Modeling and optimization of production and distribution of drinking water at VMW

We develop and discuss an operational planning model aiming at minimizing production and distribution costs in large drinking water networks containing buffers with free inflow. Modeling drinking water networks is very challenging due of the presence of complex hydraulic constraints, such as friction losses and pump curves. Non-linear, non-convex constraints result from the relationships between pressure and flow in power terms. Also, binary variables are needed to model the possibility of free inflow or re-injection of water at reservoirs. The resulting model is thus a non-convex Mixed-Integer Non-Linear Program (MINLP). A discrete-time setting is proposed to solve the problem over a finite horizon made of several intervals. A commercial solver, BONMIN, suited for convex MINLP models is used to heuristically solve the problem. We are able to find a good solution for a small part of an existing network operated by the Vlaamse Maatschappij voor Watervoorziening (VMW), a major drinking water company in Flanders

Simulation instationärer Wärmeleitungsprozesse bei der Impuls-Video-Thermographie

Um die Grundlage für eine Schichtdickenbestimmung beschichteter Materialien sowie für eine quantitative Fehleranalyse mit Hilfe des Impuls-Video-Thermographieverfahrens zu schaffen, wurden im Rahmen einer Diplomarbeit Modellrechnungen auf der BAsis der instationären Wärmeleitungstheorie durchgeführt. Zur Lösung der entsprechenden Differentialgleichungen für den ein- und zweidimensionalen Fall wurde die Finite-Elemente-Methode verwendet, wobei die speziellen Randbedingungen der Impuls-Video-Thermographieprüftechnik, einschließlich der Lichtabsorption in einer Oberflächenschicht berücksichtigt wurde

Robust Design of Pumping Stations in Water Distribution Networks

International audienceRestricted to gravity-fed networks, most water network design models minimize investment costs under a static peak water demand scenario. In networks equipped with pumping stations, design models should also account for operation costs incurred by the pump energy consumption that depends on dynamic demand and tariff. Evaluating the lifetime operation costs amounts to solve a large-scale non-convex combinatorial optimization problem for each considered design. In this paper, we address the pressurized water network design problem with a joint optimization of the pump investment and operation costs through a stabilized Benders' decomposition. To reduce the complexity of the operational subproblem, we decompose the scheduling horizon in representative days, and relax the discrete and non-convex components of the hydraulic model. We also evaluate the design robustness on stress-day scenarios and derive feasibility cuts using a dominance argument. Experiments on a typical rural branched water distribution network with one year of historical data show the accuracy of our approximations and the significant savings expected from the optimal pump resizing

Numerical methods in underwater acoustics - sound propagation and backscattering

This report summarizes an overview given at the XXXII Symposium on Hydroacoustics (SHA 2015) over several modelling techniques that are used in the context of military applications at the Research Department FWG of the German Bundeswehr Technical Centre for Ships and Naval Weapons, Maritime Technology and Research (WTD 71). For the modelling and understanding of sound propagation a physical model consisting of a tank for scaled measurements and the corresponding numerical simulation is presented. The basic formalism of stochastic ray tracing of the German Navy sonar simulation MOCASSIN is explained and compared to traditional deterministic ray tracing including the comparison with measurements. Strategies for the approximate calculation of the sonar target strength of large underwater objects with the use of boundary element methods, fast multipole methods and a ray-based algorithm are presented and the results of the calculations of several test objects are shown