1. 2006 Wind Program Peer Review
Design Codes
Jason Jonkman Sandy Butterfield
Marshall Buhl Gunjit Bir
Pat Moriarty Alan Wright
Neil Kelly Bonnie Jonkman
2006 Wind Program Peer Review
May 10, 2006

2. Outline of Presentation
Introduction & Background
State of the Art Modeling & Limitations
Program Contributions
Current & Future Work

3. Introduction & Background The Big Picture

4. Introduction & Background Modeling Requirements
Fully coupled aero-hydro-servo-elastic interaction
Wind-Inflow:
discrete events
turbulence
Waves:
regular
irregular
Aerodynamics:
induction
rotational augmentation
skewed wake
dynamic stall
Hydrodynamics:
scattering
radiation
hydrostatics
Structural dynamics:
gravity / inertia
elasticity
foundations/moorings
Control system:
yaw, torque, pitch

5. State of the Art Modeling & Limitations Wind-Inflow
Rotor Performance: steady/uniform
Design: IEC-specified deterministic, discrete inflows and an idealistic neutral turbulence simulation (supported by TurbSim)
Research: TurbSim now provides a variety of specific operating environments including flows over flat, homogenous terrain, in and near multi-row wind farms, the NWTC Test Site (complex terrain), and the Great Plains with and without the presence of a low- level jet stream

6. State of the Art Modeling & Limitations Wind-Inflow (cont)
Current Limitations
The Great Plains simulation provides low-level jet wind speed and direction profiles up to 490 m but the turbulence scaling has been extrapolated with validated data from 120 to 230 m (the top of a future 10MW turbine rotor). Data is needed within this height range for validation.
The wind farm simulations are only based on validated data up to a height of 50 m, data is needed to expand and validate this capability for modern wind farms consisting of multi-megawatt turbines for both onshore and offshore installations.
Detailed turbulence measurements and updated models are needed for a range of climatic types in order to better assess potential operating environments and aid in improving siting and turbine reliability.

7. State of the Art Modeling & Limitations Aerodynamics & Aeroacoustics
THIS SLIDE TO BE EDITED BY PAT
Rotor Performance: BEM (WT_Perf)
Design: GDW, interaction with elasticity (AeroPrep, AeroDyn)
Research: Vortex, CFD
Current Limitations:
mention what can and cannot be done
corrections for:
rotational augmentation,
dynamic stall,
unsteady wake,
etc.

8. State of the Art Modeling & Limitations Aerodynamics & Aeroacoustics (cont)
THIS SLIDE TO BE EDITED BY PAT

9. State of the Art Modeling & Limitations Offshore Waves & Hydrodynamics
Fixed-Bottom Design: Linear & nonlinear waves Morison
Floating Design: Linear wave + potential flow (floating)
Research: CFD
Current Limitations:
mention what can and cannot be done
no steep/breaking waves
no 2nd order slow-drift/sum-frequency effects
no sea current/VIV
no sea ice

10. State of the Art Modeling & Limitations Offshore Waves & Hydrodynamics

11. State of the Art Modeling & Limitations Structural Dynamics
Design: external geometrymaterial lay-ups
Loads Analysis: Modal (PreComp, BModes, FAST)
Research: Multibody, FEM (ADAMS, RCAS)
Furling - DWT
Current Limitations:
mention what can and cannot be done
No coupled modes
No flap/twist coupling
No precurve/presweep

12. State of the Art Modeling & Limitations Structural Dynamics (cont)

13. Program Contributions Users & Certification

14. Program Contributions Why Develop Design Codes In-House?
Other codes:
Bladed, FLEX5, DHAT, Phatas, HAWC2
Flexibility:
custom design for our unique requirements
Full system Vs. Component level
Support U.S. wind industry:
workshops

