Matlab pdepe diffusion help!!

Hi everyone. I'm new to Matlab. Could you please help me out with this? Your help will be very much appreciated.

I tried to define the following: d [u(1)]/dt = f( d[u(1)]/dx ) d [u(2)]/dt = f( d[u(1)]/dx )

d [u(2)]/dt is a function of d[u(1)]/dx, so I defined this in @pdexpde: d [u(2)]/dt] = constant * d[u(1)]/dt

But this takes forever to complete the run in pdepe. Could you please point out where the problem is?

Thank you very much.

regards, pw

[Muhammad Usman]

What I understand is that in your case u(2) is not an independent variable.

You might want to try: d [u(1)]/dt = f( d[u(1)]/dx ) d [constant*u(1)]/dt = f( d[u(1)]/dx )