Numerical Simulation of Swirling Flow in Complex Hydroturbine Draft Tube Using Unsteady Statistical Turbulence Models
Publication: Journal of Hydraulic Engineering
Volume 131, Issue 6
Abstract
A numerical method is developed for carrying out unsteady Reynolds-averaged Navier-Stokes (URANS) simulations and detached-eddy simulations (DESs) in complex 3D geometries. The method is applied to simulate incompressible swirling flow in a typical hydroturbine draft tube, which consists of a strongly curved 90° elbow and two piers. The governing equations are solved with a second-order-accurate, finite-volume, dual-time-stepping artificial compressibility approach for a Reynolds number of 1.1 million on a mesh with 1.8 million nodes. The geometrical complexities of the draft tube are handled using domain decomposition with overset (chimera) grids. Numerical simulations show that unsteady statistical turbulence models can capture very complex 3D flow phenomena dominated by geometry-induced, large-scale instabilities and unsteady coherent structures such as the onset of vortex breakdown and the formation of the unsteady rope vortex downstream of the turbine runner. Both URANS and DES appear to yield the general shape and magnitude of mean velocity profiles in reasonable agreement with measurements. Significant discrepancies among the DES and URANS predictions of the turbulence statistics are also observed in the straight downstream diffuser.
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Acknowledgments
This work was supported by National Science Foundation career grant 9875691 and a grant from the Energy Efficiency and Renewable Energy Office of the U.S. Department of Energy, Wind and Hydropower Technologies Office. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.
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Information & Authors
Information
Published In
Journal of Hydraulic Engineering
Volume 131 • Issue 6 • June 2005
Pages: 441 - 456
Copyright
© 2005 ASCE.
History
Received: Jul 14, 2004
Accepted: Nov 15, 2004
Published online: Jun 1, 2005
Published in print: Jun 2005
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