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DY: Fachverband Dynamik und Statistische Physik

DY 40: Posters II

DY 40.7: Poster

Thursday, March 17, 2011, 17:00–19:00, P3

Onset of Instabilities in Cooled Binary Fluids — •Jan-Hendrik Trösemeier and Jürgen Vollmer — Max Planck Institute for Dynamics and Self-Organization, 37073 Göttingen

Slowly cooling a binary fluid into the miscibility gap induces concentration gradients in the direction perpendicular to an interface separating the coexisting phases. When these gradients are too large the system becomes unstable against formation of droplets and/or convection.

The evolution of the system can be described by an appropriately adapted version of model H [1], i.e. a modified Cahn-Hilliard equation for the nonlinear diffusion of concentration coupled to the Navier-Stokes equation. In this setting we investigate the onset of convective and diffusive instabilities. Linear stability theory provides the boundaries of the region with purely diffusive demixing, i.e. the threshold for the onset of nucleation [2] and for the onset of convection. Considering terms to quadratic order provides additional insight into the dynamics beyond the onset of stability.
[1] M.E. Cates, J. Vollmer, A. Wagner, & D. Vollmer, Phil. Trans. Roy. Soc. (Lond.) Ser. A 361 (2003) 793.
[2] J. Vollmer, J Chem Phys 129 (2008) 164502.