Аннотация:The dynamics of a circular liquid lamella resulting from the collision of a water drop
with a small disc-like target was studied experimentally and theoretically. Such a type
of collision also acts as a model of drop impacts on plane surfaces in the absence
of liquid friction, and therefore for more widespread collisions of drops of inviscid
liquid with solid surfaces. We propose a simple model to describe the dynamics of
the lamella resulting from the drop impact and also predict the structure of the
liquid flow in the lamella. It is based on the observations that during the drop
collision with the target, the liquid is ejected at an approximately constant flow rate
with a velocity that significantly decreases in time. The resulting distributions of
velocities, local flow rates and film thickness in the lamella are calculated. Besides,
we have measured the distribution of the local Weber numbers by generating Machlike
rupture waves (we have called them Mach–Taylor waves) in the lamella, which
follows the Taylor theory of disintegration of fluid sheets. Unknown parameters of
the model are obtained from the comparison between the theoretical expression for
local Weber number and the experimental data. The time evolution of the lamella
diameter was obtained by numerical integration of the model. It was found that
during the lamella life, zones of metastability could be formed in the lamella. In
these zones a propagating rupture hole cannot be transported away by the flow and
it yields to destabilization. One metastability zone expands from the target towards
the external rim, and it is the opposite for the other one.