RANS MODELLING OF A SWIRLING FLOW INTERACTING WITH A CONICAL BLUFF BODY

Phase separation using swirling flows is a technique used in inline separators. In the present study, an existing separator device generates a swirling flow which interacts with a conical hollow bluff body to where the air phase is collect. We use the commercial CFD code Fluent to simulate and investigate the characteristics of single-phase turbulent swirling flow interaction with a solid conical bluff body on a laboratory-scale model. The simulation work employed different RANS turbulence models; namely, RNG k-epsilon, SST k-omega and RSM. A constant velocity was imposed at the inlet of the computational domain while a constant pressure was prescribed at the outlet. The results are validated against experimental measurements. The effect of flow rate was investigated. The resulting flow is investigated around the bluff body and within the whole outlet pipe downstream of the swirl generator because the separation depends strongly on the flow behavior in this extended region. The core flow reversal persists up to the bluff body at high flow rates. This is significant in terms of phase behavior in the separation application in addition to the loads on the bluff body. The profiles of the tangential velocity corresponded to a Rankine vortex swirling flow type along the whole axial distance. The results show that the RSM gives the best accuracy among the three RANS models compared with the experimental data. The rate of swirl decay decreases as the flow rate increases. For the lowest flow rate, the swirl decay followed an exponential trend which becomes almost linear for the highest flow rate considered. At low swirl intensities, the pressure peaks are observed on the bluff body apex while, at high swirl intensities, the reversal flow generates the lowest pressure at the centerline affecting the cone as well.