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Contact angle between different phase and wall

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Old   March 1, 2013, 00:48
Default Contact angle between different phase and wall
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Guifan Li
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Good evening,

I am trying to simulating a droplet made of oil drop into a water base.

However, I am confusing about setting up the Contact Angle between phase and between phase and wall.

for example
Quote:
boundaryField
{

sideWall
{
type alphaContactAngle;
thetaProperties
(
( water air ) 90 0 0 0
( oil air ) 90 0 0 0

( water oil ) 90 0 0 0


);
value uniform 1;
}
lowerWall
{
type alphaContactAngle;
thetaProperties
(
( water air ) 90 0 0 0
( oil air ) 90 0 0 0

( water oil ) 90 0 0 0


);
value uniform 0;
}
like in the sideWall, there are (water air) 90 0 0 0. I understand the contact angle between water and air is 90 here. But in lowerWall section, there is also (water air) 90 0 0 0. what is the difference between these two (water air)? and how can I set up the contact angle between the water and the wall? (in the breakdam-one phase, I can successfully set up the contact angle between water and wall but here is a little bit different).

Can anyone give me some suggestions please?
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Old   March 7, 2013, 03:46
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Michiel
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The second water-air is on a different patch (lowerWall as opposed to sideWall) because you can set the contact angle on each patch individually to be able to model a real-life situation in which maybe one wall is wetting with respect to the water and another wall is non-wetting (think of a glass lid and a teflon wall in a cooking pan for example).

Setting up the contact angles with the walls is just a matter of changing the 90s into something else. So to give an example: if you set the following:
Code:
lowerWall
    {
        type            alphaContactAngle;
        thetaProperties
        (
            ( water air ) 50 0 0 0
            ( oil air )120 0 0 0
            
            ( water oil ) 90 0 0 0
            
            
        );
That means that a water-air interface will have a contact angle of 50 with the lowerWall, an oil air interface will have a contact angle of 120 with the lowerWall and the water oil interface will have a 90 degree contact angle.

I am not that familiar with the multiPhaseInterFoam so I don't know what the 3 zeros in the boundaryField settings mean, but they seem like dummy variables to me. To confirm that you would have to dig into the solver code a bit.
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