Evaluation of the impact parameter in droplet-droplet collision experiments by the aliasing method

Abstract

A new method has been developed whereby the borders between the various collision outcome regimes for droplet/droplet impact can be determined. This method, called the aliasing method, is based on a small frequency shift between the droplet generating nozzles. The droplet collision outcomes, for a fixed Weber number, can then be visually followed continuously for the whole range of impact parameters during one collision experiment. The impact parameter can be evaluated numerically using the frequency shift between the droplet trains without using geometric image evaluations of the video recordings. This frequency shift and temporal aliasing method makes it possible to determine the impact parameter significantly more accurately and efficiently, compared to previous methods. The aliasing evaluation method for determining the impact parameter can also be used together with the modulation technique in order to extend the range of We numbers investigated. The new method has been validated with experiments using the water/air system.