In this work, an osmotic flow analysis with cavitation in semipermeable membrane is presented. The membrane consists of two regions, namely liquid water and vapor. The hydraulic pressure on the water side is taken to be the same as that on the salt solution side. In the first region, water flow is approximated by Poiseuille flow. However, in the second region, we assume that cavitation takes place and the flow can be approximated by Knudsen flow. An overall permeability coefficient which includes the water and vapor permeabilities is derived. It is shown that the overall permeability is a function of the osmotic pressure. It is also shown that no cavitation will occur when the pressure difference in the water flow (first region) is equal to the osmotic pressure.

osmotic flow, cavitation in porous media, Poiseuille flow, Knudsen flow.