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Julie June 5, 2002 10:41

Creating vents(faces) in a cubical volume
Dear all,

I am a mechanical student currently doing my final year project on modeling of air ventilation in a room. I have problem in creating vents/openings in the ceiling of the room of my model.

I created a cubical room using "volume create" in gambit and the vents/openings using "face create". Then I use boolean subtract to subtract the vents faces from the top face of the volume which represents the ceiling of the room.

I did a mesh of volume and face and then specify the boundary and continum zones, and export to fluent 5/6. But when I open the file from fluent it just says "skipping zones ......(not referenced by grid)" I saw that all the vents which I have created were not displayed as grid in Fluent. However all I get is the meshed volume, whose faces I have specified as walls in boundary types and the volume as fluid in continuum in Gambit.

I guess it must be conflict somewhere when I did the face and volume mesh. I tried several other methods like using face meshing for all faces and not using volume mesh at all, but it just shows error when reading the file in Fluent.

Could it be that my method of creating the vents are wrong? Please help. Thanks.

Please pardon me if my problem is very trivial. I am not taught at all in my school in using gambit/fluent. I am a new user and relies solely on the tutorials and experimenting.

med June 6, 2002 05:40

Re: Creating vents(faces) in a cubical volume
Hi, I'm also a very new fluent/gambit user, I suggest you to use only the cubical volume: I think that you don't need to substract the ceiling face from the volume, you will indicate later that is represent simply a wall. sorry if I am saying a silly thing: I'm a new user also. good luck

Erwin June 6, 2002 08:51

Re: Creating vents(faces) in a cubical volume
No; instead of subtracting (and thus removing) the faces from the side faces, use the 'face split' command. This will create subfaces for your vents on your cube sidewalls, which you can then give the correct boundary conditions.

Ashutosh June 6, 2002 10:37

Re: Creating vents(faces) in a cubical volume
First create the volume using proper command. select the solver - Fluent/UNS go for BC setting by continuum and boundary Assign fluid as continuum one face (top) as pressure-outlet or vent. Another face you have to assign as fan or velocity inlet in case of vent ( Check-up). Mesh the volume. export the mesh - file.msh read the file in fluent.


anna June 6, 2002 10:47

Re: Creating vents(faces) in a cubical volume
Hi Julie,

after creating a brick volume (your room), create smaller volumes (brick or cylinder) at the locations of your vents. You can create few points in x-, y-, and z- direction at the location of the vent, then create using these points new coordinate system, which you can use to create volumes for vent openings. Unite initial brick (room) volume with these smaller ones, and you will get what you need.


Ashutosh June 6, 2002 10:56

Re: Creating vents(faces) in a cubical volume
If you have small volume near the vent, then split the big and small volume to attach them. You might want to use hex mesh only in that case you may have to divide the big volume into small ones.

After meshing you can check the quality of mesh by using the respective icon. The elements in case of tets should not be distorted ( ?value more than 0.9 or so). Why don't you try modeling 2D case first to get better understanding of the software first. Then go for 3D case.

Julie June 6, 2002 11:27

Re: Creating vents(faces) in a cubical volume
Hey thanks all for your replies.I actually tried something similar to anna and Ashutosh's method yesterday after looking thru' the replies for the similar past problems in this forum. However spliting volumes are time consuming especially when I need to create a couple of vents.

I just saw Erwin's reply, and shall try using spliting faces tomorow. Hey thanks again to all. Just as I was really feeling vexed and helpless a few days ago, this forum really boost my spirit up again!

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