Staggered solution

[LearnerAbq]

Hi everyone,

I have to solve a coupled simulation with 5 deg. of. freedom per node as staggered. That means, i prescribe the initial condition for temprature and I want to solve it for displacement and lets say electric potential DOFs. Then I have to keep displacements and elec. Potential constant and solve it for the unknown temprature. Then the new temprature is the initial condition for the next step. How do the solution command and BCs in the input file look like? I appreciate your answers and comments in advance.

 

[FEA way]

Availability of DOFs depends on the analysis procedure and element type. Aparat from thermomechanical and thermal-electrical analyses, there are also triply coupled ones: electrical-thermal-mechanical. Of course, the initial, imposed and resulting DOF values follow the rules of physical effects. So, for example, you can apply an electric potential causing temperature increase and thus also displacement due to thermal expansion. Non-standard effects would require the use of subroutines.

 

[LearnerAbq]

Thanks for your reply. But I'm searching for a way to define it via the input file. Let's say: solve the DOF 1, 2, 3 and 11 and freeze DOF 12 and then freeze 1, 2, 3 and 11 and solve for DOF 12.
I appreciate your comments in advance.

 

[FEA way]

The numbers of degrees of freedom matter. 11 and 12 are temperatures but I guess that you want a temperature and an electric potential instead. The latter is DOF 9. So you need analysis and element types supporting these DOFs. Thus, the thermal-electrical-structural analysis is needed. You can apply an electric potential (9) that will cause a temperature (11) change and thus also a deformation (translational displacements 1-3). But to e.g. fix the displacements, apply a temperature and solve for the electric potential, something (some physical phenomenon) would have to generate that electric potential.

That's how built-in elements work. You could add your own element with different DOFs but this requires a Fortran subroutine UEL which is very hard to implement.