A common challenge faced by engineers in the hydraulic industry is the formation of free surface vortices at pump and power intakes. This undesirable phenomenon which sometimes entrains air could result in several operational problems: noise, vibration, cavitation, surging, structural damage to turbines and pumps, energy losses, efficiency losses, etc. This paper investigates the numerical simulation of an experimentally observed air-core vortex at an intake using the LTSInterFoam solver in OpenFOAM. The solver uses local time-stepping integration. In simulating the air-core vortex, the standard k − ε, realizable k − ε, renormalization group (RNG) k − ε and the shear stress transport (SST) k − ω models were used. The free surface was modelled using the volume of fluid (VOF) model. The simulation was validated using a set of analytical models and experimental data. The SST k − ω model provided the best results compared to the other turbulence models. The study was extended to simulate the effect of installing an anti-vortex device on the formation of a free surface vortex. The LTSInterFoam solver proved to be a reliable solver for the steady state simulation of a free surface vortex in OpenFOAM.

This paper presents the hydraulic study of a new manhole geometry, designed to allow the installation of separate sewer systems in narrow streets. The new manhole design comprises two chambers in one structure to manage separate flows. The new shape of the manhole generates a new flow pattern for stormwater. It is therefore important to understand the hydraulic properties of sewer systems using the newly designed stormwater manhole chamber. The present study focuses on exploring the hydraulic performance of the storm chamber, which is usually characterized by significant head losses and shockwaves, these related to different flow regimes. A physical model was used to carry out a systematic experiment to explore the flow characteristics of the manhole under both subcritical and transitional flow conditions. The results revealed an enhancement in head loss with higher amplitude waves generated at transition flow when compared with a conventional manhole.

A vortex is a ubiquitous everyday phenomenon that is observed in nature and it is formed due to the rotational motion of fluid around an axis perpendicular to the free surface. Free surface vortices are a common unwanted occurrence at hydraulic intakes which can cause serious detrimental impacts on mechanical devices such as turbines and pumps. In this paper, an experimentally observed air-core vortex is numerically simulated using the OpenFOAM LTSInterFoam solver. The LTSInterFoam solver has hitherto been mainly used for hydrodynamic studies relating to ship manoeuvrability by researchers. This solver uses a local time stepping approach to speed up convergence towards steady state conditions thus overcoming some of the challenges associated with the use of the conventional interFoam solver for the simulation of free surface vortices. The Shear Stress Transport (SST) k−ω Model was used for the simulation. There was generally good agreement when results from the study were compared with other vortex-related analytical models and experimental data. Overall, the study concludes that the OpenFOAM LTSInterFoam solver is capable of simulating free surface vortices at hydraulic intakes. However, being a steady state solver, the solver cannot account for the transient process involved in the evolution of free surface vortices.

For years, the study of free surface vortices at hydropower plant intakes has been a topical and intriguing subject among engineers and researchers. This subject will continue to attract attention especially as the world strives to meet the ever-increasing demand for energy. Despite the numerous benefits associated with hydropower, the sustainability of some hydropower plants is being threatened due to low inflows often associated with climate change. Free surface vortices associated with low water levels or submergence at plant intakes can have very detrimental consequences on the operation of hydropower plants if not addressed. Notwithstanding this, free surface vortex flows have also been found to be very relevant in emerging technologies such as the water vortex hydropower plant system. This paper, therefore, presents a state-of-the-art review of the subject including summarised historical findings, but with an emphasis on current developments, findings and research gaps to guide practitioners and researchers. In response to the research gaps identified, the authors make a number of recommendations for further studies which include establishing relationships between free surface vortices formation and turbine efficiency, development of more accurate models for critical submergence and free surface vortices, assessment of free surface vortices at multiple and multi-level intakes, establishing the relationship between free surface vortices and sediment transport at intakes, application of Computational Fluid Dynamics (CFD) shape optimization tools for intake and anti-vortex device optimisation, as well as the continuing development of CFD tools to simulate air-entrained vortices at hydropower intakes.

