Wave Celerity in Hydraulic Transients Computation for CIPP-Rehabilitated Pipes

[Abstract] Most of the water pipe infrastructure is outdated; therefore, frequent maintenance and repair works are required. To speed up the rehabilitation work and to have a more sustainable and efficient approach, trenchless methodologies have been developed in the last decades. One of the most cost-effective trenchless methods is the so-called Cured in Place Pipeline (CIPP) method, in which a resin-impregnated liner is pulled or inverted inside the host pipe and, when cured, it restores the old pipe structural and mechanical integrity. The aim of this study is to analyse the effects of the presence of a CIPP liner in a deteriorated pipe during unsteady flow for compressible fluids. In particular, the paper deals with a new formulation to compute the celerity of the wave which produces the overpressures, when the pipe wall is composed of both the host (old) pipe and the new liner, whose thickness depends on the required mechanical characteristics. The problem is strictly dependent on the mechanical properties of the liner. In order to obtain the new formula for celerity, the linear elastic problem for multi-layered pipes has been solved. The theoretical results have been validated by performing numerical simulation analysis using a Boundary Element model, with the software BEASY™. The resulting circumferential strain is integrated in the continuity equation, deriving the new formula to compute the wave celerity. The values of the celerity are dependent on the thickness and on the elastic properties of the liner. The behaviour of several combinations of thickness of the liner and Young’s modulus values has been studied and the results have been critically shown in the paper

Evolutionary optimization for water losses recognition in water supply networks

A methodology to localise the losses in the water supply networks has been developed, which requires the installation of a number of flowmeters and pressure transducers on the network and the building of a numerical model. The calibration of the model to match the recorded network parameters (pressures and discharges) is done by searching an optimal set of water demands at network nodes. The comparison between the optimal set and the standard one allows the identification of the areas where the leakages are most likely to be present. The optimal set of water demands is identified by the minimisation of an objective function. In the paper, the coupling of this objective function with three evolutionary optimisation methods based on simulated annealing (SA), genetic algorithms (GA) and modified particle swarm optimization (MPSO) have been discussed and tested on a case study. The simulations show SA risks to be trapped in unfeasible zones in its search, while the methods based on GA and MPSO perform very well because in these latter methods, the individuals constituting a population work mainly in groups. Moreover, the solution obtained by GA and MPSO can be further improved by means of a simple hill climbing procedure. Considerations on the possibility of having more than one maximum of the objective function and how they can be detected are presented

Dealing with uncertainties in losses assessment in water supply networks: preliminary results

In many countries water losses can be much larger than 50%, with great economic losses because of the energy required for pumping and for the primary treatments that very often are required. Methodologies have been developed in order to identify the areas where losses are most expected, limiting the excavations as far as possible. To this end, the authors developed a methodology which requires the installation of a number of instruments on the network, in order to measure pressures and discharges; then, the demands at the nodes are changed by means of optimization methods and the network is simulated with a computer program, in order to match the readings of the instruments; losses are higher where the demands have been most increased. In previous papers, the authors tested different evolutionary methods to identify the areas where losses are most expected, comparing results from theoretical networks that were, from all the other aspects, exactly identical. In the real world, unfortunately, differences from the simulated the real networks are not limited to the discharge demands, but other uncertainties are present. The most evident uncertainty is related to pipe roughness, which can be considered a parameter of the model; sometimes even the diameters are listed wrong. In the paper, the robustness of the proposed method is tested using networks where roughness parameters and diameters are different, changing the roughness parameter in order to determine the influence of the errors in the evaluation of the areas where losses are most expected. © 2014 WIT Press.139139148 International Journal of Sustainable Development and Planning,WIT Transactions on the Built EnvironmentAlvisi, S., Grata, S., Franchini, M., Leakage detection planning in water distribution systems", in "Management of Water Networks (2006) Proceedings of the Conference Efficient Management of Water Networks. Design and Rehabilitaion Techniques, , Bertola and Franchini (Eds), Ferrara 2006, De Angeli Editore, Milano, ItalyHalhal, D., Walters, G.A., Savic, D.A., Ouazar, D., Scheduling of water distribution system rehabilitation using structured messy genetic algorithms (1999) Evolutionary Computation, 7 (3). , MIT PressGiustolisi, O., Laucelli, D., Savic, D.A., Development of rehabilitation plans for water mains replacement considering risk and costbenefit assessment (2006) J. of Civil Engineering and Environmental Systems, 23 (3), pp. 175-190. , Taylor & Francis, UKEngelhardt, M.O., Skipworth, P.J., Savic, D.A., Saul, A.J., Walters, G.A., Rehabilitation strategies for water distribution networks: A literature review with a UK perspective (2000) Urban Water, 2, pp. 153-170Male, J.W., Walski, T.M., Slutsky, A.H., Analyzing water main replacement policies (1990) J. Water Resour. Plan. Manage, 116 (3), pp. 362-374Sundahl, A., Using break data on water pipe systems for renewal planning (1996) COST Action C3 Workshop, , 18 and 19 June 1996, BrusselsMambretti, S., (2012) Orsi E. Genetic Algorithms For Leak Detection In Water Supply Networks. 1st International Conference On Urban Water, , 25-27 April, New Forest, UKMambretti, S., Martins, P.S., Moraes, R.L., (2013) Evolutionary Computation Techniques to Assess Losses In Water Supply Networks 7th International Conference On Sustainable Water Resources Management, , 21 - 23 May, New Forest, UKBack, T., Fogel, D., Michalewicz, Z., (1997), Handbook of evolutionary computation IOP Publishing Ltd. and Oxford University Press, New York and OxfordHolland, J.H., Outline for a logical theory of adaptive systems (1962) Journal of the ACM, 9 (3). , ACMHolland, J.H., (1975) Adaptation In Natural and Artificial Systems, , University of Michigan PressGoldberg, D.E., Genetic algorithms in search, optimization and machine learning (1989) Massachusetts, , Addison-Wesley, ReadingKennedy, J., Eberhart, R., Particle Swarm Optimization (1995) Proc. IEEE Int. Conf. On Neural Networks (Perth, Australia), IEEE Service Center, pp. 1942-1948. , Piscataway, NJ, IVRossman, L.A., (2000) Epanet 2. Users Manual, , EPA Office of Research and Development U.S., Environmental Protection Agency, Cincinnat

Graph theory and community detection for elementary DMA design

In this work, with the objective of designing elementary district metered areas (eDMAs), graph theory methods and community structured algorithms are applied to the case of the water distribution network of Milano. This network is highly looped and very complex, serving about two million people. Initially, the network is subdivided into 27 eDMAs, which are the number of pumping stations in operation, obtaining three different divided networks (one from community structured algorithms and two from graph theory). Unlike other procedures based on traditional techniques to sectorize networks, the maximum size of each eDMA was not previously restricted, thus generating significantly larger districts. Afterwards, a simple algorithm was applied to aggregate the eDMAs into dynamic DMAs to reduce the energy consumption and overall pressures in the network for the hour of lowest water consumption. Results show improvement in both aspects, thus justifying the study. Further studies are recommended in order to propose other eDMAs designs and other dynamic DMAs configurations