(300e) Multi-Length Dynamics for Droplet Motion in a Microfluidic Cross-Junction

In this work, we investigate computationally the transient deformation of
a droplet flowing along the centerline of a microfluidic cross-junction
device. We consider naturally buoyant droplets with size smaller than
the cross-section of the square channels comprising the cross-junction,
and investigate low-to-strong flow rates and a wide range of fluids
viscosity ratio.  Our investigation shows that the intersecting flows at
the cross-junction act like a constriction, and thus the droplet shows
a rich deformation behavior as it passes through the micro-junction.
Our work highlights the three-dimensional effects of the asymmetric
microfluidic geometry on the droplet deformation, and the different
effects of the viscosity ratio on the droplet's overall length scales and
the local length scales at the droplet edges.  The large edge curvatures
and thus the small local length scales developed transiently, especially
at the tail of low-viscosity droplets, reveal that the current
investigation is a multi-length interfacial dynamics problem.