This tutorial walks through analysing a velocity field using Helmholtz decomposition with coarse-graining.

There are three stages in this tutorial, each with a corresponding sub-directory. See the ABOUT documentation file in each directory for the step-by-step guide to each part.

1. The 'project' directory works through the steps needed to perform the Helmholtz decompiosition
2. The 'filter' directory then illustrates how to produce spatial maps of the coarse-grained flow
3. The 'postprocess' directory shows how to compute area-averaged values and perform a scan of filter scales to produce a power spectrum

In this directory there is a python script generate_data.py. This should be run before starting the other pieces. The generated velocity field is a combination of randomly-seed vortices with specified size distribution.

• full spherical domain, 0.5 degree resolution, polar 'continents'
• velocity field is a collection of eddies of varying sizes, randomly placed throughout the globe

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In 'postprocess', there is a known issue where the python scripts that run after calling coarse_grain_helmholtz.x in the run_all_steps.sh script fail to run withour printing an error. If the coarse-graining successfully runs (i.e. directory outputs is created and populated with postprocessing_*.nc files) but the RESULTS_*.nc files are not created, then you will need to manually call the three python scripts listed at the end of run_all_steps.sh script.