Boundary conditions for an outlet
 

Hi all,
I'm studying tutorial 3, a dam break. And I changed the gravity to the positive y direction just for fun. :):):) So the liquid would go up, and I expect the liquid to exit the domain, like you have a cup of water, then you turn the cup around, and the water inside would spill out.

Thus I have to changed the boundary condition of the upper face named as 'atmosphere'.

I searched a lot from this Forum and tried different types of alpha1 and U, like inletOutlet, or zeroGradient, etc.

Here are some of my codes:

alpha1:
atmosphere
{
type inletOutlet;
inletValue uniform 0;
value uniform 0;
}

U:
atmosphere
{
type inletOutlet;
inletValue uniform (0 0 0);
value uniform (0 0 0);
}

this is one case. Another case I tried was:


alpha1:
atmosphere
{
type fixedValue;
value uniform 0;
}
U:
atmosphere
{
type zeroGradient;
}

Both cases don't work. There is always some fluid remaining in the domain.:mad:

Which boundary conditions should I choose? Can anyone help?

Could anyone help me?

Hi kongfu,

nice example. I just read your thread, but can´t really help you with that example. But here is a side, where you can read about all boundary conditions. Hope, this can help you.

http://www.openfoam.com/docs/user/boundaries.php

bye and a happy new year.
phil

Hi Phil,

Thank you very much for your help! It's very useful. I will try it. :) If I have made any progress, I will inform you.

Best regards and happy new year,
Tao