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Old   February 11, 2011, 10:12
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Giampiero
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I set a velocity_inlet and Pressure_outflow, I initialized everything from the values in the velocity_inlet.
I ll try as you explained me, I think I understand my error
News will come
Thank you so much!
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Old   February 11, 2011, 12:09
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Quote:
Originally Posted by -mAx- View Post
I don't know how you built the outer domains, but basically, once the volume with sails is meshed, then split the outer domain with the one with sails.
The surfaces will be automatically connected.
Here there is the step of the geometry, Please, if you have time can you take a look on it?
http://dl.dropbox.com/u/14610331/culla_piena.stp

I am obtaining horrible mesh, these are the steps I followed:
1) I start splitting the volume.2 using the surfaces of the sails.

2) I mesh the volume.2 using tet/hex core with a 500 interval size

3) I split the Volume.1 with the volume.2, at this point all the 3D elements created at 2) have been erased I have just surface mesh on the sails, the volume.1 looks nice with a volume.2shape cavity in the middle.
4) I mesh the Volume.1 using tet/hex core with a 8100 as interval size, i have the volume.1 meshed but the cavity is not meshed.
5) I Remesh the volume.2 using same values of 2) but the mesh is very skewed cause the faces are connected and the mesh on that faces is very large

I understand the procedure?
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Old   February 11, 2011, 12:28
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I am no more at the office, so I cannot check your step file.
But you are not suppose to reimport your geometry.
You already meshed the volume with sails. Just create bricks in the same Gambit session for extending your domain and use the sail's volume (already meshed)
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Old   February 13, 2011, 05:41
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HI Max, I have a question, I am using Gambit.
When I subtract a smaller volume from a larger one, and I chose to "retain" the smaller volume, gambit automatically creates a volume similar to the smaller volume inside the larger one. That volume off course contains faces which I don't need to set as "wall", actually I need them to be like "inexistent" when I export them in Fluent. So what type should I choose for the subtracted faces so that that they don't occur in the heat transfer process. I am only interested in the original wall of the smaller volume, and the reason I subtract them is to have separate meshes.
The large volume contains air, and the smaller one is actually a pipe whit a fluid running inside it at a constant speed, and I need to simulate the heat transfer from the air to the fluid.
Thanks, and I apologies I interfered in your conversation, whit a different subject.
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Old   February 13, 2011, 18:05
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Hello mAx, During the weekend I go further , infact I did everything as you explained, so I changed pratically everything in my approach to GAMBIT, but I obtained same results, so I decided to change something in fluent, infact I used to set the "ceiling" and the "floor" of the boundary box as Pressure-Outlet, today I set them as Wall and things went very different: I have residuals in order of 10^-6 expept for the continuity that is around 10^-3, and a nice shape of speed around the sails ( I am just surprised to see the bow sail that seems to push more than the main sail )
Now my doubt is, I was using wrong set up for the boundary conditions, what If I am using still using wrong settings?
A summary of the setting,
3ddp , segregated, K-epsilon, Simplec for Pressure-velocity coupled,
Discretization Pressure: PRESTO! Second Order all the others
Boundary set up as velocity inlet for 2 sides Pressure-outflow other 2 sides, Walls for the ceiling and the floor, wall for the sails.
All other settings as default
Something to improve? Something to change?
Thank you so much, your help is very usefull!


