OpenFOAM guide/SurfaceInterpolation;;deltaCoeffs

surfaceInterpolation::deltaCoeffs

Reciprocal of cell-to-cell (centres) distance, with orthogonality correction.

On an orthogonal grid: $C_\delta = \frac{1}{\delta}$

Where:

• $\delta$ is the cell-to-cell distance.

Standard definition: $C_\delta = \frac {\mathbf{\hat{n}} \bullet \boldsymbol \delta} {\left \vert \boldsymbol \delta \right \vert^2}$

Where:

• $\mathbf{\hat{n}}$ is the surface normal vector; and
• $\boldsymbol \delta$ is the cell-to-cell vector.

Used in OpenFOAM for stability with poor meshes: $C_\delta = \frac{1} {\text{max}\left ( \delta \bullet \mathbf{\hat{n}}, 0.05 \left \vert \delta \right \vert \right )}$