For years, the study of free surface vortices at hydropower plant intakes has been a topical and intriguing subject among engineers and researchers. This subject will continue to attract attention especially as the world strives to meet the ever-increasing demand for energy. Despite the numerous benefits associated with hydropower, the sustainability of some hydropower plants is being threatened due to low inflows often associated with climate change. Free surface vortices associated with low water levels or submergence at plant intakes can have very detrimental consequences on the operation of hydropower plants if not addressed. Notwithstanding this, free surface vortex flows have also been found to be very relevant in emerging technologies such as the water vortex hydropower plant system. This paper, therefore, presents a state-of-the-art review of the subject including summarised historical findings, but with an emphasis on current developments, findings and research gaps to guide practitioners and researchers. In response to the research gaps identified, the authors make a number of recommendations for further studies which include establishing relationships between free surface vortices formation and turbine efficiency, development of more accurate models for critical submergence and free surface vortices, assessment of free surface vortices at multiple and multi-level intakes, establishing the relationship between free surface vortices and sediment transport at intakes, application of Computational Fluid Dynamics (CFD) shape optimization tools for intake and anti-vortex device optimisation, as well as the continuing development of CFD tools to simulate air-entrained vortices at hydropower intakes. (C) 2020 The Authors. Published by Elsevier B.V. on behalf of African Institute of Mathematical Sciences / Next Einstein Initiative.

The objective of the article is to describe the methodology followed to validate the finite element model for the new method of setting pipes in a separate sewer system, using one trench to accommodate the storm pipe over the sanitary pipe “doi.org/10.1016/j.tust.2019.103019” (Abbas et al., 2019). A physical model was established in the Liverpool John Moores University (LJMU) lab to test the structural performance of two PVC pipes buried in one trench. The results of the physical model were used to validate an FE model using the same material properties and boundary conditions used in the physical model. The validation process allowed the FE model to be upgraded to a 3D FE full-scale model for testing the novel method used to place the separate sewer system.

Separate sewer systems are currently used in all new developments and are prevalent in comparison with combined sewer systems, the use of which is limited due to numerous environmental regulations. However, the narrow streets common in the United Kingdom, Europe, and other densely populated countries are usually occupied by complex networks of infrastructure services; consequently, finding space to install a traditional separate sewer system is challenging. This paper presents an original design for separate sewer systems that overcomes this challenge by combining the advantages of separate and combined sewerage systems into one sewer network. The proposed system includes a novel design for the access chamber shape that allows storm flows and foul flows to pass through it without mixing and allows one trench to accommodate both pipelines. Applying this system in a case study showed a reduction in construction costs of approximately 10% and a 16% reduction in the footprint; moreover, the construction time was decreased by 44%, and the storage capacity and retention time were increased by 280% and 200%, respectively.

The design of manholes dates back more than 100 years. However, there have been developments such as the use of new materials for the manufacture of manholes, and advances in inspection and maintenance technologies, allowing improvements to the shape of manholes. This paper presents an innovative design for manholes, created to overcome the challenges associated with the installation of separate sewer systems in narrow streets, common to both UK and EU cities. The traditional separate sewer system has two separate manholes. The proposed manhole combines these two manholes into one structure, with two separate chambers, to allow storm flow and foul flow to pass through the same manhole without mixing. The structural performance of the new design has been tested using mathematical modelling validated by experimental tests. The results are compared with the structural performance of traditional manholes. The new design shows an improved resistance to high live loads.

This paper describes the development of a model to interface a planned urban drainage system with Geographic Information System (GIS) through the introduction of open-source tools; Auto Numbering and Get Elevation to extract essential data from GIS and Excel2GIS to bridge the output data between GIS and the drainage design program. Creating a range of essential data from digital database repositories aids the development of decision-support tools for urban planners in a simulation of different urban drainage scheme scenarios and moderates the interference with other infrastructure utilities. These tools, modelled with design software and GIS platform, are tested in two case studies; the results revealing essential improvements in accuracy of output, time taken to prepare and run the model and model presentation which visualised the hydraulic design results and global location of the drainage layout on an urban master plan.

Substantial research has been conducted on single flexible pipes buried in a trench. In contrast, the objective of this study is to determine the structural performance of two buried flexible sewer pipes positioned one over the other in a single trench. An innovative configuration is designed, based around the use of an innovative manhole structure which can accommodate both foul and surface water, to solve the challenges associated with constructing separate sewer systems in narrow streets while providing additional space for other infrastructure services. The behaviours of the two flexible pipes were tested using a 3D finite element (FE) model validated with experimental data from a laboratory investigation. A modified Drucker-Prager cap soil constitutive model was used to simulate the elasto-plastic soil behaviour. The results show that this approach comprising the use of a large-diameter flexible pipe set above a small-diameter flexible pipe mitigates the strain on the smaller pipe and decreases the total deflections of both pipes and the soil.

