Experimental Investigation of Droplet-Droplet Interactions

Abstract

Shadowgraphy is an established imaging measurement method, allowing in particular to determine droplet velocity and diameter distributions. One advantage of Shadowgraphy compared to other non-intrusive measurement methods is its ability to directly observe collision and coalescence processes. As the expected collision probability in many practical two-phase flows is moderate and the acquisition frequency of the Shadowgraphy system is limited, this measurement method must be optimized for the investigation of droplet-droplet interactions. In this work it is shown that Shadowgraphy can be indeed applied to a quantitative investigation of collision events. For this purpose the software (DaVis 7.2 from LaVision) has been considerably improved with the help of its built-in macro language, allowing an automatic analysis of the measurement results. The resulting experimental procedure has been tested using measurements in a two-phase wind tunnel. Corresponding results are compared with available theoretical predictions.