Stationary motion of a self gravitating toroidal incompressible liquid   layer
  We consider an incompressible fluid contained in a toroidal stratum which is only subjected to Newtonian self-attraction. Under the assumption of infinitesimal tickness of the stratum we show the existence of stationary motions during which the stratum is approximatly a round torus (with radii r, R and R>>r) that rotates around its axis and at the same time rolls on itself. Therefore each particle of the stratum describes an helix-like trajectory around the circumference of radius R that connects the centers of the cross sections of the torus. 
Giorgio Fusco, Piero Negrini, Waldyr M. Oliva
math-ph math.DS math.MP