15. Current & Future Work Wind-Inflow
Current work:
Document the development of TurbSim
Use the TurbSim Great Plains Low-Level Jet Spectral Model to excite the 5MW Reference Turbine to assess and document the effects of these jets on LWST turbines
Analyze the available Lamar LIDAR data to obtain further validating information of Great Plains LLJ spectral model simulations
Planning for a workshop on inflow turbulence issues and training in the use of TurbSim
Future plans (2 years out):
Plan field experiment to collect data on turbulence within large, multi-megawatt wind farms
Future opportunities:
Form a multi-discipline, synergistic effort to understand the role of coherent inflow turbulence on turbine drive train dynamics and fatigue

16. Current & Future Work Aerodynamics & Aeroacoustics
THIS SLIDE TO BE EDITED BY PAT
Current work:
improved fidelity of GDW
tower influence
Future plans (2 years out):
Rewrite AeroDyn – make modular, provide hooks for other aero models
Future Opportunities:
Wind tunnel tests/NASA Ames data:
improve engineering aero modules
Aerodynamics:
add vortex aero module
Add CFD aero modules

17. Current & Future Work Offshore Waves & Hydrodynamics
Current work:
Fixed-bottom
Offshore foundations: p-y, t-z
Floating: WAMIT
Mooring dynamics: Lines
OC3 benchmarking
Future plans (2 years out):
???
Future opportunities:
breaking waves
2nd order potential flow

18. Current & Future Work Structural Dynamics

19. Current & Future Work New Horizons
Gearbox dynamics:
Gearbox housing deflection?
Missing internal gearbox loads?
Tower shadow
Controls/stability analysis
Code validation
FEM

21. Introduction & Background What are Design Codes Used For?
R&D knowledge feeds into codes:
Aero
Hydro
Controls
Etc.
Preliminary design:
Rotor performance
Material lay-ups
Detailed design:
Loads
Certification
Controller design (see Alan’s presentation)
Research:
new concepts
Benchmarking
Designers are limited by code capability

22. Introduction & Background Design / Certification Process
Explain how codes fit into the design/certification process
Preliminary design
Detailed design
research
Load cases
Quantity
type (extreme, fatigue)
Justify need for engineering models, as opposed to straight-up CFD/FEM

23. Current & Future Work Structural Dynamics

24. Current & Future Work Structural Dynamics

25. Current & Future Work Structural Dynamics

27. Outline of Presentation
Introduction & Background
Model Development
Sample Results
Conclusions
Future Work
Acknowledgements

28. Introduction & Background The Big Picture
Some wind turbines have been installed in shallow water; none in deepwater
A vast deepwater offshore wind resource represents a potential to power much of the world using floating wind turbines
Numerous platform concepts are possible
Simulation tools capable of modeling the dynamic responses are needed
GE Wind Energy 3.6 MW Turbine

30. Introduction & Background Modeling Requirements for Floating Turbines
Turbulent winds
Irregular waves
Gravity / inertia
Aerodynamics:
induction
skewed wake
dynamic stall
Hydrodynamics:
scattering
radiation
hydrostatics
Elasticity
Mooring dynamics
Control system
Fully coupled

31. Model Development Onshore Wind Turbine Simulators
FAST
Fatigue, Aerodynamics, Structures, and Turbulence
Developed by NREL/NWTC
Originated from Oregon State University
Wind turbine specific (HAWT)
Structural dynamics and controls
Combined modal & multibody rep. (modal for blades and tower)
Up to 24 structural DOFs
Preprocessor for MSC.ADAMS
MSC.ADAMS®
Automatic Dynamic Analysis of Mechanical Systems
Commercial (MSC.Software Corporation)
General purpose
Structural dynamics and controls
Multibody dynamics representation
Virtually unlimited structural DOFs
Datasets created by FAST
Both use AeroDyn aerodynamics
Equilibrium inflow or generalized dynamic wake
Steady or unsteady aerodynamics
Aeroelastic interaction with structural DOFs

32. Model Development Offshore O&G Platform Simulators
Hydrodynamic simulators for offshore platforms developed by the Center for Ocean Engineering, Massachusetts Institute of Technology (MIT)
SML Developed for
Offshore Platforms
SML
SWIM – treatment of linear and second-order frequency-domain hydrodynamics
MOTION – solutions of the large-amplitude time-domain slow-drift responses
LINES – determines the nonlinear mooring-line / tether / riser effects upon the platform
Wave MIT (WAMIT)
solves wave interaction problem using numerical panel method

