difference between the opening and outlet ?

heydari · July 26, 2015, 04:49

hi;
What is the difference between the (opening and outlet b.c) in output of open channel?

ghorrocks · July 26, 2015, 05:08

An opening will allow back flow but an outlet will not.

heydari · July 26, 2015, 08:01

hi;
When I change the boundary condition opening to outlet:
****** Notice ****** |
| A wall has been placed at portion(s) of an OUTLET |
| boundary condition (at 62.5% of the faces, 62.4% of the area) |
| to prevent fluid from flowing into the domain. |
| The boundary condition name is: outlet. |
| The fluid name is: water. |
| If this situation persists, consider switching |
| to an Opening type boundary condition instead
Why?what should I do?

Steffen595 · July 26, 2015, 18:08

as ghorrocks said:
"An opening will allow back flow but an outlet will not". Thats why a wall has been placed by the solver
http://www.arc.vt.edu/ansys_help/cfx_mod/i5500692.html
your outlet/inlet/domain is not properly defined. Check massflow at inlet and outlet, you may have big differences. Maybe one of the pressures is not defined right. Hard to guess without more information

ghorrocks · July 26, 2015, 19:14

FAQ: http://www.cfd-online.com/Wiki/Ansys...f_an_OUTLET.22

Steffen595 · July 27, 2015, 01:16

if you still struggle, upload some pictures of what you are trying to do

heydari · July 27, 2015, 08:29

Conditions are correct?

Steffen595 · July 27, 2015, 09:02

the second one, you dont have to define the walls.
Whats the domain like?
Why bulk mass flow, its not multiphase?
If you do more iterations, will it settle down eventually?
If multiphase, whats the other fluid?

heydari · July 27, 2015, 14:38

1. in this software by default does not Allocate the wall?
2. Do not we can input discharge to channel in the software?
3. I would be grateful if you explain?
4. The fluid is water!

Steffen595 · July 27, 2015, 18:34

1. you only have to define inlet and outlet. Walls if not defined are taken as smooth and under same pressure as domain.
4. I have to check, but if its single fluid, its not asking for bulk flow, just mass flow.
2. weird words in weird order. What do you want to say? Is it an open channel, so one half is air? And you put buoyancy in?

http://www.cfd-online.com/Forums/cfx...r-control.html

I see, this is related to this post.

What are you trying to do?
Plus maybe you did not use the dispersed option, then the results get weird as well

heydari · July 28, 2015, 01:20

Hello
I think the issue is clear.
However. I am an open channel. I model the geometry of the liquid form of water in the canal. It is clearly my question is:
1. are boundary conditions for this problem right?
2. My question is whether the discharge water should be in the software image above I enter?

Steffen595 · July 28, 2015, 06:20

dont get snappy? Just throwing in a few words and hoping everyone jumps to your rescue with wagging tails is not going to happen.
Anyways its an inlet and an outlet
http://oximaton.drwx.eu/files/ypol_r..._tutorials.pdf
there is a tutorial. This is for Ansys 11. Just search for newer Ansys versions, if you like, but its not much of a difference.
If you install Ansys, there is a help folder as well.
Anyways, tutorial 7 free surface flow over a bump in that .pdf file should answer all your questions

July 26, 2015, 04:49	difference between the opening and outlet ?	#1
heydari Member A.heydari Join Date: May 2015 Location: IRAN Posts: 31 Rep Power: 10	hi; What is the difference between the (opening and outlet b.c) in output of open channel?

July 26, 2015, 08:01	change the boundary condition opening to outlet	#3
heydari Member A.heydari Join Date: May 2015 Location: IRAN Posts: 31 Rep Power: 10	hi; When I change the boundary condition opening to outlet: **** Notice **** \| \| A wall has been placed at portion(s) of an OUTLET \| \| boundary condition (at 62.5% of the faces, 62.4% of the area) \| \| to prevent fluid from flowing into the domain. \| \| The boundary condition name is: outlet. \| \| The fluid name is: water. \| \| If this situation persists, consider switching \| \| to an Opening type boundary condition instead Why?what should I do?

July 27, 2015, 18:34		#10
Steffen595 Senior Member Join Date: May 2012 Location: Melbourne Posts: 161 Rep Power: 13	1. you only have to define inlet and outlet. Walls if not defined are taken as smooth and under same pressure as domain. 4. I have to check, but if its single fluid, its not asking for bulk flow, just mass flow. 2. weird words in weird order. What do you want to say? Is it an open channel, so one half is air? And you put buoyancy in? http://www.cfd-online.com/Forums/cfx...r-control.html I see, this is related to this post. What are you trying to do? Plus maybe you did not use the dispersed option, then the results get weird as well Last edited by Steffen595; July 27, 2015 at 20:13.

July 28, 2015, 01:20	B.c	#11
heydari Member A.heydari Join Date: May 2015 Location: IRAN Posts: 31 Rep Power: 10	Hello I think the issue is clear. However. I am an open channel. I model the geometry of the liquid form of water in the canal. It is clearly my question is: 1. are boundary conditions for this problem right? 2. My question is whether the discharge water should be in the software image above I enter?

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July 26, 2015, 05:08		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,716 Rep Power: 143	An opening will allow back flow but an outlet will not.

July 26, 2015, 18:08		#4
Steffen595 Senior Member Join Date: May 2012 Location: Melbourne Posts: 161 Rep Power: 13	as ghorrocks said: "An opening will allow back flow but an outlet will not". Thats why a wall has been placed by the solver http://www.arc.vt.edu/ansys_help/cfx_mod/i5500692.html your outlet/inlet/domain is not properly defined. Check massflow at inlet and outlet, you may have big differences. Maybe one of the pressures is not defined right. Hard to guess without more information

July 26, 2015, 19:14		#5
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,716 Rep Power: 143	FAQ: http://www.cfd-online.com/Wiki/Ansys...f_an_OUTLET.22

July 27, 2015, 01:16		#6
Steffen595 Senior Member Join Date: May 2012 Location: Melbourne Posts: 161 Rep Power: 13	if you still struggle, upload some pictures of what you are trying to do

July 27, 2015, 09:02		#8
Steffen595 Senior Member Join Date: May 2012 Location: Melbourne Posts: 161 Rep Power: 13	the second one, you dont have to define the walls. Whats the domain like? Why bulk mass flow, its not multiphase? If you do more iterations, will it settle down eventually? If multiphase, whats the other fluid?

July 27, 2015, 14:38		#9
heydari Member A.heydari Join Date: May 2015 Location: IRAN Posts: 31 Rep Power: 10	1. in this software by default does not Allocate the wall? 2. Do not we can input discharge to channel in the software? 3. I would be grateful if you explain? 4. The fluid is water!

July 28, 2015, 06:20		#12
Steffen595 Senior Member Join Date: May 2012 Location: Melbourne Posts: 161 Rep Power: 13	dont get snappy? Just throwing in a few words and hoping everyone jumps to your rescue with wagging tails is not going to happen. Anyways its an inlet and an outlet http://oximaton.drwx.eu/files/ypol_r..._tutorials.pdf there is a tutorial. This is for Ansys 11. Just search for newer Ansys versions, if you like, but its not much of a difference. If you install Ansys, there is a help folder as well. Anyways, tutorial 7 free surface flow over a bump in that .pdf file should answer all your questions