Pipe Slope Research Articles

A New Method to Recharge Groundwater Using Subsurface Drain

Subsurface drainage systems are widely used in agricultural area, when waterlogging and salinity are problems. Subsurface system can also help increasing the potential for infiltration. In this work, an application of subsurface drainage integrated with the decontamination system using activated carbon is proposed as a mean to recharge groundwater during the flood. Concern over the potential contaminating groundwater with urban runoff could be eliminated by the pretreated system incorporated with the recharging unit. A small model of the subsurface system envelope was tested to verify the activated carbon as a potential filled material. The result showed that the slope of the perforated pipe posed little or no effect on the flow rate in pipe due to the size of the model. For this preliminary study, it is highly possible to use activated carbon as filled material in subsurface systems for recharging groundwater.

Closure to “Pressure Surges Following Sudden Air Pocket Entrapment in Storm-Water Tunnels” by Jose G. Vasconcelos and Gabriel M. Leite

Closure to “Pressure Surges Following Sudden Air Pocket Entrapment in Storm-Water Tunnels” by Jose G. Vasconcelos and Gabriel M. Leite

Slope profile measurement of sewer inverts

Abstract This paper presents the results of a study into the quality of the measurement of the slope profile of a sewer. Slope profile measurements can be used to assess the correct alignment of newly constructed sewers or the position of sewer pipes after differential settlement. For the measurement of the sewer invert profile a sewer inspection camera equipped with an electronic tilt meter can be used. The accuracy of the results of this measurement technique is not only determined by the specifications of the electronictilt meter but also by the execution of the measurement and properties of the measured object. To assess the influence of the latter two, the sewer invert profile one sewer was measured ten times. Analysis of the measurement results showed that the random errors are small and cancel out. Therefore differences in the slope of individual sewer pipes can be measured fairly accurately. The determination of the difference in level between either end of the sewer is inaccurate because of the systematic error.

Numerical and Experimental Analysis of the Pressurized Wave Front in a Circular Pipe

AbstractThis paper focuses on pressurized wavefront behavior and an analysis of trapped air pockets. Flow behavior, trapped air-pocket pressure, and different pressurized wavefront shapes in addition to their propagation conditions were investigated to improve modeling of mixed flows with trapped air pockets in stormwater systems. Pipe slopes, inflow, and reservoir water-levels were considered in an experimental analysis of the initiation, propagation of the wavefront, and flow behavior. Results show that the formation, propagation, and stability of the wavefront shape are highly dependent on the reservoir water-level and pipe slope. Pressurized wavefronts take on different shapes depending on manhole water level, pipe slope, and air pressure. The shape of the pressurized wavefront is sharper when the initial pipe depth y* is set between 0.5 and 0.85. With low inflow, the pipe-filling phase is progressive and is accompanied by undulations with stronger curvature and short length on the free-surface flow z...

Constrained Ant Colony Optimisation Algorithm for the layout and size optimisation of sanitary sewer networks

The incremental solution building capability of Ant Colony Optimisation Algorithm (ACOA) is used in this paper for the efficient layout and pipe size optimisation of sanitary sewer network. Layout and pipe size optimisation of sanitary sewer networks requires optimal determination of pipe locations, pipe diameters and pipe slopes leading to a highly constrained mixed-integer nonlinear programming (MINLP) problem presenting a challenge even to the modern heuristic search methods. A constrained version of ACOA equipped with a Tree Growing Algorithm (TGA) is proposed in this paper for the simultaneous layout and pipe size determination of sewer networks. The method is based on the assumption that a base layout including all possible links of the network is available. The TGA algorithm is used in an incremental manner to construct feasible tree-like layouts out of the base layout, while the constrained ACOA is used to optimally determine the cover depths of the constructed layout. Proposed formulation is used to solve three hypothetical test examples of different scales and the results are presented and compared with those produced by a conventional application of ACOA in which an ad-hoc engineering concept is used for layout determination. The results indicate the effectiveness and efficiency of the proposed method to optimally solve the problem of layout and size determination of sewer networks.

