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-   -   Starcd has a bug? Buoyancy of water (http://www.cfd-online.com/Forums/cd-adapco/55256-starcd-has-bug-buoyancy-water.html)

 Laure March 26, 2006 21:03

Starcd has a bug? Buoyancy of water

Dear all, here is a very strange thing. I checked on a very simple design to be sure, here it is: || steel ||air going up|| steel || water ||

When the buoyancy of the water is not activated, then evrything is fine: the air warms up the steel which warms up the water. However, the simple fact to turn on the buoyancy for the water (not changing anything else) seems to stop the heat tranfer trough the wall, and the wall is not heated by the air, and so neither is the water!! Can someone explain that? It took me so many hours to figure it out, discovering that the programm was crap!!!! such a waste of time...unless there is a trick somewhere? Laure

 Richard March 27, 2006 03:45

Re: Starcd has a bug? Buoyancy of water

Have you checked the gravity direction?

 Laure March 27, 2006 06:05

Re: Starcd has a bug? Buoyancy of water

Yes, of course. The model works when the buoyancy is of. I just change the parameter buoyancy for the water to on, and the heat tranfer is stopped!!! That is the only parameter I changed! I really think there is a bug. Laure

 Ben March 27, 2006 06:20

Re: Starcd has a bug? Buoyancy of water

contact your local support office then...

 William Blake March 27, 2006 06:22

Re: Starcd has a bug? Buoyancy of water

It looks like a bug but What do you think should happen, when you turn on gravity for a fluid with constant density.

 Laure March 27, 2006 06:42

Re: Starcd has a bug? Buoyancy of water

The density of my fluid is not set as constant, but as isobiric, using the boussinesq approximation. But the problem is even before, because the water cannot even be warmed up, as the steel is not heated.... Laure

 Ben March 27, 2006 06:51

Re: Starcd has a bug? Buoyancy of water

its sounds like a strange one, which version are you using?

 Laure March 27, 2006 06:54

Re: Starcd has a bug? Buoyancy of water

Version 3.22. Laure

 Ben March 27, 2006 06:57

Re: Starcd has a bug? Buoyancy of water

Probably worth upgrading to the latest version (3.26), if there is a bug on something so obvious then it probably would have been fixed. Either way I would speak to your support office.

 Laure March 27, 2006 07:06

Re: Starcd has a bug? Buoyancy of water

Ok, thanks for the advice, I'll do it. I keep you up to date when I have an answer. Laure

 Steve March 27, 2006 08:35

Re: Starcd has a bug? Buoyancy of water

Better still, check the release notes for a definite on that bug. If they don't know it's been fixed (or even existed) it may well come back in a later version. Personally I've wasted days and days of my life randomly trying different versions of STAR-CD in the hope that some bug (not acknowledged as a bug by CD) has miraculously gone.

 Ben March 27, 2006 09:34

Re: Starcd has a bug? Buoyancy of water

If its not acknowledged then could it be (shock horror) operator error?

 Laure March 27, 2006 10:41

Re: Starcd has a bug? Buoyancy of water

I understand your scepticism. I would rather it to be an error of mine. However I redid the experience so many time... I can send you my .mdl if you want to try by yourself...? The disdign is so simple that it it very quickly done. Le me know, Laure

 Laure March 27, 2006 11:00

Re: Starcd has a bug? Buoyancy of water

Well, I send you the .mdl to save time to the one willing to try: it is incredible! You can download it on yousendit.com at the following adress. Unfortunately, it will stay there for a week only... The file I give you it the one without the water buoyancy.To turn the buoyancy on, go to material properties---> liquids---> buoyancy. Turn on the buoyancy for material number 5. Without buoyancy, you will see the steel being warmed up after 3 minutes very clearly. With the buoyancy on.... you can wait for ages. Here is the file, enjoy....-:(

http://s40.yousendit.com/d.aspx? id=2TNRDO8R5UKFO20KAWLVWPJWWS Laure

 Laure March 27, 2006 11:03

Re: Starcd has a bug? Buoyancy of water

Sorry the adress has been cut. Here it is: http://s40.yousendit.com/d.aspx?id=2...O20KAWLVWPJWWS Laure

 William Blake March 27, 2006 15:05

Re: Starcd has a bug? Buoyancy of water

I can't see a problem. It works with any version I've used (322,326,404). Are you sure you switch on buoyancy for material 5?

 Laure March 27, 2006 16:11

Re: Starcd has a bug? Buoyancy of water

I can't believe it works for you...! Then I'll do it the other way round: I send my file .mdl after I turned on the buoyancy (the only parameter I changed from the previous file). With my Starcd (2.22. 1), the heat transfer doesn't take place,and yes William (thanks for trying) I turned on the buoyancy for material 5!! Here is the link http://s44.yousendit.com/d.aspx?id=1...01JYESUD4U4JIM

Laure

 William Blake March 27, 2006 18:05

Re: Starcd has a bug? Buoyancy of water

No problem at all. Just do a

popt cont
getc t
cset news type 1
cplo
cset news type 5
cplo
cset news type 4
cplo

So you will see that there is the highest temperature at the top of the domain due to the convective transport on the water side.

If you switch off the buoyancy the highest temperature is near the inlet at the bottom of the domain -- pure heat conduction.

 Laure March 27, 2006 18:50

Re: Starcd has a bug? Buoyancy of water

Thanks again William. I really wish I had that!!! But it doesn't work. With the second .mdl I sent, my heat transfer doesn't work!!!! It is probably as hard to understand for you as it is for me that yours works!!;) With the left wall, it is all right, it is warmed up, but nothing for the right one! I really don't understand it. Thanks for your time anyway, I'll try on another version Wenesday...That's incredible. Laure

 Laure March 27, 2006 19:31

Re: Starcd has a bug? Buoyancy of water

I've just had an answer from StarCd supply to say that no bug is recorded for this kind of problem. However, I swear it dosn't work for me!!! Laure

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