# Impact of Main Pipe Flow Velocity on Leakage and Intrusion Flow: An Experimental Study

^{1}

^{2}

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Experimental Apparatus

^{2}). The upstream and downstream ends of the pipeline system were connected to overflow tanks for water supply and drainage, respectively. A variable-speed water pump (50AAB HLS-25-50-2, Shanghai Panda, rated power 5.5 kW, rated working pressure 0.5 MPa) and a diaphragm pressure tank (SQL600-0.6, Shanghai Panda, pressure 0.6 MPa, effective volume 120 L) constituted a pipeline pressure stabilization system to regulate the flow velocity and pressure in the pipeline. Two magnetic flowmeters (OPTIFLUX2100C, KROHNE) were installed close to the upstream and downstream ends of the pipeline, respectively. The ratio of the flow rate reading to the cross-sectional area of pipeline was taken as the flow velocity in the pipeline. The orifices discharged water to the atmosphere. To measure the profile of the orifice discharge, a camera (HDR-CX405, SONY, frame rate 50P) was installed at a position above the orifice to record the flow jet images. The images were processed with AutoCAD, then the minimum cross-sectional area at the vena contracta (the point where the diameter of the stream is the least) and the tilt angle (degree of inclination) of the outflow jet were calculated.

## 3. Results of the Orifice Outflow Study

#### 3.1. Inclination of the Circular Orifice Outflow

#### 3.2. Cross-Sectional Area and Velocity of the Circular Orifice Outflow

_{c}), can be estimated by calculating the area of the shaded sector measuring the length of x. The contraction coefficient (ε), is defined by the following equation:

^{2}in this study.

_{c}provides the orifice outflow velocity. The relationship between the outflow velocity and the main pipe flow velocity was also reported in Figure 8. From Figure 8, when the orifice pressure was about 2 m, with the increase of the main pipe flow velocity (from 0 to 1.8 m/s), the contraction coefficient decreased and the outflow velocity increased.

#### 3.3. Discharge Coefficient of the Circular Orifice

_{c}), and the outflow velocity. As mentioned in the previous section, the greater the V, the smaller the μ and the smaller the A

_{c}, but the greater the outflow velocity, which means that the contraction of the jet has a greater effect on the outflow discharge than the outflow velocity. When the orifice area is constant, A

_{c}is positively correlated with the contraction coefficient, and the outflow velocity is positively correlated with the velocity coefficient. Therefore, the main factor affecting the orifice outflow is the contraction coefficient.

#### 3.4. Effect of the Shape of the Orifice

## 4. Results of the Orifice Inflow Study

_{i}), were calculated for different scenarios and the results are shown in Figure 12.

## 5. Conclusions

- The main pipe flow velocity influenced the orifice outflow. 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 (as calculated using the conventional orifice equation) decreased.
- For the orifice outflow, three types of orifices were considered: a circular orifice to simulate a pinhole leak, a rectangular orifice to simulate a longitudinal crack in a pipe wall, and a rectangular orifice to simulate a circumferential crack. When the orifice pressures and the orifice opening areas were the same, the discharge of the circumferential orifice was the most sensitive to the main pipe flow velocity, and the discharge of the longitudinal orifice was the least sensitive.
- The main pipe flow velocity 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 the opposite pattern to that of the orifice outflow. For the same pressure difference and the main pipe velocity, the inflow discharge coefficient was larger than the outflow counterpart.
- For both the orifice inflow and outflow, the impact of the main pipe flow velocity was more significant for the lower pressure head difference across the orifice.

