Thermal energy in a cavaty flow
 

I am new to OpenFoam and I have the following situation:
i need to simulate the convection/diffusion problem with:
u=1,
v=0,
T_West=0
T_East=1
and dT/dy=0 for North and South

I need to determine the rate of convergence of the numerical solution using the OpenFoam finite volume scheme.

I just figured out how to add the temperature to IcoFoam.

But I have to plot the the log(err) vs. log(sqrt(n)) when using n total triangules in 2D since sqrt(n) is a measure of the grid space.

I was wondering if someone can help me with this... :)