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Dispersion processes in weakly dissipative estuaries: Part 2. Multiple constituent tides.
  • Annalisa De Leo,
  • Nicoletta Tambroni,
  • Alessandro Stocchino
Annalisa De Leo
University of Genoa

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Nicoletta Tambroni
University of Genoa
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Alessandro Stocchino
The Hong Kong Polytechnic University
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In the present study, we extend the analysis of the dispersion processes induced by tidal flow in weakly-dissipative estuaries discussed in the companion paper. Here we focus the attention on the flow induced by more realistic tidal waves provided by different combinations of semi-diurnal and diurnal constituents. We employ a large-scale physical model of a system composed by a large basin (open sea) and a compound tidal channel, where tides are produced as volume waves with prescribed shapes. Two-dimensional superficial velocity fields are used to study the main Eulerian and Lagrangian properties of the flow, in terms of absolute and relative particle statistics. The results suggest that the mixed character of the tides strongly influences the shape of the macro-vortices generated at the tidal inlet, whereas the overall residual currents seem to be less sensitive. Moreover, for the present tidal setting, longitudinal dispersion, the dominant dispersion process, is enhanced when the semi-diurnal constituents prevail. Finally, multiple particle statistics show regimes typical of non-local dynamics for particle separation larger than a typical injection length scale, which is the size of the tidal inlet. Non-local dynamics imply that the dispersion is dominated by flow structures larger than the mean separation length, i.e. the tidal wavelength and the size of the macro-vortices. The present results together with those discussed in Part 1, offer a thorough insight in the main dispersion processes induced by tidal flows, which are extremely relevant in the case of estuarine dynamics.