If the Reynolds number is small enough (Re<<1), then two fluids can flow in parallel in direct contact, exchanging momentum and species only by diffusion. If the interface is
stable, then this system can be used as a filter. In this problem, the flow fields in both fluids are found.
2008 Carlos Martinez and Matthew John M. Krane
Difficulty level: Junior; Solution time: 1 hour; Reference: J. P. Brody,et al., "Biotechnology at Low Reynolds Numbers," Biophysical Journal., v.719, pp. 3430-3441,