Computational modeling on slug flow phenomenon in inverted siphon and improving its performance

Abstract

Slug flow is one of the flow patterns that occur in transmission systems containing two‐phase flow. Large air bubbles trapped in these systems block the flow and expose the structure to undesirable pressures and sharp fluctuations. In this research, numerical modeling has been performed using CFD technique in OpenFOAM software by InterFoam solver. Pressure fluctuations and their magnitude induced by slug flow in inverted siphon have destructive effects on the structure life. Combining the loads exerted by the pressure fluctuations induced on the structures with other loads may exceed the bearing loads of structure. In the inverted siphon, placing the ribs to reduce the damages exerted by slug flow were investigated. Different placements of ribs with different heights on the sloping parts of inverted siphon were modeled numerically. Study of flow characteristics showed that d/Hc ratio (d and Hc represent the rib height and duct height, respectively) can greatly balance the negative pressures and also improve the average pressures in the structure. The results showed that the use of ribs, the probability of forming slugs with pressure drop and severe fluctuations decreased and the maximum and minimum pressures improved about 25% and 20%, respectively.