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Formula for water hammer calculation

asked Feb 28, 2014 in Engineering by RichS29 (4,320 points)
Is there any approximation formulas for calculating water hammer?

1 Answer

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answered Mar 2, 2014 by odadmin (21,030 points)

The execc pressure due to water hammer can be calculated by the Joukowsky equation:

dP = Zh × Q


  •  dP is overpressurization, Pa;
  • Q is the volumetric flow, m3/s;
  • Zh is the hydraulic impedance, expressed in kg/m4/s.

Hydraulic impedance Zh defined by:

Z_h = \frac{\sqrt{\rho \, B_\mathit{eff}}}{A}


  • ρ the density of the liquid, kg/m3;
  • A cross sectional area of the pipe, m2;
  • Beff effective modulus of compressibility of the liquid in the pipe, expressed in Pa.