Abstract

This study presents the results from detailed experiments of the two-phase pressurized flow behavior during the rapid filling of a large-scale pipeline. The physical scale of this experiment is close to the practical situation in many industrial plants. Pressure transducers, water-level meters, thermometers, void fraction meters, and flow meters were used to measure the two-phase unsteady flow dynamics. The main focus is on the water–air interface evolution during filling and the overall behavior of the lengthening water column. It is observed that the leading liquid front does not entirely fill the pipe cross section; flow stratification and mixing occurs. Although flow regime transition is a rather complex phenomenon, certain features of the observed transition pattern are explained qualitatively and quantitatively. The water flow during the entire filling behaves as a rigid column as the open empty pipe in front of the water column provides sufficient room for the water column to occupy without invoking air compressibility effects. As a preliminary evaluation of how these large-scale experiments can feed into improving mathematical modeling of rapid pipe filling, a comparison with a typical one-dimensional rigid-column model is made. Keywords: Experimentation, Large-scale pipeline, Unsteady flow, Two-phase flow, Air–water interface, Flow-regime transition

Abstract

This research introduces an inverse transient-based optimization approach to automatically detect potential faults, such as leaks, partial blockages, and distributed deteriorations, within pipelines or a water distribution network (WDN). The optimization approach is named the Pipeline Examination Ordinal Symbiotic Organism Search (PEOS). A modified steady hydraulic model considering the effects of pipe aging within a system is used to determine the steady nodal heads and piping flow rates. After applying a transient excitation, the transient behaviors in the system are analyzed using the method of characteristics (MOC). A preliminary screening mechanism is adopted to sift the initial organisms (solutions) to perform better to reduce most of the unnecessary calculations caused by incorrect solutions within the PEOS framework. Further, a symbiotic organism search (SOS) imitates symbiotic relationship strategies to move organisms toward the current optimal organism and eliminate the worst ones. Two experiments on leak and blockage detection in a single pipeline that have been presented in the literature were used to verify the applicability of the proposed approach. Two hypothetical WDNs, including a small-scale and large-scale system, were considered to validate the efficiency, accuracy, and robustness of the proposed approach. The simulation results indicated that the proposed approach obtained more reliable and efficient optimal results than other algorithms did. We believe the proposed fault detection approach is a promising technique in detecting faults in field applications. Document type: Article

Abstract

Air pockets generated during emptying operations in pressurized hydraulic systems cause significant pressure drops inside pipes. To avoid these sudden pressure changes, one of the most widely used methods involves the installation of air valves along the pipeline route. These elements allow air exchange between the exterior and the interior of the pipe, which alleviates the pressure drops produced and thus prevents possible breaks or failures in the structure of the installation. This study uses a mathematical model previously validated by the authors in smaller installations to simulate all hydraulic variables involved in emptying processes over time. The purpose of these simulations is the validation of the mathematical model in real large-scale installations, and to do this, the results obtained with the mathematical model are compared with actual measurements made by the partner company. The hydraulic system selected for the study is a pipeline with a nominal diameter of 400 mm and a total length of 1020 m. The results obtained from the mathematical model show great similarity with the experimental measurements, thus validating the model for emptying large pipes. Document type: Article

Abstract

Optimisation of water distribution system design is a well-established research field, which has been extremely productive since the end of the 1980s. Its primary focus is to minimise the cost of a proposed pipe network infrastructure. This paper reviews in a systematic manner articles published over the past three decades, which are relevant to the design of new water distribution systems, and the strengthening, expansion and rehabilitation of existing water distribution systems, inclusive of design timing, parameter uncertainty, water quality, and operational considerations. It identifies trends and limits in the field, and provides future research directions. Exclusively, this review paper also contains comprehensive information from over one hundred and twenty publications in a tabular form, including optimisation model formulations, solution methodologies used, and other important details. Document type: Article

Abstract

Submarine pipelines have been extensively used for marine oil and gas extraction due to their high efficiency, safety, and low price. However, submarine pipelines are vulnerable to extreme waves (i.e., tsunami waves). Previous research has often used solitary waves as a basis for studying the impacts of tsunami waves on submarine pipelines, although the hydrodynamic characteristics and wave properties drastically differ from those of real-world tsunami waves. This paper numerically investigates the hydrodynamic characteristics of tsunami waves interacting with submarine pipelines, but instead uses an improved wave model to generate a tsunami-like wave that more closely resembles those encountered in the real-world. The tsunami-like wave generated based on a real-world tsunami wave profile recorded during a 2011 tsunami in Japan has been applied. Given the same wave height, simulation results show that peak hydrodynamic forces of the tsunami-like wave are greater than those of the solitary wave. Meanwhile, the duration of the acting force under the tsunami-like wave is much longer than that of the solitary wave. These findings underline the basic reasons for the destructive power of tsunamis. It is also noted that the hydrodynamic forces of the pipeline under the tsunami-like wave increase with wave height, but will decrease as water depth increases. In addition to the single pipeline, the complicated hydrodynamic characteristics of pipelines in tandem arrangement have been also numerically studied. It is believed that the findings drawn from this paper can enhance our understanding of the induced forces on submarine pipelines under extreme tsunami waves. Document type: Article

