Numerical simulations of viscoelastic particle migration in a microchannel with triangular cross-section

Area of Science:

• Fluid Dynamics
• Microfluidics
• Rheology

Background:

• Particle migration in microchannels is crucial for microfluidic applications.
• Viscoelastic fluid behavior, particularly the second normal stress difference, significantly impacts particle dynamics.
• Understanding these effects is key to designing advanced microfluidic devices.

Purpose of the Study:

• To investigate spherical particle migration in a triangular microchannel filled with viscoelastic fluid.
• To analyze the influence of the second normal stress difference and secondary flows on particle trajectories.
• To explore the potential for designing size-based separation devices.

Main Methods:

• Direct numerical simulations were employed under inertialess conditions.
• Two constitutive equations modeled the viscoelastic fluid, varying the second normal stress difference.
• Particle trajectories were analyzed across a range of Weissenberg numbers and confinement ratios.

Main Results:

• Without significant second normal stress difference, particles migrate to the centerline or nearest wall.
• Relevant second normal stress difference induces secondary flows, creating complex particle dynamics and additional equilibrium positions.
• Channel centerline stability is inverted, driving particles to corners or recirculation zones.

Conclusions:

• The second normal stress difference dramatically alters particle migration in triangular microchannels.
• Complex secondary flows lead to new equilibrium positions and particle trapping.
• The observed centerline instability offers opportunities for developing efficient size-based microfluidic separation technologies.