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Simulation of Flow Characteristics in Groyne Fields Using a Particle Tracing Approach

Author(s): Michael Tritthart; Marcel Liedermann; Helmut Habersack

Linked Author(s): Michael Tritthart, Marcel Liedermann, Helmut Habersack

Keywords: Groyne fields; Retention times; Particle tracing; 3D numerical modelling; River flow

Abstract: Spatio-temporal characteristics of the flow field in groyne areas play an important role for a number of biotic processes. A profound knowledge of the distribution of retention times and water ages is therefore a prerequisite for the development of integrative biotic-abiotic models in instream retention zones. Experimental determination of these parameters involves timeconsuming field work and is often limited to the water surface. This paper presents a method for direct modelling of retention times and water ages using computational fluid dynamics. A numerical particle-tracing method is applied to the results obtained from a threedimensional model for turbulent river flow. This approach allows for taking into account both the inherently three-dimensional nature of flows and the spatial distribution of turbulence structures. Virtual particles are released at several locations within an instream retention pool, and their paths and travel times to and from the main stream are traced using a random-walk approach which uses the turbulent kinetic energy flow property as scale indicator of randomness. Travel times of several numerical experiments are averaged to yield mean retention times. The modelling approach has been validated by comparing it with results obtained during a field experiment in a groyne field of the Danube River between Vienna and Bratislava. The application of the validated model to different runoff values shows that small variations of discharge lead to significant changes in flow conditions and retention times within the groyne field. In particular it was found that the maximum retention times occur at mean annual flow conditions and are smaller for both lower and higher river discharges.


Year: 2007

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