Waterhammer in Non-Rigid Pipes: Precursor Waves and Mechanical Damping

When a pipe can move, waterhammer effects are altered by the existence of precursor waves, i.e. longitudinal elastic strain waves in the pipe walls, modified by the presence of the fluid. Theory and experiment show that precursor waves cannot be ignored, if the effect of longitudinal strain is to be considered; conventional waterhammer theory is thus unsatisfactory. Flexural waves may also occur. It was found experimentally that pipe motion caused mechanical damping of the waterhammer–greater than the viscous damping. Viscoelastic piping also gave rise to strong mechanical damping, even without pipe motion.