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determine surface height without input (open channel ; free surface and bottom) given

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Old   December 30, 2013, 04:09
Default determine surface height without input (open channel ; free surface and bottom) given
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hi all, happy welcome the new year,

I really need your help,

i hve tried this with open channel, i think it's not proper way, because i set the height of the surface, but in my case, i should make the water can adapt surface height by gravity work on it without input given (without entering data in open channel ; free surface and bottom), then the water free out like a waterfall into the tank.

please, help me. thank you so much


surface vortex3.jpg

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Old   December 30, 2013, 04:17
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sorry my question is, what parameter and boundary should i use? thx
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Old   December 30, 2013, 05:05
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Then normal BC's like velocity inlet and pressure outlet. For postprocessing the height of your surface will be given with the product of the volume fractions
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Old   December 30, 2013, 06:18
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thx but do i still use VOF - "open channel" in model and without click open channel in multphase tab on BC

or only VOF ?
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Old   December 30, 2013, 07:04
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Only VOF with open channel flow at first stage
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Old   December 30, 2013, 08:48
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what first stage is mean? sorry, i can't understand. please, explain to me. i'm new inthis field

it's my work, but still divergence, after set the BC as your suggest.

Transient with VOF + open channel, BC, Volocity inlet : 1,4 m/s and Pressure outlet (default),

then compute from velocity inlet, then calculate with 200 iteration.

mesh.jpg
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Old   December 30, 2013, 10:20
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I only suggested to USE VOF since you said that open channel flow is not quite giving the right results. You have to check the whole setup and five us more details. By the way why did you start with the open channel hydraulics? Do you have experimental values for the heights of waves at inlet and outlet?. Your Geometry looks like a cyclone. And the mesh is very coarse.

I suggest to start with tutorial or simple duct and carry on a VOF simulation of free surface flow.
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Old   December 30, 2013, 11:37
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with pleasure, i will give the the detail,

open channel hydraualics? sorry..i don't know where it start,
and i don't have any experimental values of the wave height for both inlet and outlet,

actually, this is simplification case of my work, because i'm new. i simplify the case as water free out to the tank.

yes, you correct it is a cyclone, i want make water vortex flow, with hole outlet in bottom of tank, but it is still so far for me to understand to make this simulation..
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Old   December 30, 2013, 11:51
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i'm sorry about the mesh, i thought because it's just example, it's okay if i use coarse mesh to speed the iteration, i will correct it
thx
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Old   December 31, 2013, 08:33
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hi hi,, sorry to make you wait long Zaktatir, i hve worked quite much in this day,,

here is the details, please

1.A dimensi.jpg

1.B mesh.jpg

1.C GENERAL.jpg

1.D MODEL.jpg

1.E MATERIAL.jpg

i feel, i'm wrong in solution control and solution initialization,
and other such, BC and CellZoneCondition bacause i put default

btw the mesh quality is not good enough, is it?
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Old   December 31, 2013, 08:35
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1.F PHASE.jpg

1.G CELL ZONE CONDITION.jpg

1.HBOUNDARY CONDITION.jpg

1.I SOLUTION METHOD.jpg

1.J SOLUTION CONTROL.jpg
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Old   December 31, 2013, 08:38
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1.K MONITOR.jpg

1.L SOLUTION INITIALZATION.jpg

1.M CALCULATION ACTIVITIES.jpg

1.N RUN CALCULATION.jpg
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Old   December 31, 2013, 19:52
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hi, Zaktatir

i did as ur suggest to start it with simple duct, i hve made a tub with a duct on it in 2D,
and it work

but i got problem, the case,

I want to fill the tub until it is full with water in 2D. I use time step size low = 0,1; number of time step = 100; auto save every(time step) = 10

i need time until 60 s, until the tub is full but in interation (before the tub is full) i got error message in 2 s, . the tub is not full yet

what things should i change?


ps: error "Global courant number is greater than 250.00 The
velocity field is probably diverging. Please check the solution
and reduce the time-step if necessary."


thanks alot, if you can help me, this now.

happy new year

Attachment 27667
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Old   January 2, 2014, 14:38
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thx Zaktatir, i've solved the problem now,
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