  In liquid spray applications, the sprays are often created by the formation
and destabilization of a liquid sheet or jet. The disadvantage of such
atomization processes is that the breakup is often highly irregular, causing a
broad distribution of droplet sizes. As these sizes are controlled by the
ligament corrugation and size, a monodisperse spray should consist of ligaments
that are both smooth and of equal size. A straightforward way of creating
smooth and equally sized ligaments is by droplet impact on a mesh. In this work
we show that this approach does however not produce monodisperse droplets, but
instead the droplet size distribution is very broad, with a large number of
small satellite drops. We demonstrate that the fragmentation is controlled by a
jet instability, where initial perturbations caused by the injection process
result in long-wavelength disturbances that determine the final ligament
breakup. During destabilization the crests of these disturbances are connected
by thin ligaments which are the leading cause of the large number of small
droplets. A secondary coalescence process, due to small relative velocities
between droplets, partly masks this effect by reducing the amount of small
droplets. Of the many parameters in this system, we describe the effect of
varying the mesh size, mesh rigidity, impact velocity, wetting properties,
keeping the liquid properties the same by focusing on water droplets only. We
further perform Lattice Boltzmann modeling of the impact process that
reproduces key features seen in the experimental data.
