CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   FloEFD, FloWorks & FloTHERM (http://www.cfd-online.com/Forums/floefd-floworks-flotherm/)
-   -   FloEFD fluid volume not recognized (http://www.cfd-online.com/Forums/floefd-floworks-flotherm/70037-floefd-fluid-volume-not-recognized.html)

Edd November 12, 2009 11:40

FloEFD fluid volume not recognized
 
I've been working with a model which contains a fluid volume. I've done several simulations with this model successfully. Now I seem to have a nasty problem after I changed one component in the assembly.

The component I changed (different config of the component) made the internal fluid volume somewhat larger. The fluid volume is still enclosed with solids. FloEFD gives rebuild errors and my "water in" and "water out" boundary conditions are not valid anymore.

When I go to the "check geometry" window in FloEFD and try to find the fluid volume I get the following error: "Boolean operations failed. Please check your model."

I really can't figure out what went wrong. When I change the component back to its original form FloEFD will still give me all these errors! Does this sound familiar to someone? Any feedback is appreciated.

CP85 November 13, 2009 03:47

When you did the "Check Geometry",
did you have the "Check for invalid contacts" checkbox activated?
Are there any invalid contacts?

Do you have a very complex geometry?
Sometimes this makes problems.
If it is so I export the model to step and then reimport it. This often works for me.

Are you sure your modell is really closed?
Did you check it by subtracting your model from a large Solid.
Sometimes there are very small holes, where you do not expect them to be.

Edd November 13, 2009 06:21

Thanks for your reply. There were no invalid contacts. I decided to build up my model from scratch again. I got the same problem and I started suppressing parts one by one. I now finally got it to work. It turned out that the "auto generated lids" on the water in and output were causing the problem :confused:. I got rid off these lids and closed the volume by sealing off the parts themselves (using boss/base on the openings). I did not get any error since that modification fortunately.

I still can't figure out what went wrong because the lids did close the volume and I did some simulations with these lids before. But this is a work-around I can live with.

cring November 16, 2009 12:22

Boolean error message
 
The geometry error may be caused by the inlet/outlet feature and its respective lid feature having concentric surfaces of exactly the same radius. I have experienced the same problem in the past and, in working with the folks at Flomerics, resolved the issue by creating a small difference in the radius values. My suggestion is to create a slight interference. A small gap may force the mesh unnecessarily tight - depending on your settings - to capture the fluid flow in the narrow space created.

Hope this is of some use in your problem.

Boris_M December 12, 2009 09:35

It can happen if some parts of the model are not totally constrained or fixed in space that they were moved accidently somehow when clicking on it with still moving mouse or so. Usually the lids work just fine except the hole of the lid has no perpendicular depth to the surface. Imagine a hole that goes in on a slight angle.
A very good way is indeed the deactivating of the parts part by part to find the source. If it worked before and the surrounding of the lid didn't change it should work afterwards except as I said, it was moved.

Archana February 9, 2011 00:28

A detatiled "How to do CFD analysis in a butterfly valve ?" is what i am looking for..
It would be kind of you if you could help me...
Thanks and regards
Archana


All times are GMT -4. The time now is 19:45.