How to deal with the case with Vdem/Vcfd = [1,2]?

Dear all,

I have a question that, as we know for the unresolved model, the particle size should smaller than the CFD cell size, and the value of Vcfd/Vdem = [3,10], for big particles, as Vdem/Vcfd >10, maybe we can consider to use the Resolved model. But in this between, how to deal with the case with Vdem/Vcfd in the range of [1,2]. Is there any volume fraction model can deal with this? Whether the tri-linear volume fraction model can deal with this? If could, is the tri-linear volume fraction can only be used for cubic cell (cell_x = cell_y = cell_z)?

Thank you!

Detian
2016.6.12