In many areas of the world water distribution systems are operated intermittently. The alternate filling and emptying of the pipe network leads to effects, which have negative impacts on water meter accuracy. For example, air that is present in the pipe network due to the emptying process must exit the network during the subsequent filling process. A part of this air is discharged through service connections and, thus, through water meters. In this paper, a study is presented in which the measurement error of single-jet and multi-jet water meters due to the filling process of an empty pipe is investigated experimentally. From the start of air flow to the steady-state flow of water, several causes of measurement errors can be distinguished, such as pure air flow, the impact of the water front on the impeller, the existence of two-phase flow or unsteady flow conditions. For both meter types, it has been discovered that the measurement error is mainly caused by the air flow. The experimental results show that up to 93% of the air volume in the pipe is registered by the water meters. Based on these results, an approach for estimating the measurement error for both meter types is presented.
Studenten aus Karlsruhe initiieren, planen und verwirklichen eigenverantwortlich ingenieurstechnische Entwicklungsprojekte weltweit. In diesem Bericht werden die Herausforderungen eines solchen Projektes am Beispiel der im Sommer 2013 fertiggestellten Hängebrücke im Süden Sri Lankas dargestellt. Neben der Suche nach einem passenden Projekt stellen die Finanzierung sowie die Vorbereitung des Teams auf kulturelle Eigenheiten fundamentale Aufgaben dar. Bei der Planung muss eine Konstruktion entwickelt werden, die den besonderen Beanspruchungen durch den srilankischen Dschungel dauerhaft trotzt und in einer einfachen Bauweise ohne schwere Baumaschinen und ausgebildete Fachkräfte gebaut werden kann. Um dies zu erreichen ist es erforderlich, sich in mancher Hinsicht von den im Studium gelernten Standards und Techniken zu lösen und eigene Konzepte zu entwerfen. In der knapp viermonatigen Bauphase sorgen Kommunikationsprobleme, Schwierigkeiten bei der Terminplanung und Materialbeschaffung sowie Tropenstürme für einen abwechslungsreichen Alltag auf der Baustelle. Nach dem Abschluss des Projektes zeigt sich, dass vor allem ein verlässliches Team, Durchhaltevermögen und die enge Zusammenarbeit mit den Menschen vor Ort für die erfolgreiche Umsetzung unabdingbar sind.
Challenge Sri Lanka – prospective engineers build suspension bridge in the jungle
Students from Karlsruhe University initiate, plan and develop engineering projects worldwide with sole responsibility. In summer 2013 they built a suspension bridge in a small village in the Sri Lankan jungle. This report is going to show and emphasize the challenges which come along with conducting such a project. Next to the project itself the funding needs to be discussed clearly as well as the fact that the whole team needs to be confronted with possible cultural differences and characteristics. Considering the construction of the suspension bridge it needs to be kept in mind that the material needs to be extremely solid due to the Sri Lankan humid climate. The construction of the bridge is supposed to be planned as simple as possible. University students and villagers who are not familiar with working on a construction site are going to build the bridge. In addition for logistical reasons it is not possible to bring and move big construction machines into the Sri Lankan jungle. Therefore it is necessary to throw acquired knowledge overboard and to come up with own creative concepts and ideas. The suspension bridge had been built and finished within four months. Because of communication problems, tropical storms as well as difficulties in accurate project planning and purchasing no day on the construction site was like the other. Looking back a reliable team, staying power and a close cooperation with the villagers is indispensable for completing such a tremendous project successfully.
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