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Comparison of Numerical and Experimental Investigations of Trashrack Losses

Author(s): Hubert Meusburger; Felix Hermann; Roland Hollenstein

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Keywords: Trashrack loss; Direct-Numerical-Simulation (DNS); Large EddySimulation (LES) Vortex

Abstract: Trashracks, consisting of an array of bars, are typical inlet devices of river power plants which prevent large obstacles from damaging the turbines. They produce energy losses which increase significantly as the spacing of bars decreases. This paper presents a comparison between different numerical methods and experimental investigations to predict these losses for arbitrary inflow conditions to trashracks. First, simulations with high resolution grids using either the Direct Numerical Simulation (DNS) technique or a Large Eddy Simulation (LES) are made, depending of the Reynolds number. These simulations cover only a small part of a trashrack domain, typically 3 or 4 bars, but they allow a precise description of the flow phenomena which occur upstream, between and downstream of the bars. As the bar spacing reduces, substantial changes in the flow structure occur. The results of simulations are then compared with experimental results on such trashracks in laboratory scale. Different inflow angles were examined. The velocity range extended from 0. 50 m/s to 1. 5 m/s, while the blockage ration lie between 0. 18 and 0. 54. The numerical and experimental agree.


Year: 1999

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