SMS:RMA4

RMA4
Model Info
Model type	Finite element water quality transport numerical model in which the depth concentration distribution is assumed uniform. It computes concentrations for up to 6 constituents, either conservative or non-conservative, within the computational mesh domain.
Developer	Resource Management Associates United States Army Corps of Engineers (USACE)
Web site	RMA4 web site
Tutorials	General Section Mesh Editing Observation Overview Sensitivity Models Section RMA4

RMA4 is a finite element water quality transport numerical model. RMA4 was designed to simulate the depth-average advection / diffusion process in an aquatic environment. The model can be used for the evaluation of any conservative substance that is either dissolved in the water or may be assumed to be neutrally buoyant within the water column. The model is also used for investigating the physical processes of migration and mixing of a soluble substance in reservoirs, rivers, bays, estuaries and coastal zones. The model is useful for evaluation of the basic processes or for defining the effectiveness of remedial measures. For most applications, the model utilizes the depth-averaged hydrodynamics from RMA2. The input hydrodynamics solution can be either a steady state or a dynamic simulation and is used to compute particle dispersions.

Functionality

RMA4 has been applied to:

• Define horizontal salinity distribution.
• Trace temperature effects from power plants
• Calculate residence times of harbors or basins
• Optimize the placement of outfalls
• Identify critical area for oil spills or other pollutants spread
• Monitor water quality criterion within game and fish habitats
• Determine the limits of salinity intrusion
• Perform flushing analysis
• Turbidity monitoring
• SMS does not support BOD/DO modeling with RMA4 because of issues with RMA4.

Using the Model / Practical Notes

• RMA4 includes support of the SI card which controls what units the engine will use. If SI is set to 0, the model runs with English units. If it is set to 1, the model runs in metric units. SMS saves the SI card based on the coordinate system (projection) specified by the user. However, it is recommended that metric units be used for RMA4. This applies to the hydrodynamics that are fed into RMA4 as well.
• RMA4 is more sensitive to mass gain/loss than RMA2 across large closed boundary angles. The suggested minimum boundary angle between any two adjacent elements is 10°. This becomes a very great concern, as this applies simply to the wet/dry interface and not to the outer mesh boundary.
• RMA4 should not be used to evaluate highly volatile materials such as gasoline, nor materials that do not mix with water, such as oil. Although RMA4 has been used to measure temperature effects from such locations as power plant discharges, this is not a recommended application. Although the documentation claims to be able to model up to 6 constituents, the SMS developers have never had success with more than a single constituent at a time. Multiple constituents require multiple boundary condition files, each with values for one of the constituents. Multiple constituents can be named and joined through the Data Calculator and exported to a single file for future use.
• Card order matters. The RMA4 run control and full print files are very helpful for determining what options are being used.
• The TABS models are built to expire after a set date. You can download the latest version from the Software Updates section of the Aquaveo website.

Graphical Interface

SMS provides a graphical interface that is designed to allow users to visualize the projects they are creating, easily modify project parameters, and view the solutions produced by the RMA4 model. See RMA4 Graphical Interface for more information.

The RMA4 Graphical Interface contains tools to create and edit an RMA4 simulation. The simulation consists of a geometric definition of the model domain (the mesh) and a set of numerical parameters. The parameters define the boundary conditions and options pertinent to the model.

The interface is accessed by selecting the 2D Mesh Module and setting the current model to RMA4. If a mesh has already been created for a RMA4 simulation or an existing simulation read, the mesh object will exist in the Project Explorer and selecting that object will make the 2D Mesh module active and set the model to RMA4. See the Mesh Module documentation for guidance on building and editing meshes as well as visualizing mesh results.

The interface consists of the 2D Mesh Module Menus and tools augmented by the RMA4 Menu. See RMA4 Graphical Interface for more information.

Saving RMA4

When you do a File | Save As... the following files get saved in the *.sms

• *.mat referenced to new save location
• *.mat referenced to new save location
• *.qsl referenced to new save location (RMA4 solution file)
• *.sol referenced to new save location and original location (RMA2 solution file)

Related Topics

• SMS Models Page
• TABS Models
• RMA2

External Links

• CHL RMA4 Frequently Asked Questions [1]