33. Model Development Coupling Hydrodynamics with Aeroelastics
FAST and the ADAMS processor upgraded to add:
support platform DOFs
platform loading
SML and WAMIT used where applicable
Add hydrodynamic loading and mooring system dynamics here
Add support platform kinematics & kinetics here

34. Model Development Support Platform Kinematics & Kinetics
Introduce support platform DOFs to FAST and the ADAMS preprocessor:
translational: surge, sway, heave
rotational: roll, pitch, yaw (assume small rotations)
Include dynamic couplings between motions of platform and turbine:
all position, velocity, and acceleration expressions are now affected by the platform DOFs
the wind turbine’s response to wind and wave excitation is fully coupled through the structural dynamics
Support Platform DOFs

35. Model Development Support Platform Kinematics & Kinetics (cont)
The equations of motion (EoMs) in FAST are derived and implemented using Kane’s Dynamics:
complete, nonlinear aeroelastic EoM:
Total external load on the support platform:
hydrodynamic added mass important since ρwater ≈ ρstructure (aerodynamic added mass not important since ρair « ρstructure)
to avoid making the EoM implicit, separate out the added mass components from the rest of the load: + +

36. Model Development Hydrodynamic Loading—Possible Realizations
Advantages
Disadvantages
Application
Linear Frequency Domain
Many codes available from offshore O&G industry
Results presented in summary form (RAOs or statistics)
Rigid payload
No nonlinear dynamic characteristics
No transient events
Morison’s Equation Time Domain
Easy to implement
Easy to incorporate nonlinear / breaking waves
Diffraction term only valid for slender base
No wave radiation or free surface memory
No added mass-induced coupling between modes
True Linear Time Domain
Satisfy linearized governing BVPs exactly, without restriction on platform size, shape, or manner of motion
Frequency domain solution used as input
Linear waves only
No 2nd order effects

37. Model Development Hydrodynamic Loading (cont)—Assumptions
Assume – Potential Flow:
incompressible and inviscid fluid
irrotational flow
subject only to conservative body forces
Assume – Linearization of Hydrodynamics Problem:
wave amplitudes are much smaller than wavelengths
translational motions of platform are small relative to its size
application of superposition
Limitations:
no nonlinear wave kinematics
no 2nd order slow-drift excitation
no 2nd order sum-frequency effect
no sea current or vortex-induced vibrations (VIVs)
ignore potential loading from floating debris or sea ice

38. Model Development Hydrodynamic Loading (cont)—Overview
Aij and fi must be defined in:
Problem is split into separate and simpler problems:
Scattering: seek loads on platform when it is fixed and incident waves are present Froude-Kriloff, diffraction
Hydrostatics: seek loads on platform when it is in equilibrium and there are no waves present buoyancy
Radiation: seek loads on platform when it oscillates in its various modes of motion with no incident waves present, but waves radiate away added mass, radiation damping

39. Model Development Hydrodynamic Loading (cont)—Scattering
Wave excitation:
Wave elevation:
= FFT of White Gaussian Noise
= wave spectrum
= complex wave excitation force per unit wave amplitude, depending on:
geometric shape of platform
frequency and direction of incident wave
proximity to seabed, free surface, etc.
sea current / forward speed
solution to the frequency domain problem
Wind and Wave Spectra
White Guassian Noise

40. Model Development Hydrodynamic Loading (cont)—Hydrostatics
= static buoyancy from Archimede’s Principle:
generally cancels with the weight of the floating body and the weight in water of the mooring lines; separated out due to turbine flexibility
= change in hydrostatic load from the effects of:
waterplane area changes in displaced volume
center-of-buoyancy vector cross product moments

41. Model Development Hydrodynamic Loading (cont)—Radiation
Aij and = impulsive added mass and radiation kernel, determined from solution to frequency domain problem:
and = added mass and damping, depending on:
geometric shape of platform
proximity to seabed, free surface, etc.
Wave radiation damping loads exhibit memory effects, meaning they depend on the history of platform motion:
= ith component of load at t due to unit impulse in speed of DOF j
and or
frequency of oscillation
sea current / forward speed

