Droplet clustering in sprays

In this contribution, the spatial particle distribution in sprays of different atomizers is analyzed. Steady and unsteady particle structures are identified by evaluating the interparticle arrival time statistics at a certain position, which is the time increment between two succeeding particles. In addition to its characteristics of size and velocity, each particle exhibits an individual interparticle arrival time that is used to identify unsteady characteristics in the flow. Unsteadiness in sprays is thereby of interest for several reasons and in several applications, for example, in the combustion industry. A typical example of an unsteady spray behaviour is droplet clustering which can be caused, for example, by pulsating liquid disintegration procedures or particle interaction with large-scale eddy structures in the gas. The aim of the investigation is the analysis of such unsteady spray conditions. The evaluation of spray unsteadiness is done by means of point wise and time resolved PDA measurements in the spray of a pressure and twin-fluid atomizer, respectively.