# Partitioned pipe with FSI - OF and ccx

Hello
Hope you are all well
I have been trying to run a simulation for a collapsing pipe but only with the midsection with FSI (using OF and CCX).

. I first ran the case with no patches for the blue section and I had no deformation in the mid-section.
I looked at the partitioned pipe flow case ( Partitioned pipe flow | preCICE - The Coupling Library) and realized that maybe I should have some patches in those positions however, should I use the same " fixedFluxExtrapolatedPressure" boundary condition as used in the partitioned pipe? How else can I make sure the flow continues to the mid-section from the fluid only part? Or would I take a different approach since I am also using CalculiX?
I am using pimpleFoam

Would appreciate some clarity on this

Thank you

This is what i get on the solid side after coupling:

Writing DISPLACEMENTDELTAS coupling data with ID ‘2’.

—[precice] relative convergence measure: relative two-norm diff of data “DisplacementDelta” = inf, limit = 1.00e-03, normalization = 0.00e+00, conv = true
—[precice] relative convergence measure: relative two-norm diff of data “Force” = inf, limit = 1.00e-03, normalization = 0.00e+00, conv = true
—[precice] All converged
—[precice] WARNING: The coupling residual equals almost zero. There is maybe something wrong in your adapter. Maybe you always write the same data or you call advance without providing new data first or you do not use available read data. Or you just converge much further than actually necessary.
—[precice] Time window completed
—[precice] iteration: 1 of 50, time-window: 10 of 10000, time: 0.0009, time-window-size: 0.0001, max-timestep-length: 0.0001, ongoing: yes, time-window-complete: yes, write-iteration-checkpoint
initial energy (at start of step) = 0.000000e+00

displacement is almost zero in all iterations meaning coupling is not happening correctly. I currently have fixedGradient = 0 at the interface inlet and fixedvalue=0 at the interface outlet (7 patches total).