Experimental and Numerical Study on Water Filling and Air Expelling Process in a Pipe with Multiple Air Valves under Water Slow Filling Condition

Abstract

This paper investigates the physical processes involved in the water filling and air expelling process of a pipe with multiple air valves under water slow filling condition, and develops a fully coupledwater–air two-phase stratified numerical model for simulating the process. In this model, the Saint-Venant equations and the Vertical Average Navier–Stokes equations (VANS) are respectively applied to describe the water and air in pipe, and the air valve model is introduced into the VANS equations of air as the source term. The finite-volume method and implicit dual time-stepping method (IDTS) with two-order accuracy are simultaneously used to solve this numerical model to realize the full coupling between water and air movement. Then, the model is validated by using the experimental data of the pressure evolution in pipe and the air velocity evolution of air valves, which respectively characterize the water filling and air expelling process. The results show that the model performs well in capturing the physical processes, and a reasonable agreement is obtained between numerical and experimental results. This agreement demonstrates that the proposed model in this paper offers a practical method for simulating water filling and air expelling process in a pipe with multiple air valves under water slow filling condition.

​Experimental investigations on characteristics of water-air two-phase flows during water fillings in undulation pipelines

“…The results showed that the rapid compression of an enclosed air pocket caused its temperature to rise, accompanied by the white mist phenomenon of water vapor. Liu et al [17] experimentally and numerically studied the low velocity water-filling process in a simple pipeline system with multiple air valves and incorporated the air valve model into the gas phase equation as a source term to study water-air two-phase stratified flow, and the experimental air velocity and pressure are in agreement with the numerical results. Huang et al [18] utilized PIV to investigate the water flow velocity near the entrapped air pockets at the local high-point of pressurized pipelines.…”

Numerical and Experimental Study on the Process of Filling Water in Pressurized Water Pipeline

“…The pressure in the pipeline fluctuates greatly, resulting in a complex and changeable water-gas two-phase flow pattern. This directly affects the safe operation of the water supply system [4]. Many water supply projects to be built have the characteristics of long pipelines, large flows, and great elevation fluctuations [5].…”