Time dependent non linear problem


In FreeFEM, is it possible to deal with a time dependent non linear problem like this one :

\nabla^2 A = - \sigma(dA/dt) * dA/dt

with sigma, a non linear function.

I saw that I must use a uold variable for the time-dependent part, and uu for the non linear part, but how can I mix both of them. Should I create a uuold maybe ?

Thank you in advance,

Best regards,


The only problem is to write de scheme in time and prove the scheme is stable and convergente.

After than no real problem on idea is

make a Fixed point also with 3 value
A, Ap, Al

Ap = A; // previous value
for (iter = ...
    Al = A 
   \nabla^2 A = - \sigma((Al-Ap)/dt) * (A-Ap)/dt
   if( ||Al-A|| < eps) break
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