# Time dependent non linear problem

Hello,

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 ?

Best regards,

Jeremie

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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