Jason JonkmanSandy ButterfieldNeil Kelley Marshall BuhlGunjit BirBonnie Jonkman Pat MoriartyAlan WrightDaniel Laird 2006 Wind Program Peer Review May 10, 2006 Design Codes

Wind Program Peer Review Outline of Presentation  Introduction & Background  State of the Art Modeling & Limitations  Program Contributions  Current & Future Work

Wind Program Peer Review Introduction & Background The Big Picture

Wind Program Peer Review Introduction & Background Design Loads Analysis  Design requirements are dictated by IEC standards  100s-1000s of design load case (DLC) simulations must be considered Load Case Matrix Critical Locations

Wind Program Peer Review 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

Wind Program Peer Review Introduction & Background Coupled Aero-Hydro-Servo-Elastic Simulation

Wind Program Peer Review State of the Art Modeling & Limitations Wind-Inflow Current Approach Limitations  IEC-specified deterministic, discrete gusts/direction changes  IEC-specified turbulence (TurbSim)  Idealistic  Neutral stability conditions only  TurbSim includes models for site-specific environments: –flows over flat, homogenous terrain –flows in/near multi-row wind farms –flows at the NWTC Test Site (complex terrain) –flows in the Great Plains with/without the presence of a low-level jet (LLJ)  Need data between 120m – 230m to validate LLJ model  Need data above 50m within wind farms to validate and expand wind farm models  Need data from a variety of climates  Need offshore data Design Research

Wind Program Peer Review State of the Art Modeling & Limitations Aerodynamics & Aeroacoustics Current Approach Limitations  Aerodynamics: – blade-element/momentum – generalized dynamic wake – empirical corrections: rotational augmentation dynamic stall, skewed flow  Aeroacoustics: – advanced empirical models  Post stall and high yaw aerodynamics not well predicted: –rotational augmentation –dynamic stall/unsteady wake coupling  Accurate noise predictions for airfoils, but less so for turbines: –no tower shadow model –inaccurate tip noise model  Aerodynamics: –vortex-wake methods –CFD  Aeroacoustics: –nonlinear propagation models –CAA  Need more experience & expertise with codes  Need aerodynamic wake and pressure distribution measurements  Need full wind turbine acoustic measurements Design (AeroDyn) Research

Wind Program Peer Review State of the Art Modeling & Limitations Offshore Waves & Hydrodynamics ( HydroDyn ) Current Approach Limitations  Diffraction term only valid for slender base  No wave radiation or free surface memory  No added mass- induced coupling between modes  No nonlinear steep / breaking waves  No 2 nd order effects: –slow-drift –sum-frequency  No sea ice loading  Need validation data Design (Fixed) Research (Floating)

Wind Program Peer Review State of the Art Modeling & Limitations Structural Dynamics Current Approach Limitations  Combined modal/multibody formulation (FAST): –modal: blades, tower –multibody: platform, nacelle, generator, hub, tail  Deflection limits  Conventional config- urations only: –no coupled modes –no flap/twist coupling –no precurve –no presweep  Multibody (MSC.ADAMS ® )  Finite-element method (FEM)  Modeling gearbox dynamics is difficult  Difficult to obtain reduced order models for controls & stability analysis  Computationally expensive Design Research GE 3.6 MW Prototype with Precurved Blades 1 st mode 2 nd mode Conventional 3- Bladed Upwind

Wind Program Peer Review Program Contributions Users & Certification

Wind Program Peer Review Program Contributions Success Stories AOC 15/50 Clipper 2.5MW Liberty Bergey XL50 Southwest Windpower STORM NorthWind 100 GE 1.5MW

Wind Program Peer Review Program Contributions Development & Support  Why does the U.S. DOE support codes development?: –design codes are a practical way for us to transfer wind energy knowledge to the industry –allows for customization flexibility –commercial products are black boxes  We support U.S. wind industry through: –websites –technical support –solicitation of user requirements –workshops NWTC Design Codes Website

Wind Program Peer Review Current & Future Work Wind-Inflow  Current work: –implemented Great Plains LLJ spectral model –use this spectral model to determine the effect these jets have on multi-MW LWSTs –document the development of TurbSim  Future plans (next 2 years): –analyze available Lamar LIDAR data to further validate Great Plains LLJ spectral model –hold a workshop on inflow turbulence issues and TurbSim training  Future opportunities: –plan field experiment to collect data on turbulence within large, multi-MW wind farms –form a multi-discipline, synergistic effort to understand the role of coherent turbulence on turbine drivetrain fatigue Sample TurbSim Wind Profiles

Wind Program Peer Review Current & Future Work Aerodynamics & Aeroacoustics  Current aerodynamics work: –improved fidelity of unsteady wake model –tower influence  Current aeroacoustics work (reduced scope): –wind tunnel tests (Virginia Tech) –CFD, CAA & propagation codes (Penn State)  Future plans (next 2 years): –rewrite AeroDyn – make modular; provide hooks for other aerodynamic models –validation using wind tunnel (NASA Ames) and field measurements –add tower shadow noise model  Future Opportunities: –more wind tunnel and field tests –improve codes: aerodynamics – vortex-wake and CFD methods aeroacoustics – CAA prediction for tower shadow and tip noise CFD of Blade Tip Vortex (Uzun et al, 2006)

Wind Program Peer Review Current & Future Work Offshore Waves & Hydrodynamics  Current work: –Develop HydroDyn for linear hydrodynamic loading of fixed- bottom and floating systems –benchmarking via participation in IEA Annex XXIII OC 3  Future plans (next 2 years): –offshore foundations: implement p-y & t-z curves –mooring dynamics: interface LINES module (MIT) –support SeaCon studies –WFO analysis of ITI floating barge concept  Future opportunities: –add nonlinear breaking waves –add sea ice loading –add 2 nd order effects –experimental validation Sample OC 3 Simulation Results

Wind Program Peer Review Current & Future Work Structural Dynamics

Wind Program Peer Review Current & Future Work New Horizons  Gearbox dynamics: –gearbox failures might be the result of our codes inability to capture the internal gear & bearing loads properly  Stability analysis: –the potential for instabilities increase for advanced concepts like flexible rotors and floating turbines  Tower shadow: –need tower wake measurements and model updates to support design improvements of downwind rotors  Code validation: –all models must be validated with experimental data

Wind Program Peer Review