Multiphysics modelling

[RD09]

Dear all,

Currently, I am writing user element for multiphysics model with 4 dof. I want to solve this using staggered way with help of PARTITION command. In first partition, I want to solve problem for first 3 dof while 4 dof is frozen. However, there is coupling of 4 dof in the stiffness matrix and residual of first 3 dof. If I want to the use value of 4 dof from previous timestep while solving the partition 1 in current time step then should I save 4 dof as a special history variable or program will automatically takes previous value?

Thank you,
RD

[Prof. R.L. Taylor]

We store 3-values in the ul(*,*,*) array. u(*,*,1) is the value at current solution state.  ul(*,*,2) is the increment between the current and previous solution, and ul(*,*,3) is the increment in the current solutilon.  Thus the solution at the previous time is ul(*,*,1) - ul(*,*,2).

Note tangents for partitioned solution is just the diagonal block corresponding to the active dog's.  The coupling between partitions is never used, but would be if you did a monotonic solution.

[RD09]

Thank you so much Professor!

As you said, I only have diagonal block in the tangent matrix. However, there is multiplication of 4 dof to diagonal block corresponding to the first 3 dof.
I will try to implement as per your suggestion.

Thank you,
RD