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Old   August 21, 2006, 11:53
Default please help if you can?
  #1
sihat
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would you please send me and explain to me how to specify the boundary conditions in 3D cylinder walls and i want to specify inlet ,outlet, wall1,wall2 and wall3 at gambit best regard sihat
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Old   August 22, 2006, 03:31
Default Re: please help if you can?
  #2
Albert F.
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I imagine that you have meshed the cylender, haven't you? When you mesh the cylinder you work with three faces the lateral, the top and the bottom. The boundary conditions has to be specified to all of this faces depending of what you need.
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Old   August 22, 2006, 04:33
Default Re: please help if you can?
  #3
sihat
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thanks i mean that i want to use the lateral face in three boudary conditions wall1, wall2 and wall3 and i want to use the bottom one as inlet and the top one as out let so my problem how to specify these three walls in lateral face(i mean how to devide the lateral face in 3walls different boudary conditiond) so help if u can thanks so much
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Old   August 22, 2006, 04:39
Default Re: please help if you can?
  #4
Albert F.
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I don't know if I understand the problem but if I were you I would creat three different faces but I'm sure that there is another easily way to do this. I'm sorry but I can't help you.
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Old   August 22, 2006, 06:37
Default Re: please help if you can?
  #5
Jason
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Before you mesh the geometry, you should split the surface of the cylinder to create the three surfaces that will be your walls. If it's all real geometry, then create a face that intersects the surface of the cylinder at each location where you want to create an edge for the walls, then use the face-split function. Once you have the three walls, then you can mesh your geometry and define the BCs as normal (at the top of the screen it's the blue/green grid icon... if you haven't learned this yet, you MUST read the tutorials for Gambit...).

Good luck, and hope this helps, Jason
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Old   August 22, 2006, 10:47
Default Re: please help if you can?
  #6
sihat
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thanks so much Janson for your valuable advice iam really want to devide face-2 in the sylider geometry which i create it using gambit into 6-walls boundary conditions in additions to face-1 as inlet and face-3 as outlet. so my broblem i want to know how to create 6 walls from face-2 as boundary conditions.i think you got it and i wait for your help. thanks alot sihat
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Old   August 22, 2006, 11:16
Default Re: please help if you can?
  #7
Jason
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Like I said, split the face-2 into whatever faces you want. Do this before you mesh, or else you'll have to re-mesh anyway. The way to split is: Create a surface that intersects face-2. Then select the face split tool (not the volume split, the face split) to split face-2 where it intersects the surface you created. You can do this for each place you want to split face-2.

Hope this helps, and good luck, Jason
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Old   August 22, 2006, 21:10
Default Re: please help if you can?
  #8
sihat
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thanks Jason so much and iam sorry for bothering you. would you please explain to me in my email in details how to create a surface that intersect surface -2. i mean please sxplain to me in details how to do this things thanks so much for your valuable help sihat
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Old   August 23, 2006, 07:17
Default Re: please help if you can?
  #9
Jason
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You need to go through the Gambit tutorials. There are many different ways of creating faces (you could do a bottom-up approach where you create vertices, attach them with edges, then create a face using the edges, or you could do a top-down approach where you have Gambit create a rectangular face of certain size and then move it to the location you want, or yet still you could create an edge that represents one edge of the face and extrude it in a vector direction or along an edge to create a face).

I'll do my best here, but whether or not this helps, you really need to go through the Gambit tutorials.

Assuming your cylinder is centered along the X axis, with a radius of 1 and a height of 5 (with one face coincident with the YZ plane, so that the other is at X=5).

In the face toolbar, select the create face icon (top row of the face commands toolbar, second from the left, looks like a rectangle with dimensions on the bottom and right side) and create a face with a height of 2" and a width of 5" that goes in the +X +Y direction. Then select the modify icon (second row, all the way to the left) and pick the rectangle you just created. Change it from "move" to "copy" and set the number of copies to two. Change the operation to "rotate" and click the "Define Axis" button. You want to pick the +X axis as your axis of rotation in the window that pops up and then click "OK" to close the window. Enter 180 as the angle of rotation and then click "Apply". Now you've got a cylinder with three intersecting faces sticking out every 180deg. Next click the "split face" icon (it's right next to the modify icon). First select the outer face of the cylinder as the object you want to split, then select one of the radial faces (make sure "connected" is on and "bidirectional" and "retain" are off). Do this again to split the cylindrical face with the other two radial faces.

You really need to go through the tutorials. And you should also look through the manual. Until you understand why you're doing something, what I described above is just a series of steps and won't help you in the long run.

Hope this helps, and good luck, Jason
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Old   August 23, 2006, 22:37
Default Re: please help if you can?
  #10
sihat
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thanks so much Jason for your support and we highly appreciate. and i shall try thanks again so much. sihat
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Old   August 24, 2006, 12:52
Default Re: please help if you can?
  #11
sihat
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hi Jason to day i try so many time all yhe approach you send me to devide phase-2 in cylidrical geometry and i coud't succeed and i did't understand the step modify and then move-copy -rotate--etc. i do all the step you sent me and finally i coudn't see the phaces! can you give me more explanation sorry again for bothering u,and really it is more urgent to me.becuse i have to use the time thanks so much sihat
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