title: Fluid mixing from viscous fingering.
abstract: Mixing efficiency at low Reynolds numbers can be enhanced by exploiting hydrodynamic instabilities that induce heterogeneity and disorder in the flow. The unstable displacement of fluids with different viscosities, or viscous fingering, provides a powerful mechanism to increase fluid-fluid interfacial area and enhance mixing. Here we describe the dissipative structure of miscible viscous fingering, and propose a two-equation model for the scalar variance and its dissipation rate. Our analysis predicts the optimum range of viscosity contrasts that, for a given Péclet number, maximizes interfacial area and minimizes mixing time. In the spirit of turbulence modeling, the proposed two-equation model permits upscaling dissipation due to fingering at unresolved scales.
authors.affiliation: Massachusetts Institute of Technology, 77 Massachusetts Ave, Building 48-319, Cambridge, Massachusetts 02139, USA.
authors.forename: Birendra
authors.initials: B
authors.lastname: Jha
authors.forename: Luis
authors.initials: L
authors.lastname: Cueto-Felgueroso
authors.forename: Ruben
authors.initials: R
authors.lastname: Juanes
mesh_terms: D057446:Hydrodynamics; D008962:Models, Theoretical; D017711:Nonlinear Dynamics; D012212:Rheology / Q000379:methods*; D013997:Time Factors; D014783:Viscosity