Abstract

There are two key issues in the safety assessment of the water distribution system (WDS). One is how to evaluate the safety levels of water supply for customers, while the other is how to describe the importance of a pipe for the global or local WDS. The water demand guarantee rate (DGR) and the water demand failure rate (DFR) are proposed. The mathematical expectations of the DGR and DFR describe the average customer’s water safety levels for the first issue. Moreover, the unit influence of pipe failure (UIPF) is put forward for the second issue. It describes the importance of the pipe for the global or local system. Several cases show how to calculate the above values with the pressure-driven model. It is also shown how to find key pipelines in the WDS. The results show that the method can provide an effective reference for real-life WDS management. Document type: Article

Abstract

This article reveals the change law of the head loss and critical deposition velocity during hydraulic transmission of a solid–liquid two-phase pipeline. This article also establishes a physical test model. A single variable is used to conduct the experimental research by changing the conditions of the pipeline flow rate, the sediment concentration, and the reverse slope degree. Based on an analysis of the test process, a new formula is proposed to determine the critical sedimentation rate of the pipeline that considers a change in the adverse slope. By analyzing the variation rule of the hydraulic slope of the pipeline sediment in different states and comparing the hydraulic slope of the horizontal pipeline and reverse pipeline in different states, different factors that influence head loss are revealed. Finally, the measured value of this test is compared with the Durand equation and the Worster equation. It was found that the measured value of this test was more similar to the Durand equation. This study not only provides theoretical support for sand removal in pipelines but also promotes sedimentation in reservoirs. Document type: Article

Abstract

Seismic activity of small, medium or high intensity has a destructive effect on existing water supply and distribution networks. In the scholar literature, these are included in Class I&mdash Vital Performance Systems, whose operation must be uninterrupted in case of a seismic event. Water networks are also essential for the safe operation of certain critical subsystems in the event of an earthquake (fire-extinguishing systems, etc.), in order to avoid loss of human lives, reduce adverse environmental impacts and limit damage caused by fires. The article proposes a seismic safety system for the water transport pipelines obtained by designing, executing and testing an experimental design, a system that can be used to increase the seismic resilience of the water supply and distribution network pipelines. The experimental data obtained were verified on the basis of the theoretical data available in the literature. The results of the research are particularly useful and can be proposed for use from the stage of designing new networks to providing expertise for existing networks, for establishing the most-stressed areas in which to be installed, and for implementing both execution and at the same time rehabilitation and upgrading. Document type: Article

Abstract

Climate change, urbanization and water pollution cause adverse effects and rehabilitation costs that may exceed the carrying capacity of cities. Currently, there is no internationally standardized indicator framework for urban Integrated Water Resources Management (IWRM). The City Blueprint® is a first attempt and aims to enhance the transition towards water-wise cities by city-to-city learning. This paper provides a three step revision of the City Blueprint Framework (CBF) based on data of 45 municipalities and regions in 27 countries: (1) A distinction has been made between trends and pressures (on which urban IWRM has a negligible influence) and IWRM performances. Therefore, a separate trends and pressures framework has been developed; (2) Only the purely performance-oriented indicators have been selected from the CBF. Furthermore, the indicator accuracy and boundaries have been re-assessed, and new indicators have been added; (3) By analyzing correlations and variances, the performance-oriented indicators have been rearranged in order to establish a proportional contribution of all indicators and categories to the overall score, i.e., the Blue City Index®. In conclusion, six indicators have been removed because of insufficient accuracy, overlap or lack of focus on IWRM. Seven indicators have been added, i.e., secondary and tertiary wastewater treatment, operation cost recovery, green space and three indicators concerning solid waste treatment. The geometric aggregation method has been selected because it emphasizes the need to improve the lowest scoring indicators. In conclusion, the improved CBF is more performance-oriented and therefore more suitable to assist cities in their transition towards water-wise cities. Document type: Article

Abstract

Water transmission pipelines, which transport bulk water into storage facilities, usually have a tree-type configuration with large dimensions; thus, the breakage of a pipeline may cause a catastrophic service interruption to customers. Although drain efficiency is closely related to the number of washout and control valves and their locations, there is no useful guideline. This paper proposes a valve locating method by introducing numerical analyses to enumerate drainage time and zone. A time integration method, combined with the Newton–Raphson algorithm, is suggested to resolve drainage time, while considering the friction loss in gravitational flow. A drain direction matrix, which shows drain direction and coverage, is derived using a network searching algorithm. Furthermore, a feasible practical approach is presented by introducing a critical horizontal slope, a major washout valve, drainage indices, and control valve embedment. The developed method is first applied to simple pipes to validate the drainage time module. Subsequently, the model is expanded to the CY transmission line, which is one of the BR water supply systems in South Korea currently in operation. The results reveal that three drain valve locations have been neglected, and the addition of control valves guarantees consistent drain time below the operational criteria. Document type: Article