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-   -   meshing and boundary condition (https://www.cfd-online.com/Forums/fluent/81495-meshing-boundary-condition.html)

no183 October 28, 2010 10:57

meshing and boundary condition
 
http://imgur.com/6IB9n.jpg
As the picture show, the computer casing is mesh on the component (motherboard, HDD, etc) but this is not i want as i want to know the heat flow profile that inside the casing, which is the area not been mesh, so how do i done that?
and what is the boundary condition i can set?

-mAx- October 29, 2010 02:03

you are meshing the outer surfaces of components, which is correct since they are surface limits of your domain
Just check if you can select components as volume. If yes, then you need to delete them, as far as you don't want to compute any solid conduction.

no183 October 29, 2010 06:52

can, but it select the whole casing, i cant choose anything..

-mAx- October 29, 2010 06:58

so you only have one volume, and components surfaces are part of the volume, right?
It means your components are empty and only their outer surfaces will be meshed.
So that is correct.
You try to compute heat transfer in the domain defined between the casing and components (boolean substract between whole casing and components results in what you actually have)

no183 January 5, 2011 03:32

sorry, away from online since holiday..
Now, i still cant get what u mean, is it anyone here can assist me on that? give me a step by step tutorial

no183 January 5, 2011 03:35

btw, any tutorial for fluent and gambit?

-mAx- January 5, 2011 04:26

provide me your .dbs file

no183 January 5, 2011 07:45

how? email?

no183 January 5, 2011 07:47

i save it in stp file

-mAx- January 5, 2011 08:24

send the dbs file (save your session in Gambit).
In this way I can observe errors you can have.
Upload the file on a share server like rapidshare or whatever

no183 January 5, 2011 10:00

http://rapidshare.com/files/440932754/test.zip
here it is..
kindly state what u have done, i mean how u done it, as i am still a learner. thanks

-mAx- January 6, 2011 02:20

1 Attachment(s)
As I thought, you only have solid elements.
Since you want to compute heat exchange, you don't need solid elements, but the air volume contained in your model.
If you enable shaded mode (render icone) you will see that your box isn't close at the top (cf picture)
So I would create a surrounding volume (englobing all your solid elements) and substract this closed box with all your solid elements.
Create a surface by sweeping edge 2112 with vector (0 -440 0)
Create a volume by sweeping created face with vector (0 0 -190.5)
That will be your surrounding volume.
Finally substract all your solid elements from this volume. The result will 2 volumes, with one small you need to delete
If you look at the bottom (shaded mode on) you will see that you don't have the solid elements anymore, but only their outter surfaces.
Tha'ts what you need.
Attachment 5981

no183 January 6, 2011 09:09

bro, i manage to do the first 2 step.. but the third step how? frankly, i am idiot in FLUENT, as this model i drawn from solidwork, this is my first time using FLUENT, forgive my weakness.

-mAx- January 6, 2011 09:38

1 Attachment(s)
volume/substract
right-click on the icon (actually the unite icon is displayed)
Attachment 5987

no183 January 6, 2011 09:44

ya, i get that, but which subtract to which.

-mAx- January 6, 2011 09:50

*biggest volume as first entry
a*ll other (solid parts) as second entry (understand you can select multiple volumes)

no183 January 6, 2011 09:56

hmm, what is the biggest volume btw, there are few volume that can be selected at the casing..

-mAx- January 6, 2011 10:00

the biggest volume, is the one you just created (the one generated with your 2 succesfully steps)
In other words: none of your imported (solid) parts

no183 January 6, 2011 10:03

so is the last volume created, in other word, the largest number?

-mAx- January 6, 2011 10:11

independantly from your volume id, select the volume surrounding the others.
It will be red displayed. If it is not the volume you want, click on the middle clik of your mouse, it will select another, etc...
Once you selected the right one, check its name in the pick-box
Else you open the journal file or the transcript file (or navigate in the transcript window) and check the id given to the volume after the sweep face operation.

no183 January 6, 2011 10:15

i already done it..
http://rapidshare.com/files/441109902/testv2.zip
have a look whather is correct or not, i feel like something strange, why did the PSU top part, FDD front part, CD ROM front part is gone.

no183 January 6, 2011 10:15

i already done it..
http://rapidshare.com/files/441109902/testv2.zip
have a look whather is correct or not, i feel like something strange, why did the PSU top part, FDD front part, CD ROM front part is gone.