42. Model Development Mooring System Dynamics
A mooring system restrains a support platform with cable tension, depending on:
excess buoyancy of platform
platform location / motion
cable weight in water
hydrodynamic loading
seabed friction
geometrical layout of cables
If the mooring compliance was linear:
Mooring dynamics introduced in FAST and ADAMS by interfacing with LINES module:
ignores effects of bending stiffness
Oil Rig TLP

43. Model Development Calculation Procedure Summary

44. Sample Results Baseline Wind Turbine & Platform Properties
NREL baseline
5MW rating
126m diameter
90m hub height
700,000kg mass
Wave Excitation in X-Direction
Platform:
MIT design
TLP
19m diameter
17m draft
134,000kg mass
Baseline Wind
Turbine with TLP
Added Mass and Damping
in Surge
Radiation Kernel in Surge

45. Sample Results MSC.ADAMS Simulation

46. Sample Results FAST & ADAMS Verification

47. Sample Results MSC.ADAMS Simulation

48. Conclusions
Developed simulation tools capable of modeling a variety of floating wind turbines:
started with FAST and ADAMS preprocessor
added support platform DOFs:
surge, sway, heave
roll, pitch, yaw
added hydrodynamic loading:
scattering
hydrostatics
radiation
added mooring system dynamics (Lines)
Established critical capability to help the US wind industry evaluate design options for deepwater wind development
use SML or WAMIT as preprocessor

49. Future Work Using simulation capability: New model development:
characterize dynamic response and identify critical loads and instabilities
assess the role of wind turbine control to provide platform stability and loads mitigation
New model development:
2nd order effects
sea current and VIVs
loading from sea ice
fixed-bottom support bases and breaking waves
blade torsion DOF and coupled modes
Model validation and refinement

50. Acknowledgements
Walt Musial & Sandy Butterfield of NREL for leading US offshore wind research program
Erik Withee of US Navy for initiating study at MIT
Kwang Lee of MIT for verifying output of SWIM
Libby Wayman of MIT for modifying SWIM
My Ph.D. Committee at CU, UW, NREL, & MIT for evaluating the project

52. Introduction & Background Contrasting Modeling Requirements
Offshore Oil & Gas Platforms
Rigid and static
Steady winds in analysis
Linear frequency domain analysis
Passive
Offshore Fixed-Bottom Turbines
Rigid support structure
Little coupling between turbine and support structure motions
Separation of dynamic response and wave spectra
Shallow water / breaking waves
Onshore Wind Turbines
Flexible and dynamically active
Turbulent winds in analysis
Nonlinear time domain analysis
Controllable
Offshore Floating Wind Turbines
Compliant support structure
Significant coupling between turbine and platform motions
Response and wave spectra coalescence
Deepwater / linear waves

53. Model Development Hydrodynamic Loading—Assumptions
Assume – Potential Flow:
incompressible and inviscid fluid; irrotational flow
subject only to conservative body forces
Assume – Linearization of Hydrodynamics Problem:
wave amplitudes are much smaller than wavelengths
translational motions of platform are small relative to its size
application of superposition
problem is split into 3 separate and simpler problems: (scattering, hydrostatics, radiation)
Limitations:
no nonlinear wave kinematics
no 2nd order slow-drift excitation
no 2nd order sum-frequency effect
no sea current or vortex-induced vibrations
ignore potential loading from floating debris or sea ice

54. Model Development Hydrodynamic Loading—Scattering
Scattering: seek loads on platform when it is fixed and incident waves are present
Found by IFFT of the product of wave spectrum, normalized complex wave excitation force, and FFT of White Gaussian Noise
Froude-Kriloff, diffraction loads depend on:
amplitude, frequency, direction of incident waves
geometric shape of platform
proximity to seabed, free surface, etc.
sea current / forward speed
solution to frequency domain problem
Wind and Wave Spectra