## Author Contributions

## Funding

## Conflicts of Interest

## References

- Beuken, R.H.S.; Lavooij, C.S.W.; Bosch, A.; Schaap, P.G. Low leakage in the Netherlands confirmed. In Proceedings of the 8th Annual Water Distribution Systems Analysis Symposium (WDSA 2006), Cincinnati, OH, USA, 27–30 August 2006. [Google Scholar]
- Mutikanga, H.E.; Sharma, S.; Vairavamoorthy, K. Water loss management in developing countries: Challenges and prospects. J. Am. Water Works Assn.
**2009**, 101, 57–68. [Google Scholar] [CrossRef] - Besner, M.C.; Prevost, M.; Regli, S. Assessing the public health risk of microbial intrusion events in distribution systems: Conceptual model, available data, and challenges. Water Res.
**2011**, 45, 961–979. [Google Scholar] [CrossRef] [PubMed] - Yu, T.C.; Jin, H.F.; Zhang, T.Q.; Shao, Y.; Wu, X. Experimental observation on factors affecting intrusion volumes during low or negative pressure events. J. Water Supply Res. Technol.-Aqua
**2016**, 65, 396–406. [Google Scholar] [CrossRef] - Mora-Rodriguez, J.; Delgado-Galvan, X.; Ramos, H.M.; Lopez-Jimenez, P.A. An overview of leaks and intrusion for different pipe materials and failures. Urban Water J.
**2014**, 11, 1–10. [Google Scholar] [CrossRef] - Lambert, A.O. International report: Water losses management and techniques. Water Sci. Technol. Water Supply
**2002**, 2, 1–20. [Google Scholar] [CrossRef] - Van Zyl, J.E.; Clayton, C.R.I. The effect of pressure on leakage in water distribution systems. Proc. Inst. Civ. Eng.-Water Manag.
**2007**, 160, 109–114. [Google Scholar] [CrossRef] - Cassa, A.M.; van Zyl, J.E.; Laubscher, R.F. A numerical investigation into the effect of pressure on holes and cracks in water supply pipes. Urban Water J.
**2010**, 7, 109–120. [Google Scholar] [CrossRef] - Ferrante, M.; Massari, C.; Brunone, B.; Meniconi, S. Experimental Evidence of Hysteresis in the Head-Discharge Relationship for a Leak in a Polyethylene Pipe. J. Hydraul. Eng-ASCE
**2011**, 137, 775–780. [Google Scholar] [CrossRef] - Massari, C.; Ferrante, M.; Brunone, B.; Meniconi, S. Is the leak head-discharge relationship in polyethylene pipes a bijective function? J. Hydraul. Res.
**2012**, 50, 409–417. [Google Scholar] [CrossRef] - De Marchis, M.; Fontanazza, C.M.; Freni, G.; Notaro, V.; Puleo, V. Experimental Evidence of Leaks in Elastic Pipes. Water Resour. Manag.
**2016**, 30, 2005–2019. [Google Scholar] [CrossRef] - Ssozi, E.N.; Reddy, B.D.; van Zyl, J.E. Numerical Investigation of the Influence of Viscoelastic Deformation on the Pressure-Leakage Behavior of Plastic Pipes. J. Hydraul. Eng.
**2016**, 142, 04015057. [Google Scholar] [CrossRef] - Fox, S.; Collins, R.; Boxall, J. Experimental Study Exploring the Interaction of Structural and Leakage Dynamics. J. Hydraul. Eng.
**2017**, 143, 04016080. [Google Scholar] [CrossRef] - Lin, C.C. A Hybrid Heuristic Optimization Approach for Leak Detection in Pipe Networks Using Ordinal Optimization Approach and the Symbiotic Organism Search. Water
**2017**, 9, 812. [Google Scholar] [CrossRef] - van Zyl, J.E.; Lambert, A.O.; Collins, R. Realistic Modeling of Leakage and Intrusion Flows through Leak Openings in Pipes. J. Hydraul. Eng.
**2017**, 143. [Google Scholar] [CrossRef] - Mora-Rodriguez, J.; Delgado-Galvan, X.; Ortiz-Medel, J.; Ramos, H.M.; Fuertes-Miquel, V.S.; Lopez-Jimenez, P.A. Pathogen intrusion flows in water distribution systems: According to orifice equations. J. Water Supply Res. Technol.-AQUA
**2015**, 64, 857–869. [Google Scholar] [CrossRef] - Jan, C.-D.; Nguyen, Q.-T. Discharge Coefficient for a Water Flow through a Bottom Orifice of a Conical Hopper. J. Irrig. Drain Eng
**2010**, 136, 567–572. [Google Scholar] [CrossRef] - McLemore, A.J.; Tyner, J.S.; Yoder, D.C.; Buchanan, J.R. Discharge Coefficients for Orifices Cut into Round Pipes. J. Irrig. Drain Eng.
**2013**, 139, 947–954. [Google Scholar] [CrossRef] - Noack, C.; Ulanicki, B. Modelling of Soil Diffusibility on Leakage Characteristics of Buried Pipes. In Proceedings of the 8th Water Distribution Systems Analysis Symposium, Cincinnati, OH, USA, 27–30 August 2006; pp. 1–9. [Google Scholar]
- Collins, R.; Boxall, J. Influence of Ground Conditions on Intrusion Flows through Apertures in Distribution Pipes. J. Hydraul. Eng.
**2013**, 139, 1052–1061. [Google Scholar] [CrossRef] [Green Version] - Yu, H.F.; Li, X.G.; Sui, H.; Xu, C.C.; Li, H. Simulation of Orifice Flow Influenced by Lateral Flow in a Trough-Type Liquid Distributor. Chem. Eng. Technol.
**2013**, 36, 1975–1984. [Google Scholar] [CrossRef] - Patterson, J.; Page, N.W.; Ritchie, J.B. Contraction coefficients for compressible flow through axisymmetric orifices. Int. J. Mech. Sci.
**1970**, 12, 405–415. [Google Scholar] [CrossRef] - International Organization for Standardization. Measurement of Fluid Flow by Means of Orifice Plates, Nozzles, and Venturi Tubes Inserted in Circular Cross Section Conduits Running Full; International Organization for Standardization: Geneva, Switzerland, 1976. [Google Scholar]
- Wang, X.; Li, A.; Sobey, A.J.; Tan, M. Investigation into the effects of two immiscible fluids on coefficient of discharge during Compartment Flooding. Ocean Eng.
**2016**, 111, 254–266. [Google Scholar] [CrossRef] [Green Version]

