RMA2 - The RMA2 model is a 2-D finite element hydrodynamic numerical model, models, modeling, modelling
RMA2 DESCRIPTION
RMA2
RMA2 is a two-dimensional depth averaged finite element hydrodynamic numerical model. It computes water surface elevations and horizontal velocity components for subcritical, free-surface flow in two-dimensional flow fields. RMA2 computes a finite element solution of the Reynolds form of the Navier-Stokes equations for turbulent flows. Friction is calculated with the Manning's or Chezy equation, and eddy viscosity coefficients are used to define turbulence characteristics. Both steady and unsteady state (dynamic) problems can be analyzed.
Origin Of RMA2
The original RMA2 was developed by Norton, King and Orlob (1973), of Water Resources Engineers, for the Walla Walla District, Corps of Engineers, and delivered in 1973. Further development, particularly of the marsh porosity option, was carried out by King and Roig at the University of California. Subsequent enhancements have been made by King and Norton, of Resource Management Associates (RMA), and by the Waterways Experiment Station (WES) Hydraulics Laboratory, culminating in the current version of the code supported in TABS-MD.
Applications For RMA2
RMA2 has been applied to calculate water levels and flow distribution around islands; flow at bridges having one or more relief openings, in contracting and expanding reaches, into and out of off-channel hydropower plants, at river junctions, and into and out of pumping plant channels; circulation and transport in water bodies with wetlands; and general water levels and flow patterns in rivers, reservoirs, and estuaries.
Capabilities Of RMA2
RMA2 is a general purpose model designed for far-field problems in which vertical accelerations are negligible and velocity vectors generally point in the same direction over the entire depth of the water column at any instant of time. It expects a vertically homogeneous fluid with a free surface.
RMA2 has these capabilities:
- Identify errors in the network.
- Accept either English or standard SI units.
- Restart (Hotstart) the simulation from a prior RMA2 run and continue.
- Simulate wetting and drying events.
- Adjust for wetting and drying by element.
- Account for Marsh Porosity wetting and drying (wetlands).
- Account for effects of the earth's rotation.
- Apply wind stress involving frontal (storm) passages.
- User-selectable turbulent exchange coefficients, Manning's n-values, temperature, etc.
- or user-selectable equations for automatic dynamic assignment of Manning's n-value by depth.
- or user-selectable Peclet number for automatic dynamic assignment of turbulent exchange coefficients.
- Model up to five different types of flow control structures.
- Compute flow across continuity check lines.
- Provides for user-defined computational guidelines such as:
- Wet/dry parameters.
- Iteration controls.
- Revisions within a time step.
- Accepts a wide variety of boundary conditions:
- Angle/velocity magnitude by node.
- Velocity components by node.
- Water surface elevations by node/line.
- Discharge by node/element/line.
- Tidal radiation by line.
- Discharge as a function of elevation by line.
- Wind speed and direction by node/element or element material type.
Limitations Of RMA2
RMA2 operates under the hydrostatic assumption meaning accelerations in the vertical direction are negligible. It is two dimensional in the horizontal plane. It is not intended to be used for near field problems where vortices, vibrations, or vertical accelerations are of primary interest. Vertically-stratified flow effects are beyond the capabilities of RMA2. RMA2 is a free-surface calculation model for subcritical flow problems. More complex flows where vertical variations of variables are important should be evaluated using a three-dimensional model such as RMA10.
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