Stratification-induced reorientation of disk settling through ambient density transition

Area of Science:

• Fluid dynamics
• Particle transport
• Geophysics

Background:

• Gravity-driven settling is a fundamental particle transport process.
• Natural fluids often exhibit density stratification, affecting particle dynamics.
• Previous studies acknowledged stratification's effect on spheres and aggregates, but not non-spherical particles like disks.

Purpose of the Study:

• To investigate the influence of particle shape on settling dynamics in density-stratified fluids.
• To experimentally demonstrate how continuous density transitions modify disk settling velocity and orientation.

Main Methods:

• Experimental investigation of disk settling dynamics.
• Utilizing a two-layer ambient fluid with a continuous density transition.
• Analysis of particle orientation and settling velocity in a low Reynolds number regime.

Main Results:

• Disk settling dynamics are more complex than spheres or aggregates.
• Disks undergo five distinct settling phases with orientation shifts from horizontal to vertical.
• Two local minimum settling velocities were observed within the density transition layer.
• Settling behavior is dependent on density differences, stratification strength, and transition layer thickness.

Conclusions:

• Particle shape critically influences settling behavior in stratified fluids.
• Density stratification introduces complex dynamics, including multi-phase settling and velocity variations, for non-spherical particles.
• Understanding these dynamics is crucial for accurate modeling of particle transport in natural and engineered systems.