Mathematical question on boundary conditions

[jones79]

Hello!

I have a mathematical question about boundary conditions.

Since it is possible in Multiphysics to apply different boundary conditions to

on boundary I wonder how this is solved mathematically, as they are not

all independent of each other.

E.g.

I have four BCs on a wall in my model:

- Start temperature

- Convection

- Heat flux

- Radiation

For the first time step start temperature is applied first I guess. Then the fixed heat flux,

but is is not complete independent of the others, as is changes the temperature.

But radiation and convection both change the temperature, too, and depend on it.

(T_surface - T_inf, same to power of 4 for radiation).

Can someone of you explain this to me?

Kind regards,

Walter

[hupn]

Hi Water,

You are right that radiation and convection boundary conditions are different. They can be thought as results based boundary conditions. To get the proper solution in this case, non-linear iterations are performed inside the finite element solver. Only when the heat balance is reached, the solution converges.

And for start temperature, it is actually not a boundary condition, instead, it is an initial condition. For Autodesk simulation, there is another boundary loading called "Applied temperature", which generally could be thought as the dirichlet boundary condition. 

P. Hu

[jones79]

Thanks for the good explanation!

Kind regards,

Walter