Reverse osmosis has been emerged as one of the most used technologies to desalinate water. Present
study investigates steady three dimensional flows and mass transfer in the feed channel for a brackish
water desalination process by using reverse osmosis membranes. Flow and the mass transfer in the feed
channel are governed by Navier–Stokes and mass transport equations. The channel containing cylindrical
shaped spacers is bounded by membranes. Computational fluid dynamics simulations are conducted for
the range of the Reynolds number 100 6 Re 6 800. The laminar flow model is employed when Re ¼ 100
while SST k—x turbulence model is employed when Re P 400. Membranes are treated as a functional
surface where water flux is determined from local concentration and pressure by employing the
solution-diffusion model of the reverse osmosis. The influence of three dimensional flow structures on
the concentration polarization and the potential fouling over the membrane surface is discussed. It is
shown that high water flux regions and low concentration regions coincide with low wall shear regions.
The high intensity concentration polarization sites correlates directly with the high potential fouling
sites. Spacers enhance the membrane performance and they help to alleviate concentration polarization.