Three-Dimensional Tidal Flow in an Elongated, Rotating Basin (original) (raw)

Two-Layer Tidal Circulation in a Frictional, Rotating Basin

Journal of Physical Oceanography, 2010

The three-dimensional tidal circulation in an elongated basin of arbitrary depth is described with a coupled barotropic and baroclinic two-layer model on the f plane. As long as friction is not dominant, near-standing waves are present on the interface as well as on the surface. The surface pattern is principally determined by the product of the tidal barotropic wavenumber by the basin length. The interface deformation is determined by a baroclinic equivalent, usually a much larger number. As a result, the shape of the interface is characterized by horizontally smaller features than the surface. If the product of the tidal baroclinic wavenumber by the basin width is greater than one, both lateral and axial modes can be excited at the interface. If these modes are near resonant, large internal tides can be forced directly by the co-oscillating surface tide at the basin entrance. The amplitude and phase of the baroclinic component are sensitive functions of the density anomaly and the...

Modelling the Three-Dimensional Tidal Flow Structure in Semi-Enclosed Basins

Coastal areas are generally intensely used areas with high population density and economic activity. On a basin scale the tide directly determines water levels and currents in a basin. These flow characteristics furthermore determine the shape of the basin itself, for example the forming and evolution of tidal sandbanks, which in turn influences the flow pattern. Because of its importance for various human and natural activities the modelling of tidal flow has been studied by many authors in the past. This has lead to depth-averaged (2DH) and 3D models amongst others

Vertical circulation in shallow tidal inlets and back-barrier basins

Continental Shelf Research, 2007

In this paper, we analyse the contribution of tidally induced drift in the surface layer to the overall dynamics of wellmixed tidal basins undergoing drying and flooding. The study area covers the East Frisian Wadden Sea (German Bight, Southern North Sea), which consists of seven tidal basins. The major interest is focused on the tidal basin behind the islands of Langeoog and Spiekeroog and the inlet connecting it with the North Sea. The comparison between theoretical concepts, results from direct observations, and simulations with a numerical model helps to understand the underlying physics controlling the tidal response. The data were collected during the period 1995-1998 and consist of cross-channel ADCP transects. The identification of the dominant spatial patterns and their temporal variability is facilitated by applying an EOF analysis to the data. The numerical simulations are based on the 3-D primitive equation General Estuarine Transport Model (GETM) with a horizontal resolution of 200 m and terrain-following vertical coordinates. We find distinct differences between the temporal variability of the transports near the surface and those in deeper layers of the tidal inlets. The near surface transport is dominated by the tidally induced drift (similar to the Stokes drift), whereas the deeper layer transport is dominated by asymmetries caused by the hypsometric properties of the intertidal basins. These transports, when averaged over a tidal period, have opposite directions and compensate each other. This explains the establishment of a vertical overturning cell: landward motion in the upper layers and seaward motion in the deeper parts of the tidal channels. This vertical circulation cell is also observable in our numerical simulations and shows a clear dependency of the temporal asymmetry in the transport patterns on the local depth. In deep tidal channels, the overall properties of the tidal signal show a clear ebb dominance, whereas in the shallow extensions of the channels the transports during flood are larger than during ebb. Although, our research area can be characterized as a well mixed estuary, baroclinicity associated with the fresh water flux from the coast can substantially affect vertical overturning. r

Tidal flow field in a small basin

Journal of Geophysical Research, 2003

1] The tidal flow field in a basin of small dimensions with respect to the tidal wavelength is calculated. Under these conditions, the tide becomes a standing wave oscillating synchronously (with a flat water surface) over the whole basin. The shallow water equations can thus be strongly simplified, expressing the discharge vector field in terms of a potential function and a stream function. The potential function can be independently solved with the continuity equation, and is responsible for the total water balance in the basin. Moreover, the flow field derived from the potential function is shown to represent the tidal motion in a deep basin with flat bottom. Departures from this situation are treated with a stream function, that is, a correction for the potential function solution, and is solved through the vorticity equation. The stream function accounts for the nonlinear inertial terms and the friction in the shallow water equations, as well as bottom topography. In basins where channels incise within shallow tidal flats, the solution demonstrates that friction redistributes momentum, increasing the flow in the channels and decreasing it on the flats. The model is tested in San Diego Bay, California, with satisfactory results.

On the exact shape of the horizontal profile of a topographically rectified tidal flow

Geophysical & Astrophysical Fluid Dynamics, 1987

and by differential bottom friction. These finite intervals over which the residual velocity profiles exist for a step-like topography are not reproduced by harmonic truncation of the basic equation. This method gives exponentially decaying profiles, indicating spurious horizontal diffusion of vorticity. In terms of orders of magnitude, the method of harmonic truncation is reliable for residual velocity produced by vortex stretching but it overestimates the residual velocity produced by differential bottom friction by a factor 2.

Basic flow field in a tidal basin

Geophysical Research Letters, 2002

1] A simplified model for tidal flow in a basin is presented. The model is based on the assumption of a flat water surface oscillating synchronously in the tidal basin. Under this hypothesis the depth-averaged continuity equation becomes a Poisson equation that can be easily resolved at each instant of the tidal cycle. This formulation, which is particularly valid for small, deep basins, provides a simplified solution of the depth-integrated shallow water equations and suggests a possible approach to model long-term morphodynamic evolution of tidal basins. The model is tested in San Diego Bay, California, and the results are briefly discussed.

Lateral Circulation in a Partially Stratified Tidal Inlet

2018

Using a three-dimensional, hydrostatic, primitive-equation ocean model, this study investigates the dynamics of lateral circulation in a partially stratified tidal inlet, the Barataria Pass in the Gulf of Mexico, over a 25.6-hour diurnal tidal cycle. Model performance is assessed against observational data. During flood tide, the lateral circulation exhibits the characteristics similar to that induced by differential advection, i.e., lateral flow consists of two counter-rotating cells and is convergent at the surface. The analysis of momentum balance indicates that, in addition to the pressure gradient and vertical stress divergence, nonlinear advection and horizontal stress divergence are also important contributors. During ebb phase, the lateral circulation is mostly eastward for the whole water column and persisting for almost the whole period. The surface divergence suggested by the differential advection mechanism lasts for a very short period, if it ever exists. The main momen...