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When the Joukowsky Equation Does Not Predict Maximum Water Hammer Pressures

[+] Author Affiliations
Trey W. Walters

Applied Flow Technology, Colorado Springs, CO

Robert A. Leishear

Leishear Engineering, LLC, Aiken, SC

Paper No. PVP2018-84050, pp. V004T04A018; 10 pages
  • ASME 2018 Pressure Vessels and Piping Conference
  • Volume 4: Fluid-Structure Interaction
  • Prague, Czech Republic, July 15–20, 2018
  • Conference Sponsors: Pressure Vessels and Piping Division
  • ISBN: 978-0-7918-5165-4
  • Copyright © 2018 by ASME


The Joukowsky equation has been used as a first approximation for more than a century to estimate water hammer pressure surges. However, this practice may provide incorrect, non-conservative, pressure calculations under several conditions. These conditions are typically described throughout fluid transient text books, but a consolidation of these issues in a brief paper seems warranted to prevent calculation errors in practice and to also provide a brief understanding of the limits and complexities of water hammer equations.

To this end, various issues are discussed here that result in the calculation of pressures greater than those predicted by the Joukowsky equation. These conditions include reflected waves at tees, changes in piping diameter, and changes in pipe wall material, as well as frictional effects referred to as line pack, and the effects due to the collapse of vapor pockets. In short, the fundamental goal here is to alert practicing engineers of the cautions that should be applied when using the Joukowsky equation as a first approximation of fluid transient pressures.

Copyright © 2018 by ASME
Topics: Water hammer



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