Levich Institute Special Seminar Announcement, 11/18/2005

Friday, 11/18/2005
2:00 PM
Steinman Hall, Room #1M-22
(Levich Institute Conference Room)

Professor Jean-Pierre Hulin
Laboratoire FAST
Universite de Paris - Orsay

"Buoyancy Driven Mixing in Long Tilted Tubes"


Gravity induced mixing of two miscible fluids in a long tube is studied experimentally as a function of the tilt angle from the vertical, the viscosity and the density contrast, using both light absorption and laser induced fluorescence techniques. The flow regimes display a transition from diffusive turbulent mixing for tubes close to vertical towards a laminar parallel counter flow of the two fluids for large tilt angles. This transition will be shown to be due to a segregation of the two fluids in the tube section induced by the transverse gravity component. At large tilt angles, the counterflow velocity is determined by viscous dissipation in the bulk of the flow and satisfies a scaling law reflecting a balance between buoyancy and viscosity. At low and medium tilt angles, the mixing process is controlled by a balance between buoyancy and inertia : the velocity of the displacement front of each fluid by the other will be shown to be directly related to the measured density contrast at the front. (Work in collaboration with T. Seon, B. Perrin, D. Salin and E.J. Hinch)