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boundary conditions in FLUENT VOF for open channel flow

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Old   March 24, 2011, 05:04
Default boundary conditions in FLUENT VOF for open channel flow
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Gillian
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Hi guys,

I have been working on the simulation of flow in a channel through a baffle using VOF FLUENT. I encountered a few problems and would appreciate it if you could please give me some suggestions:


Currently I am using two separate inlets for water and air. The BC for air is set as pressure inlet. I have tried 3 types of BC for water (pressure-inlet, mass flow, and velocity - as the velocity is known) but the simulation somehow gave me a flow direction that looks like the water flows from outlet back to the inlet. The outlet is set as 1 outlet (for both water and air) and operated as pressure outlet. The top surface of air is also set as pressure outlet.

I am wondering if there is some problems with my current setting ?

Your suggestions are very much appreciated.

Gillian
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Old   March 24, 2011, 05:36
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hi.
you should not separate the inlet or outlet for water and air.it's better to use OPEN CHANNEL FLOW by switch it's toggle on and set the inlet and outlet as PRESSURE INLET/OUTLET one and entered your data.also it's better too use ''explicit'' method {define>models>multiphase.....}
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Old   March 26, 2011, 09:03
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hi momech,

Thanks a lot for the suggestion!
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Old   April 5, 2011, 00:58
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Hi,

I tried the simulation with one inlet for the two phase but could not get the results right. The solution still did not converge and another serious issue is the results gave me reverse flow at the inlet.

My boundary conditions are:
1. inlet: pressure inlet, with specifying the flow depth at the inlet
2. outlet: pressure outlet, with flow depth specified (which is lower than in the inlet, due to pressure drop across the baffle)
3. upperbound : I have tried either pressure outlet and symmetry.

Would appreciate it very much if anyone please give me some suggestions on how to solve the problem of reverse flow at the inlet during the simulation.

Indeed, I tried to use velocity inlet as BC for inlet. However, I am a bit confused of how to come up with the volume fraction of water and air respectively (in my physical model, the flow is at 0.04 m/s). Besides, it seemed that with velocity inlet, I could not initialize using open channel initialization. Can anyone give me some suggestions on how should i set velocity inlet BC for open channel ?

Thanks a lot!

Gillian
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Old   April 5, 2011, 08:08
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Hi newcomer
I did the 3D open channel case with cutwater and get acceptable results, it seems that you didn't patch your desired area/volume with water and its velocity after initialize.

best regards.
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Old   April 16, 2013, 18:13
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Quote:
Originally Posted by newcomer View Post
Hi guys,

I have been working on the simulation of flow in a channel through a baffle using VOF FLUENT. I encountered a few problems and would appreciate it if you could please give me some suggestions:


Currently I am using two separate inlets for water and air. The BC for air is set as pressure inlet. I have tried 3 types of BC for water (pressure-inlet, mass flow, and velocity - as the velocity is known) but the simulation somehow gave me a flow direction that looks like the water flows from outlet back to the inlet. The outlet is set as 1 outlet (for both water and air) and operated as pressure outlet. The top surface of air is also set as pressure outlet.

I am wondering if there is some problems with my current setting ?

Your suggestions are very much appreciated.

Gillian
Hi guys;
anyone can help me with setting the boundary conditions in the open channel flow? Thanks
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Old   April 16, 2013, 18:18
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did u figure out the problem, if u did, could u help me. Thank you.
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Old   June 2, 2013, 08:32
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Quote:
Originally Posted by newcomer View Post
Hi,

I tried the simulation with one inlet for the two phase but could not get the results right. The solution still did not converge and another serious issue is the results gave me reverse flow at the inlet.

My boundary conditions are:
1. inlet: pressure inlet, with specifying the flow depth at the inlet
2. outlet: pressure outlet, with flow depth specified (which is lower than in the inlet, due to pressure drop across the baffle)
3. upperbound : I have tried either pressure outlet and symmetry.

Would appreciate it very much if anyone please give me some suggestions on how to solve the problem of reverse flow at the inlet during the simulation.

Indeed, I tried to use velocity inlet as BC for inlet. However, I am a bit confused of how to come up with the volume fraction of water and air respectively (in my physical model, the flow is at 0.04 m/s). Besides, it seemed that with velocity inlet, I could not initialize using open channel initialization. Can anyone give me some suggestions on how should i set velocity inlet BC for open channel ?

Thanks a lot!

Gillian
I have exactly this problem .
I am using "Open channel flow" option in inlet and outlet boundaries. It is look like water goes up in pressure inlet boundary.
Where is the origin of the free surface and bottom. Is it in bottom of any boundary or origin of coordinates?
help me please.
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Old   June 3, 2013, 03:07
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Quote:
Originally Posted by mkhodier View Post
Hi guys;
anyone can help me with setting the boundary conditions in the open channel flow? Thanks
Hi
please read "Heave and Pitch Simulation of Ship hull moving through head sea waves" tutorial
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Old   June 6, 2013, 14:23
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Thank you for replying. Could you please send me the tutorial, I can't find it. Thank you for your help.
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Old   June 10, 2013, 11:19
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Can you post you email address? I can sent it across to you.

OJ
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Old   June 10, 2013, 13:18
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mkhdcpu1@yahoo.com Thank you for your help
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Old   June 10, 2013, 13:53
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saeed.azsh88@gmail.com thank you
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Old   July 7, 2013, 04:33
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Old   July 17, 2013, 02:51
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tomo.umor@gmail.com thanks for help
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Old   July 22, 2013, 16:37
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servicesamigo@gmail.com If it's still out there, thanks!
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Old   July 29, 2013, 04:38
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I am also searching for the tutorial, if someone would send it to:

matthias.hoefler@rwth-aachen.de
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Old   July 29, 2013, 11:58
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I have not received it yet either, I guess it no longer is out there
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Old   August 10, 2013, 03:46
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Hi,
Thank you
mostafashamsi.es99@yahoo.com
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Old   August 25, 2013, 09:05
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I have some problem with my boundary condition that how i utilize the neumann condition(∂φ/∂x = 0) at outlet. Can i select pressure outlet at outlet?
my inlet condition is :
flat velocity profile =40m/s
Re=1.916*10^5
turbulent intensity=4.5%
And Inlet height of duct=5mm


I select velocity inlet at inlet because my flow is incompresible.
And axis boundary condition applied along the centerline.
and no slip condition at wall.

pls help me.
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