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Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia
Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of
Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
Overview of Sandia Wind Turbine Blade
Analysis May 31, 2012
Sandia Blade Workshop
Brian Resor Blade Design Tools and System Analysis Lead
Wind Energy Technologies Department Sandia National Laboratories
Problem and Strategy
Simulation and analysis demands associated with aggressive Sandia wind energy technology projects constantly push the limits of the state of the art in wind turbine blade structural and full system aeroelastic simulation
Strategy:
• Utilize a hybrid of existing design codes and in-house developments to meet Sandia needs
• Complement the NREL NWTC Design Codes and commercially available codes
• Create new capabilities only when capabilities do not exist
Beam Properties
Blade Design with NuMAD
3
ANSYS 11.0SP1
JUN 3 2009
16:04:19
DISPLACEMENT
STEP=1
SUB =3
FREQ=9.056
PowerGraphics
EFACET=1
AVRES=Mat
DMX =.328723
1
X
Y
Z
*DSCA=6
XV =-1
DIST=4.376
XF =.266038
YF =-.250333
ZF =3.978
Z-BUFFER
pseudoSERI8
0
1,000
2,000
3,000
4,000
5,000
6,000
7,000
8,000
9,000
0 0.2 0.4 0.6 0.8 1
BlFract
FlpStff (kN/m^2)
EdgStff (kN/m^2)
Modal
ANSYS FE Model
Materials & Layups
Stack Placement
Blade Geometry
NuMAD NuMAD:
Numerical Manufacturing
And Design Tool
ANSYS Analysis
Buckling
Stress &
Strain
Aeroelasticity: The Structural Design & Analysis Cycle
Beam Model:
Up to 6 DOF per node
Wind turbine blades include
• Variable section shapes with twist,
• Multiple materials and composite layups (glass, carbon, balsa, foam, epoxy, adhesives)
• One or more shear webs
Aerodynamic and
structural dynamic
loads applied to the
model
Full system aeroelastic simulation
FAST or ADAMS & AeroDyn
NuMAD History (Nu)merical (M)anufacturing (A)nd (D)esign tool for wind turbine blades
Released initially ~2001 at Sandia; written in Tcl
Experienced a few hurdles along the way:
• Concerns regarding offset node shell element formulations Created motivation for development of tools such as PreVABS/VABS as well as 2D sectional analysis
approaches; some pursued blade models made of brick elements
• Concerns regarding amount of time required to build and solve models
• Concerns about an increasing number of bugs in NuMAD, likely associated with more recent operating systems
A NuMAD tutorial was held at this workshop 2 years ago where it was decided to pursue a major update of the NuMAD tool for the benefit of Sandia users, as well as users in the research community at large
The beginnings of a Matlab-based NuMAD was born in late 2010
Public release of new version planned for end of summer 2012
A 9m Sandia CX-100 example:
NuMAD Interface
Thanks to Jonathon Berg of Sandia for his dedication and
meticulous work toward a complete overhaul and upgrade
of NuMAD!
Sandia Blade Models
CX-100 9m
TX-100 9m
BSDS 9m
Generic WindPACT 33.25m Concept
62.5m Concept
100m Concept
SNL 100m blade
Offshore SHM studies
Active aero load control
Blade reliability collaborative
Radar blade investigations
Sensor blade 1 & 2
Hydro blade acoustics
Scaled underwater turbine
Sandia Supported Projects
New Features of NuMAD 2012
Matlab-based user interface
• Fast
• Bug free
• Easy to customize and develop
Sweep and/or prebend
Excel input
Output for CFD geometry
NREL FAST Blade file output
• 2D method: NREL PreComp
• 3D method: Beam Property Extraction (BPE)
Classical flutter analysis
Blade Sweep/Prebend
Arbitrary blade reference axis can be defined
Excel Input
An advanced user feature
Enables easy parametric inputs
Automatic computation of intermediate airfoil shapes
Easy definition of numerous ply drops
Easy definition of layup stacks; similar to manufacturing drawings
Easy sharing of blade model information
Output for CFD Geometry NuMAD -> Plot3D data format
CX-100 Blade Surface in Pointwise®
Loads application to the FE Model
Normal, tangential and pitching forces can be mapped from BEM simulation (AeroDyn) to all skin nodes in the blade model
Beam Properties Computation Two-Dimensional Approach Pros
• Readily and freely available
• Computationally efficient
Cons
• Limited to 2D analysis
• Simple examples below:
