Post on 07-May-2020
SHF Conference on Cavitation, Hydraulic Machines. Air in Water Pipes.
June 5-6th, 2013, Grenoble, France
Experimental and numerical study of the tip vortex (Application to Kaplan Turbine)
J.Decaix, (HEVS) M. Dreyer, (LMH-EPFL) C. Münch-Alligné, (HEVS) M. Farhat, (LMH-EPFL)
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SHF Conference on Cavitation, Hydraulic Machines. Air in Water Pipes.
June 5-6th, 2013, Grenoble, France
OVERVIEW OF THE PRESENTATION
1.Hydronet 2 Project 2.Experimental Part 3.Numerical Part 4.Experiment vs Numerical 5.Conclusion
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SHF Conference on Cavitation, Hydraulic Machines. Air in Water Pipes.
June 5-6th, 2013, Grenoble, France
Hydronet 2 Project
Multidisciplinary consortium
Simulation of sand erosion
Tip vortex cavitation
Instability of pump-turbine
HydroPower design
Plant monitoring
To improve the Design, Manufacturing and Operation of HydroPower Plants
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SHF Conference on Cavitation, Hydraulic Machines. Air in Water Pipes.
June 5-6th, 2013, Grenoble, France
TIP VORTEX CAVITATION (TVC)
Problematic: • Tip vortex cavitation → severe erosion in axial turbines • Origin: vortex roll up in the gap at the tip of the blades • Remedy (anti-cavitation lip): inefficient • Influence of gap width? • Scale up rules? (actual model tests not reliable)
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SHF Conference on Cavitation, Hydraulic Machines. Air in Water Pipes.
June 5-6th, 2013, Grenoble, France
TIP VORTEX CAVITATION (TVC)
Goals : Experimental and numerical investigations of TVC for a better understanding of the physical phenomena Case study: Naca0009 hydrofoil with variable gap width
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SHF Conference on Cavitation, Hydraulic Machines. Air in Water Pipes.
June 5-6th, 2013, Grenoble, France
EXPERIMENTAL PART
Tools : • Stereo PIV (Particle Image Velocimetry)
Goals : Measure the tip vortex velocity field for various operating conditions:
• Inlet velocity: 5 m/s → 20 m/s • Incidence angle: 3° → 12° • Gap width: 0 mm → 20 mm
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SHF Conference on Cavitation, Hydraulic Machines. Air in Water Pipes.
June 5-6th, 2013, Grenoble, France
EXPERIMENTAL PART Stereo PIV setup:
• LMH cavitation tunnel
• Hydrofoil: Naca0009
• Variable gap width
• 200 mJ YAG laser
• Seeding particles: 20 µm hollow glass spheres
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SHF Conference on Cavitation, Hydraulic Machines. Air in Water Pipes.
June 5-6th, 2013, Grenoble, France
EXPERIMENTAL PART
PIV working principle:
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SHF Conference on Cavitation, Hydraulic Machines. Air in Water Pipes.
June 5-6th, 2013, Grenoble, France
EXPERIMENTAL PART Stereo PIV principle:
Need of a proper optical calibration!
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SHF Conference on Cavitation, Hydraulic Machines. Air in Water Pipes.
June 5-6th, 2013, Grenoble, France
EXPERIMENTAL PART Stereo PIV setup:
Combining the left and right velocity field: 3D velocity field
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SHF Conference on Cavitation, Hydraulic Machines. Air in Water Pipes.
June 5-6th, 2013, Grenoble, France
EXPERIMENTAL PART Velocity field processing:
• Correction of vortex wandering • Mean velocity and vorticity field calculation
Instantaneous Vortex center
Realignment of velocity field before averaging!
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SHF Conference on Cavitation, Hydraulic Machines. Air in Water Pipes.
June 5-6th, 2013, Grenoble, France
NUMERICAL PART
Goals : To perform the numerical simulations of the experimental cases
Tools : • Ansys CFX 14.0 commercial solver • OpenFoam 2.1.0 open source solver
Modelling : Reynolds Average Navier-Stokes computations coupling with standard two-equations turbulence models : k-ε or k-ω SST
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SHF Conference on Cavitation, Hydraulic Machines. Air in Water Pipes.
June 5-6th, 2013, Grenoble, France
FIRST COMPUTATIONS Configurations :
• Incidence angle : α = 10° • Inlet velocity : Uinlet = 5.4 m/s or 10.2 m/s Regap ≈ 105
• Gap value : 5 mm, 10 mm and 15 mm
Mesh : 2.9 millions of points with 30 points in the gap
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SHF Conference on Cavitation, Hydraulic Machines. Air in Water Pipes.
June 5-6th, 2013, Grenoble, France
COMPARISON BETWEEN SOLVERS Position of the tip vortex measured from the maximum of the Q-criterion
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Configuration: U = 10.2 m/s , α = 10°, gap = 10 mm
SHF Conference on Cavitation, Hydraulic Machines. Air in Water Pipes.
June 5-6th, 2013, Grenoble, France
Q-Criterion
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z
y
Definition
Q = 1/2 (||Ω||2 −||S||2)
With: • Ω: Rotation rate tensor • S: Strain rate tensor
SHF Conference on Cavitation, Hydraulic Machines. Air in Water Pipes.
June 5-6th, 2013, Grenoble, France
COMPARISON BETWEEN SOLVERS
Vertical position of the tip vortex downstream the Naca
Configuration : • Uinlet = 10.2 m/s • α = 10°
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SHF Conference on Cavitation, Hydraulic Machines. Air in Water Pipes.
June 5-6th, 2013, Grenoble, France
COMPARISON BETWEEN SOLVERS
Spanwise position of the tip vortex downstream the Naca
Configuration : • Uinlet = 10.2 m/s • α = 10°
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SHF Conference on Cavitation, Hydraulic Machines. Air in Water Pipes.
June 5-6th, 2013, Grenoble, France
COMPARISON BETWEEN COMPUTATIONS AND EXPERIMENT
Comparisons : • Done on a plan located 35 mm downstream the
trailing edge x = 85 mm
• Focus on the velocity and vorticity fields
• Position of the vortex core determined from the axial
vorticity
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SHF Conference on Cavitation, Hydraulic Machines. Air in Water Pipes.
June 5-6th, 2013, Grenoble, France
AXIAL VORTICITY
Experiment Computation (OpenFoam)
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Configuration: U = 10.2 m/s , α = 10°, gap = 10 mm
SHF Conference on Cavitation, Hydraulic Machines. Air in Water Pipes.
June 5-6th, 2013, Grenoble, France
VORTEX POSITION Configuration: α = 10° ; U = 10.2 m/s ; Gap = 10 mm
SHF Conference on Cavitation, Hydraulic Machines. Air in Water Pipes.
June 5-6th, 2013, Grenoble, France
CONCLUSION AND OUTLOOK
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Experimental Part PIV set up with correction of the wandering motion Acquisition of data for several flow configurations Analysis of the velocity and vorticity fields evolution with
tip vortex confinement
Numerical Part Comparison between CFX 14.0 and OpenFoam 2.1.0 for
different flow configurations Comparison between solver results and experimental data
for different flow configurations
FUTURE A deeper investigation of the tip vortex in cavitating and non-cavitating configurations