[flowgeek]

hi all,

i'm trying to simulate the wetting of a moving wall with dynamic contact angles.
So as a very simple test case i made a vertical rectangular channel half filled with water and one wall moving. (see attached image)

the boundaryconditions for the moving wall are:

alpha.air:

type dynamicAlphaContactAngle
theta0 130;
thetaA 110;
thetaR 150;
uTheta 1e-07;
limit gradient;
value nonuniform List<scalar>
...

U

type fixedValue
value uniform (0.01 0 0);


it seems to me - also looking at the code which i halfway understant - that for the calculation of the dynamic contact angle only the fluid velocity is used and not the relative velocity of the fluid with respect to the moving wall --> this results in a contact angle with the wall of 130° instead of 170° (the calculation of the contact angle in this BC are a bit odd)

An error to report? or is there another way to choose the velocity BC?

Attachment 73765

[vortex_shedding]

Probably you have already found a solution to this issue. If not, then I should mention that this is a known bug in the dynamic contact angle BC. You can read this bug report:

https://bugs.openfoam.org/print_all_...-1&show_flag=0

A possible fix has been suggested:

Line 145 of dynamicAlphaContactAngleFvPatchScalarField is where the calculation is being done. Change this line to :

return theta0_ * (1 - tanh(uwall/uTheta_) * sign(uwall/uTheta_) ) - thetaA_ * neg(uwall) * tanh(uwall/uTheta_) + thetaR_ * pos(uwall) * tanh(uwall/uTheta_);

[flowgeek]

hi,

thanks for the reply and the suggested solution!
no i haven't found a proper solution to the issue - i had to cheat quite a bit...
(can you post the link to the bug report again, or the issue number? i cannot open it...)

[2538sukham]

How did you quantify the contact angle on the moving wall? I have a moving wall which pushes fluid so I have a moving line contact angle on the curved surface of the cylinder. i am assuming that assigning zeroGradient which ensures 90 degree contact angle results in wiggles when the liquid bulk rises due to the moving wall. Is there something which I can do?