Experimental studies of air pocket movement in a pressurized spillway conduit

Undesired air entrainment in a bottom outlet conduit causes pressure transients, leading to conduit vibrations, blowbacks and discharge pulsations and thus endangers operational safety. In this study, the propagation velocity of a solitary air pocket and the characteristics of its critical velocity were examined in experiments conducted using a 240-mm-diameter pipe. Air pocket movement depends on the pipe diameter, slope, roughness and air pocket size. The critical pipe Froude number for initiating downstream movement of an air pocket is smaller in a larger pipe, most likely due to the scale effect and/or to a smaller reduction in the effective cross-sectional area. The critical velocity in rough pipes was found to be independent of the air pocket size. A minimum Froude number was suggested for a rough pipe instead of a critical pipe Froude number because the air removal process was found to involve successive air losses from the air pocket caused by turbulence.

Well-Balanced Scheme for Modeling Open-Channel and Surcharged Flows in Steep-Slope Closed Conduit Systems

AbstractThe model presented in this paper preserves lake at rest conditions in sloped prismatic conduits. These schemes are based on the two-governing equation model in which open-channel flows are simulated using the Saint-Venant equations and pressurized flows using the compressible water hammer equations. The model in this paper preserves lake at rest conditions (horizontal still water) regardless of the conduit slope, resolves moving jump discontinuities over dry beds in sloped conduits, and resolves small perturbations from steady states, even when adjacent to dry regions. The preserving steady-state capability of this model is of particular importance in continuous long simulations when the conduits are relatively steep (|So|>∼0.5%. Two main contributions are presented in this paper, namely, (1) a new method for water stage reconstruction is presented that preserves lake at rest conditions regardless of the pipe slope, and (2) a horizontal system of coordinates, instead of the commonly used inclined...

Optimal design of a sewer line using Linear Programming

Wastewater collection systems greatly contribute to the cost of the overall municipal sewerage system; a cost-effective design of the collection system will provide significant savings towards the cost of wastewater services. It is impossible to evaluate the full impact that each pipe size and slope would have on the overall cost of the collection system with intuitive designs. However, these solutions generally satisfy the design objectives within the given constraints. A survey of the literature indicates that various optimisation techniques are being applied for least-cost solutions. In general these approaches provide continuous pipe sizes, which are converted to closest commercial sizes for adoption, which would heavily dilute the optimal outcome. Search methods are also adopted to obtain cost-effective design solutions using directly commercial pipe sizes, which are computationally expensive. In the design of a sewerage system, a sewer line is a basic unit occurring repeatedly in the design-process and finally the combinations of these basic units formulate the complete sewer system. However, the branch sewer lines, main sewers, trunk sewers, pumping stations, treatment plant and outfall sewers are in general the main components of an urban wastewater collection, treatment and disposal systems. A method has been developed to optimise this basic unit using Linear Programming technique without transforming nonlinear objective function or constraint equations into linear functions and incorporating commercially available pipe sizes directly in the problem formulation. The current research area of optimal sewer system design is focusing equally on economic considerations and hydraulic feasibility and moving away from conventional design guidelines based on only self cleaning velocity concepts for node to node sewer link hydraulic design. This paper is a step forward in developing optimal design approaches of sewer systems.

Numerical investigation of the effects of combining sewer junction characteristics on the hydraulic parameters of flow in fully surcharged condition

AbstractIn this study, the effects of different parameters on flow structure and flow hydraulics for combining sewer junction consisting of manhole and lateral inflow were investigated numerically. For this purpose, the effects of dimension variations, main and lateral pipe slope, angle and the joint position of lateral pipe beside manhole, manhole geometry, and the outflow rate of manhole on flow structure and energy loss coefficients were investigated. Results show that the rate of energy loss decreases by heightening the installation position of lateral pipe beside manhole. In addition, it was shown that the slope variations of main and lateral pipes and outflow rate do not affect the rate of energy loss.

Damage Discrimination Analysis with QuantificationTheory for Sewage Pipe System

The damage caused by the aging of sewage pipe systems has become one of the major rising problems in modern cities. The traditional method to search for damage points of sewage pipes is the use of cameras and human observation. However, the use of these methods to check all the sewage pipes in the city will require a great deal of time and money. In this paper, a quantitative analysis on sewage pipe damage is reported. This study utilized the results of the sewer investigation in Tokyo. Based on this analysis, a quantification theory type II is proposed to describe the relationship between various factors that contribute to the damage of sewage pipe systems. Thus, these factors, including pipe diameter, number of years since installation, type of road and foundation, overburden, and pipe slope, can be used to judge if the sewage pipe displays corrosion, cracks, or breakage. As a result, the diagnosis model can be used to determine the likely extent of damage to an existing sewage pipe system.

