The separation of fluid-fluid mixtures is a major issue in various sectors. The liquid-liquid hydro-cyclone has a wide range of applications in various sectors due to its great efficiency in separating fluid mixtures, ease of installation, and low cost. In crude oil production, high water is consumed following the degrading of production quality, high processing costs, costs, and environmental impacts. Axial hydro cyclone is a tool for Downhole Oil/Water Separation (DOWS) in the petroleum production industry, but it has limitations. The main purpose of this work is to simulate the effect of compacting the conventional inline hydro cyclone with a converging-diverging nozzle on the oil/water dynamic flow and the separation process to resolve the high water cut problem. This study presents a three-dimensional simulation to compute fluid dynamics using the mixture multiphase and SST k-omega turbulence models for Reynolds numbers less than 66000. The operational flow variables are a mixture: flow rate (14, 28, and 56 m3/h) and oil/water ratio (15/85, 25/75, 30/70, and 35/65). Results indicate an enhancement in the axial and tangential velocity components by 15% and 50%, respectively, for the proposed design compared with the conventional cyclone. The oil separation efficiency for the new design is 89%, while for the conventional cyclone is 60%.
