Wave Refraction on Coarse Meshes

Updated 2016/07/31: This post is now outdated. SWAN has been updated to improve its treatment of the spectral propagation velocities, so these limiters are not needed. Please see this post.

Updated 2012/04/12: This is an old page. It persists on this site for posterity, but the information presented below is no longer up-to-date. When you are done here, then please click forward to this page, which describes how to control refraction errors with limiters on the spectral propagation velocities.

Updated 2011/08/30: Added a link to Part 2.

Updated 2010/02/11: Added refraction as a nodal attribute.

At the end of my instruction manual on how to compile and run SWAN+ADCIRC, I noted that wave refraction can cause problems in regions where the resolution of the bathymetry is insufficient. We worked around this problem by turning off the refraction on the local sub-meshes that were not in our region of interest. On this page, I will provide more description of exactly what can go wrong when waves are allowed to refract on coarse meshes, and I will share more details about our work-around.

It should be noted that wave refraction will always be a problem whenever any wave model is applied on a coarse mesh. This is a general numerical problem whenever the user is trying to compute waves turning over more than 90° in one spatial step. This would be a problem with SWAN, WAM, STWAVE or any other wave model, regardless of if/how they are coupled to a circulation model. As we will see, it is the coarse mesh that causes problems with wave refraction.

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How to Compile and Run SWAN+ADCIRC

As noted in many of my conference presentations, we have run successfully the coupled SWAN+ADCIRC model on Katrina and Rita on our SL15 mesh without any problems. This is a good sign that everything may be working correctly, but it still needs to be tested. The only way to know if the coupled model is bulletproof is by shooting a bunch of bullets at it.

Coupling-Schematic

If you want the coupled model, then please follow the link at the bottom of the ADCIRC website to request the latest release version. Here is an instruction manual on how to compile and run SWAN+ADCIRC.

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Conference: USNCCM 2009

JC Dietrich, JJ Westerink, CN Dawson, M Zijlema, LH Holthuijsen, G Stelling, RA Luettich Jr. “Coupled, Unstructured Grid, Wave and Circulation Models: Validation and Resolution Requirements.” 10th U.S. National Congress on Computational Mechanics, The Ohio State University, Columbus, Ohio, 15-19 July 2009.

Conference: SWAN 2009

JC Dietrich, JJ Westerink, M Zijlema, LH Holthuijsen, CN Dawson, RA Luettich Jr. “Implementation and Validation of the Coupled UnSWAN+ADCIRC Model.” 1st SWAN Workshop, TU Delft, Delft, The Netherlands, 8-10 June 2009.

Conference: ADCIRC 2009

JC Dietrich, JJ Westerink, M Zijlema, LH Holthuijsen, CN Dawson, RA Luettich Jr, JG Fleming. “Validation of the Unstructured, Highly-Scalable, Integrally-Coupled, ADCIRC-UnSWAN Model.” 13th ADCIRC Workshop, NOAA, Silver Spring, Maryland, 20-21 April 2009.

Conference: FEF 2009

JC Dietrich, JJ Westerink, M Zijlema, CN Dawson, RA Luettich Jr. “Coupled, Unstructured Grid, Wave and Circulation Models: Validation and Resolution Requirements.” 15th International Conference on Finite Elements in Flow Problems, Chuo University, Tokyo, Japan, 1-3 April 2009.

FigureGen v.32

Updated 2012/06/05: This version of FigureGen has become outdated, but is maintained on this page for reference. Please click here to be redirected to the newest version.

FigureGen is a FORTRAN program that creates images for ADCIRC output files. It reads sparse (fort.63, fort.64, etc.) and full (maxele.63, maxwvel.63, etc.) output files, grid (fort.14, etc.) files, and nodal attributes (fort.13) files. It plots contours, contour lines, and vectors. Using FigureGen, you can go directly from the ADCIRC input and output files to a presentation-quality figure, for one or multiple time snaps, without having to use SMS.

The following example depicts the significant wave heights during Hurricane Katrina in the Gulf of Mexico:

Significant wave heights (m) during Katrina (2005) in the Gulf of Mexico.

This program started from a script written by Brian Blanton. I converted it to FORTRAN because I am more familiar with that language, and I added the capability to plot vectors, among other things. But, at its core, FigureGen behaves like a script, and it uses system calls to tell other software how to generate the figure(s).

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Conference: WUGNM 2008

JC Dietrich, JJ Westerink, S Tanaka, M Zijlema, LH Holthuijsen, CN Dawson, RA Luettich Jr, JG Fleming, BO Blanton, H Lander, M Reed. “Coupled, Unstructured Grid, Wave and Circulation Models: Preliminary Results.” 7th International Workshop on Unstructured Grid Numerical Modelling of Coastal, Shelf and Ocean Flows, Bedford Institute of Oceanography, Halifax, Nova Scotia, Canada, 17-19 September 2008.