Björn Kjerfve

Numerical Hydrodynamic Modelling

As estuaries are three dimensional and time dependent, numerical models have been developed to overcome the simplifications inherent to the already studied analytical models (simple geometry, steady-state) and calculate estuarine circulation and salinity distributions. These models can be numerically integrated at selected grid points spatially distributed in the system domain; the governing partial differential equations use methods of finite-difference or finite-elements in curvilinear horizontal coordinates or sigma vertical coordinates, respectively.

Hydrodynamic Formulation: Mass and Salt Conservation Equations

When hydrographic properties and motions in an estuary have spatial and temporal variation, they are termed as non-uniform and unsteady, as opposed to uniform and in steady-state.

Introduction to Estuary Studies

The word estuary is derived from the Latin word aestus which means tide, also the adjective aestuarium has tidal or abrupt high wave as a meaning, an environment highly dynamic with changes due to natural forces. This word is generally used to indicate the place where the river meets the sea, characterizing a coastal river discharge.

Physical Properties and Experiments in Estuaries

The investigation of processes and how estuarine systems function, presents distinct aspects, being conducted with various purposes and objectives.

Circulation and Mixing in Steady-State Models: Partially Mixed Estuary

The first steady-state analytical model for determining time mean longitudinal velocities in a coastal plain estuary was developed by Pritchard and Kent (1956) using the lateral and longitudinal components of the equation of motion, the tidal velocity amplitude, and the relationship between the vertical and lateral eddy stress.

Mixing Processes in Estuaries: Simplifyed Methods

The classical definition of an estuary establishes that it is a partially closed water body with openings to the adjacent ocean, where the seawater is diluted by fresh water of the fluvial drainage basin. The input of fresh water decreases the potential energy of the water column, which is supplied by tidal energy through the mixing process produced on the bottom and internal shear instabilities.

Circulation and Mixing in Steady-State Models: Salt Wedge Estuary

Now that we have laid in the previous chapters the basic estuarine hydrodynamic framework, let us present in the following chapters practical applications of the analytical and numerical studies on the circulation in estuaries and its influence in the distributions of properties concentration.

Circulation and Mixing in Steady-State Models: Well-Mixed Estuary

In this chapter, the analytic model of circulation and mixing in a well-mixed and laterally homogeneous estuary (Types 1 or D) will be presented.

Hydrodynamic Formulation: Equations of Motion and Applications

Estuarine hydro- and thermodynamics processes control a variety of physical phenomena which are described by the water level, field of motion (tidal currents and gravitational circulation), and hydrographic properties (salinity, temperature, pressure).

Reduction and Analysis of Observational Data: Flux and Transport of Properties

Aspects related to the numerical treatment and analysis of observational data, which were included as items of the project component list (Table 4.1, Chap. 4) necessary to the project development, will be presented in this chapter. This comprises data reduction and analysis of scalar (hydrographic properties and tide) and vector (current velocity) data sampled in the water column (vertical profiles) and/or as temporal time series.