Creating SWAN Model Output

Owned by Kester Scandrett
Last updated: 01 Oct, 2020 by Duy Pham
4 min read

EE allows the user to build input files for SWAN and then run SWAN directly from within EE. Note that this is not a fully integrated dynamic coupling between SWAN and EFDC at this stage. Instead, EFDC will use the final SWAN output as input for the external wave model.

The steps to run SWAN from EE are as follows: First it is necessary to create a SWAN input file. This can be done from Model Control window, RMC on Wave sub-tab under Modules tab| SWAN Model frame | Generate Inputs as shown in Figure 1.

After selecting this option, the Export to SWAN file from is opened as shown in Figure 2. 

Figure 1  External Waves: SWAN Model options.


The user should select which input data is required for their SWAN model as shown in Figure 2. The SWAN Settings button provides further options for the generation of the SWAN inputs. The SWAN User's Guide should be consulted for details on how to select these parameters (http://www.swan.tudelft.nl/). If the user also intends to export the wind series for use in SWAN, the start and end times should be selected as well as the time step under Time Options frame for this data.

Figure 2  External Waves: Generate SWAN Input Files.

EE also facilitates setting the offshore boundary conditions for SWAN with the Boundary Conditions button. Selecting this opens the form shown in Figure 3. Beside the local wind-generated waves which are computed in the model domain by providing wind data for each model grid cell and turning on wind growth in SWAN, the user can user can also take into account the influence of external waves (i.e., swells) acting on the model domain. EE detects the open boundary locations and lets the user edit each boundary condition for SWAN model. There are three options for each boundary condition group:

  • No Wave, i.e. no external wave actions are taken into account at the selected boundary group.
  • Constant: constant wave parameters in time including waves wave height, wave period, wave direction, and directional spreading are provided for the selected boundary group.
  • Time Varying: wave parameters for the selected boundary group are varying in time and are provided in files for at least two points lying on the boundary section. The distance indicates the location along the boundary of the data point with respect to from the first grid cell (I1,J1) of the boundary group. The total length of the boundary is provided in the text box Length (m). The data file format is the TPAR file described in SWAN User’s Manual. Wave parameters at every grid cell along the boundary group will be interpolated by SWAN based on the given data files.

Figure 3  External Waves: SWAN Boundary Conditions.

The user should also ensure they have selected the correct path to generate the SWAN input files. If the path is incorrect, use the Browse button in the Export SWAN Input Directory frame (Figure 2) to navigate to the folder that you want to create the SWAN input files. Finally select OK button to create the SWAN input files.

Once the SWAN input files have been created the user should proceed to the Wave setting window by RMC on Wave sub-tab under Modules tab of Model Control window. Whenever External Wave Model option has been selected the Run SWAN button is displayed. As explained earlier, this provides the option of running SWAN directly from within EE (though not at the same time as EFDC is running i.e. it is not dynamically linked).

Selecting the Run SWAN button displays the form shown in Figure 4. The user should browse to the work path for the SWAN input files if necessary. They should then browse to the SWAN executable file. The SWAN exe is installed as part of the installation package for EE. SWAN is freeware under the GNU license and the executable and source code may be downloaded from the University of Technology, Delft http://www.swan.tudelft.nl/

The user should the select the Run button to run the SWAN model. After the SWAN model has finished running the user should select the Create a New Data Set checkbox under Wave Forcing from an External Wave Model frame and use the Convert from SWAN Results option to import SWAN output into EE.


Figure 4  External Waves: Run SWAN internally from EE.