A three-dimensional weakly nonlinear dynamics on tide-induced Lagrangian residual current and mass-transport |
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| Authors: | Feng Shizuo |
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| Institution: | (1) Shandong College of Oceanology, Shandong, China |
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| Abstract: | In recent years, studies of the environmental hydrodynamics in coastal seas and tidal estuaries have placed focus on the processes
which determine the “fate” of longer-term transport. The lagrangian residual current has been recognized as an important factor
which affects the longer term transport processes since it is more relevant to use a Lagrangian mean velocity rather than
an Eulerian mean velocity to determine the origin of Water masses. In the present paper, an attempt is made to formulate a
three-dimensional dynamics on the tideinduced Lagrangian residual current and mass-transport based upon a three-dimensional
weakly-nonlinear model of tides. The Lagrangian residual velocity is shown to be the sum of the mass-transport velocity, which
is the sum of the Eulerian residual velocity and the Stokes’ drift velocity, and the Lagrangian residual drift velocity which
is dependent on the tidal current phase. This reveals that it is the mass-transport velocity which is the tidal cycle Eulerian
mean of the Lagrangian residual velocity and that the mass-transport velocity is correct to the second order of approximation
rather than to the first order. And then, a new longer-term transport equation which correctly describes the Lagrangian nature
of transport processes without introducing the Fickian hypothesis for tidal dispersion is derived. In fact, the convection
can be correctly represented by the Eulerian mean of the Lagrangian residual velocity, as the convective velocity in the longer-term
transport equation is nothing but the mass-transport velocity.
Submitted for IAMAP/IAPSO Joint Assembly, August 5–16, 1985, Honolulu, Hawaii U.S.A. |
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