Wind turbine modeling using ANSYS
Dr.-Ing. Robert Meier-Staude
[email protected] Dr.-Ing. Martin Kuntz
[email protected] © 2006 ANSYS, Inc. All rights reserved.
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Table of Contents
• Acoustics modelling with CFD – Turbulence modeling for acoustics – Applications
• Transitional turbulence for wind turbine applications – Model – Applications © 2006 ANSYS, Inc. All rights reserved.
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Turbulence
•
•
Character
– Increased losses – Delayed separation with pressure gradients – Increased energy transport – Increased heat flux – Increased mixing – Noise
– Three dimensional – Transient – Many scales
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Effects on flow
3
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Turbulence
•
•
Character
– Increased losses – Delayed separation with pressure gradients – Increased energy transport – Increased heat flux – Increased mixing – Noise
– Three dimensional – Transient – Many scales
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Effects on flow
4
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CFD for Acoustics: Overview Flow induced noise
Sound generation
Acoustic source prediction
CFD
Near field CFD Sound propagation
Acoustic waves computation Far field Acoustics code
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Acoustic Source Prediction • Wave equation
• Pressure fluctuations Dipoles
• Velocity fluctuations Quadrupoles 2
∂ Tij ∂ ρ ∂Q ∂ Fi 2 ∂ ρ − − co = + 2 2 ∂ xi ∂ xi ∂x j ∂t ∂ xi ∂t 2
2
Tij = ρ U iU j + ( P − c ρ ) δ ij − τ ij 2 o
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CFD for Acoustics: Near field Flow induced noise
Sound generation
Sound propagation
Acoustic source prediction
Acoustic waves computation
CFD
Near field CFD
Far field Acoustics code © 2006 ANSYS, Inc. All rights reserved.
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Acoustic Cavity • Henshaw (2000) • L×W×D= 5×1×1 • Depth = 0.1 m • Iso-surfaces of Ω² − S² = 1 × 105 s-2
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Acoustic Cavity
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Cavity: Pressures Fluctuations Pressure amplitude
Power spectrum density 1E+8
30
1E+7
SAS Model
SAS Model
20
1E+6
15
1E+5
10
PSD [Pa^2/Hz]
Pressure amplitude [KPa]
Experiment
Experiment
25
5 0 -5 -10
1E+4 1E+3 1E+2 1E+1
-15
1E+0
-20 -25
1E-1
-30
1E-2
0E+0
1E-1
2E-1
3E-1
4E-1
0
Time [s]
200
400
600
800
1000 1200 1400
Frequency [Hz]
K29 © 2006 ANSYS, Inc. All rights reserved.
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Car Mirror
Computations carried out at Volkswagen © 2006 ANSYS, Inc. All rights reserved.
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CFD for Acoustics: Near field Flow induced noise
Sound generation
Sound propagation
Acoustic source prediction
Acoustic waves computation
CFD
Near field CFD
Far field Acoustics code © 2006 ANSYS, Inc. All rights reserved.
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CFD for Acoustics: Far field Flow induced noise
Sound generation
Acoustic source prediction
CFD
Near field CFD
Sound propagation
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Acoustic waves computation 13
Far field Acoustics code ANSYS, Inc. Proprietary
P [Pa]
FW-H Application for Fan Noise
R
=
1
ϕ
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m
Power spectral density [W/m2]
1BPF
14
2 BPF
ϕ = 45 ϕ = 60 ϕ = 75
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Gutin’s Noise Model
Steady-State Static Pressure
R
=
1
m
SPL = 19.9 dB (f = 200 Hz, BPF)
Marine Propeller
ϕ = 60 Receiver’s Position © 2006 ANSYS, Inc. All rights reserved.
Acoustic Pressure [Pa] 15
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Broadband Noise Source Models • • •
High surface acoustic power in the A pillar wake
Proudman’s formula for acoustic power Acoustic source intensity for surface (boundary layer) noise Jet noise source models
– Ribner – Goldstein •
Surface Acoustic Power (dB)
Source terms in acoustic equations
Prominent noise sources
– Lilley’s equation – Linearized Euler equations •
Require steady state RANS results (k-e, k-w, RSTM) only
Isosurface of Lilley’s Total Noise Source © 2006 ANSYS, Inc. All rights reserved.
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CFD for Acoustics: Summary Flow induced noise
Sound generation
Acoustic source prediction
CFD
Near field CFD Sound propagation
Acoustic waves computation Far field Acoustics code
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Laminar turbulent transition Turbulent boundary layer
Laminar boundary layer
Transition region
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Transition on compressor blade
RGW Compressor FSTI = 1.25 % Rex = 430 000 Reθc = 400
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Transition on compressor blade
Turbulent ζ = 0.19
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Experiment ζ = 0.097
20
Transition model ζ = 0.11
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2D Wind Turbine Airfoil Tu Contour Transition
Transition
Transition
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NREL Wind Turbine Intermittency Transitional Streamlines
Blue = Laminar Red = Turbulent
7 m/s
10 m/s
20 m/s
3D radial flow in the separated region
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NREL Wind Turbine: Torque Turbulent (20 m/s)
Transitional (20 m/s)
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Transition model: Summary • Correlation based transition model has been developed – Based strictly on local variables – Applicable to unstructured massively parallelized codes
• Onset prediction is completely automatic – User must specify correct values of inlet Tu and RT
• Major transition mechanisms captured – Natural – Bypass – Separation
• Good predictions of 2D (up to AoA = 9°) and 3D Wind Turbine performance © 2006 ANSYS, Inc. All rights reserved.
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CFX FLUENT Thank You! © 2006 ANSYS, Inc. All rights reserved.
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