Abstract
The classic orifice equation is commonly used to calculate the leakage and intrusion rate for pressurized pipelines with cracks on the pipe wall. The conventional orifice equation does not consider the effect of the flow velocity in the main pipe, and there is a lack of studies on this matter. For this technical note, the influence of the main pipe flow velocity on the outflow and inflow through a crack on the pipe wall was studied in the laboratory. The experimental results show that the impact of the main pipe flow velocity can be significant. When the pressure difference across the orifice was constant, with the increase of the main pipe flow velocity, the outflow velocity increased, but the contraction area of the jet and the outflow discharge coefficient decreased. By comparing orifices with different shapes, it was found that the discharge from the circumferential crack was most sensitive to the main pipe flow velocity. In addition, the main pipe flow promoted the orifice inflow. When the pressure difference across the orifice was constant, with the increase of the main pipe flow velocity, the inflow discharge coefficient increased, which is the opposite pattern to that of the orifice outflow.
Highlights
The leakage in water distribution systems (WDSs) is a global problem, with the leakage rate typically ranging from about 10% in well-managed systems [1], to more than 30% in some developing countries such as India and China [2]
The orifice inflow in WDSs is submerged flow, which means that the head loss orifice inflow study, circular orifice in was and the water pipe internal was controlled sudden expansion from the vena contracta theused, downstream body
A series of laboratory experiments were conducted to study the effect of the main pipe flow velocity on the water leakage and intrusion
Summary
The leakage in water distribution systems (WDSs) is a global problem, with the leakage rate typically ranging from about 10% in well-managed systems [1], to more than 30% in some developing countries such as India and China [2]. Managing leaks in WDSs is an important part of water supply safety management, since contamination intrusion through cracks in the pipe wall may occur during low or negative pressure events and this is a significant threat to public health [3]. Researchers studied the effect of the flow velocity in a main channel on the side discharge through an orifice under different liquid levels and pore sizes in a trough-type liquid distributor using computational fluid dynamics (CFD) simulations [21]. The study reported in this technical note focuses on the effect of the main pipe flow velocity on the leakage and intrusion through cracks on the pipe wall. The key findings of this experimental study are summarized in the conclusion section
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