QUESTION:

When trying to do an FSI (FLOTRAN-structure) analysis, the following message consistently appears:

Error - "inverse subroutine was supplied with a singular matrix"

I should note too that I have come across this problem a while back. No matter what I did I kept getting the same error. What I eventually ended up doing was not having the fluid and structural volumes/meshes touch each other except for the area of interest. If I recall correctly, that error arises when there's something wrong with the fsi flagged surfaces. I tried flagging a small portion of the model to see if this leads anywhere.



ANSWER:

The attached input files were created to test the conditions described below:

1) mdl04a.inp: ALL HEX MESH, PRES=0 BOUNDARY DOES NOT TOUCH FSIN (RUNS FINE)
2) mdl04b.inp: CFD WEDGE ELEMS, PRES=0 BOUNDARY DOES NOT TOUCH FSIN (RUNS FINE)
3) mdl04c.inp: CFD WEDGE ELEMS, PRES=0 BOUNDARY TOUCHES FSIN (APPLICATION ERROR)
4) mdl04d.inp: ALL HEX MESH, PRES=0 BOUNDARY TOUCHES FSIN (RUNS FINE)
5) mdl04e.inp: ALL HEX MESH (UNEQUAL SIZE), PRES=0 BOUNDARY TOUCHES FSIN (RUNS FINE)


What this means for you is you should either:

a) ensure pure hex mesh - it'll run whether or not the PRES=0 boundary touches the FSIN, or,
b) extend wedge mesh so that it extends beyond and fully encloses the FSIN surfaces


QUESTION:

When trying to do an FSI (FLOTRAN-structure) analysis, the following message consistently appears:

Error - "inverse subroutine was supplied with a singular matrix"

I should note too that I have come across this problem a while back. No matter what I did I kept getting the same error. What I eventually ended up doing was not having the fluid and structural volumes/meshes touch each other except for the area of interest. If I recall correctly, that error arises when there`s something wrong with the fsi flagged surfaces. I tried flagging a small portion of the model to see if this leads anywhere.



ANSWER:

The attached input files were created to test the conditions described below:

1) mdl04a.inp: ALL HEX MESH, PRES=0 BOUNDARY DOES NOT TOUCH FSIN (RUNS FINE)
2) mdl04b.inp: CFD WEDGE ELEMS, PRES=0 BOUNDARY DOES NOT TOUCH FSIN (RUNS FINE)
3) mdl04c.inp: CFD WEDGE ELEMS, PRES=0 BOUNDARY TOUCHES FSIN (APPLICATION ERROR)
4) mdl04d.inp: ALL HEX MESH, PRES=0 BOUNDARY TOUCHES FSIN (RUNS FINE)
5) mdl04e.inp: ALL HEX MESH (UNEQUAL SIZE), PRES=0 BOUNDARY TOUCHES FSIN (RUNS FINE)


What this means for you is you should either:

a) ensure pure hex mesh - it`ll run whether or not the PRES=0 boundary touches the FSIN, or,
b) extend wedge mesh so that it extends beyond and fully encloses the FSIN surfaces





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