A database and model to support proactive management of sediment-related sewer blockages

Due to increasing customer and political pressures, and more stringent environmental regulations, sediment and other blockage issues are now a high priority when assessing sewer system operational performance. Blockages caused by sediment deposits reduce sewer system reliability and demand remedial action at considerable operational cost. Consequently, procedures are required for identifying which parts of the sewer system are in most need of proactive removal of sediments. This paper presents an exceptionally long (7.5 years) and spatially detailed (9658 grid squares – 0.03 km2 each – covering a population of nearly 7.5 million) data set obtained from a customer complaints database in Bogotá (Colombia). The sediment-related blockage data are modelled using homogeneous and non-homogeneous Poisson process models. In most of the analysed areas the inter-arrival time between blockages can be represented by the homogeneous process, but there are a considerable number of areas (up to 34%) for which there is strong evidence of non-stationarity. In most of these cases, the mean blockage rate increases over time, signifying a continual deterioration of the system despite repairs, this being particularly marked for pipe and gully pot related blockages. The physical properties of the system (mean pipe slope, diameter and pipe length) have a clear but weak influence on observed blockage rates. The Bogotá case study illustrates the potential value of customer complaints databases and formal analysis frameworks for proactive sewerage maintenance scheduling in large cities.

Layout and size optimization of sanitary sewer network using intelligent ants

The incremental solution building capability of ant algorithm is exploited in this paper for the efficient layout and pipe size optimization of sanitary sewer network. Layout and pipe size optimization of sewer networks requires that the pipe locations, pipe diameters and pipe slopes are optimally determined. This problem is a highly constrained Mixed-Integer Nonlinear Programming (MINLP) problem presenting a challenge even to the modern heuristic search methods. In this paper, the Ant Colony Optimization Algorithm (ACOA) is equipped with a Tree Growing Algorithm (TGA) to efficiently solve the sewer network layout and size optimization problem and its performance is compared with the conventional application of the ACOA. The method is based on the assumption that a base layout including all possible links of the network is available. The TGA is used to construct feasible tree-like layouts out of the base layout defined for the sewer network, while the ACOA is used to optimally determine the pipe diameters of the constructed layout. An assumption of sewer flow at maximum allowable relative depth is made allowing for the calculation of the optimal pipe slopes in the absence of any pump and drop in the network. Two different formulations are, therefore, proposed and their performances are tested against hypothetical problems. In the first formulation, ACOA is used in a conventional manner for pipe size optimization while an ad hoc engineering concept for the layout determination. In the second formulation, however, ACOA equipped with TGA is used to simultaneously determine both the layout and pipe sizes of the network. Proposed formulations are used to solve three hypothetical test examples of different scales and the results are presented and compared. The results indicate the ability of the proposed method to optimally solve the problem of layout and size determination of sewer networks.

Physical Disintegration of Toilet Papers in Wastewater Systems: Experimental Analysis and Mathematical Modeling

Physical disintegration of representative toilet papers was investigated in this study to assess their disintegration potential in sewer systems. Characterization of toilet papers from different parts of the world indicated two main categories as premium and average quality. Physical disintegration experiments were conducted with representative products from each category according to standard protocols with improvements. The experimental results were simulated by mathematical model to estimate best-fit values of disintegration rate coefficients and fractional distribution ratios. Our results from mathematical modeling and experimental work show that premium products release more amounts of small fibers and disintegrate more slowly than average ones. Comparison of the toilet papers with the tampon applicators studied previously indicates that premium quality toilet papers present significant potential to persist in sewer pipes. Comparison of turbulence level in our experimental setup with those of partial flow conditions in sewer pipes indicates that drains and small sewer pipes are critical sections where disintegration of toilet papers will be limited. For improvement, requirements for minimum pipe slopes may be increased to sustain transport and disintegration of flushable products in small pipes. In parallel, toilet papers can be improved to disintegrate rapidly in sewer systems, while they meet consumer expectations.

