mitchell01, a FreeFem++ code which sets up and solves Mitchell's test problem #2, the reentrant corner, trying 5 different values for the angle.
The computer code and data files described and made available on this web page are distributed under the MIT license
A web site at NIST describes these and many other problems: http://math.nist.gov/amr-benchmark/index.html
mitchell_02A defines the "reentrant corner" problem, using an angle of OMEGA = PI + 0.01.
mitchell_02B defines the "reentrant corner" problem, using an angle of OMEGA = 5 PI /4.
mitchell_02C defines the "reentrant corner" problem, using an angle of OMEGA = 6 PI /4.
mitchell_02D defines the "reentrant corner" problem, using an angle of OMEGA = 7 PI /4.
mitchell_02E defines the "reentrant corner" problem, using an angle of OMEGA = 8 PI /4.