Asymmetric swirling flows in composite pipe bends

When two bends are combined in a twisted S form, the outlet velocity has a nonuniform profile due to a secondary circulation. If this deformed flow is introduced into the next bend located downstream, an oscillatory or spiral type of secondary flow will occur in the downstream bend. In this paper, this type of flow is analyzed theoretically and experimentally. Three types of flow are considered: oscillatory swirling flow, spiral swirling flow, and suspended swirling flow. The results are confirmed by experimental data and compared with those available from earlier investigations.