 2624 CD, Delft, The Netherlands |
| Abstract: | A three-dimensional numerical model with a prognostic salinity field is used to investigate the effect of a partial slip bottom boundary condition on lateral flow and sediment distribution in a transect of a tidally dominated channel. The transect has a symmetrical Gaussian cross-channel bottom profile. For a deep, well-mixed, tidally dominated channel, partial slip decreases the relative importance of Coriolis deflection on the generation of cross-channel flow patterns. This has profound implications for the lateral distribution of residual salinity that drives the cross-channel residual circulation pattern. Transverse sediment transport, however, is always found to be governed by a balance between advection of residual sediment concentration by residual lateral flow on the one hand and cross-channel diffusion on the other hand. Hence, the changes in the cross-channel distribution of residual salinity modify the lateral sediment distribution. For no slip, a single turbidity maximum occurs. In contrast, partial slip gives a gradual transition to a symmetrical density distribution with a turbidity maximum near each bank. For a more shallow, partially mixed tidal channel that represents the James River, a single turbidity maximum at the left bank is found irrespective of the near-bed slip condition. In this case, semi-diurnal contributions to sediment distribution and lateral flow play an important role in cross-channel sediment transport. As vertical viscosity and diffusivity are increased, a second maximum at the right bank again exists for partial slip. |
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