Fluid circulation and solute distribution in a binary fluid mixture: Self-organization under osmosedimentation

In this work a theoretical analysis of the osmosedimentation process is presented. We investigate the role played by small-density non-uniformities in inducing fluid circulation and mass transport in a viscous binary mixture under a strong centrifugal field. We find that a Boussinesq term considered in the momentum equation is of fundamental importance in the convection–diffusion process. The strong centrifugal forces that develop in the solution as a result of the small-density inhomogeneities are responsible for the emergence of a dissipative structure: the fluid can show a complex arrangement of convection cells leading to solute mass redistribution. Time evolution of the cell patterns (convection cells and solution concentration cells) during the first stages of the osmosedimentation process is presented. The results are significant as a clue for understanding pattern formation in systems investigated in the laboratory.