Chosen Tool: PreComp
• Available from NREL NWTC
Three-Dimensional Approach Pros
• Includes three dimensional effects: Boundary conditions and warping
Cons
• Requires creation of the finite element model
Chosen Tool: Beam Property Extraction (BPE)
• Created by David Malcolm, GEC/DNV
• See Malcolm, 2007 Wind Energy for more info
0
1
2
3
4
5
6
7
-0.2 0 0.2 0.4 0.6 0.8
-0.4
-0.2
0
0.2
Blade Span
Chord
Undisplaced nodes
Displaced nodes (exaggerated)
dxdyxyxEflapEI 2),(_ , (1)
dxdyyyxEedgeEI 2),(_ , (2)
dxdyyxyxGGJ ))(,( 22 and (3)
dxdyyxEEA ),( (4)
Calculate Beam Properties Resor,B. “Uncertainties in Prediction of Wind Turbine Blade Flutter.” AIAA SDM 2011
Resor,B. “An Evaluation of Wind Turbine Blade Cross Section Analysis Techniques.” AIAA SDM 2010
0 0.2 0.4 0.6 0.8 1-0.01
0
0.01
0.02
0.03
0.04
0.05
BlFract
Edg
EA
Of (
m)
VABS
BPE
PreComp
0 0.2 0.4 0.6 0.8 1-0.01
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
BlFract
Edg
cgO
f (m
)
VABS
BPE
PreComp
0 0.2 0.4 0.6 0.8 110
-3
10-2
10-1
100
101
BlFract
Edg
Iner
(kg*
m)
VABS
BPE
PreComp
0 0.2 0.4 0.6 0.8 110
-3
10-2
10-1
100
101
BlFract
Flp
Iner
(kg*
m)
VABS
BPE
PreComp
0 0.2 0.4 0.6 0.8 110
6
107
108
109
1010
BlFract
EA
Stff
(N/m
)
VABS
BPE
PreComp
0 0.2 0.4 0.6 0.8 110
3
104
105
106
107
108
BlFract
Edg
Stff
(N*m
2 )
VABS
BPE
PreComp
0 0.2 0.4 0.6 0.8 110
2
103
104
105
106
107
108
BlFract
Flp
Stff
(N*m
2 )
VABS
BPE
PreComp
0 0.2 0.4 0.6 0.8 110
2
103
104
105
106
107
108
BlFract
GJS
tff (N
*m2 )
VABS
BPE
PreComp
0 0.2 0.4 0.6 0.8 110
0
101
102
103
BlFract
BM
assD
en (k
g/m
)
VABS
BPE (215 kg)
PreComp (177 kg)
Edge EA Offset Edge Inertia Edge CG Offset
Flap Inertia EA Stiff. Edge Stiff.
Mass Dens. Flap Stiff. GJ Stiff.
Comparing three techniques: BPE, 2D Section & VABS
Sandia Classical Flutter Capability
SNL legacy capability (Lobitz, Wind Energy 2007) utilized MSC.Nastran and Fortran to set up and solve the classical flutter problem.
• Requires numerous manual iterations to find the flutter speed
A new Matlab based tool has been developed in 2012 by Brian Owens, Texas A&M
• Starting point: Emulate all assumptions of the legacy Lobitz tool
• Continued development and verification: automated iterations, higher fidelity modeling assumptions
0
10
20
30-10 -5 0 5 10
-10
-5
0
5
10
(m)
K&C Magnified Flutter Mode, freq=11.87 hz, RPM=61.8
(m)
(m)
0
10
20
30-10 -5 0 5 10
-10
-5
0
5
10
(m)
K&C Magnified Flutter Mode, freq=11.87 hz, RPM=61.8
(m)
(m)
Flutter Mode Shape
0,,, 0 uKKKuKuCCuMM acstcaCa
Matrix Description
M, C, K Conventional matrices
(with centrifugal stiffening)
Ma(Ω), Ca(ω, Ω), Ka(ω, Ω) Aeroelastic matrices
CC(Ω) Coriolis
Kcs(Ω) Centrifugal softening
Ktc Bend-twist coupling
100m Blade Flutter Parameter Study
Resor and Griffith. “Aeroelastic Instability of Very Large Wind Turbine Blades.” Scientific Poster. EWEA Copenhagen, 2012.
Data shown are from classical flutter
analyses of various wind blade
sizes:
• SNL 9-meter CX-100 experimental
blade [Resor, 2011]
• WindPact 33.25-meter 1.5MW
concept blade [Lobitz, 2007]
• SNL 62.5-meter blade (preliminary
design)
• SNL 100-meter blade concept
0 0.2 0.4 0.6 0.8 1-1
-0.5
0
0.5
1
x/L
Flutter Mode Shape at 2.1 Hz
Uz
x
Future Work in Aeroelasticity Areas for future research:
Perform blade beam property validations
• Torsion matters: Passive load alleviation via bend twist coupling or blade geometry
Flexible, nonlinear blades
Large deflection blades
Blade materials response characterization
Accurate determination of blade loads
• Especially extreme loads
Continued aeroelastic instability (flutter) tool development and validation
• Will be required for very large blade concepts
Our Goals
Provide Sandia and its partners with a state of the art blade modeling capability and also
Enable the entire research community to benefit from these developments to do cutting edge research
Remainder of 2012 …
• Package and release NuMAD (source and compiled), supporting tools and example blade models
• Software will be available by end of the summer on the Sandia Wind Energy Technologies website
And beyond …
• Some time available for maintenance and integration of externally generated ideas
• There are extensive plans for internal use at Sandia and among partners, which will drive future developments