YANG Kai-lin, GUO Yong-xin, FU Hui, GUO Xin-lei (State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, China Institute of Water Resources & Hydropower Research, Beijing 100038, China)

Abstract: The pipe water-filled process is a complicated hydraulic transient, in which the water flow experiences the transition from the unpressurized unsteady flow to the pressurized flow. Since it is lack of the relevant prototype and model observation data, ones know little on the pipe water-filled process. Based on the investigation of the hydraulic similarity laws, it is proved herein that for a pipe, as long as the pressurized flows in it are hydraulically similar, the unpressurized flows are also sure to hydraulically similar. Furthermore, the design and application of the pipe water-filled model are discussed on a case where the water-filled flows are those by gravity. The pipe water-filled model tests show that the air pressure and density in the pipe change little in water filling when the air vents are positioned reasonably along the pipeline, which means that the free liquid surface flows can be regarded as the unpressurized flows. Meanwhile, when the air velocities in the air vents are less than 100 m/s, the change of the air pressure and density are small and can be neglected in analysis.

Key words: pipe, water filling, water hammer, unpressurized unsteady flow, model similarity law

Published in: Journal of Hydraulic Engineering, Vol. 43, No. 10, 2012