title: Spontaneous Core Rotation in Ferrofluid Pipe Flow.
abstract: Ferrofluid flow along a tube of radius R in a constant axial magnetic field is revisited. Our analytical solution and numerical simulations predict a transition from an initially axial flow to a steady swirling one. The swirl dynamo arises above some critical pressure drop and magnetic field strength. The new flow pattern consists of two phases of different symmetry: The flow in the core resembles Poiseuille flow in a rotating tube of the radius r_{*}<R, where each fluid element moves along a screw path, and the annular layer of the thickness R-r_{*}, where the flow remains purely axial. These phases are separated by a thin domain wall. The swirl appearance is accompanied with a sharp increase in the flow rate that might serve for the detection of the swirling instability.
authors.affiliation: Max Planck Institute for Dynamics and Self-Organization, 37077 Göttingen, Germany.
authors.forename: Alexei
authors.initials: A
authors.lastname: Krekhov
authors.affiliation: Department of Mechanical Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel.
authors.forename: Mark
authors.initials: M
authors.lastname: Shliomis