How to Make a Mesh (AdH) from Scratch (15 pages)

how to make a mesh (adh) from scratch

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Author: Barbara Donnell (USACE ERDC-CHL)

Last Modified: 9-18-2011

How to Make a Mesh (AdH) from Scratch

Background and Data Gathering

Define the Purpose
Define a clear purpose of the modeling exercise. Understand the reason behind running the model.
Understand the physical forcing(s) of the system. Do you foresee the purpose expanding to include
other issues, such as salinity intrusion or sedimentation? Consider if the proposed changes to the
system will affect boundary condition locations. Will the time/energy/effort/money used for modeling
pay off?

Pre-Model Data Gathering
Go on a treasure hunt to find bathymetry data, learn about the system and determine the model
domain and boundary condition locations. Data gathering has evolved away from “paper maps” to
electronic downloads from the web or from GIS data base(s). A detailed bathymetry data set is essential
to a successful model. Go visit the site and talk to the locals. Take the time to review previous studies,
publications, and become familiar with NOAA station locations.

Bathymetry data can be found in many different formats: charts, GIS data bases, shape files with Z-
values, digital survey data (ADCP), or “fly overs” (LIDAR). ADCP and/or LIDAR data sets are popular
choices. These data sets can be enormous! Be prepared to address whether you have enough
computer memory and processor speed to process the data.

Select the Appropriate Model
You must choose a numerical model that addresses the physics at the site. Consider if the system is
vertically mixed or stratified? Will wetting and drying occur? Consider the dimensionality of the
problem (1D, 2D, 3D). Examine historical field data records to determine if the system can be modeled
by 2D type model, or if a 3D model is required. Determine if the water velocities are critical or sub-
critical. Are there unusual features in the system (weirs, control structures, etc) or extreme test
conditions (dam breaks, fish ladders, etc)?

Select the Computation Environment
When selecting what computer(s) to use, there are two categories to consider: where will the pre- and
post- processing be done, and where will the numerical model be run.

A desktop computer is necessary.

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