-mAx- January 6, 2011 10:26

1 Attachment(s)
I cannot download your file yet, but I will tonight at home.
Here is what I have after the substract operation.
Outter domain's surface are hidden
Attachment 5988

no183 January 6, 2011 10:38

is ok bro, take your time. I really appreciate your help and patience for my weakness.
Anyway, is there any tutorial for gambit, which cover everything i mean. The original turotial which school given to us, is SUX. cover nothing, and all is easy stuff, which cover in CAD like subtract, unite how to draw only.. do u have any tutorial bro?
oh yea, bro i saw ur pic, i mean the file u uploaded. I still not sure whether mine is correct, but when i see yours, i still can see there is 2 hole at the drive bay (1 at 5"25 1 at 3"5). It is closed. I remember i draw it on solidwork, it is closed.

-mAx- January 6, 2011 10:48

provide me your step file (from solidworks) and your tutorial
I will check if it really SUX...
;)

no183 January 6, 2011 20:50

There u go, this is the actual project file.. neglect all the file i upload before..
http://rapidshare.com/files/441201516/Desktop.zip
about the tutorial, it is a hardcopy which i copy from what lecturer has done during the lecture :(

-mAx- January 7, 2011 02:14

-what is the difference between the 2 step files?
-On those 2 files, there are more parts which don't appear in your dbs file (like fans, etc...)
Is it deliberate?
Anyway, you need to do the same thing: creating surrounding box and substracting solid elements.

no183 January 7, 2011 14:59

sorry for the late reply, my line was down for whole day.
Yes, the 2 step file is different from the dbs i gave u previously. The dbs file was the first version of my drawing, just ingore the dbs file. Just help me with these 2 step file, i need to know how to do it. I already try the idea u mentioned, but fail :(

-mAx- January 10, 2011 02:49

* Import your step file
* unite all the volumes
*create the surrounding box
* substract the united volumes FROM the box

no183 January 10, 2011 10:05

the uniting process take long time huh. the surrounding box is the box i create like last time ? Just a cube closing the whole case?

-mAx- January 10, 2011 10:08

Quote:

Originally Posted by no183 (Post 289863)
the uniting process take long time huh.

yes :D
Quote:

Originally Posted by no183 (Post 289863)
the surrounding box is the box i create like last time ? Just a cube closing the whole case?

yes

no183 January 10, 2011 10:10

is it just the 4 step as what u say? unite everything, then subtract the volume? i get subtracting volume to from volume 1 give empty result, FOR BOTH CASE.

-mAx- January 10, 2011 10:19

you created the surroundig box after you united all solid volumes (from your import), right?
Then create the surrounding box.
Then go to substract Real Volumes, and pick the surroundig box in the first panel ("Volume")
Finally choose the united volume in the second panel ("Substract Volumes")
If you don't succeed, post a picture from your gambit window after the substract operation

no183 January 10, 2011 10:19

hey, where did u learn ur fluent? i mean from zero knowledge to such a level today.

-mAx- January 10, 2011 10:23

Quote:

Originally Posted by no183 (Post 289868)
hey, where did u learn ur fluent? i mean from zero knowledge to such a level today.

By experiencing problems and fixing them, you will learn a lot.
;)

no183 January 10, 2011 10:31

ok, i manage to do it already. what next? btw, i dont even have the basic, how do experiencing problem and fix them :(

-mAx- January 10, 2011 10:41

Ok if your fluid domain is ready, you can try to mesh it on the fly (it will fail) but all the warnings and errors you will get in the transcript fwindow will be usefull.
You will be able to localize small edges, sharp angles, etc...
But prior to mesh it, I would do a basic tutorial. Send me your email, I will send your a tutorial

no183 January 10, 2011 10:43

sent the pm to u

no183 January 10, 2011 11:01

so u want i do everything inside d tutorial?

no183 January 10, 2011 11:02

Hey, it is the official FLUENT tutorial, can i have all of it ? Unforunately i dont have it as my Institution never give us the tutorial.


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