Water hammer (wave speed)


Water hammer (or, more generally, fluid hammer) is a pressure surge or wave caused when a fluid (usually a liquid but sometimes also a gas) in motion is forced to stop or change direction suddenly (momentum change). A water hammer commonly occurs when a valve closes suddenly at an end of a pipeline system, and a pressure wave propagates in the pipe. It is also called hydraulic shock. The wave speed due to the peak pressure, if the valve is closed abruptly, depends on the fluid compressibility

Related formulas


α0Wave speed at the peak pressure (m/s)
KBulk modulus of elasticity of the fluid (Pa)
ρDensity of the fluid (kg*m-3)
Vfluid's velocity (m/s)
aWave speed (m/s)
EElastic modulus of the pipe (Pa)
DInternal pipe diameter (m)
tPipe wall thickness (m)
cParameter due to system pipe-constraint condition on wave speed (dimensionless)