[Krzychu (Chris)]

Hi all,

recently I updated my CFX and I noticed a problem with my results.

My transient FSI simulation on was running without a problem on CFX 14. It is a straight pipe with high deformations of the outer wall. Velocity inlet and opening outlet driven by pressure.

When I run the same simulation after the update on CFX 15 I noticed a problem with data from a monitor point on the inlet. The values of pressure and velocity started oscillating forming a jigsaw. See attachment.

I used the same settings and input data for CFX 15 and for CFX 14. I checked that the denser the mesh the higher oscillations and reducing the time step has no effect. Also the position update frequency did not affect the problem.

Any ideas why this happened and how to fix it?

Thanks
Krzychu

[Krzychu (Chris)]

OK an update.

I have located the exact step at which the problem occurs.

One of the steps to get the transient velocity and pressure functions for boundaries, was copying data from a properly solved rigid case (noFSI) and pasting it into the FSI case. Exactly same values used exactly the same way. I did this like so:
- I opened the editor in the no FSI case, [ctrl+a]
- copied the entire function part with pressure and velocity functions [ctrl+c]
- pasted everything it into the FSI case. [ctrl+a] [ctrl+v]

When I imported the same data from a file (the same file I used for the noFSI case, using the import data right click function), the jigsaw disturbance did not occur in the results. Very interesting find.

My guess is there are some settings for interpolation, that are not available in the command editor (the default displayed values), but can be overwritten by not including it. Could this be true or is there something else?

FYI. The part that I copied looked like this (and looks the same after data import):

LIBRARY:
CEL:
&replace FUNCTION: press
Argument Units = [s]
Option = Interpolation
Profile Function = Off
Result Units = [Pa]
INTERPOLATION DATA:
Data Pairs = 0,6.242430516,0.05,6.242430516,0.0516502,-2.830197094,0.0533003,-11.69655293,0.0549505,-20.21249487,0.0566006,.... /and so on/
Extend Max = On
Extend Min = No
Option = One Dimensional
END
END
END
END