The use of a finite element (FE) method and selection of the appropriate model to simulate soil elastoplastic behaviour has confirmed the importance and sensitivity of the soil properties on the accuracy when compared with experimental data. The properties of the filling soil play a significant role in determining levels of deformation and displacement of both the soil and subterranean structures when using the FE model simulation. This paper investigates the impact of the traffic load on the filling soil deformation when using the traditional method, one pipe in a trench, and a new method, two pipes in a single trench one over the other, for setting up a separate sewer system. The interaction between the buried pipes and the filling soils has been simulated using an elastoplastic FE model. A modified Drucker–Prager cap constitutive model was used to simulate the stress-strain behaviours of the soil. A series of laboratory tests were conducted to identify the elastoplastic properties of the composite soil used to bury the pipes. The FE models were calibrated using a physical lab model for testing the buried pipes under applied load. This allows the FE model to be confidently upgraded to a full-scale model. The pipe-soil interactions were found to be significantly influenced by the soil properties, the method of placing the pipes in the trench and the diameters of the buried pipes. The deformation of the surface soil was decreased by approximately 10% when using the new method of setting up the separate sewer.

The design of the sewer system in hilly regions has a different concept from other areas due to the high flow velocity generated in the system that characterises a sloped system. The flow velocity of sewage or stormwater in the sewer system is limited by design criteria, using minimum velocity to avoid settlement of suspended solids in the pipes and maximum velocity to keep the solute homogeneous (fluid and suspended solids) and avoid pipe erosion. Maintaining these limits of the velocity within hilly regions is challenging and designers usually use steep cascade manholes to dissipate the fluid flow energy. This paper presents a new manhole design to mitigate stormwater flow energy, which is more critical than sewage flow in such areas, and using the traditional normal steps manhole for the sewage chamber. The new manhole design includes two chambers, an inner chamber used as in the traditional manhole for sewage and an outer chamber used for stormwater flow. The hydraulic properties of the new manhole have been explored using a physical model in laboratory conditions and compared with traditional manhole performance. The laboratory results are used for validation and are compared with computational fluid dynamic model outputs of the new design. The hydraulic performance of the new design reveals improvement in decrease in the flow energy of stormwater and increase in the capacity of storage for the stormwater network.

A manhole is one of the main elements of a sewer network; it is a structure used to gain access to the sewer for inspection and maintenance. A collapse of this structure can cause a serious pollution problem and nuisance because the sewage may spill into residential areas. Stability of the manhole structure depends on the correlation between the manhole material and soil material and the contacting area. This paper presents an experimental investigation for testing the performance of manholes buried in the sand under a live load, firstly, when using a traditional manhole design buried in the sand and, secondly, when using a new manhole design which has a large external surface area compared with the traditional one, buried in the sand. A rectangular cell filled with sand and embedded in a hydraulic rig was used to simulate a live load applied to buried manholes in the lab. The results demonstrated how the external surface of a manhole plays a significant role in the behaviour of the manhole structure against different loads. The new design of a manhole buried in the sand has a high resistance to live loads compared with the traditional manhole shape, even under a heavy weight.

This chapter discusses much of the issues related to modeling of existing hydropower plants with the Akosombo Hydroelectric Dam as a case study. The re-engineering techniques to optimize turbine intake for critical water levels would also be discussed. These optimization techniques are vital for existing hydropower plants since it is difficult to predict and model climate and weather precisely.

The Iowa formula is one of the most traditional methods used to estimate the deflection of a buried flexible pipe. Separate sewer system pipelines, set in one trench, can be found at intersections these in one trench often located at crossroads. The traditional Iowa formula however, does not account for the deformation of two pipes placed in one trench, this information critical for road and other infrastructure design. This paper presents the results from testing a new method to set up separate sewer pipelines when buried in parallel in sand. The results have been used to validate an improvement to the Iowa method used to calculate the deformation of flexible pipes set in one trench, one over the other, or when the pipes intersect at different levels, again within one trench. The improved method was tested by lab experiments through the application of a series of loads on two pipes laid in one trench, using a hydraulic rig to simulate road traffic (live loads), this compared to the results when setting one pipe in a trench. Two PVC pipes and the soil properties of the trench were examined. The results have been compared to experimental data, the two pipe system integrity validated against the standard requirements for flexible pipes buried in soil.

