Incipient motion of solitary air pockets in a rectangular pipe
2013 (English)In: Journal of Applied Water Engineering and Research, Vol. 1, no 1, 58-68 p.Article in journal (Refereed) Published
The operation of bottom-outlet gates often gives rise to entrained air in the form of air pockets in the conduit under full-flow conditions. If unexpectedly released, it would cause problems for both personnel security and operational function. The present study addresses, through experimentation, the incipient movement of solitary air pockets in a rectangular pipe. A horizontal pipe and a 9.6° downward-inclined pipe are examined. The cross-section of the pipe measures 200 mm (width) by 250 mm (height). As distinct from a circular pipe, an air pocket in the rectangular pipe exhibits, at its incipient motion, a shape that depends mainly on factors such as the sloping angle of the pipe, cross-sectional location of the air pocket and its volume. These factors also determine the critical velocity of the air pocket. The experiments have shown that only small air pockets can exist under the roof. The corner is a cross-sectionally equilibrium position for larger air pockets. The air pocket in the corner position takes the shape of an elongated rectangular prism in the horizontal pipe and a triangular prism in the sloping one. When compared with a circular pipe, the critical velocity of air pockets in the rectangular pipe is lower if the pipe is horizontal and higher if it has a downward inclination.
Place, publisher, year, edition, pages
Taylor & Francis, 2013. Vol. 1, no 1, 58-68 p.
bottom outlet, rectangular conduit, air entrainment, incipient motion, critical velocity, experiments
IdentifiersURN: urn:nbn:se:kth:diva-141191OAI: oai:DiVA.org:kth-141191DiVA: diva2:695567
QC 201402112014-02-112014-02-112014-02-11Bibliographically approved