UNK

Basic Information

Name of Program

UNK

Version-Date

January 2020

Description-Date

September 2022

Catchwords

post-processor
numerical simulation
spectral wave model
unstructured mesh
two-dimensional
transient, non-linear
action density balance equation
waves, sea, swell
wave propagation
shoaling
refraction due to depth variation
refraction due to current variation
energy input due to wind action
nonlinear dissipation due to wave-turbulence interactions
dissipation due to wave-bottom interaction
portable SMP and SIMD programming using OpenMP
automatic determination of time-step in agreement with CFL-condition
constant alternative bathymetry depth
dynamic bathymetry depth
Storage of the content of the ASCII input control files in netcdf.nc (as a variable)
Storage of MD5 hash values ​​of input files in netcdf.nc (as a variable)

Acknowledgment: This project took advantage of netCDF software developed by UCAR/Unidata (www.unidata.ucar.edu/software/netcdf/).

Short Description of Functionality

Method

Program UNK (unstructured k-model) is a post processor for different mathematical current models and can be used to compute the development, propagation and dissipation of waves, sea and swell in the ocean, coastal waters or estuaries. UNK uses as a computational core the Spectral Wave Model with Nonlinear Dissipation - K-Modell, see also literature below - which was developed at the GKSS-Forschungszentrum.
From version 7.x on UNK processes input files with alternative or dynamic bathymetry depth, the first indicating a constant depth, which differs from the rigid layer depth.

Physical Processes

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

• conservation of wave action density (action density balance equation);
• advection of wave action density due to currents;
• shoaling of waves due to variation of water depth and/or current velocity;
• refraction of waves due to horizontal gradients of water depth and/or current velocity;
• wind forcing at the free surface;
• dissipation due to turbulent diffusion;
• dissipation due to bottom friction.

Computational Results

• integral wave parameters for waves, sea and swell:
  • significant wave height;
  • wave peak period;
  • wave mean period TM-1;
  • wave period TM1;
  • wave period TM2;
  • wave mean direction;
  • wave mean directional spread;
  • acceleration (due to radiation stress).
• two-dimensional spectra for waves, sea and swell:
  • frequency-direction wave spectrum.

Validation Document

See literature below.

Input-Files

1. steering data (filetype unk.dat).
2. steering data for the k-model (filetype k_model.dat).

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

Output-Files

More details concerning output files can be found on the fact sheet for filetype k_model.dat. In addition to these files the following files are also generated:

1. (optional) informative printer file (Dateityp unk.sdr);

Methodology

please refer to documentation/literature

Program(s) to run before this Program

DATACONVERT, DIDASPLIT, DIDAMERGE, METDIDA, NCDVAR, NCMERGE, TM2DIDA, TR2DIDA, UNTRIM

Program(s) to run after this Program

ABDF, DAVIT, DIDAMERGE, DIDARENAME, DIDASPLIT, HVIEW2D, NCDELTA, NCDVAR, NCMERGE, NCPLOT, NCVIEW2D, XTRDATA, XTRLQ2, ZEITR

Additional Information

Language

Fortran90

Additional software

-

Original Version

G. Lang

Maintenance

Working group SIM

Documentation/Literature

• example files: please refer to $PROGHOME/examples/unk/
• Schneggenburger, C. (1998) : Spectral Wave Modelling with Nonlinear Dissipation, dissertation, 117 pages, report no. GKSS 98/E/42, GKSS-Forschungszentrum Geesthacht.

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