Prescribing the motion of a set of particles in a 3D perfect fluid
  We establish a result concerning the so-called Lagrangian controllability of the Euler equation for incompressible perfect fluids in dimension 3. More precisely we consider a connected bounded domain of R^3 and two smooth contractible sets of fluid particles, surrounding the same volume. We prove that given any initial velocity field, one can find a boundary control and a time interval such that the corresponding solution of the Euler equation makes the first of the two sets approximately reach the second one. 
Olivier Glass (CEREMADE), Thierry Horsin (LM-Versailles)
math.AP cs.SY math.OC