mitchell_10, a FreeFem++ code which sets up and solves Mitchell's problem 10, "the interior line singularity".
The information on this web page is distributed under the MIT license.
A web site at NIST describes these and many other problems: https://math.nist.gov/amr-benchmark/index.html
mitchell_10a defines the "interior line singularity" problem on the [-1,+1]x[-1,+1] square with parameters ALPHA = 2.5, BETA = 0.0.
mitchell_10b defines the "interior line singularity" problem on the [-1,+1]x[-1,+1] square with parameters ALPHA = 1.1, BETA = 0.0.
mitchell_10c defines the "interior line singularity" problem on the [-1,+1]x[-1,+1] square with parameters ALPHA = 1.5, BETA = 0.6.