Abstract:
The Environmental Fluid Dynamics Code (EFDC Hydro) is a state-of-the-art
hydrodynamic model that can be used to simulate aquatic systems in one, two,
and three dimensions. It has evolved over the past two decades to become one of
the most widely used and technically defensible hydrodynamic models in the
world. EFDC uses stretched or sigma vertical coordinates and Cartesian or
curvilinear,
... orthogonal horizontal coordinates to represent the physical
characteristics of a water body. It solves three-dimensional, vertically
hydrostatic, free surface, turbulent averaged equations of motion for a
variable-density fluid. Dynamically-coupled transport equations for turbulent
kinetic energy, turbulent length scale, salinity and temperature are also
solved. The EFDC model allows for drying and wetting in shallow areas by a mass
conservation scheme. The physics of the EFDC model and many aspects of the
computational scheme are equivalent to the widely used Blumberg-Mellor model
and U. S. Army Corps of Engineers? Chesapeake Bay model. EFDC's role in the
TMDL Toolbox will be to provide necessary hydrodynamic inputs to WASP, the
advanced receiving water quality model.
EFDC Preprocessor:
In order to facilitate the setup and application of EFDC, a preprocessor is
being developed. The preprocessor will be composed of two major components: the
Curvilinear Grid Generator and the EFDC Model Interface. Together these
components will enable users to generate curvilinear-orthogonal grids, simulate
aquatic systems in 1, 2, or 3-dimensions, link 2-D grids to 1-D grids, quickly
and easily set and change critical modeling parameters, and make use of
watershed loading model results and monitoring data for boundary conditions.
The Curvilinear Grid Generator enables a user to generate
curvilinear-orthogonal grids that are required for the numerical model. It will
significantly decrease the repetitive effort typically required through manual
grid generation methods. Grid generation will be conducted interactively and
intuitively through the interface and associated controls. Key features of the
tool include:
-GIS interface
-Model domain designation through user control point designation
-Automatic insertion of grid boundary points based on control point
designation
-Automatic curvilinear-orthogonal grid generation
-Model grid conversion to GIS shape file format
-Cell mapping between EFDC and WASP
Once a grid has been generated, it's necessary to set and calibrate pertinent
modeling parameters. The EFDC interface simplifies the setup and application of
EFDC through a user-friendly graphical interface and associated windows. It
supports input of EFDC model run control and model parameter designation, and
it links directly to boundary condition/source data, e.g. watershed model
output and point source contributions. Key features of the tool include:
-Database-oriented interface
-Visual linkage to the model grid
-Visual linkage to point and nonpoint source inputs
-New model parameter addition and accommodation
-Direct linkage to WRDB for boundary condition designation/generation
[Summary provided by the EPA.]