  Binary droplet collisions are of importance in a variety of practical
applications comprising dispersed two-phase flows. The background of our
research is the prediction of properties of particulate products formed in
spray processes. To gain a more thorough understanding of the elementary
sub-processes inside a spray, experiments and direct numerical simulations of
binary droplet collisions are used. The aim of these investigations is to
develop semi-analytical descriptions for the outcome of droplet collisions.
Such collision models can then be employed as closure terms for scale-reduced
simulations. In the present work we focus on the collision of droplets of
different liquids. These kinds of collisions take place in every spray drying
process when droplets with different solids contents collide in recirculation
zones. A new experimental method has been developed allowing for high spatial
and time resolved recordings via Laser-induced fluorescence. The results
obtained with the proposed method will be compared with DNS simulations. The
viscosities of the droplets are different whereas the interfacial tension and
density are equal. The liquids are miscible and no surface tension is acting
between the two liquids. Our intention is to discover elementary phenomena
caused by the viscosity ratio of the droplets.
