The effect of axial tube elasticity on water hammer pressure

Pressure surge generation due to instantaneous stopping of liquid flows in a finite straight tube was investigated both theoretically and experimentally. As a result of longitudinal deformation and displacement of the tube, waterhammer pressure varies with time and momentarily exceeds the value predicted by Joukowski. An elastic tube with concentrated masses at both ends is considered in the theoretical analysis. Momentum equations are derived for these masses using the appropriate Riemann's formulas for the longitudinal waves in the tube walls and for the waves in the liquid. The solving of these equations leads to the pressure traces at the tube end loaded by waterhammer effects. These traces were compared with experimental ones. Experiments were performed in a tube in which flow was suddenly stopped by means of an initially water-driven piston. This piston stopped suddenly at the tube end. Agreement and discrepencies between theoretical and experimental results are explained and discussed.