Discussion Forum

I have to solve two coupled pde equations depends mutually. I have given these equations as follows

1)
∂T/∂t+∇∙(-c*∇T)=∅1(T)*∂u/∂t ;
where c =constant, and 1 initial condition (T at (t=0)=308K) and then 4 boundary conditions and BCs are
(at r=0, ∂T/∂r=0 or insulated; at r=r_outer, c*∂T/∂r=-h_out*(308-T);
at z=0,c*∂T/∂z=-h_(out*) (308-T); at z=L,c*∂T/∂z=-h_out*(308-T); )
Which is given by the following steps “add physics>> mathematics >> classical PDEs>> heat equation”
given the coefficients and source term according to the requirements.


2)
∂u/∂t=k_so*exp(E/(R*T))*(f(T)-u)
with initial condition (∂u/∂t)at t=0 = 0.0001 which is given by the steps “ mathematics>> pde interfaces >> general form pde (g)” and given the coefficients and source term according to the requirements


But error is showing that

failed to evaluate variable.
- Variable: comp1.u
- Geometry: 1
- Domain: 1
Failed to evaluate expression.
- Expression: d(d((-(comp1.Tt-comp1.S*comp1.delt_H*pd(comp1.u,t))*test(comp1.T)-0.2812*comp1.Tr*test(comp1.Tr)-0.2812*comp1.Tz*test(comp1.Tz))*(dvol),{test@0}),co
What should I do? Anyone please help….