Abstract
The transport of a colouring solute, driven by the buoyant displacement of microscopic suspended particles, and in the absence of net flow, is studied experimentally in a Hele Shaw cell. Initially, a sharp interface between a transparent fluid without particles and an underlying coloured suspension is obtained. From this situation, the suspended particles rise, carrying the solute in the form of a fingering instability across the interface, where a light transmission technique is used to measure the local solute concentration. This one attains an asymptotic value that increases with the solid fraction ϕ of suspended particles, and decreases with the distance to the interface. The solute mass discharge also increases with ϕ, always being relatively small (< 3%). The onset and development of the instability as the mechanism driving the transport of the solute is discussed.
Highlights
The flow and sedimentation of suspended granular particles occurs in many natural processes
The Hele-Shaw cell is composed of two Plexiglas plates (25 cm × 16 cm × 1.2 cm) screwed together, one has a groove in its inner face, in which an O-ring is housed to seal the interior of the cell once the fourteen screws are adjusted
We have studied the transport of a solute by buoyant suspended particles in a Hele-Shaw cell in the absence of net flow
Summary
The flow and sedimentation of suspended granular particles occurs in many natural processes. When suspended particles and a solute coexist, the presence of particles modifies the local constitutive properties (e.g., density, viscosity), which in turn affects significantly the transport of the solute [4]. This issue has been studied numerically and in lab experiments in cylindrical conduits and Hele-Shaw cells, and at different spatial scales, mainly for pressure-driven flows [5,6,7] with neutrally buoyant particles, or even including the effect of gravitational settling [8]
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