Abstract— <p>The use of swirling fluid flows in the working area of equipment contributes to a significant intensification of various technological processes. Consequently, vortex-type devices represent promising and highly efficient equipment, necessitating their thorough investigation. The performance of a gas–liquid vortex device is influenced by the droplet size distribution, and since several distinct zones can be identified within the device, it is essential to determine the droplet size distribution for each of them. This study analyzes the droplet formation mechanism resulting from the secondary breakup of the separated liquid film on the surface of a vane-type swirler in the transverse separation zone. By evaluating the influence of individual factors on the breakup process of jets, droplets, and liquid films, it is demonstrated that the experimental approach to studying the secondary breakup of the separated liquid film is the only justified method. It is established that using the relationship between droplet diameter and jet diameter, along with an empirical correlation derived from generalized data on the mean droplet diameters of low-viscosity liquids formed during the breakup of a separated liquid film, it is possible to estimate, in the first approximation, the probability of secondary breakup. Based on experimental data examining the droplet size distribution at the outlet of a tangent swirler in a vortex device, it is found that the modal droplet size increased by a factor of 6.3 and the droplet size distribution follows a lognormal distribution. This indicates a strong influence of random factors governing the interaction and breakup processes in the transverse separation zone.</p>