In order to investigate inlet bubble size distribution, gas phase concentration, and swirling intensity in the swirling flow field of a vane-type separator, both flow loop experiments and numerical studies have been conducted in this work. The bubble size distributions and fractions of local voids were determined using a Malvern RTsizer and electrical resistance tomography, respectively, while the numerical simulations were conducted by coupling the RNG k- εturbulent and mixture multiphase models. As a result, a suitable model for predicting the bubble size distribution parameters d 32 and d max was developed. In addition, the effects of inlet mixture flow rate, inlet void fraction, and liquid viscosity on the core size of the gas phase in the swirling flow field were determined, and the impact of the gas phase on swirling intensity was characterized using the swirling number. The obtained results can be used in designing vane-type separators for the crude oil extraction industry