[behcfd]

Hi dears. I'm new to openfoam and I wanna simulate filling of an empty tank (full of air) using interFoam and vof and RNGkepsilon model. In my geometry there is a baffle. my inlet velocity is 0.03 m/s and the tank has 10m length and 1m height. I use adjustable time step so that the courant number set smaller than 1. I've confused because at the beginning of the simulation solution diverged even for laminar simulation in order to decreasing time step to 10^-34 and smaller. I set Co to 0.1 and refined the mesh but the problem was not resolved yet!! Can anyone help me???

Initial condition= alpha.water=0, U=0;
boundary conditions:
inlet: alpha.water=1, U=0.03, p-rgh=zeroGradient.
outlet: I checked both of inletoutlet and zero gradient for alpha & U.
atmosphere: zero total pressure for p-rgh. pressureInletOutlet velocity.

[wouter]

dear behcfd,

Did you search the forum, because I answered a very similar question before:

http://www.cfd-online.com/Forums/openfoam-solving/137179-filling-tank-water.html

but there are probably a lot more places to look.

hope this helps
Wouter

[behcfd]

Dear wouter, tnx a lot. I didn't find shared link before! I read the link but I have some questions yet! I don't understand which one of my boundary conditions is incorrect.
Do I have to change inlet p-rgh from zeroGradient to fixedFluxPressure and is this enough? and what is the physical reason of it? I didn't realize why in this problem the degrees of freedom is not equal to the number of variables.

my problem is a little different from that post and my geometry is a channel so that the upper patch is atmosphere instead of wall and water leaves tha channel at outlet. I attached the simple form of my geometry...thanks

[farazarbabi]

Hi,
I did not understand the physics of your problem well. You have a vessel full of air and you want to fill it with liquid water, right? So why do you want to use turbulence model?
Nevertheless, based on the given info and assuming you have a decent geometry and mesh, I recommend using the following BCs.:

alpha:
inlet
{
type inletOutlet;
inletValue uniform 1;
value uniform 1;
}

outlet
{
type zeroGradient;
}

p_rgh:

inlet
{
type fixedFluxPressure;
value uniform 1;
}

outlet
{
type totalPressure;
p0 uniform 0;
U U;
phi phi;
rho rho;
psi none;
gamma 1;
value uniform 0;
}

U:
outlet
{
type pressureInletOutletVelocity;
value uniform (1 0 0);
}

and for the upper wall use the damBreak tutorial BCs for atmosphere.

[behcfd]

Thanks dear faraz. yes, I have a channel full of air and I want to fill it with liquid water until water overflow from baffle. after overflow the state of flow becomes steady gradually. Inlet flow is turbulant and Re=3500 so i must use turbulence models like related papers.

I tried your suggested boundary conditions. but still my results are incorrect. near down-wall a big circulation region appear that is not correct! I don't know which of my boundary conditions are incorrect!

[farazarbabi]

Did it converge? How are you sure it is incorrect? Can you put a snapshot here?

Originally Posted by behcfd

Thanks dear faraz. yes, I have a channel full of air and I want to fill it with liquid water until water overflow from baffle. after overflow the state of flow becomes steady gradually. Inlet flow is turbulant and Re=3500 so i must use turbulence models like related papers.

I tried your suggested boundary conditions. but still my results are incorrect. near down-wall a big circulation region appear that is not correct! I don't know which of my boundary conditions are incorrect!

[behcfd]

yes, I compared velocity profiles and steramlines nearly after 100sec from beginning of overflow. after this time the flow become nearly steadystate and the profiles don't change with time.
I compared my results with related paper and experimental results and they are very different! I attached the streamlines of water that is correct and my results. as you see for my simulation a circulation region appear near down-wall that is incorrect.

[farazarbabi]

What is the reference?

Originally Posted by behcfd

yes, I compared velocity profiles and steramlines nearly after 100sec from beginning of overflow. after this time the flow become nearly steadystate and the profiles don't change with time.
I compared my results with related paper and experimental results and they are very different! I attached the streamlines of water that is correct and my results. as you see for my simulation a circulation region appear near down-wall that is incorrect.

[behcfd]

Experimental and Numerical Approach to Enlargement of Performance of Primary Settling Tanks, A. Razmi, B. Firoozabadi, and G. Ahmadi.

you can download it from here:

https://www.google.nl/url?sa=t&rct=j...82001339,d.d2s

[farazarbabi]

I can't say what is wrong based on the information I have. I guess the geometry might have a problem (there is no baffle in these simulations, right?). And I see a streamline at the left-up corner, which is strange, because no water should flow to that side, so check the left wall B.C. too. Also make sure no-slip B.C. is applied correctly to the walls.
Moreover, make sure the simulation has reached to steady state condition, reading this can be helpful:

http://www.openfoam.org/version2.0.0/steady-vof.php

Cheers,
Faraz

Originally Posted by behcfd

Experimental and Numerical Approach to Enlargement of Performance of Primary Settling Tanks, A. Razmi, B. Firoozabadi, and G. Ahmadi.

you can download it from here:

https://www.google.nl/url?sa=t&rct=j...82001339,d.d2s

[behcfd]

thanks again dear faraz.
unfortunately I checked boundaries and geometry but I didn't find the reason of bad results! my geometry is like the paper. it hasn't any intermediate baffle (case1 in the paper).
I feel confused a lot!

[me12p1006]

Hi,

I am trying to solve water filling bottle tutorial from long back (http://www.tfd.chalmers.se/~hani/kur...Hemida_VOF.pdf). I am not getting reasonable results.

I used inlet velocity as 0.1 m/sec. I am attaching my FOAM files. Please kindly let me know what mistake I am doing.