Large water-hammer pressure for column separation in pipelines

Abstract

Water-hammer pressures in a pipeline due to the collapse of a vapor cavity adjacent to a valve are investigated. A water-hammer event is initiated by the closure of a valve in a simple reservoir-pipeline-valve system. The sequence of events following an instantaneous valve closure leading to the formation and collapse of a vapor cavity and the resultant occurrence of a short-duration pressure pulse are described. Short-duration pressure pulses result from the superposition of the valve-closure water-hammer wave and the wave generated by the collapse of the vapor cavity. The resulting maximum pressure may exceed the Joukowsky pressure generated from the initial valve closure. A series of numerical model analyses exhibiting short-duration pressure pulses are presented. In addition, experimental results supporting the findings of the numerical studies are also presented. Experimental plots of hydraulic grade line versus time exhibit short-duration pressure pulses of different shape and characteristics.