boundary conditions in FLUENT VOF for open channel flow
 

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.
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.....}
good lock.

hi momech,

Thanks a lot for the suggestion!

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

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.

Hi guys;
anyone can help me with setting the boundary conditions in the open channel flow? Thanks

did u figure out the problem, if u did, could u help me. Thank you.

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.:confused::confused:
Where is the origin of the free surface and bottom. Is it in bottom of any boundary or origin of coordinates?
help me please.

Hi
please read "Heave and Pitch Simulation of Ship hull moving through head sea waves" tutorial

Thank you for replying. Could you please send me the tutorial, I can't find it. Thank you for your help.

Can you post you email address? I can sent it across to you.

OJ

mkhdcpu1@yahoo.com Thank you for your help

saeed.azsh88@gmail.com thank you

ybhargav93@gmail.com thank u

tomo.umor@gmail.com thanks for help

servicesamigo@gmail.com If it's still out there, thanks!

I am also searching for the tutorial, if someone would send it to:

matthias.hoefler@rwth-aachen.de

I have not received it yet either, I guess it no longer is out there

Hi,
Thank you
mostafashamsi.es99@yahoo.com

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.

Hi all,

I found this video and I think it could help to get a better understanding of how to make VOF setup :)

Guida Setting VOF Fluent

please help me: open channel modeling problem
 

Hi
Dear friends.
I'm trying model a simple rectangular channel steady-state flow on Fluent by VOF: open channel condition.
Something cause a problem and affect the results.
the geometry of my channel is 30x30cm by 0.002 slope which the channel length is 10 m ; and the flow depth is 10cm.
According to the
http://0up.ir/up10/guest/3.png
and
http://0up.ir/up10/guest/out.png
boundary conditions considered as pressure- inlet &outlet and the top of my channel considered as pressure inlet according to the Fluent Help!
I've tried many B.C. to all the boundaries. but the velocity of air at the inlet considered about 90m/s!!!!! which it increases along the channel to end and reaches to 690m/s!!!!!!!!!!!
how can it possible???? and i cant fix it
also, density reports shows the water (Secondary phase) is under the air (First phase), which it is true.
but the main problem is the air velocity in Domain. Pics.>>>>>
http://0up.ir/up10/guest/1.png
http://0up.ir/up10/guest/2.png
http://0up.ir/up10/guest/t1.png
Please help me to solve this problem.

Hi Javidcfd,

I would use pressure-inlet at inlet, pressure-outlet at outlet, wall for the floor and symmetry for the rest of surfaces.

Taking a look at your mesh, I would try to refine it at the free surface region as well. Have you activated gravity option? Where is your reference pressure location? Have you marked and patched your region?

hi javidcfd
i have a model close to your one, but mine is flat (without bed inclination)
but i have some problems with it, how can i contact with you .. i really need your help

Fluent- multiphase help
 

I'm searching for "Heave and Pitch Simulation of Ship hull moving through head sea waves" tutorial. Please anyone send me the zip file, my mail id is sbsazeda@gmail.com
Thanks....

Tutorial
 

Can anyone share the tutorial with me please?

g_muizer@yahoo.es

Me too please very much.

killerudy@gmail.com

Hi, can anyone share the "Heave and Pitch Simulation of Ship hull moving through head sea waves" tutorial to me please. Thank you!

sharmainepook@gmail.com

Tutorial
 

can I use periodic flow for simulate open channel flow with Fluent by using VOF model?

Hi
I had the same problem (high velocity flow from outlet to domain!!!!), It is because of reference of pressure which you have to determine in "operation condition" menu. Don't forget to check specified density
Good Lock everyone.

Hey if anyone is still having continuity convergence issues, I think I may have a solution. I posted a similar question a few weeks ago and updated it with the answer:

https://www.cfd-online.com/Forums/fl...tml#post639515

Good luck!

Please send me this tutorial. I am unable to find it.
tamarmeesam@gmail.com