CFD Modeling of Two-Phase Flow (Oil/Air) with and without Rotary Mixer Inside a Vertical Pipe for Upstream of Multiphase Pump

The multiphase pump is essential for transporting oil well mixtures, but it is sensitive to multiphase flow regimes. This study investigates using rotary mixers upstream of a multiphase pump to ensure a homogeneous gas–liquid mixture, preventing gas lock and enhancing pump performance. Computational Fluid Dynamics (CFD) simulations in ANSYS Fluent examine air-oil mixing in a vertical pipe with varying gas volume fractions (GVF) (5–20%) and mixer speeds (1500–3500 rpm). Results show that the rotary mixer improves gas–liquid homogeneity significantly, with power requirements approximately 2.8 times higher than without the mixer due to increased pressure drop. Higher GVF slightly enhances mixing efficiency, while reduced mixer speed further improves it by lowering turbulence, aiding air dispersion. Notably, reducing speed from 3500 to 1500 rpm raised the uniformity index (UI) from 45.9% to 58.9% before the mixer and from 65 to 73% after, highlighting speed optimization’s impact on mixing efficiency. These findings suggest that positioning the mixer near the pump inlet (around 4 cm) can enhance performance and prevent operational issues in multiphase flow applications.