CFD Prediction of Erosion Wear in Centrifugal Slurry Pumps for Dilute Slurry Flows

The paper discusses numerical prediction of erosion wear trends in centrifugal pump casing pumping dilute slurries. The casing geometry is considered two-dimensional. Discrete Phase Model (DPM) in FLUENT 6.1® is utilized to obtain dilute slurry flow field through the pump casing employing two-way coupling. Standard k — ε model is used for turbulence. Effect of several operational parameters viz. pump flow rate, pump speed (RPM), particle diameter and various geometry conditions viz. tongue curvature, slope of the discharge pipe and casing width is studied. Qualitative trends of erosion wear is described for these operational and geometric parameters with an idea to lower the wear rates and to make the wear pattern along the casing wall as uniform as possible. For example, with increase in pump flow rate, wear rates tends to even out whereas with increased casing width, wear rates are found to decrease.

도시침수 저감을 위한 최적 우수관망 설계 모형

우수관망의 최적 설계에 관한 기존의 연구 모형들은 설계강우에 대하여 관거의 연결, 관경 및 관 경사 등을 최소의 비용을 목적으로 최적화하여 왔다. 그런데 우수관망에서의 관거 내의 흐름은 관경, 관 경사와 특히 관망의 구성 형태에 따라서크게달라진다. 기존의최적우수관망설계모형들은설계유량을만족시키는것에국한되었으며, 설계기준을초과하는 강우에 따른 침수의 발생은 관망의 설계에 어떠한 고려도 되지 않았다. 본 연구에서는 우수관망을 구성함에 있어서 관거 내 흐름을 분산시키고 제어함을 목적으로 한다. 이것은 관망 구성에 따른 관거 내 흐름의 중첩효과를 제어함으로써 가능하며, 이러한 흐름의 제어를 통하여 설계기준을 초과하는 강우에 대해서 우수관망에서의 내수침수 발생은 저감될 수 있다. 본 연구에의 최적 우수관망 설계 모형(Optimal Sewer Layout Model, OSLM)은 내수침수 발생을 저감시키기 위해 흐름의 중첩효과를 고려하여 관거 내 흐름을 분산시키고 제어하기 위하여 개발되었다. 이 모형은 최적화를 위하여 유전자알고리즘(Genetic Algorithm, GA)를 이용하였으며, 수리학적 분석을 위하여 SWMM(Storm Water Management Model)을 연계하였다. 모형의 적용은 유역면적 44 ha의 서울시 하계 배수분구에 이루어졌으며, 현재의 우수관망 구성에 대하여 도출된 최적 우수관망에서는 지속기간 30분의 설계강우에 대하여 7.1%의 유출구 첨두유출량 감소와 20년 빈도의 지속기간 1시간 초과강우에 대하여 24.2%의 침수 발생량 저감 효과를 나타내었다. In the previous researches for storm sewer design, the flow path, pipe diameter and pipe slope were determined to minimize the construction cost. But in the sewer networks, the flows can be changed according to flow path. The current optimal sewer layout models have been focussed on satisfying the design inflow for sewer designs, whereas the models did not consider the occurrences of urban inundation from excessive rainfall events. However, in this research, the sewer networks are determined considering the superposition effect to reduce the inundation risk by controlling and distributing the inflows in sewer pipes. Then, urban inundation can be reduced for excessive rainfall events. An Optimal Sewer Layout Model (OSLM) was developed to control and distribute the inflows in sewer networks and reduce urban inundation. The OSLM uses GA (Genetic Algorithm) to solve the optimal problem for sewer network design and SWMM (Storm Water Management Model) to hydraulic analysis. This model was applied to Hagye basin with 44 ha. As the applied results, in the optimal sewer network, the peak outflow at outlet was reduced to 7.1% for the design rainfall event with 30 minutes rainfall duration versus that of current sewer network, and the inundation occurrence was reduced to 24.2% for the rainfall event with 20 years frequency and 1 hour duration.

