Basic flow field in a tidal basin (original) (raw)
Related papers
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.
Hydraulic modelling of tidal circulation and flushing in coastal basins
The Paper highlights the increasing concern of planners and designers for the hydroenvironmental problems relating to tidal circulation and flushing in small coastal basins, harbours, and marinas, and the use of physical and mathematical models as design tools to address such problems. Details are given of techniques frequently adopted in using both physical and mathematical models to quantify tidal flow patterns and water exchange characteristics of harbours and marinas. Emphasis is placed on comparative studies where alternative basin geometries and/or bathymetries are proposed. Advantages and disadvantages of both modelling techniques are considered. An example application of each approach is presented. The main purpose of the two studies was to investigate effects of basin geometries on the tidal flow and flushing features for two specific sites-one in the USA, the other in the UK. Results of both studies are reported, together with an interpretation of the data and a summary of the findings. Notatioo C , initial spatial average tracer concentration for volume considered C, spatial average tracer concentration for same volume after n tides E average per cycle exchange coeflicient n number of tides of simulation R average per cycle retention coeflicient T P R tidal prism ratio
A 2D Tide-Averaged Model for the Long-Term Evolution of an Idealized Tidal Basin-Inlet-Delta System
Journal of Marine Science and Engineering, 2018
We present a model for the morphodynamics of tidal basin-inlet-delta systems at the centennial time scales. Tidal flow is calculated through a friction dominated model, with a semi-empirical correction to account for the advection of momentum. Transport of non-cohesive sediment (sand) is simulated through tidal dispersion, i.e., without explicitly resolving sediment advection. Sediment is also transported downslope through a bed elevation diffusion process. The model is compared to a high-resolution tide-resolving model (Delft3D) with good agreement for different hydrodynamic and sedimentary settings. The model has low sensitivity with respect to temporal and spatial discretization. For the same spatial resolution, the model is about five orders of magnitude faster than tide-resolving models (e.g., Delft3D), and about three orders of magnitude faster than tide-resolving models that use a morphological acceleration factor. This numerical efficiency makes the model suitable to assess ...
A model of morphological behaviour of tidal basins
Coastal Engineering, 1994
A one-dimensional semi-empirical model is presented, which simulates the morphological behaviour of a tidal basin in response to a change in one or more of the extrinsic conditions. The model is based on three equilibrium parameters: the channel cross-sectional area, the fiats' surface area and the flats' level. The model is tested for three scenarios, namely a partial closure, an accelerated sea level rise and a change in the tidal range. It is verified by simulating changes in the Friesche Zeegat, the Netherlands, for which model results are compared with measurements.
Modeling of channel patterns in short tidal basins
Journal of Geophysical Research, 2005
1] We model branching channel patterns in short tidal basins with two methods. A theoretical stability analysis leads to a relationship between the number of channels and physical parameters of the tidal system. The analysis reveals that width and spacing of the channels should decrease as the slope of the bottom profile and the Shields parameter increase and as the mean water depth decreases. In general, the channel depth should halve at every bifurcation. These theoretical results agree well with the field data from the Dutch Wadden Sea. A numerical model based on Delft3D, a software system of WL/Delft Hydraulics, is used to simulate the time evolution of a channel network in a geometrically simplified basin of similar dimensions as the Wadden Sea basins. The resulting channel network displays a three-times branching behavior, similar to the three-to four-times branching patterns observed in the Wadden Sea. The simulated channel pattern satisfies the relation derived from the theoretical analysis. The results of this pattern analysis provide for additional validation of two-dimensional/three-dimensional process-based morphodynamic models of tidal basins.
Modelling the three-dimensional tidal flow structure in semi-enclosed basins
2009
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 The first analytical 3D-model that describes tidal flow in a semi-enclosed basin using Kelvin and Poincare modes with partial slip was created for this research. For this the method devised by Mofjeld (1980) for 3D tidal flow along a single coast with viscosity and no-slip was extended, thereby following Taylor’s approach (1921). As a reference situation the Northern Part of the North Sea was modeled and the properties ...
Depth‐Averaged 2‐D Model of Tidal Flow in Estuaries
2004
A depth-averaged 2-D numerical model for unsteady tidal flow in estuaries is established using the finite volume method on non-staggered, curvilinear grid. The 2-D shallow water equations are solved by the SIMPLEC algorithm with the Rhie and Chow's momentum interpolation technique. The convection terms are discretized by one of the hybrid upwind/central difference scheme, exponential difference scheme, QUICK scheme and HLPA scheme. The algebraic equations are solved using the strongly implicit procedure (SIP). The model is capable of handling the drying and wetting problem due to the variation of water surface elevation. The model has been tested in Tokyo Bay and San Francisco Bay. The tests show that the present model is very stable and efficient. The simulated water elevation and flow velocity are in good agreement with the measured data.
2006
Abstract: Details are given herein of the refinement and application of a two-dimensional depth integrated numerical model to predict geo-morphological changes in tidal basins. An Alternating Direction Implicit finite difference algorithm has been used for solving the governing differential equations, which consist of the conservation of mass and momentum for the hydrodynamics, the transport equation for suspended sediment fluxes and the sediment mass conservation equation for bed level changes. The model includes several ...
Int. Conf. on Hydroscience and Engineering, 2006
Details are given herein of the refinement and application of a two-dimensional depth integrated numerical model to predict geo-morphological changes in tidal basins. An Alternating Direction Implicit finite difference algorithm has been used for solving the governing differential equations, which consist of the conservation of mass and momentum for the hydrodynamics, the transport equation for suspended sediment fluxes and the sediment mass conservation equation for bed level changes. The model includes several criteria for the initiation of motion (i.e. Shields (1936), Kolahdoozan (1999) and Zanke (2003)). As the flow is highly turbulent, and its components have a random nature, many researchers have tried to express the sediment transport processes by using stochastic approaches. In the current study, both deterministic and stochastic methods were included in the numerical model to show their accuracy and efficiency. To evaluate the numerical model results laboratory measurements were used, obtained from an earlier experimental programme. In these evaluations, long term bed level changes in a laboratory model harbour were used for verification of the model. Comparisons were made using different criteria for the initiation of motion, with the results highlighting that the unsteadiness in the flow parameters included in the numerical models had a major effect on the bed level changes in comparison with the turbulence structure of the flow.
A simplified model to describe the flow field on tidal floodplains
2012
1] The response of vegetated tidal wetlands to environmental changes is governed by vegetation-flow-landscape feedbacks occurring over large spatial and temporal scales, and thus typically studied using simplified models. Here, we present a new simplified approach to describe frictionally dominated tidal flows, characteristic of tidal wetlands. The derivation of the model follows from an expansion of the momentum and mass conservation equations in terms of small dimensionless parameters, which arise once the relevant variables are suitably scaled. A comparison with a full-fledged finite element model indicates that the proposed simplified approach ensures a reliable description of the flow field; suggesting that the model provides a key advancement to study the bio-morphodynamic feedbacks which shape intertidal landscapes. Citation: Van Oyen, T., S. Lanzoni, A. D'Alpaos, S. Temmerman, P. Troch, and L. Carniello (2012), A simplified model for frictionally dominated tidal flows, Geophys.