Flow asymmetry associated with astronomical tides: implications for the residual transport of sediment
Hoitink, A.J.F.; Hoekstra, P.; Van Maren, D.S. (2003). Flow asymmetry associated with astronomical tides: implications for the residual transport of sediment. J. Geophys. Res. 108(C10): 8 pp. http://dx.doi.org/10.1029/2002JC001539
In: Journal of Geophysical Research. American Geophysical Union: Richmond. ISSN 0148-0227; e-ISSN 2156-2202, meer
Tidal current asymmetry is usually associated to nonlinear tidal interactions in shallow water, generating compound tides and overtides. The present paper demonstrates that tidal asymmetry is not only caused by nonlinear tidal interaction, but is also generated by astronomical tides in absence of shallow-water effects. In particular, the K1, O1, and M2 constituents give an asymmetrical periodic flow pattern, with the largest peak velocities persistently in the same direction. A theoretical explanation for this phenomenon is presented, and an inventory is made of other, subordinate constituents that may contribute to repetitive asymmetric flow patterns. Tidal current asymmetry may induce residual transport of sediment. Analytical expressions are derived which quantify the residual transport of sediment due to the K1, O1, and M2 tides, as a function of the phases and amplitudes of these constituents, and the time lag between variation in suspended sediment transport and flow velocity. The residual transport induced by the K1, O1, and M2 tides is compared to the residual transport due to the asymmetry associated with the M2 and M4 tides. The former mechanism is particularly relevant in diurnal, or mixed, mainly diurnal tidal regimes, where the K1 and O1 tides are dominant.
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