Distribution characteristics of non-Newtonian fluid swirling flow field in a vane-type separator

Most of the fluids encountered in the oil and gas exploitation process exhibit non-Newtonian fluid characteristics, which presents new challenges for the treatment of produced liquid. In this paper, the Eulerian multiphase model and the power law model were coupled to simulate the distribution characteristics of non-Newtonian fluid swirling flow fields in a vane-type separator. Larger oil droplets are able to migrate to the pipe center at relatively weak vortex intensities, which helps to accelerate the formation of the oil core. Due to the rapid decay of the vortex strength, the tangential velocity of the oil droplets drops more rapidly than that of the axial component, thereby reducing the axial energy loss. As the volume fractions of inlet oil increase, the oil core becomes more pronounced, but the convergence of the oil phase gets worse. During the migration, the interaction between dense oil droplets increases the viscosity of the non-Newtonian fluid and decreases the tangential velocity, leading to a maximum apparent viscosity at the center of the pipe. A higher vortex intensity tends to stabilize the vortex core, whilst higher flow velocities, which increases rotational velocities at the exit of the deflection section, deforms the vortex more severely. Moreover, higher inlet flow velocities contribute to better convergence of the oil cores. All these factors are important to better understand the smooth characteristics of non-Newtonian fluids and to provide a theoretical basis for future design and optimization of efficient separators.