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Title: Numerical simulation of swirling flow in complex hydroturbine draft tube using unsteady statistical turbulence models

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 degree 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.
Authors:
 [1] ;  [1] ;  [2]
  1. University of Minnesota
  2. ORNL
Publication Date:
OSTI Identifier:
930779
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Hydraulic Engineering; Journal Volume: 131; Journal Issue: 6
Research Org:
Oak Ridge National Laboratory (ORNL)
Sponsoring Org:
EE USDOE - Office of Energy Efficiency and Renewable Energy (EE)
Country of Publication:
United States
Language:
English
Subject:
13 HYDRO ENERGY; HYDRAULIC TURBINES; TUBES; COMPUTERIZED SIMULATION; INCOMPRESSIBLE FLOW; VORTEX FLOW; NAVIER-STOKES EQUATIONS; FLOW MODELS; COMPRESSIBILITY; REYNOLDS NUMBER