Numerical simulations of a compact inline gas–liquid separator: A comparison between RANS and a hybrid LES-RANS approach

Two computational fluid dynamics approaches are adopted to simulate the single-phase and the gas–liquid flow field generated by a compact inline separator based on the generation of a swirling flow. The results of a detached eddy simulation, DES, combining a large eddy approach with the realizable k-ε turbulence model were compared to RANS results and experimental data from the literature. The DES better replicates the experimentally observed velocity fluctuations, pressure drop, gas distribution and gas–liquid separation profiles, with respect to the RANS approach. A population balance equation was solved in the flow fields produced by the two simulation approaches, and important differences were found in the mean bubble characteristic diameter spatial distributions, possibly due to the different predictions of the local values of turbulent dissipation rates, which affect the bubble breakup and coalescence phenomena.