Hydrodynamic interaction in confined geometries

This article gives an overview of recent theoretical and experimental findings concerning the hydrodynamic interaction between liquid-embedded particles in various confined geometries. A simple unifying description emerges, which accounts for the various findings based on the effect of confinement on conserved fields of the embedding liquid. It shows, in particular, that the hydrodynamic interaction under confinement remains long-ranged, decaying algebraically with inter-particle distance, except for the case of confinement in a rigid linear channel.