[doubtsincfd]

The dynamic contact angle implementation in OF is:
const vectorField nf(patch().nf());

// Calculated the component of the velocity parallel to the wall
vectorField Uwall(Up.patchInternalField() - Up);
Uwall -= (nf & Uwall)*nf;

// Find the direction of the interface parallel to the wall
vectorField nWall(nHat - (nf & nHat)*nf);

// Normalise nWall
nWall /= (mag(nWall) + SMALL);

// Calculate Uwall resolved normal to the interface parallel to
// the interface
scalarField uwall(nWall & Uwall);

return theta0_ + (thetaA_ - thetaR_)*tanh(uwall/uTheta_);

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1. What is Up?
2. nf & Uwall is inner product of nf and Uwall. Wont it give component normal instead of parallel to the wall?