Flow Simulation of Francis Turbines Using Hybrid RANS-LES Turbulence Models

Timo Krappel (), Albert Ruprecht and Stefan Riedelbauch
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Timo Krappel: Institute of Fluid Mechanics and Hydraulic Machinery
Albert Ruprecht: Institute of Fluid Mechanics and Hydraulic Machinery
Stefan Riedelbauch: Institute of Fluid Mechanics and Hydraulic Machinery

A chapter in High Performance Computing in Science and Engineering ‘14, 2015, pp 417-431 from Springer

Abstract: Abstract The operation of Francis turbines in part load condition causes high pressure fluctuations and dynamic loads in the turbine as well as high flow losses in the draft tube. Owing to the co-rotating velocity distribution at the runner blade trailing edge a low pressure zone arises in the hub region finally leading to a rotating vortex rope in the draft tube. The goal of this study is to reach a quantitatively better numerical prediction of the flow at part load and to evaluate the necessary numerical depth with respect to effort and benefit. The focal point of the investigations is on flow simulations of part load conditions using two different kinds of hybrid RANS-LES turbulence model approaches: Scale Adaptive Simulation (SAS) and Improved Delayed Detached Eddy Simulation (IDDES). The flow simulations are done for a high specific speed Francis turbine and a low specific speed Francis pump turbine. The mainly dominating flow phenomenon, the rotating vortex rope, with a frequency of around one third of the runner frequency, requires long physical time and therefore long computational time using many processors.

Keywords: Turbulence Model; Guide Vane; Draft Tube; Spiral Casing; Turbulent Eddy Viscosity (search for similar items in EconPapers)
Date: 2015
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Persistent link: https://EconPapers.repec.org/RePEc:spr:sprchp:978-3-319-10810-0_28

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DOI: 10.1007/978-3-319-10810-0_28

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