Discussion Forum

Hello,

I am trying to couple two physics using "Coefficient Form PDE". The equations are related in such a way that the dependent variable of the first equation is the input for the second equation.

1. du/dt=D(d^2u/dx^2)
2. du/dt=(D/RT). u. (d^2u2/dx^2)

Where, u and u2 are the dependent variables and D,R, T are constant [As Coefficient Form PDE use "u" as dependent variable by default].
I have built the geometry and implemented the first equation using Coefficient Form PDE.

Then I have solved the first equation using Time Dependent study. So I have solution for u. Now I would like to write the second equation in the second physics "Coefficient Form PDE". When I write the second equation as a "Source Term f" then it says invalid expression.

In the source term field of the second pyhsics I wrote, ut-((D/(R*T)*(u*u2xx))
Maybe the second physics does not recognise the dependent variable of the first physics.

Is it possible to write directly the dependent variable of one physics to another physics?
If it is not possible then how can I couple these two physics?
I would be grateful if someone helps me to get rid of this problem. I know there is a lot of genius people here. To make my explanation easier I have attached the built mph file named as "test.mph". Thanks in advance. Please Please......