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-   -   Contact angle between different phase and wall (http://www.cfd-online.com/Forums/openfoam-pre-processing/113917-contact-angle-between-different-phase-wall.html)

 liguifan March 1, 2013 00:48

Contact angle between different phase and wall

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?

 michielm March 7, 2013 03:46

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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