Where does water hammer collide?

In hydraulics, water hammer is the pressure surge that races through a pipe when a moving column of liquid is suddenly decelerated, as when a valve slams shut: the liquid's momentum is converted into a steep rise in pressure that travels back and forth as a wave and can shake or burst pipework. McQueen's 1932 Water hammer and surge tanks treats the surge together with the surge tanks and air chambers used to absorb it, and Ghidaoui and colleagues' 2005 A review of water hammer theory and practice surveys the modern transient-flow theory. The referent is a transient pressure wave in a closed conduit, described by a pressure rise and a wave speed, unrelated to a clinical pulse beyond the shared image of a sharp knock.[1][2]

Unit

The transient pressure rise and wave speed in a closed conduit

Recovery means

Not applicable

Measured by

Predicted from the Joukowsky relation and recorded with pressure transducers during rapid valve closure

In cardiology the water-hammer, or Corrigan, pulse is a physical sign: an arterial pulse that rises abruptly and then collapses just as quickly, felt most clearly in aortic regurgitation, where blood leaks back through the valve so a large stroke volume is followed by rapid runoff. Palfrey's 1952 Auscultation of the Corrigan or water-hammer pulse describes how the sign is elicited and heard. The name was borrowed from a Victorian toy that knocked when inverted, but the referent is a pulse-waveform sign of valve disease, not a pressure wave in plumbing.[3]

Unit

The shape and amplitude of the arterial pulse waveform across a heartbeat

Recovery means

The sign recedes when the underlying aortic valve lesion is corrected

Measured by

Elicited by palpation with the arm raised and characterised on the arterial pressure tracing