Slope effect on core-annular flow

To facilitate the flow of heavy viscous oils in a pipe, a water-lubricated transport is generally used. The water migrates into the regions of high shear at the pipe wall where it lubricates the flow. The pumping pressures are balanced by wall shear stresses in the water, the process therefore requires pressures comparable to pumping water alone, with no dependence on the viscosity of the oil. This means that significant savings in pumping power can be derived from this process, provided that it is well monitored. Indeed, the flow of a water/oil mixture in a pipe has two main characteristics. First, the fluids can adopt different spatial arrangements called flow regimes, and second, the presence of a water layer at the channel wall significantly reduces the global pressure drop. In this paper, an experimental investigation was performed on the effect of pipe slope and fluids flow rates on flow regimes, pressure drop and interfacial instability.

Application of cellular automata to sewer network optimization problems

A Cellular Automata approach is introduced in this paper for the optimal design of sewer network problems. The solution of sewer network optimization problems requires the determination of pipe diameters and average pipe cover depths, minimizing the total cost of the sewer network subject to operational constraints. One constraint of the problem, namely, the maximum relative depth of flow, is first used to define the pipe diameters in terms of the pipe slope and, hence, the nodal elevation of the network. As a result, the sewer network optimization problem is redefined, in terms of the network nodal elevations, and the resulting problem is solved using a Cellular Automata (CA) approach. The nodes of the network are used as the CA cell, with the corresponding elevations as CA cell states. The updating rule of the proposed CA is then derived by requiring the stationary total penalized objective function of the problem, with respect to the cell state. The proposed method is used to solve two benchmark examples and the results are compared to those obtained by other methods. The results indicate that the proposed method is highly efficient compared to alternative methods, while producing comparable results.

From a Model of Lossy Flared Pipes to a General Framework for Simulation of Waveguides

This paper deals with the theory and application of waveguide modeling of lossy flared acoustic pipes, relying on the Webster-Lokshin equation. This model describes the propagation of longitudinal waves in axisymmetric acoustic pipes with a varying cross-section, visco-thermal losses at the walls, and without assuming planar waves or spherical waves. Solving this model for a piece of pipe leads to a two-port system made of four transfer functions which mimic the global acoustic effects. Moreover, introducing some relevant physical interpretations makes it possible to separate elementary effects due to the geometry of the piece of pipe (section, slope, and curvature) and isolate corresponding elementary transfer functions. From this decomposition a framework is obtained which allows to recover some digital waveguide models introduced earlier in the literature. This work contributes to the standardization of some different waveguide models, and brings a higher level of refinement that is visco-thermal losses combined with curvature effects.

EXPERIMENTAL STUDY ON PIPING FAILURE OF NATURAL DAM

The failure of natural dam may occur with a variety of failure modes which includes overtopping, seepage or piping, sudden sliding etc. Natural dams may fail due to seepage or piping because they have not undergone systematic compaction and they may have high porosities. In-depth knowledge of the mechanism of the dam failures by seepage or piping and measured data are still lacking. Extensive laboratory experiments are carried out to study enlargement of the pipe due to internal erosion and resulting outflow hydrographs by varying size of initial pipe, lake water level, lake water volume, slope and location of the pipe. This paper highlights limitations of simplified models used to predict outflow hydrograph due to piping failure of the dam based on experimental results and provides data set for the validation of numerical model. Experimental results show that the initial size, slope and location of pipes have significant effects on magnitude and occurrence time of peak discharge.

Predicting Sewer Conditions for Large Collection Systems: The L.A. Experience

Predicting Sewer Conditions for Large Collection Systems: The L.A. ExperienceThe purpose of this presentation is to discuss a cost-effective method to evaluate the risk of failure to prioritize pipes for inspection based on a sewer condition prediction algorithm. This sewer condition prediction algorithm utilizes pipe age, material, slope, and pipe length in its risk of failure determination. The algorithm could easily be adjusted to incorporate additional factors such as...Author(s)Regidia MayrenaC. Bryan TrussellFernando GonzalezDoug WaltersAli PoostiSourceProceedings of the Water Environment FederationSubjectSession 10: Asset Management - New Tools to Repair Old ProblemsDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2011ISSN1938-6478SICI1938-6478(20110101)2011:18L.454;1-DOI10.2175/193864711802638968Volume / Issue2011 / 18Content sourceWEFTECFirst / last page(s)454 - 457Copyright2011Word count103Subject keywordsCondition assessmentcollection systems planning toolspredictive modelingwastewaterGIS applications