Sewer systems that convey both sanitary sewage and stormwater through a single pipe are referred to as combined sewer systems. This system diverts all flows exceeding the design capacity to the receiving watercourses in heavy rain events. Therefore, environmental regulations limit the use of this system and separate sewer systems are currently used in all new developments. However, the UK, most other European, and other countries usually have narrow streets occupied by a complex network of infrastructure services. About 70% of sewer systems in the UK and Europe are combined systems. Finding a space in which to place another two sets of pipes (in a separate sewer system) is therefore challenging. This research is regarding a design which is capable of overcoming this challenge by a modified system for the sewer networks. The system includes a proposed new design for the manhole shape, which will allow the storm flow and the foul flow to pass through the same manhole without mixing and allows using one trench to set two pipelines. This will bring economic advantages by decreasing construction cost by about 30% plus extra protection for the environment by separating sewage from stormwater, decrease footprint by 16% and construction time by 18%.

The U.S. Environmental Protection Agency (EPA) has clearly stated that what was considered state-of-the-art sewage pollution control a century ago is no longer valid for today. This paper presents a new design, integrating the advantages of a combined sewer system and a separate sewer system into one system, to comply with 21st century requirements (sustainability, protection of public health, and reduced cost). One trench is used for two pipelines, a storm pipe on top of a sanitary pipe. Experimental tests were conducted in the laboratory installing two PVC pipes, one on top of the other. A series of loads have been applied to measure the behaviour of the new system when compared to the traditional method of laying a separate sewer system. This approach reduces the initial cost, footprint, and construction time. This method promises improved sewer drainage system performance as new technologies significantly affect future configurations of urban drainage management.

The development of new technologies has made it possible to build models for sewerage systems which include the history and background for each element. Most developed and developing countries have built digital databases for infrastructure services. However, the referencing and numbering systems for various elements in the database are still applied in different ways. The result is that each area has its own system for identifying the sewer system's elements depending on the originator such as designers, water utilities or city authorities. The resulting databases are very confusing and comparison with other databases is difficult. This paper proposes a standardised system methodology for national and international sewer identification by using the area code for the country, city, sub area, type of sewer (sanitary, storm or combined), and numbering of the elements (X, Y) in the network, using numbering of manholes as a reference. Innovative software matched with GIS was used to number sewer systems.

This paper presents the results regarding an experimental and numerical study about a buried PVC pipe and its interaction with the surrounding soil. The interaction between a buried pipe and the composite soil has been simulated by using elastoplastic finite element models to determine the levels of deformation in the pipe and settlement in the soil. A series of loading configuration tests were conducted, using a prototype trench, in which a flexible pipeline was buried in composite soil layers of known properties. The resulting data from these tests were used to validate output mathematical models using a Mohr Coulomb Plasticity model in one case, and a Dragger Prager model in the second to simulate the stress-strain behaviours of a composite soil and a buried PVC pipe. The pipe-soil interactions were found to be influenced by the pattern of soil and bedding layers, thereby establishing that the properties of the soil play a significant role in determining levels of deformation and displacement of a sewer pipe cross-section. The use of ABAQUS, a finite elements package, and selection of the appropriate model to simulate soil elastoplastic behaviour, has confirmed the importance, significance and sensitivity of the soil material properties on the numerical simulation accuracy when compared with experimental data.

A number of vortex flow control (VFC) devices for urban drainage systems are investigated computationally at high flow rates, for which a confined vortex dominates the flow regime. A range of turbulence models, including both eddy viscosity and Reynolds stress closures, are compared with in-house experimental measurements of head loss and internal pressure measurements. Single-phase and multi-phase (free surface) calculations are also compared. Very good agreement with the experimental data was obtained when the swirl parameter of the device was below 3·14 for predictions made using the Reynolds stress closure formulations. For devices with swirl parameters above this value, the computational methodology was found to under-predict the head loss of the device. This was attributed to poor calibration of the turbulence model for swirling flow scenarios in which the pressure gradient and diffusive (turbulent) forces in the flow are comparable.