55. Model Development Hydrodynamic Loading—Hydrostatics
Hydrostatics: seek loads on platform when it is in equilibrium and there are no waves present
Found by summing static buoyancy and its change with platform displacement
Buoyancy load depends on:
waterplane area
loacation of center-of-buoyancy

56. Model Development Hydrodynamic Loading—Radiation
Radiation: seek loads on platform when it oscillates in its various modes of motion with no incident waves present, but waves radiate away
Found by convolution of platform velocity and radiation kernel
Radiation kernel found by sin- or cosine-transform of added mass or damping matrices
Added mass, radiation damping loads depend on:
history of platform motion (memory effect)
geometric shape of platform
proximity to seabed, free surface, etc.
sea current / forward speed
solution to frequency domain problem

57. Model Development Mooring System Dynamics
Oil Rig TLP
A mooring system restrains a support platform with cable tension, depending on:
excess buoyancy of platform
platform location / motion
cable weight in water
hydrodynamic loading
seabed friction
geometrical layout of cables
Mooring dynamics introduced in FAST and ADAMS by interfacing with LINES module:
ignores effects of bending stiffness

58. Model Development Calculation Procedure Summary
MODIFY THIS TO INDICATE WHERE SWIM/WAMIT and LINES ARE!!!

59. Introduction and Background Previous Studies—Fixed-Bottom
Several wind turbine simulators have been expanded to model fixed-bottom offshore support structures:
use linear wave theory for irregular sea and nonlinear Stream Function theory for regular sea wave kinematics
use Morison’s equation for hydrodynamic loading:
Fixed-Bottom Offshore Turbine
DUWECS

60. Introduction and Background Previous Studies (cont)—Floating
A few simulators have been developed for the preliminary analysis of floating support structures:
frequency domain:
Bulder et al — found RAOs and amplitude standard deviations of the 6 rigid body modes for a tri floater design
Lee — performed similar analysis for TLP and Spar Buoy designs
Results — natural frequencies of platform can be designed away from peak of wave spectrum
time domain:
Henderson — used RAOs to prescribe platform motion in state domain
Withee — hydrodynamic loading via Morison’s eq. for a TLP
Fultan et al — hydrodynamic loading via Morison’s eq. for a TLP
Results — platform motions have little effect on power performance and rotor loads, but a large effect on nacelle and tower loads
Response Amplitude
Operator (RAO)

61. Introduction and Background Previous Studies (cont)—Onshore Controls
Disturbance Accommodating Control (DAC) has been used to design multiple-input, multiple-output (MIMO) controllers to mitigate loads and stabilize flexible modes of onshore wind turbines
References:
Stol and Balas
Hand and Balas
Wright and Balas
Disturbance Generator
Plant
Generator Torque
Nacelle Yaw
Blade Pitch
Control Actions
Plant State Estimator
Composite Estimator
Disturbance Estimator

62. Thesis Statement and Objectives Limitations of Previous Studies
Developed dynamics models are limited in capability:
do not permit multiple platform and mooring configurations
frequency domain models ignore turbine flexibility, nonlinear dynamic characteristics, and transient events
time domain models ignore the effects of:
platform size in the diffraction problem
wave radiation damping and free surface memory
added mass-induced coupling between modes of motion
Load results are demonstrated through few simulations:
must be verified through a rigorous loads analysis
No attempt to mitigate the increased loads through the application of simple or advanced control theory

63. Thesis Statement and Objectives Goals of Work
To develop simulation tools capable of modeling the fully coupled aeroelastic and hydrodynamic responses of a variety of floating offshore wind turbines
To identify critical loads and/or instabilities that are brought about by the dynamic couplings between and within the turbine and platform in the presence of combined wind and wave loading
To design, simulate, and assess the effectiveness of an advanced controller to mitigate unwanted loads and/or instabilities using generator torque, blade pitch, and/or nacelle yaw

65. Approach and Methods Design Loads Analysis
Involves verifying structural integrity by running a series of design load cases (DLCs)
IEC for onshore or IEC for offshore
Load Case Matrix
Critical Locations

66. Approach and Methods Design Loads Analysis (cont)
Using FAST, I will compare load case simulation results between the onshore and offshore configurations:
use NREL’s baseline wind turbine and reference site
pick one candidate support platform concept and subset of DLCs
Identify critical loads and/or instabilities brought about by the dynamic couplings and combined wind and wave loading
Q: Is power performance degraded?
Q: Where and by how much are loads increased?
Q: What are the dominant instabilities?

