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ISSN 1439-4111
The origin of secondary currents and subaqueous sediment patterns in natural rivers is analysed from first principles. For this purpose, simulations of sediment transport in canonical turbulent open channel flows are performed using a numerical technique that resolves all relevant flow scales and the dynamics of the individual sand grains. The high-fidelity datasets reveal the fundamental importance of individual coherent structures for the development of sediment patterns and secondary flows.
Umfang: XXIX, 303 S.
Preis: 56.00 €
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The transport of bacteria in turbulent river-like environments is addressed, where bacterial populations are frequently encountered attached to solids. This transport mode is investigated by studying the transient settling of heavy particles in turbulent channel flows featuring sediment beds. A numerical method is used to fully resolve turbulence and finite-size particles, which enables the assessment of the complex interplay between flow structures, suspended solids and river sediment.
Umfang: XV, 258 S.
Preis: 51.00 €
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This book addresses the turbulence-driven mean secondary motions in straight open duct flow with rectangular cross-section. Despite its weak intensity, the secondary flow influences the primary velocity distribution significantly. Coherent structure analysis showed that the secondary flow is the statistical footprint of quasi-streamwise vortices, and the unique mean flow pattern is a consequence of a vortex sorting mechanism that is only effective in the vicinity of free surface.
Umfang: XXVI, 174 S.
Preis: €57.00 | £52.00 | $100.00
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This book investigates the formation of subaqueous patterns by means of high-fidelity numerical simulations which resolve all the relevant scales of the flow and the sediment bed. This is required to provide a space- and time-resolved information on the flow field and the sediment bed. Secondly, detailed analysis of the generated data allows to address the different governing mechanisms involved in the formation of patterns as well as to access the validity of various existing models.
Umfang: XXIII, 142 S.
Preis: €51.00 | £47.00 | $90.00
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This book contributes to the fundamental understanding of the physical mechanisms that take place in pseudo turbulent particulate flows. In the present work we have considered the sedimentation of large numbers of spherical rigid particles in an initially quiescent flow field. We have performed direct numerical simulations employing an immersed boundary method for the representation of the fluid-solid interface. The results evidence that depending on the particle settling regime (i.e.\ Galileo number and particle-to-fluid density ratio) the particles may exhibit strong inhomogeneous spatial distribution. It is found that the particles are preferentially located in regions with downward fluid motion. The particles inside clusters experience larger settling velocities than the average. The flow in all flow cases is observed to exhibit characteristic features of pseudo-turbulence. The particle-induced flow field is further found to be highly anisotropic with dominant vertical components. The results indicate that, in the present flow configurations, the collective and mobility effects play significant role for the particle and fluid motion.
Umfang: XIX, 238 S.
Preis: €59.00 | £54.00 | $104.00
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This thesis aims to contribute to a better understanding of turbulent open channel flow, sediment erosion and sediment transport. The thesis provides an analysis of high-fidelity data from direct numerical simulation of (i) open channel flow over an array of fixed spheres, (ii) open channel flow with mobile eroding spheres, (iii) open channel flow with sediment transport of many mobile spheres. An immersed boundary method is used to resolve the finite-size particles.
Umfang: XXXII, 154 S.
Preis: €51.00 | £47.00 | $90.00
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Die Errichtung von Hochwasserretentionsräumen entlang von Flüssen ist eine verbreitete Maßnahme zur Verbesserung des Hochwasserschutzes. Durch die zusätzlichen Überflutungsflächen können vermehrt Schadstoffe aus der Hochwasserwelle in das Grundwasser eingetragen werden. Dies kann zu einer Gefährdung der Trinkwasserressource in den Flussauen führen. In der vorliegenden Arbeit wird eine Methode zur Risikoberechnung für eine Grundwassergefährdung in einem Hochwasserretentionsraum vorgestellt.
Umfang: XIV, 185 S.
Preis: €32.50 | £30.00 | $57.00
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Die Auswirkungen von Baumpflanzungen auf die Durchlüftung von innerstädtischen Straßenzügen wurden in Windkanalexperimenten und in numerischen Simulationen untersucht. Die Baumpflanzungen führten zu geringeren Windgeschwindigkeiten und höheren verkehrsbedingten Schadstoffbelastungen aufgrund eines verminderten Luftaustausches mit der Umgebung. Ein Modell zur Bestimmung der Auswirkungen von Baumpflanzungen auf die verkehrsbedingte Schadstoffbelastung in Straßenschluchten wurde entwickelt.
Umfang: 142 S.
Preis: €29.90 | £28.00 | $53.00
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Simultaneous 2D pressure and 2D velocity information at the rough water-sediment interface of streambeds were gained by a newly developed measurement setup. In the bed the pressure fluctuations decay exponentially within the first 1-2 equivalent sand roughnesses. Structural findings concerning coherent flow structures are consistent with models originally developed for smooth walls. A significant bed destabilizing flow-pressure pattern was identified for the first time.
Umfang: IV, 153 S.
Preis: €27.90 | £26.00 | $49.00
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In der vorliegenden Arbeit wurde mit der Entwicklung einer differentiellen Turbulenzsaule das advektionsfreie Turbulenzprofil einer offenen Gerinnestromung im Labor nachgebildet. Hierin konnten die Prozesse der Feinsedimentdynamik nachgebildet und gemessen werden. Die Ergebnisse beschreiben den Prozessablauf in der Feinsedimentdynamik und dienten als Grundlage fur die Entwicklung und Validierung eines Modells zur Bilanzierung der Feinsedimentdynamik in der Wassersaule.
Umfang: VI, 129 S.
Preis: €29.90 | £28.00 | $53.00
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