A　2D　finite　element　model　was　developed　to　describe　the　forward　osmosis　(FO)　process　under　steady-state　conditions.　Two　approaches　are　applied　to　study　forward　water　and　reverse　salt　fluxes.　In　the　first　approach,　the　mathematical　equations　are　formulated　based　on　the　bulk　concentration　differences　between　the　feed　and　the　draw　solutions.　Transfer　resistances　arising　from　internal　concentration　polarization,　external　concentration　polarization　and　reverse　salt　flux　are　considered.　The　second　approach　is　based　on　a　complete　computational　fluid　dynamic　(CFD)　model,　both　the　constrictivity　factor　and　the　sorption　coefficient　are　considered　to　enhance　the　accuracy　of　prediction.　The　CFD　model　provides　a　more　realistic　representation　of　the　FO　process　than　the　first　simple　approach.　Our　CFD　model　shows　that　the　concentration　profile　within　the　membrane　support　layer　is　a　result　of　the　coupled　interaction　between　the　dilutive　internal　concentration　polarization　and　the　reverse　solute　diffusion　from　the　draw.　Increasing　porosity　or　decreasing　tortuosity　is　not　always　desirable　since　it　will　also　increase　reverse　salt　flux.　Forward　water　and　reverse　salt　fluxes　are　independent　on　tortuosity　or　porosity　alone,　but　dependent　on　their　ratios.　This　work　offers　significant　insights　into　developing　high　performance　FO　membranes　with　suitable　porosity　and　tortuosity,　thereby　reducing　internal　concentration　polarization　and　reverse　salt　diffusion.　©　2020　Elsevier　B.V.