convergence/ advise for permeability study

CFDnewbie

hi,

I'm intending to conduct permeability study through micropores using CFD. at a known inlet velocity i need to measure the pressure drop across my micropore specimen.

will like experts out there to advise on (1) what kind of convergence criteria or level should i set (1E-5??)? (2) how do i evaluate error in CFX? (i intend to do grid refinement as well)

any other kind of advise is greatly appreciated.

thanks in advance