67. Approach and Methods Controls Design
I will use DAC to design MIMO state-space controllers to mitigate detrimental loads and/or instabilities:
pick one or two of the critical loads and/or instabilities
extend linearization capability of FAST to include states and disturbances associated with platform motion and wave loading
implement and test controller in FAST/Simulink interface
Q: Can independent pitch, torque, or yaw be used to
control combinations of wind and wave loading?
including side-to-side loading?
Q: Are actuators other than pitch, torque, and yaw
required for controllability?
Q: What measurements are needed for observability?
blade root & shaft strain gages, nacelle accelerations, etc.?

68. Approach and Methods Project Scope
As I get deeper in depth, I narrow my focus

69. Recent Progress Support Platform Kinematics & Kinetics
Add support platform kinematics & kinetics here

70. Recent Progress Support Platform Kinematics & Kinetics (cont)
Assume small rotations:
rotation order doesn’t matter
use linearized Euler transformation:
Orthogonal Rotations 1 X Y Z x y z
Not an orthonormal transformation
:. use a correction
The closest orthonormal matrix in the Frobenius norm sense is [U][V]T where [U] and [V] are the matrices of eigenvectors inherent in the Singular Value Decomposition (SVD) of the matrix

71. Recent Progress Hydrodynamic Loading
Add hydrodynamic loading and mooring system dynamics here

72. Work Plan Review Background Literature September 2005
Learn fundamentals of marine hydrodynamics
Identify computational methodologies used by other simulation tools developed for offshore wind turbines
Examine requirements for determining design loads
Learn about design process for advanced controls
Develop Simulator December 2005
Add support platform DOFs to FAST
Develop a support platform hydrodynamics loading model and interface it to FAST and ADAMS
Interface LINES module to FAST and ADAMS
Verify response predictions between FAST and ADAMS and frequency domain results
Publish AIAA paper on model development activities

73. Work Plan (cont) Establish Baseline Turbine & Site February 2006
Identify baseline turbine rating and reference site location
Establish aerodynamic and structural properties
Define a baseline control system
Create FAST and ADAMS models
Identify and design candidate support platform concepts
Establish a design basis at the reference offshore site
Perform Design Loads Analysis October 2006
Pick one of the candidate support platform concepts for subsequent analysis
Identify a subset of DLCs to run
Run DLCs to determine on- and offshore design loads
Compare results to identify critical loads and/or instabilities
Publish conference paper on modeling results

74. Work Plan (cont) Controls Design March 2007
Pick one or two critical loads and/or instabilities for subsequent analysis
Design an advanced torque, pitch, and/or yaw controller to mitigate the unwanted loads and/or instabilities
Implement and simulate the controller in FAST
Assess the effectiveness of the controller
Complete Requirements of Ph.D May 2007

75. Thesis Contributions
Develop simulation tools capable of modeling a variety of floating offshore wind turbines
Characterize the dynamic response and identify critical loads and instabilities
Assess the role of wind turbine control to provide platform stability and loads mitigation
Establish a critical capability to help the US wind industry evaluate design options for deepwater wind development

76. Introduction and Background Wind Turbine Fundamentals
Wind Speed
Power 1 2 3
Rated
Cut-In
Cut-Out
Generator Torque
Nacelle Yaw
Blade Pitch
Control Actions

77. Introduction and Background Why Offshore?
GE Wind Energy 3.6 MW Turbine
Higher-quality wind resource:
less turbulence, smaller shear
stronger, more consistent winds
Economies of scale:
avoid logistical constraints on size
Proximity to loads:
many demand centers near coastline
Increased transmission options:
access to less heavily loaded lines
Potential for reducing land use, noise, and aesthetic concerns

