Transport dynamics of isotropic and anisotropic microparticles in inertio-elastic vortex flows

Spherical particles and fibers are common in biological and environmental flows and their transport dynamics are strongly affected by interaction with the flow structure. Here we focus on the response of spherical and elongated model particles to a single vortex flow field. For this purpose, we use a microfluidic cross-slot geometry, to generate a well characterized, stationary, three-dimensional streamwise vortex at moderate Reynolds number. Our experimental results, supported with numerical simulations, show that as the diameter of the spherical particles is increased, they are progressively expelled from the vortex core. This trend is further enhanced when the fluid's elasticity is slightly increased. Initial observations also indicate complex interactions between fibers and a vortical flow field, depending on fiber size and initial orientation. This work provides a fundamental contribution to the study of particle–flow interactions and for the improvement of particle sorting and transport techniques with possible environmental, industrial, and pharmaceutical applications.