numerical investigation of the swirling flow and the...
TRANSCRIPT
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Numerical investigation of the swirling flow
and the vortex control in a straight diffuser
Ivana Buntic-Ogor
Timo Krappel
Oliver Kirschner
Albert Ruprecht
Institute of Fluid Mechanics and Hydraulic Machinery
University of Stuttgart
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
• Introduction / Motivation
• Test rig and swirl generator
• Available measurements
• Numerical setup
• Numerical results and comparison
• Conclusion
Contents
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Introduction / Motivation
• In hydro power industrial praxis swirling flow appears mostly in the
Francis turbines as a consequence of the part or over load
operation
• Appearance of the vortex rope
• High power losses
• Vortex rope causes strong pressure
pulsations which can lead to resonance
• Prediction of vortex rope of the industrial importance
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Test rig
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Swirl generator
80 mm
130 mm
2 x 8,6°
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Swirl generator and straight cone
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Available measurements
• Numerous measurements for different operational points have been
carried out. Varied were:
• blade angle (15°-30° opening)
• total discharge (30-45 m3/h)
• discharge of axial jet (0-1m3/h)
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Available measurements
• Numerous measurements for different operational points have been
carried out. Varied were:
• blade angle (15°-30° opening)
• total discharge (25-45 m3/h)
• discharge of axial jet (0-1m3/h)
• Measurements type:
• visualization
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Available measurements
• Numerous measurements for different operational points have been
carried out. Varied were:
• blade angle (15°-30° opening)
• total discharge (30-45 m3/h)
• discharge of axial jet (0-1m3/h)
• Measurements type:
• visualization
• pressure fluctuations (30 mm before and after the cone)
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Available measurements
• Numerous measurements for different operational points have been
carried out. Varied were:
• blade angle (15°-30° opening)
• total discharge (30-45 m3/h)
• discharge of axial jet (0-1m3/h)
• Measurements type:
• visualization
• pressure fluctuations (directly before and after the cone)
• LDA (47,5 mm downstream the blade – axial and circumferential
velocity profiles)
LDA
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Available measurements
• Numerous measurements for different operational points have been
carried out. Varied were:
• blade angle (15°-30° opening)
• total discharge (30-45 m3/h)
• discharge of axial jet (0-1m3/h)
• Measurements type:
• visualization
• pressure fluctuations (directly before and after the cone)
• LDA (downstream the blade axis)
• PIV (in the cone)
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Available measurements
• Numerous measurements for different operational points have been
carried out. Varied were:
• blade angle (15°-30° opening)
• total discharge (30-45 m3/h)
• discharge of axial jet (0-1m3/h)
• Measurements type:
• visualization
• pressure fluctuations (directly before and after the cone)
• LDA (downstream the blade axis)
• PIV (in the cone)
• Aim:
• to obtain different velocity profiles / swirl distributions
• test the idea to control vortex rope with axial water jet
• to use the data for further research
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Numerical setup
• Computational domain
• with swirl generator
• only downstream the swirl generator
• Mesh
• not exaggerate with mesh size → different meshes up to 2Mil. (for
case with swirl generator)
• the same was used as in the previous studies with in-house code
• software – ICEM (hexa)
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
• boundary conditions
• numerics (see Dellenback Abrupt Expansion OpenFOAM case study)
• Turbulence models: standard k-ε, kOmegaSST, kOmegaSSTF (filtered
kOmegaSSTF), wall function
• unsteady calculations with transientSimpleFoam (initialized with steady
ones)
Variable Inlet Walls Outlet
U profile1DfixedValues fixedValue(0 0 0)
zeroGradient
p zeroGradient zeroGradient fixedMeanValue
k 1,5(Ua*0,05)^2 zeroGradient zeroGradient
ε k^1,5/lt(lt=0,1R)
zeroGradient zeroGradient
ω k^0,5/(0,09lt) zeroGradient zeroGradient
νt/ν 35,6
Numerical setup
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Numerical results• Case with swirl generator
• position 1
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Numerical results• Case with swirl generator
• position 2
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Numerical results• Case with swirl generator
• reason for discrepancy – extensive zone of separation
• will be more investigated
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Numerical results
• Case without swirl generator
• averaged LDA measurements as inlet profile
• blades 30° opening
• Q = 25 and 40 m3/h
• no jet
• modified inlet profile from the complete simulation (previous
study with in-house code)
• blades 30° opening
• Q = 45 m3/h
• no jet
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Numerical results
• Q = 25 m3/h
k-ε SST SSTF
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Numerical results
• Q = 25 m3/h
k-ε SST SSTF
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Numerical results
• Q = 25 m3/h
k-ε SST SSTF
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Numerical results
• Q = 40 m3/h
k-ε SST SSTF
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Numerical results
• Q = 40 m3/h
k-ε SST SSTF
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Numerical results
• Q = 40 m3/h
k-ε
SST SSTF
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Comparison
Discharge [m3/h]
Frequency [Hz]
Amplitude [bar]
Simulation Experiment Simulation Experiment
sst sstf sst sstf
25 9,39 10,99 8,54 0,0022 0,0016 0,002
40 14,39 14,55 13,49 0,0067 0,0071 0,007
Discharge [m3/h]
Strouhal nr.[-]
Simulation Experiment
sst sstf
25 0,54 0,63 0,495
40 0,52 0,52 0,488
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Numerical results
• Q = 45 m3/h, modified inlet profile
LRR
RSMLaunder-Gibson
RSM
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Conclusion
• Presentation of IHS test rig – measurements can be
used for further research / test case
• Test rig and swirl generator
• Different operational points numerically simulated
• Investigation of turbulence models
(kOmegaSST, kOmegaSSTF)
• Comparison with experiments → good agreement
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010
University of Stuttgart
Institute of Fluid Mechanics and Hydraulic Machinery
Acknowledgements
• To our colleagues, guest researchers, guest students and students
who has been doing the measurements
• All OpenFOAM community
Buntic-Ogor I. et al., Numerical investigation of the swirling flow and the vortex control in a straight diffuser
5th OpenFOAM Workshop, Chalmers University of Technology, 21-24.06.2010