79. Introduction and Background Why Floating?

80. Model Development Hydrodynamic Loading—Possible Realizations
Frequency Domain Representation
find Response Amplitude Operators (RAOs)
ignore turbine flexibility
ignore nonlinear dynamic characteristics
ignore transient events
Morison’s Representation
valid for slender, vertical, surface-piercing cylinders
Easily incorporate nonlinear and breaking waves
ignore effects of platform size in diffraction problem
ignore wave radiation damping and free surface memory
ignore added mass-induced coupling between modes of motion
True Linear Hydrodynamic Representation in the Time Domain:
satisfy the linearized governing BVPs exactly without restriction on platform size, shape, or manner of motion
Response Amplitude
Operator (RAO)

81. Thesis Statement and Objectives Limitations of Previous Studies
Developed dynamics models are limited in capability:
do not permit multiple platform and mooring configurations  important to have for configuration trade-off studies
the frequency domain models ignore turbine flexibility, nonlinear dynamic characteristics, and transient events  important considerations for wind turbines
the time domain models ignore the effects of:
platform size in the diffraction problem  important for large platforms
wave radiation damping and free surface memory  important for platforms with compliance
added mass-induced coupling between modes of motion  important for platforms that are not axisymmetric
Load results are demonstrated through few simulations:
must be verified through a rigorous loads analysis  important to characterize the dynamic response and identify design-driving loads
No attempt to mitigate the increased loads through the application of simple or advanced control theory  important to minimize cost

82. Thesis Statement and Objectives Hypothesis
Existing aeroelastic models can be expanded to include the important loading and responses representative of floating offshore wind turbines
and will demonstrate that the increased dynamic complexity produces detrimental loads and/or instabilities,
which can then be mitigated through the development of advanced controls
This work is critical to determining the most technically attractive and economically feasible floating wind turbine design

83. Codes for Component and Full System Level Analysis
Determine loads throughout full system for component level analysis
Multi-physics model
Industry-specific
Developed for particular application (FAST, etc.)
Component Level
Determine design integrity of individual components based on specified loads
Single-physics model
Not industry-specific
Commercial products available (ANSYS, etc.)

84. Model Fidelity for Multi-Physics Simulation Tools

85. Approach and Methods Development of a Coupled Simulator (cont)
24 degrees of freedom (DOFs) available for 3-bladed, 22 DOFs available for 2-bladed turbine:
blade flexibility: 2 flap and 1 edge mode DOF per blade
tower flexibility: 2 fore-aft and 2 side-to-side mode DOFs
drivetrain: 1 variable generator speed DOF and shaft torsion DOF
nacelle yaw: 1 yaw hinge DOF
rotor teeter: 1 rotor teeter hinge DOF with optional 3 (for 2-bladed rotor only)
rotor-furl: 1 furl hinge DOF of arbitrary orientation and location between the nacelle and rotor
tail-furl: 1 furl hinge DOF of arbitrary orientation and location between the nacelle and tail
platform: 3 translation (surge, sway, and heave) and 3 rotation (roll, pitch, and yaw) DOFs
1st mode
2nd mode
Modal
Representation

86. Users and Certification

87. FAST, ADAMS & AeroDyn Interaction

88. Recent Progress Support Platform Kinematics & Kinetics (cont)
The equations of motion (EoMs) in FAST are derived and implemented using Kane’s Dynamics
Kane’s EoM for holonomic system:
Generalized active forces:
Generalized inertia forces:
Partial angular velocities:
= # of rigid bodies
= rigid body i
= mass center of rigid body i
Partial linear velocities:

89. Platform Concepts: Analysis Capabilities X
Tension Leg Platform (TLP)
Taut Leg Spar Buoy
Wind Turbine On Boat
Monopile
Disk Buoy with Catenary Moorings
Tripod
Lattice
Tri Floater

90. Future Offshore Code Development Direction
Modeling of fixed bottom support structures
monopiles
multiple-member support structure
P-y foundations
shallow water (breaking) waves
2nd order mean (wave drift), difference-frequency (slow drift), and sum-frequency wave loading
Sea current / forward speed effects
Model validation and refinement