Effects of sediment-induced stratification on floe breakup in an idealized tidal estuary: A numerical modelling study |
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Authors: | X H Wang |
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Institution: | (1) School of Physical, Environmental and Mathematical Sciences, University of New South Wales, Australian Defence Force Academy, Canberra, Australia |
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Abstract: | Floe breakup dynamics are studied by a sediment transport numerical model in an idealized tidal estuary that has a constant
water depth and rapid flocculation of cohesive sediments. The focus is placed on the effects of boundary layer stratification
induced by a bottom nepheloid layer on floe breakup and size distribution in the water column. In a neutrally stratified estuary,
the floe size distribution follows a parabolic function with maximum values at the surface and bottom. The sediment-induced
stratification in the bottom boundary layer increases the median floe sizes. Furthermore, sediment-voided convection caused
by the settling lutocline generates significant turbulent kinetic energy dissipation and reduces floe size at the depth where
the convective mixing happens. Below that depth, a weak local maxima in the floe size is predicted due to presence of the
lutocline. The effect of sediment-stratified bottom boundary layer on the floe breakup can be consistently approximated by
a linear regression between the maximal floe size and flux Richardson number. |
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Keywords: | floe floe breakup tidal estuary nepheloid layer numerical modelling |
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