**Figure 2.**Photos of the three orifices: (

**a**) the circular orifice, (

**b**) the circumferential orifice, and (

**c**) the longitudinal orifice.

**Figure 5.**Photos showing that the inclination of the circular orifice outflow (θ) varied with the main pipe flow velocity (V).

**Figure 6.**Relationship between the outflow inclination (θ) and the main pipe flow velocity (V) under various orifice pressure conditions (1 to 5 m).

**Figure 8.**Variations of the orifice contraction coefficient and the orifice velocity according to the main pipe flow velocity (circular orifice, 2 m orifice pressure).

**Figure 9.**Variations of the outflow discharge coefficient of a circular orifice according to the main pipe flow velocity under different pressure conditions (1 to 20 m).

**Figure 10.**The outflow jets from differently-shaped orifices: (

**a**) longitudinal; (

**b**) circular; (

**c**) circumferential.

**Figure 11.**Outflow discharge coefficients for orifices in different shapes and orientations, with the main pipe flow velocity varying from 0.4 to 1.5 m/s and a constant orifice pressure of about 2 m.

**Figure 12.**Inflow discharge coefficients for the circular orifice (with pipe internal pressure at 2 m and external pressure at 4, 6 and 8 m).

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Shao, Y.; Yao, T.; Gong, J.; Liu, J.; Zhang, T.; Yu, T.
Impact of Main Pipe Flow Velocity on Leakage and Intrusion Flow: An Experimental Study. *Water* **2019**, *11*, 118.
https://doi.org/10.3390/w11010118

**AMA Style**

Shao Y, Yao T, Gong J, Liu J, Zhang T, Yu T.
Impact of Main Pipe Flow Velocity on Leakage and Intrusion Flow: An Experimental Study. *Water*. 2019; 11(1):118.
https://doi.org/10.3390/w11010118

**Chicago/Turabian Style**

Shao, Yu, Tian Yao, Jinzhe Gong, Jinjie Liu, Tuqiao Zhang, and Tingchao Yu.
2019. "Impact of Main Pipe Flow Velocity on Leakage and Intrusion Flow: An Experimental Study" *Water* 11, no. 1: 118.
https://doi.org/10.3390/w11010118