Time dependent bc's

[Colin McAuliffe]

Dear all,

Is it possible to specify an edge with a time dependent bc which has a specified displacement for a certain time range, and traction free bc's thereafter? One option is to do a restarted analysis but I would prefer to avoid that if possible.

Thanks
Colin

[Prof. R.L. Taylor]

In a serial run you can change boundary conditions during a single execution.  So it is possible to do what you describe.

In a parallel solution you probably cannot do it since the equation structure is determined when you partition.

[Colin McAuliffe]

Ok thanks. I am using parallel so I think I'll try to make a function that alters the eq. structure manually. Could you point me to the subroutine that sets up the eq. structure?

[Prof. S. Govindjee]

It may be possible if the equations are blocked.  In that case all the equations are in the matrix allocation.  However, if you change the fill of the matrix mid computation, it will be important to kill and then reallocate the memory for the matrix since petsc memorizes the non-zero pattern on the first assembly.