Postprocessing of particle fields

Background

$$ \bar\phi _ { cell } = \frac {\sum \phi_{i}}{denominator}, \ i\in cell, \ i\in mask $$

where denominator depends on the type of operation we are performing:

• If we are performing sum operation, $denominator = 1$
• If we are performing average operation, $denominator = \sum 1,\ i\in cell$
• If we are performing averageMask operation, $denominator = \sum 1, i\in cell,\ i\in mask$