Evidence of a cyclonic regime in a precessing cylindrical container
  We report experimental observations obtained by particule image velocimetry (PIV) of the behavior of a flow driven by rotation and precession of a cylindrical container. Various hydrodynamical regimes are identified according to the value of the control parameter which is the ratio of the precession frequency to the rotation frequency. In particular when this parameter is increased from small values, we have observed an induced differential rotation followed by the apparition of permanent cyclonic vortices. 
W.Mouhali, T.Lehner, J.L\'eorat, R.Vitry
physics.flu-dyn