population balance model
 

I am using population balance model for solid particles forming in a chemical reaction. Over time these particles grow and get larger than the mesh size (Mean particle diameter is more than mesh size). However, when I check the volume fraction of solid particles (phase 2) I see very small values (10 ^-7). Is the reporting volume fraction actually volume of solid divided by total volume of fluid? or divided by volume of each Cell? I suppose if it's volume fraction of each cell, I should have seen volume fraction of 1 for some of the cells because there are some particles larger than cells. right?