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# Formula for water hammer calculation

Is there any approximation formulas for calculating water hammer?

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

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

dP = Zh × Q

Where:

•  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:

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

Where:

• 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.