Author(s): Chang Lin; Chia Hsun Lu; Ting Liu; James Yang
Linked Author(s): James Yang
Keywords: Ir pocket; High-speed particle image velocimetry; Shear layer; Interface; Horizontal pipe
Abstract: The presence of air pockets in a pipeline system often causes reduction in its efficiency and shortens its service life. Potential safety hazards arise in some cases from air blowout or blowback. It is thus of interest to examine the water flow field at air pockets and the feature of water-air interface. This study applied flow visualization technique and high-speed particle image velocimetry (HSPIV) to investigate characteristics of flow fields at stationary solitary air pockets in a fully-developed horizontal pipe flow. Experiments were performed in a Plexiglas pipe having an inner diameter of 9. 6 cm, with Titanium dioxide powder as tracer for measurements. The results show that a horseshoe vortex and reverse flow pattern existed both up-and downstream of the air pockets. A deformable air pocket in the turbulent flow caused streamwisely a random movement of both stagnation and separation points around their mean positions. An intermittent flow re-attachment occurred also downstream of the mean separation point. The air-water interface was not stationary but moved with the adjacent water flow.
Year: 2014