# Mathematical Model TRIM-3D

### From BAWiki

## Short Description

The mathematical model TRIM-3D is based on the finite difference method. In contrast to the two-dimensional (depth-averaged) mathematical model TRIM-2D, TRIM-3D is a fully three-dimensional model. TRIM-3D was designed to solve several transient nonlinear partial differential equations (pde's). The model is actually used to study one ore more of the following physical processes:

- transport of water (conservation of the water mass)
- transport of linear momentum (conservation of linear momentum)
- transport of salinity (conservation of the dissolved salt mass)

The model takes into account hydrodynamic pressure in the water body (non-hydrostatic pressure distribution). A simplifying hydrostatic approximation can be alternatively used. This approximation might be useful for natural systems with negligible vertical accelerations (compared with gravity).

TRIM-3D was developed by Prof. V. Casulli (Trento University, Italy). In the framework of a scientific cooperation TRIM-3D has been successfully installed in the year 1996 at BAW-DHs computers. It has been integrated into BAW-DHs numerical modelling toolbox and is now used on a routine basis in the context of different real-world projects concerning estuarine flow and transport processes. Meanwhile the code of TRIM-3D has been optimized to improve performance on multiprocessor vector computers.

There exists a up to now no Standard Validation Document for TRIM-3D which would provide the potential user with information about the capabilities and limitations of the model.

## Preprocessors

## Programs for Simulation

- TR2VOR: generation of a compact version of the bathymetry-file together with some index arrays which are required during the simulation run for optimal performance on vector computers
- TR2LQ2: generation of a profile topography which is necessary to output results from a TRIM-3D simulation run along profiles
- TRIM-3D: simulation run

## Postprocessors

- Conversion of Computed Results: general purpose prostprocessors for the conversion of data.
- Analysis of Calculated Results: tidal characteristic numbers, tide-independent characteristic numbers, tidal harmonic analysis and comparative analysis.
- Spread-Sheet Calculations for Computed Results: application of the spread-sheet program MS Excel (TM) to display and modify computed results.

- TR3MODATE: modification of date and time in a hydrodynamic results file if this hydrodynamic state should be used as initial state for a different date
- TR3KACHEL: generation of sections (tiles); topography as well as data are cut into pieces out of the result files for the entire computational domain for any desired section (tile).
- GVIEW2D: graphical display of time series at selected locations
- LQ2PRO: Visualization of data along profiles
- HVIEW2D: graphical display of 2D synoptic or data analyses results
- VVIEW2D: graphical representation of CFD-data for vertical sections

## General Data Flow

Graphical representation of general flow of data related to a TRIM-3D application (with German text only). This graphical representation is also available in Encapsulated PostScript Format.

## Example Applications

- tide independent characteristic numbers of salinity for a cross section in the Ems Estuary.
- propagation of short waves in a harbour basin (text available in German only)
- Animations of salinity and flow velocity in the Außenems estuary
- A Second Order Lagrangian Method for Large Eddy Simulation
- secondary currents in river turns, first results related to the project
*Minimierung der Unterhaltungsmaßnahmen im Bereich des Blexer Bogens*(Lower Weser Estuary) --- available in German only

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