boundaray conditions

Mosayeb 92 · June 21, 2015, 06:26

hello
I've started learning fluent recently and I'm a newcomer here.
please help me with boundary conditions.
I've attached a picture.I want the fluid to inter cylinder A and at 1,leave the cylinder A at 2,flow through cylinder B (there is NO gap between A & B. I made it in order to show faces 2 & 3) and exit from 4.
So faces 1 & 4 are VELOCITY INLET & PRESSURE OUTLET respectively and cylindrical faces around A & B are WALL.

I wonder what would be the boundary condition type for faces 2 & 3 ?

Thanks.

bhanuday.sharma · June 23, 2015, 02:56

Dear If you are begginer than start by doing some tutorials first. Download tutorial files and just do these. At first you will not understand even a bit of what you are doing. but trust on ANSYS and trust me.. and complete at least 3-4 tutorials. You will not face this problem again.

Mosayeb 92 · June 23, 2015, 04:06

Thanks for your reply
Actually I don`t have that much time to read 3-4 tutorials and I have to finish a task quickly!! However, I`ve read some.
This picture is just for asking my question, but the problem I have is related to the boundary type of some faces like 2 & 3 in the picture.
Do you have any idea about that??
All the best

pakk · June 23, 2015, 04:26

Faces 2 and 3 are strictly speaking not boundaries, as they are not on the outside.

Normally, you would use one cylinder for such a problem, unless there is a good reason to use two. As far as your description goes, you have no reason to use two cylinders.

So if this would be a quiz, and the question would be "what kind of boundaries are 2 and 3", my answer would be: "useless boundaries".

Mosayeb 92 · June 23, 2015, 04:44

This is just the easiest way I could ask my question and is not a quiz. l`m working on something similar to these two cylinders.
I have to use two cylinders. How can I make the fluid flow through both of them?!

pakk · June 23, 2015, 04:56

You don't have to use two cylinders, or at least you did not explain why.

Unless you have a good reason, use ONE cylinder. It will make everything much easier.

pakk · June 23, 2015, 05:08

But, if you would have a good reason (which I don't believe), you should make these surfaces interfaces. And couple them with a mesh interface. And this gives many problems, also for experienced users.

You say you have to finish the task quickly, so avoid interfaces. Make the mesh such that you don't have surfaces inside your volume. Trust me, it will make it all easier.

Mosayeb 92 · June 23, 2015, 05:13

Thanks alot Pakk.

June 23, 2015, 05:08		#7
pakk Senior Member Join Date: Nov 2013 Posts: 1,965 Rep Power: 26	But, if you would have a good reason (which I don't believe), you should make these surfaces interfaces. And couple them with a mesh interface. And this gives many problems, also for experienced users. You say you have to finish the task quickly, so avoid interfaces. Make the mesh such that you don't have surfaces inside your volume. Trust me, it will make it all easier. Mosayeb 92 likes this.

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June 23, 2015, 02:56		#2
bhanuday.sharma New Member Bhanuday Sharma Join Date: Jun 2015 Posts: 18 Rep Power: 10	Dear If you are begginer than start by doing some tutorials first. Download tutorial files and just do these. At first you will not understand even a bit of what you are doing. but trust on ANSYS and trust me.. and complete at least 3-4 tutorials. You will not face this problem again.

June 23, 2015, 04:06		#3
Mosayeb 92 New Member Mosayeb Join Date: Jun 2015 Posts: 11 Rep Power: 10	Thanks for your reply Actually I don`t have that much time to read 3-4 tutorials and I have to finish a task quickly!! However, I`ve read some. This picture is just for asking my question, but the problem I have is related to the boundary type of some faces like 2 & 3 in the picture. Do you have any idea about that?? All the best

June 23, 2015, 04:26		#4
pakk Senior Member Join Date: Nov 2013 Posts: 1,965 Rep Power: 26	Faces 2 and 3 are strictly speaking not boundaries, as they are not on the outside. Normally, you would use one cylinder for such a problem, unless there is a good reason to use two. As far as your description goes, you have no reason to use two cylinders. So if this would be a quiz, and the question would be "what kind of boundaries are 2 and 3", my answer would be: "useless boundaries".

June 23, 2015, 04:44		#5
Mosayeb 92 New Member Mosayeb Join Date: Jun 2015 Posts: 11 Rep Power: 10	This is just the easiest way I could ask my question and is not a quiz. l`m working on something similar to these two cylinders. I have to use two cylinders. How can I make the fluid flow through both of them?!

June 23, 2015, 04:56		#6
pakk Senior Member Join Date: Nov 2013 Posts: 1,965 Rep Power: 26	You don't have to use two cylinders, or at least you did not explain why. Unless you have a good reason, use ONE cylinder. It will make everything much easier.

June 23, 2015, 05:13		#8
Mosayeb 92 New Member Mosayeb Join Date: Jun 2015 Posts: 11 Rep Power: 10	Thanks alot Pakk.