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Old   October 24, 2010, 08:54
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Quote:
Originally Posted by Hasselhoff View Post
For windows I use heat flux boundaries. What kind of turbulence model are you using?
I use k-epsilon turbulence model.
Can you write things you enter in T file for windows (Type and Value) to define heat flux boundaries?
Best,
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Old   October 24, 2010, 09:01
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Is it required to use one of the turbulence models as long as one only cares about general temperature distribution? Let's say I don't care much about eddies development, all I care about is just temperature distribution through the building structure. Is turbulence a key factor?

Just to speed up the process, I would try to simplify my simulation as much as possible, therefore skip turbulence.

Is it an acceptable, common procedure?

Thanks,
K
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Old   October 24, 2010, 09:56
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I will post my settings tomorrow, I don't have access to it now I was using the k omega SST for this one I think.

@ paka: if you chose to stay within the laminar setup, you don't need any turbulence model. Just chose the "laminar" model and switch turbulence to "off". It depends on your task if that makes sense. I wouldn't suggest it for a setup like the one above. There are some papers out there, discussing the adequate turbulence modeling for a given task..
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Old   October 24, 2010, 18:14
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Yes, thank you, but my question was rather towards what is a general procedure, tendency in solving such problems, where one only cares how temperature spreads across the building?

I just don't really imagine why turbulence would play important role in HVAC. Can anyone enlighten me

Thanks!
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Old   October 25, 2010, 04:46
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In HVAC, we have low Reynolds numbers and high turbulence ratios (10-75%). Especially the turbulent normal stresses near walls and the transition effects at the inlets influence the flow.
Airflows underneath the ceiling feature certain phenomena like the “coanda effect” and the rearrangement of turbulent normal stresses which is in the end effecting the temperature distribution as well as the velocity. A laminar flow cannot consider these aspects, standard turbulence models also do not catch up completely..

“The user of a turbulence model is more like a test pilot.. [..]”

//Michael
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Old   February 16, 2012, 05:56
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Quote:
Originally Posted by maysmech View Post
Here is geometry of the problem.
It is a room with 6 inlet fans at ceiling with T=290K and U=0.1 m/s. A window with 305 K is shown and walls and door have zeroGradient temperature.




Good day!

I would like to make a case, where a room with 2 windows (inlet and outlet for ventilation) is defined. I would like to define this geometry in a stl file with some program (http://www.rhino3d.com/) but I don't know how to implement that window is a different patch than walls (different BC). Could this be done like in tutorials/mesh/snappyHexMesh/snappyMultiRegionHeater where there are more than 1 stl file each as a different patch? I don't want to try to solve my problem like in tutorials/mesh/snappyHexMesh/motorBike where inlet and outlet are defined in blockMeshDict and are not on stl defined geometry (motorbike).

I completed a few tutorials and modified one of them succesfully (stl file generated in Mathematica, meshed with sHM, result is below).

I was browsing this forum and found above quoted post and would politely ask, if it is possible, anyone could send me case files for this or similar ventilation problem. My e-mail: podergajs.matej@gmail.com

Thank you for any reply and sorry for posting so long arter the last post.
Matej Podergajs

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Old   January 29, 2015, 03:01
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hello,I started to leran openfoam.i have proplem when i work with chtregion simplefoam and i cant solve this error.
this error is:
Create time



--> FOAM FATAL IO ERROR:
keyword regions is undefined in dictionary "/home/sahar/Desktop/fasle4/constant/regionProperties"

file: /home/sahar/Desktop/fasle4/constant/regionProperties from line 18 to line 20.

From function dictionary::lookupEntry(const word&, bool, bool) const
in file db/dictionary/dictionary.C at line 402.

FOAM exiting

sahar@sahar-S451LB:~/Desktop/fasle4$
can you hlep me?how can solve this problem.
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Old   January 29, 2015, 22:41
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Quote:
Originally Posted by sa har View Post
hello,I started to leran openfoam.
Hello, and welcome to the forum!

Quote:
Originally Posted by sa har View Post
i have proplem when i work with chtregion simplefoam and i cant solve this error.
First of all, as you said you just started learning OpenFOAM, please, take a look at this page URGENTLY to start getting inside chtMultiRegion cases. And please, read carefully THE WHOLE page and try to do EVERYTHING it's said to do. Once you have done it all, you can come back again to the forum to ask any doubt that may come out.

Flash forward Mode ON
Quote:
Originally Posted by sa har View Post
Thank you, Alex. It's a very useful site and I learnt a lot about cht cases after reading it!
You're welcome!
Flash forward Mode OFF


Quote:
Originally Posted by sa har View Post
this error is:
Create time



--> FOAM FATAL IO ERROR:
keyword regions is undefined in dictionary "/home/sahar/Desktop/fasle4/constant/regionProperties"

file: /home/sahar/Desktop/fasle4/constant/regionProperties from line 18 to line 20.

From function dictionary::lookupEntry(const word&, bool, bool) const
in file db/dictionary/dictionary.C at line 402.

FOAM exiting

sahar@sahar-S451LB:~/Desktop/fasle4$
can you hlep me?how can solve this problem.
As I said, you have to learn a little more about OpenFOAM before asking about that. After you have studied the site I gave you above, maybe you can find it out on your own! Otherwise, I can help you!

TIP (as a newbie gift): This error says that you haven't defined the regions field within the constant/regionProperties dictionary or maybe you don't even have such dictionary within the constant directory. If you still don't know what I am talking about, please, work hard with the basic case you can find in the page I gave you.

Flash forward Mode ON
Quote:
Originally Posted by sa har View Post
Oooohhh! Thank you Alex, you are the best!
You are welcome, again!
Flash forward Mode OFF


Hope it is useful for you to start playing with OF and chtMultiRegion cases!

Regards,

Alex


Btw, this is a very old post, you could have posted it somewhere else or opened a new thread in order to get help.
__________________
I'm newbie in OpenFOAM's world and not an English-speaking, so if I make any mistake a correction will be welcome!
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Old   January 30, 2015, 02:26
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Quote:
Originally Posted by zfaraday View Post
Hello, and welcome to the forum!


First of all, as you said you just started learning OpenFOAM, please, take a look at this page URGENTLY to start getting inside chtMultiRegion cases. And please, read carefully THE WHOLE page and try to do EVERYTHING it's said to do. Once you have done it all, you can come back again to the forum to ask any doubt that may come out.

Flash forward Mode ON

You're welcome!
Flash forward Mode OFF



As I said, you have to learn a little more about OpenFOAM before asking about that. After you have studied the site I gave you above, maybe you can find it out on your own! Otherwise, I can help you!

TIP (as a newbie gift): This error says that you haven't defined the regions field within the constant/regionProperties dictionary or maybe you don't even have such dictionary within the constant directory. If you still don't know what I am talking about, please, work hard with the basic case you can find in the page I gave you.

Flash forward Mode ON

You are welcome, again!
Flash forward Mode OFF


Hope it is useful for you to start playing with OF and chtMultiRegion cases!

Regards,

Alex


Btw, this is a very old post, you could have posted it somewhere else or opened a new thread in order to get help.
thanks Alex,i try to understand and solve my problem with page that you said.
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Old   February 12, 2015, 19:46
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Quote:
Originally Posted by maysmech View Post
The other problem is how can we define T B.C for windows.

I think fixedValue is not a good assumption for windows temperature.
Hi maysmech. I am trying to simulate a similar case to yours, i.e., with forced flow through fans. I am using buoyant BoussinesqSimpleFoam but always receive this error:

Continuity error cannot be removed by adjusting the outflow.

How did you set your inlet and outlet BC?

Thank you in advance.
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