http://dl.dropbox.com/u/14610331/sail_speed.PNG
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Old   February 14, 2011, 02:07
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Quote:
Originally Posted by Tramph View Post
HI Max, I have a question, I am using Gambit.
When I subtract a smaller volume from a larger one, and I chose to "retain" the smaller volume, gambit automatically creates a volume similar to the smaller volume inside the larger one. That volume off course contains faces which I don't need to set as "wall", actually I need them to be like "inexistent" when I export them in Fluent. So what type should I choose for the subtracted faces so that that they don't occur in the heat transfer process. I am only interested in the original wall of the smaller volume, and the reason I subtract them is to have separate meshes.
The large volume contains air, and the smaller one is actually a pipe whit a fluid running inside it at a constant speed, and I need to simulate the heat transfer from the air to the fluid.
Thanks, and I apologies I interfered in your conversation, whit a different subject.
Retain option should be enabled if you need later the volume used for the boolean operation.
What do you mean with "Inexistent"?
If you only want to have separate mesh, maybe you can use a split.
A picture may help to understand
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Old   February 14, 2011, 02:24
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Quote:
Originally Posted by bishop_house View Post
Hello mAx, During the weekend I go further , infact I did everything as you explained, so I changed pratically everything in my approach to GAMBIT, but I obtained same results, so I decided to change something in fluent, infact I used to set the "ceiling" and the "floor" of the boundary box as Pressure-Outlet, today I set them as Wall and things went very different: I have residuals in order of 10^-6 expept for the continuity that is around 10^-3, and a nice shape of speed around the sails ( I am just surprised to see the bow sail that seems to push more than the main sail )
Now my doubt is, I was using wrong set up for the boundary conditions, what If I am using still using wrong settings?
A summary of the setting,
3ddp , segregated, K-epsilon, Simplec for Pressure-velocity coupled,
Discretization Pressure: PRESTO! Second Order all the others
Boundary set up as velocity inlet for 2 sides Pressure-outflow other 2 sides, Walls for the ceiling and the floor, wall for the sails.
All other settings as default
Something to improve? Something to change?
Thank you so much, your help is very usefull!


http://dl.dropbox.com/u/14610331/sail_speed.PNG
I would treat your ceiling as velocitiy inlet.
But I am not experienced in this kind of calculation, so there is lots of chance, I am not right.
Regarding SIMPLEC & PRESTO, maybe you have a good reason to use them. Did you try to run your job with standard settings?
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Old   February 14, 2011, 04:38
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Quote:
Originally Posted by -mAx- View Post
Retain option should be enabled if you need later the volume used for the boolean operation.
What do you mean with "Inexistent"?
If you only want to have separate mesh, maybe you can use a split.
A picture may help to understand
Using split seems to be the case here, thanks Max
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Old   February 14, 2011, 06:59
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Max, if I want to consider my object surrounded by air, like saying it is situated outside whit a external temperature of 20 C, how do I do that?
I heard I should create a cube and have my object inside it....or
is there any other way to set the external temperature whitout having to create that additional cube?
Thanks
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Old   February 14, 2011, 07:06
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If the flowfield around your pipe isn't an interest for you, I would just consider the solid pipe and the flowfield in the pipe.
So 2 volumes (one solid and one fluid).
And set the extern surface from pipe with your 20° (air temperature).
But I am not so familiar with termal...
If you still have questions about it, open a new thread: you will have more chance getting replies with people familiar with thermal stuffs
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Old   February 14, 2011, 07:54
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Actually the pipes(copper whit water inside at a constant speed), is inside a casing, here is a image to know what I'm talking about http://www.igneus.ie/images/flat_plate_cut_away.jpg . And from what are you saying I should set the external faces of that casing ( aka. the glasing and aluminium frame from the picture) to a constant temperature?
All those elements you see in the picture, I have done, meshed and exported in fluent successfully, I just need to know how to set the external temperature
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Old   February 14, 2011, 08:04
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Quote:
Originally Posted by -mAx- View Post
If you still have questions about it, open a new thread: you will have more chance getting replies with people familiar with thermal stuffs


Then no, I thought it was really a pipe outside.
Here your pipes are in a confined room.
So I would substrat your pipes (retain option enabled for solid condiction in pipes) from casing (formed from aluminimum fram and glasing)
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Old   February 14, 2011, 09:07
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I tried subtracting, and by doing so I got other faces created which I don't need, but now I splited the big volume whit the smaller one inside ( aka. the absorber plate and the pipes), and so I got the faces whit "shadows" imported in fluent, and at the moment I'm running the simulation this way to see the difference.
Anyway I'll keep you in touch whit what I progress, if it's okay whit you. Thanks alot
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