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Strange behaviour because of contact angle (interfoam)

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Old   January 12, 2011, 11:16
Default Strange behaviour because of contact angle (interfoam)
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As this is my first post in this forum I would like to say "Hello" to everybody.

I just started with OpenFOAM and mesh-based CFD in general. I wanted to simulate the process shown on the following picture.

http://img98.imageshack.us/img98/2114/overviewc.png

A viscous fluid is pulled under a blade (by a conveyor belt) to form a thin tape. The conveyor belt speed is given through the lower wall boundary velocity in the desired direction (here x direction). My first approach was using the damn break tutorial as a starting point. Using the settings from the tutorial was quite successfull.The only thing i changed was the the viscosity of the former "water". It was set to 4 Pa s.

I played a little around and used different boundary conditions so that the surface tension effects between the wall and interface are no longer ignored.

After some reading I came up with with following setting for the walls in the alpha1 file:

Wall
{
type constantAlphaContactAngle;
theta0 30;
value uniform 0;
limit none;
}

and the p_rgh:

Wall
{
type fixedFluxPressure;
adjoint no;
}

Now strange things happen as seen in the following screenshot:


http://img209.imageshack.us/img209/9...actangle30.png

These effects are directly related to the contact angle and seem to be more extreme at higher viscosity difference between the two fluids. If an angle of 90 is chosen everything works fine.

I was wondering if somebody could tell me the cause of the extreme curving of the surface. In my opinion the contact angle should not have such a big effect on the fluid behaviour in the reservoir. I suspect it might have something to do that simulation is not "relaxed" at the first timestep in the area near the walls (contact angle of 90 because of initial geometry) and the resolution of the mesh.

Thanks in advance,
Kim123
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contact angle, interfoam, viscous laminar

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