Influences of binary drop collisions on droplet spectra

Highly concentrated droplet-laden two-phase flows occur in many technical applications, such as fuel injection in internal combustion engines, and in chemical reactors. Mechanical interactions of the droplets by collisions represent an important elementary phenomenon in zones of high spatial droplet concentration and large relative velocities of the droplets. The stable or unstable interactions modify the spectra of drop velocity and size and, therefore, the heat and mass exchange characteristics of the drop ensemble. Modelling of highly concentrated, droplet-laden two-phase flows, which is indispensable for an efficient layout of technical apparatus, must therefore account for the collisional interaction of the droplets. In the literature we find only marginal information about the stability of drop collisions, and in particular about the production of new (satellite) droplets after unstable collisions, so that the modelling mentioned is only partly possible to date. The present project fills this gap by experimental investigations on unstable binary droplet collisions and on the drop ensembles they produce. Non-Newtonian fluids are included in the experiments.