**Question:**

How does Tecplot calculate cell or face-centered quantities?

**Answer:**

Tecplot uses simple arithmetic averaging to calculate cell- (face-) centered quantities.

Integrations are done using the trapezoidal method, which is second-order accurate. For each cell, the cell-centered value of the quantity being integrated (integrand) is multiplied by the volume of the cell, and the result is summed over all cells. If the integrand is node-centered, the cell-centered average is calculated as an arithmetic average of the values at the corners of the cell. If the integration is performed over (ordered-zone) faces instead of cells:

- If the integrand is nodal data, the nodal values of the face nodes are averaged.
- If the integrand is cell-centered, the values of the cells to either side of the face are averaged.