Resolve two pde with FF++

i havethe two following problems:

(we add periodic boundary conditions to the two problems.
I have the following code FF++ to calculate the approximate solutions of two problems and compare the curves of solutionsreg.edp (3.3 KB)
The problem is that the derivative of solutions are note periodic. I don’t understand the reason. Please can any one check the FF++ code and tell me if there is an error?
Thank you in advance.


your solution is periodic and the derivative are also periodic :

see your script after a small modification

solve square:mesh Th=square(N,N,[x+0.2,y]);
add with a more graphics.
reg.edp (3.4 KB)

Thank you so much Frédéric Hecht