An Experimental Study on the Water Hammer with Cavity Collapse under Multiple Interruptions

Li Zhao,Wensheng Han,Liang Zhou,Qiaoning Wang,Tong Wang,Rongchu Wu,Yusi Yang,Pengli Wang

doi:10.3390/w12092566

Abstract

Pressurized pipeline system damage is primarily caused by the highly destructive water hammer force. Currently, research on water hammer-caused collapse is mostly based on single-point collapse cases, but water hammer research, which involves multipoint collapse, is insufficient. Here, we establish an experimental platform to realize water hammers with multipoint collapse. With different schemes, i.e., various initial flow rates and valve closing speeds, we observed the hydraulic transient process with a high-speed camera, analyzed its characteristics and explained experimental phenomena with theoretical knowledge. Using experimental data analysis, we summarized the influencing factors and laws of the cavity length and water hammer pressure. Flow and pressure data for the different schemes were recorded to provide basic simulation data. Water column separation experimental phenomena were observed: completely atomized, completely cavitated and partially cavitated, and both cavitated and atomized. At the pump outlet, three hydraulic transition states occurred simultaneously in the horizontal pipe section: completely atomized, completely cavitated, and both cavitated and atomized. Two hydraulic transition states occurred in the knee region: completely and partially cavitated, and without atomization. The experimental results reveal that the initial flow rate and valve closing speed greatly affect the water hammer pressure rise and cavity length. The higher the initial flow rate and valve closing speed are, the larger the water hammer pressure rise and cavity length are.

Highlights

With the rapid development of long-distance water conveyance projects, their safety guarantee is becoming increasingly important
By initial flow rate and valve closing speed, we evaluated the experimental phenomena and measured changing the initial flow rate and valve closing speed, we evaluated the experimental phenomena datameasured and summarized the water hammer factors and control mechanism
The transient states observed at the knee of the tubeline (Point 2) include the complete and incomplete flow interruption states

Summary

Introduction

With the rapid development of long-distance water conveyance projects, their safety guarantee is becoming increasingly important. Because of the complexity of the water hammer phenomenon, researchers do not fully understand it, especially when water hammers with multipoint collapse occur in a pipeline system, which highly complicates the situation [1,2]. The water hammer phenomenon with multipoint collapse is the main cause of pipe burst accidents [3]. Due to the complexity of the water hammer with multipoint collapse, relevant formation mechanisms and influencing factors remain unclear [4]. In certain conditions, such as when a pipeline valve is quickly opened or closed or when a pump is accidentally activated or stopped, water hammer pressure fluctuations may occur [5,6]. When the pressure in the pipe drops to the vapor pressure level of the liquid, it will

Methods

Discussion

Conclusion