TU Berlin

Chair of Water Resources Management and Modeling of HydrosystemsAbstract

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Abstract

On the one hand, urban water systems are stressed by numerous loads, for example contaminations from treated wastewater, industry, runoff of streets and on the other hand their functioning is highly desirable to maintain the urban environment. The impact of the contaminations can be predicted with numerical models which help to understand and identify the relevant processes and which can be applied to design engineering measurements.

This doctoral thesis deals with two- and three-dimensional numerical simulations of hydrodynamics and conservative transport processes in two urban surface water systems of Berlin, a section of the river Spree and the Unterhavel water system, both characterized by slow flow velocities. For this purpose, the TELEMAC modelling system was used and 2D as well as 3D simulations were carried out considering various conditions: low, mean and high discharge, tracer injection points and diffusivity. Finally, the impact of mean and strong winds was considered for the Unterhavel.

The section of the river Spree has a very simple geometry and is stressed by combined sewer overflow which is idealized as conservative tracer. The project area under investigation here and within the research project SPREE-2011 is located in Berlin, Friedrichshain-Kreuzberg. This study aims to show the impacts of installed storage tanks on the hydraulics and water quality. The numerical results show that the impacts of the tanks on the hydraulics are small, and the transport is strongly advection-dominated except for low flow conditions. The results indicate that a 3D model is only necessary in the direct area surrounding the injection point.

The geometry in the Unterhavel water system is highly complex and therefore it is a challenge for stable 3D simulations. This study aims to improve understanding 2D and 3D flow and transport processes in the Unterhavel and to determine dominated processes and parameters. The results show that the Wannsee is strongly influenced by the injection at the Teltow channel but only slightly influenced by the injection at Pichelssee. In addition, a tracer injected in the north at Pichelssee mainly flows from North to South through the system. Moreover, the transport is mainly advection-dominated, except in stagnation areas where (turbulent) diffusion becomes visible. In the case without wind, the 3D profiles of velocity and tracer are parabolic in large parts of the domain, except in special stagnation areas. Finally, in the case of strong wind, strong 3D flow and transport effects occur with different flow directions in a profile at the surface (following the wind direction) and opposite flow direction at the bottom as well as complex horizontal and vertical circulations.

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