Author(s): Marton Zsugyel; Tamas Tel; Janos Jozsa
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Keywords: No Keywords
Abstract: The application of chaos theory in the context of fluid dynamics in general, and fluvial conditions in particular is still an evolving research field. In order to present the chaotic advection behaviour and its basic features in River Danube in Hungary buoys supplied with GPS were released in the vicinity of groins and a detailed analysis of their trajectories was carried out, which is an inherently Lagrangian approach. Due to the preliminary character of the investigations, a small number of buoys were used, which were of course unable to provide a complete picture and proof on the chaotic features, nevertheless, were suitable to find some indication of such behaviours. These include the determination and inter-comparison of the Lyapunov exponent. It is also worth noting that the surface buoys sampled the uppermost layer of the flow, only. In order to give a more extended characterization of the mixing the adaptation of unsteady 2-and 3D numerical flow models, the latter supplied with various turbulence and LES modules, is underway. Apart from using more (say a dozen) buoys in a next field measurement campaign, such numerical models could offer flow velocity field time series to better identify the presence of coherent structures as stable and unstable manifolds, known as elements playing the role of Lagrangian barriers that hinder local transversal material transfer, and avenues that significantly channel transport. In the longer term a more realistic picture on the mixing properties of rivers in the vicinity of groins, as frequently used river training works is expected to obtain.
Year: 2010