Experimental study of a buoyancy-driven instability of a miscible horizontal displacement in a Hele-Shaw cell

Abstract

When a given fluid displaces another less viscous miscible one in a horizontal Hele- Shaw cell, the displacement is stable from the viscous point of view. Nevertheless, thin stripes perpendicular to the moving interface can be observed in the mixing zone between the fluids both in rectilinear and radial displacements. This instability is due to buoyancy effects within the gap of the cell which develop because of an unstable density stratification associated with the underlying concentration profile. To characterize this buoyancy-driven instability and the related striped pattern, we perform a parametric experimental study of viscously stable miscible displacements in a horizontal Hele-Shaw cell with radial injection. We analyze the influence of the flow rate, the thickness of the gap, and the relative physical fluid properties on the development and characteristics of the instability. © 2014 AIP Publishing LLC.