Air entrapped in gravity pipeline systems

Abstract

Large air pockets entrapped in pipelines reduce the effective pipe cross-section, causing an increase in energy loss. Air accumulates at high points along the line throttling the flow and may ultimately cause a complete conduit blockage. Despite researchers having studied these phenomena, air binding is still commonly found in aqueducts, since there is a lack of understanding on the movement of air bubbles and pockets in closed conduits. This study proposes a simplistic method to predict the movement of air bubbles and pockets in downward sloping pipes which can be used either to solve air binding in existing pipelines or to prevent its occurrence in new pipelines from design stage. An experimental investigation was conducted to validate the proposed analytical method. The analysis revealed that problems related with entrained air are commonly unnoticed until a major operational failure such as an increase in head losses, violent blowbacks, or overflowing structures occurs.

Keywords:

• Air binding
• air pockets
• downward sloping pipes
• energy losses
• entrapped air
• pipeline

Acknowledgements

The authors acknowledge the helpful comments of Prof. Hubert Chanson, University of Queensland, Australia.

Additional information

Notes on contributors

Carlos A. Gonzalez

IAHR Member, [email protected]