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,