ABSTRACT
Swirling flow problems are associated with intake structures of different types which are prone to vortex formation. Problems arise from air entrainment and swirl intrusion at the transition from free surface to pressure flow conditions. In most of the cases, asymmetry in the approach flow field due to geometrical conditions causes vortex formation, but there are also special hydraulic processes responsible for swirl production in geometrically symmetric installations, even with an ideal velocity distribution in the approach flow. Vortex formation must be tolerated, provided that operational problems due to dangerous air and swirl entrainment can be eliminated. Stable vortices are characterized by a steady production of swirl in the approach flow field. Regarding the entrained swirl, with otherwise equal conditions the indicated swirl angle is independent of the flow rate and also independent of the occurrence of air ingestion. The chapter also presents an overview of the key concepts discussed in this book.
