UNTRIM

2.x / April 2005

November 2013

## Catchwords

numerical simulation
finite difference method
finite volume method
unstructured orthogonal grid
two-dimensional, three-dimensional
hydrostatic, non-hydrostatic
reynoldsaveraged Navier Stokes equations (RANS)
tidal dynamics (long waves)
wave propagation (short waves, wave spectrum)
transport of conservative tracers (salt, temperature, suspended sediments)
numerical method UNTRIM
morphodynamic sub-model SEDIMORPH
portable SMP-programming using OpenMP

## Short Description of Functionality

Method

The three-dimensional finite difference / finite volume numerical model UNTRIM can be used to simulate flow and transport processes in different free-surface flow problems. In contrast to conventional finite difference methods UnTRIM is able to operate on an unstructured orthogonal grid.

Physical Processes

The following physical processes are currently taken into account by UNTRIM:

• reynoldsaveraged Navier-Stokes equations (RANS)
• local acceleration (inertia)
• Coriolis acceleration
• hydrostatic or non-hydrostatic pressure
• horizontal turbulent viscosity
• vertical turbulent viscosity influenced by density stratification
• bottom friction
• wind friction
• sources and sinks
• transport of tracers
• local rate of change of concentration
• advective rate of change of concentration
• optional flux limiter : Minmod, van Leer or Superbee
• horizontal turbulent diffusivity
• vertical turbulent diffusivity influenced by density stratification
• settling of particles, deposition and erosion (for suspended sediments)
• sources and sinks
• sinks with immediate return inflow at a different location, with optional modification of inflow-temperature as well as -salinity

Computational Results

• free surface elevation
• current velocity
• concentration of tracers (e.g. salinity, temperature, suspended load)
• vertical turbulent eddy-viscosity
• hydrodynamic pressure
• water density

If a three-dimensional simulation is carried through the depth-averaged results are also computed in addition to the three-dimensional ones.

Validation Document

additional physical sub-models The numerical method UnTRIM is coupled to the following (independent) physical sub-models:

1. morphodynamic computational package SediMorph: for details please refer to sedimorph.dat.
2. spectral wave model k-model: for details please refer k_model.dat

### Input-Files

1. main input data (filetype untrim_main.dat).
2. Hydrodynamics and Salt Transport (filetype untrim_hyd.dat);
3. Atmosphere (filetype untrim_atm.dat);
5. Equation of State (filetype untrim_eqs.dat);
6. Morphodynamic Evolution (filetype untrim_mor.dat);
7. Suspended Sediment Transport (filetype untrim_sus.dat);
8. Wind Waves (filetype untrim_wav.dat).

Notice: further input files can be found on the file description pages of the aforementioned files.

### Output-Files

the number and type of result files does mainly depend on the output parameters chosen for the different physical sub models. Typically the following types of files will be generated:

1. file with modified computational grid (filetype untrim_grid.dat);
Notice: this (modified) system file must be used during postprocessing of computational results in the overall domain;
2. (optional) file with modified profile topography (filetype profil05.bin);
Notice: this (modified) profile topography must be used during postprocessing of computational results along profiles;
3. (optional) system file for specific locations (filetype location_grid.dat);
Notice: this system file must be used for postprocessing of results generated for specific locations.
4. (optional) computational results for the overall domain, at specific locations or along profiles (filetype dirz.bin.r, dirz.bin.i and dirz.bin);
5. (optional) restart files, which are necessary for a later continuation of the simulation (filetype dirz.bin.r, dirz.bin.i and dirz.bin);
6. (optional) informative printer file (Dateityp untrim_main.sdr);
7. (optional) trace of program execution (filetype untrim_main.trc).
8. message file (filetype untrim.msg); parts of this file can be visualised and processed using UNTRIMMONITOR.

Fortran90

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