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October 15, 2010, 14:28 
InterFoam contact angle

#1 
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Joao Miranda
Join Date: Oct 2010
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Usually in a VOF method the contact angle is introduced in the simulation in the calculation of the curvature. The curvature near the boundary is determined based the vector normal to the surface. The vector normal to the surface is calculated from the contact angle.
The vector normal to the surface, n=(nx,ny,nz) is related to the angle by: ny/SQRT(nx^2+nz^2)=cot(theta) According to the following paper: Chen Fang, Carlos Hidrovo, Fumin Wang, John Eaton, Kenneth Goodson, 3D numerical simulation of contact angle hysteresis for microscale two phase flow, International Journal of Multiphase Flow, Volume 34, Issue 7, July 2008, Pages 690705 the calculation of the contact angle becomes complicated in corners, where two angles exist. The calculation of the vector normal do the surface becomes impossible for angles smaller than 45 degrees. The vector n=(1,ny,nz) is related to the angle by: ny=cos(theta1)/(1cos(theta1)^2cos(theta2)^2) nz=cos(theta2)/(1cos(theta1)^2cos(theta2)^2) These equation only work for cos(theta1)^2+cos(theta2)^2>1 How are these calculations handled in InterFoam? Specifically, how are contact angles handled in corners? 

September 4, 2011, 03:06 
It's not the calculation that becomes impossible ....

#2 
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Michiel
Join Date: Oct 2010
Location: Delft, Netherlands
Posts: 97
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I know this question is about a year old, but maybe for the benefit of other openfoam (or CFD) users it is good to know:
The reason that there is no solution to the equations for 45 degrees or less is that it is an unphysical situation to have a contact line in the corner if the CA is below 45 degrees. If this happens, you will get a corner with the low CA fluid completely filling the corners: so called gutter flow. Check out Concus and Finn or Oron for more details on the math behind this: * Concus and Finn, On The Behavior Of A Capillary Surface In A Wedge, PNAS, 1969 * Ajaev and Homsy, Modeling Shapes and Dynamics of Confined Bubbles, ARFM, 2006 In some situations, the existence of these `gutters' is essential to describe the physics of twophase microflows: * van Steijn et al., Flows Around Confined Bubbles And Their Importance In Triggering Pinchoff, Phys. Rev. Lett., 2009 Last edited by michielm; September 4, 2011 at 10:44. Reason: Wrong reference 

January 31, 2014, 08:40 
Conatct angle in multiphaseinterfoam

#3 
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Rajesh
Join Date: Jul 2012
Location: New Delhi
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Hi,
Could anyone tell me the implementation of dynamic contact angle in multiphaseInterfoam solver? There are four contact angle values to be input for multiphaseInterFoam, via.. equlibrium contact angle, Utheta, Advancing contact angle, Receding contact angle. I found some details , how contact angle is being calculated in multiphaseInterFoam as follows, θ = (θA − θR ) ∗ tanh(uwall/uθ) my question is when i use no slip boundary condition, u wall is zero then the theta on left hand side is also becomes zero. Then how the contact angle effect is being imposed in multiphaseinterFoam under no slip BC. First of all, is this solver requires all four contact angle to be defined? Please help me to understand this contact angle issue. 

August 26, 2014, 11:29 
Contact Angle Correction

#4 
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Vignesh
Join Date: Oct 2012
Location: Darmstadt, Germany
Posts: 59
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Hi everyone !
I am trying to understand how contact angle is corrected in interfoam based on theta value given either as input (constant contact angle mode) or calculated dynamically. I started looking at the function correctcontactangle in interfaceProperties.C and i am confused as to how it corrects the contact angle . The correctcontactangle function is given below Code:
void Foam::interfaceProperties::correctContactAngle ( surfaceVectorField::GeometricBoundaryField& nHatb, surfaceVectorField::GeometricBoundaryField& gradAlphaf ) const { const fvMesh& mesh = alpha1_.mesh(); const volScalarField::GeometricBoundaryField& abf = alpha1_.boundaryField(); const fvBoundaryMesh& boundary = mesh.boundary(); forAll(boundary, patchi) { if (isA<alphaContactAngleFvPatchScalarField>(abf[patchi])) { alphaContactAngleFvPatchScalarField& acap = const_cast<alphaContactAngleFvPatchScalarField&> ( refCast<const alphaContactAngleFvPatchScalarField> ( abf[patchi] ) ); fvsPatchVectorField& nHatp = nHatb[patchi]; const scalarField theta ( convertToRad*acap.theta(U_.boundaryField()[patchi], nHatp) ); const vectorField nf ( boundary[patchi].nf() ); // Reset nHatp to correspond to the contact angle const scalarField a12(nHatp & nf); const scalarField b1(cos(theta)); scalarField b2(nHatp.size()); forAll(b2, facei) { b2[facei] = cos(acos(a12[facei])  theta[facei]); } const scalarField det(1.0  a12*a12); scalarField a((b1  a12*b2)/det); scalarField b((b2  a12*b1)/det); nHatp = a*nf + b*nHatp; nHatp /= (mag(nHatp) + deltaN_.value()); acap.gradient() = (nf & nHatp)*mag(gradAlphaf[patchi]); acap.evaluate(); } } } Can anyone point me to some reference where it is explained or Can someone explain how the code !! Thanks for your time
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Thanks and Regards Vignesh 

Tags 
contact angle, corner, interfoam 
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