engleski

Hydraulics of stratified two-layer flow in Rječina Estuary

The salinity distributions in the micro-tidal channel of Rječina estuary, in Croatia, are thoroughly studied through intensive sampling campaigns. The salt wedge is developed at the downstream river part, and its length is found to be directly related to Rječina River discharges. The length of the wedge is also dependant, but in smaller intense, to tidal phases. Strong vertical stratification was observed throughout the tidal cycle, proving the limited vertical mixing between salt and freshwater layer. Bottom topography also plays a major role in wedge propagation, especially during small river discharges. A one-dimensional model for two-layer stratified flow, based on Schijf-Schoenfeld model, was developed and used. Results of literature review were confirmed – the interfacial friction factor cannot be satisfactorily correlated neither with Reynolds, Froude nor Keulegan number. The average interfacial factor was found to be best correlated with the number ReRi3, in which Re and Ri are Reynolds and overall Richardson number respectively. Comparison of the modelled and measured shapes of the density interface lines suggests that the interfacial friction factor varies along the wedge and that the use of the length averaged interfacial friction factor is not sufficiently accurate.

Stratified flow; two-layer; estuary

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