cell growth rate

nirupam

I am solving a CFD problem for a room using Fluent. I wish to reduce number of cells in my problem. When I increase the volume growth rate to reduce no. of cells problem of truncation error comes in. Somebody has suggested me that I may divide the single zone into multiple zones, keeping the volume growth rate low and abruptly changing the size of the cells, say by a factor of 2 to 3, at the interface boundary.

I wish to seek expert guidance on this, i.e. (1) what should be the volume growth rate in a hexahederal mesh within a single zone and (2) by what factor can I increase the cell size while moving from one zone to another zone.

thanks