Seminar Ko Okumura

Ochanomizu University

On the bubble breakup in confined geometries

Formation of a fluid drop has been extensively studied as a typical case
of the singular dynamics widely observed in nature. The singular
dynamics is often self-similar: shape at different times collapsing on a
master curve after rescaling. The self-similar dynamics has been
categorized as either universal or non-universal: the master curve is
independent from or dependent on the length scales that set the initial
boundary conditions, as if memory is erased or retained. In the
previously known cases, where the axismmetry is maintained, only a
single length scale is available for the boundary conditions, a tube
radius, and, thus, there is no possibility of partial memory. Here, we
confined the system to break the axismmetry to introduce three length
scales, revealing a third category of incomplete universality: the
master curve is dependent on the smallest scale but independent on the
other two scales. Affecting of only the smallest length scale on the
master curve underscores the importance of scale separation for the
emergence of universality: near the singularity physics at small scales
becomes important. We also discuss the continuous generation of bubbles
in a different confined geometry, in which Tate’s law for the breakup
condition, expressing a capillary-gravity balance, is violated due to
viscosity. All results are convincingly shown by clear experimental data.