wind turbine aeromechanics research at umd · 1.1 offshore wind power resource evaluation and wind...

PI: James D. Baeder ([email protected]) Alfred Gessow Rotorcraft Center of Excellence

Department of Aerospace Engineering Wind Energy Thrust Leader, UMERC University of Maryland, College Park

Wind Turbine Aeromechanics Research at UMD

Maryland Offshore Wind Farm Integrated Research NREL/NTWC June 30, 2015

Anholt Wind Farm

University of Maryland College Park Bowie State / Frostburg State

Maryland Offshore Wind Farm Integrated Research

Offshore Wind Energy is Inherently Multi-Disciplinary •  Assembled a team across five departments at three universities to

support eight faculty members and eight students in research !  Leverages existing expertise at UMERC, ESSIC, CALCE and AGRC !  Significant cost share from UMCP campus !  Research focused on two major thrust areas !  Builds a foundation for long-term OSW research in Maryland

Research Thrusts Co-PIs GRA/URA Refined Wind Resource Characterization For Next-Gen Prognostics & Health Management 1.1 Offshore Wind Power Resource Evaluation and Wind Forecasting 1.2 Development of a Maintenance Option Model to Enable Optimized OSW Farm Sustainment 1.3 Frostburg Testbed and Data Analysis 1.4 Prognostics and Health Management of Offshore Wind Turbine

Zeng

Sandborn Eltayeb Azarian

GRA GRA URA GRA

Innovative Wind Turbine Aeromechanics to Aid Energy Capture 2.1 Wake Alleviation Devices for OSW Turbines 2.2 CFD Modeling of OSW Turbines and Wake Interactions 2.3 3D Rotor Design for Maximum Mechanical Performance and Safety 2.4 Advanced Composite Couplings for Passive Fatigue Loads Reduction in OSW Turbines

Jones

Baeder Goloubev Chopra

GRA GRA URA GRA

List of Research Tasks and Co-PIs and Student Support

Thrust 2 Objectives: This thrust addresses key offshore wind turbine aeromechanic issues through a balanced experimental / computational / analytical program to:

(1) evaluate the effect of blade-mounted devices on the structure, strength and dissipation of the turbine wake at laboratory scales; and

(2) validate CFD modeling of laminar/turbulent transition and other turbulence modeling issues for investigating 2-D airfoil characteristics as well as 3-D slotted tips and tubercle shaped leading edges; and

(3) develop state-of-the-art comprehensive aeromechanics analysis for investigating the effects of tailored composite couplings on vibratory loads.

This thrust is a collaboration between AGRC (UMCP Department of Aerospace Engineering) and Bowie State University.

Thrust 2: Innovative Wind Turbine Aeromechanics to Aid Energy Capture



Task 2.1 Wake Alleviation Devices for OSW Turbines (UMCP/AGRC: Anya Jones, Vera Klimchenko)



•  Evaluate(effec+veness(of(blade(mounted(devices( on( the( dissipa+on( of( wind(turbine(wake(

Objec+ve((

Methods(

•  Sub=scale(wind(tunnel(tes+ng(•  PIV(used(to(iden+fy(and(analyze(wake(structures(behind(wind(

turbine(•  Evaluate(effect(of(blade(mounted(devices(on(energy(produc+on(

U""͚"

Baseline( Winglet( Serrated(

Small Scale Wind Turbine Design



Diameter(=(8.4(in2(

Design(TSR""of"6(

Tower"Height"=(10(in(

Low(Reynolds(airfoil(SG6040"

Root"Chord"=(1.173(in(

Tip"Chord"=((1/4)(Root(Chord(

Linear(Taper(

Op+mum(Rotor(Theory(used(to(calculate(twist(necessary(to(achieve(design(TSR(•  Twist"at"the"root"is(30.2(degrees(•  Twist"at"the";p"is(=3.7(degrees(

Wind Tunnel and PIV Setup



FOV(1( FOV(2(

FOV(3(

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FOV(4(

Four(Fields(of(View((FOV)(for(PIV(•  S;tched"together"•  Can"look"at";me@averaged"and"instantaneous"snapshots(

Baseline(Case(Average(Velocity(U""͚"

U""͚"

U""͚"

Time=Averaged(Total(Velocity(for(3(Cases(

Velocity(Cut(at(x/D(=(=1.8((

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Snapshot(of(Total(Velocity((and(Vor+city(for(3(Cases(

Current Work



1.  Characterize(the(strength(of(the(+p(vor+ces(

2.  Validate(the(theory(that(blade(mounted(devices(can(weaken(+p(vor+ces(

3.  Analyze(wake(recovery(by(comparing(the(+me=averaged(data(for(the(three(cases(

Task 2.2 CFD Modeling of OSW Turbines and Wake Interactions (UMCP/AGRC: James Baeder, Taylor Rinehart)



Introduction - Motivation •  Sandia 100-meter all-glass HAWT blade design (13.2 MW) for

offshore wind turbine applications !  High-resolution CFD – CSD simulations expensive for design and

analysis of multiple new configurations !  Accurate aeroelastic analysis tools needed for quick estimates of

aerodynamic/structural loads, and rotor thrust/torque

•  Aeroelastic analysis tools depend on reduced-order aerodynamic modeling (2-D airfoil characteristics, stall models) !  Lift / Drag/ Pitching moment queried from look-up tables !  Experiments costly to generate airfoil tables for new airfoil designs

over wide range of angles of attack & Reynolds numbers !  CFD simulations provide an affordable alternative for generating

look-up tables if accurate !  Use of GPGPU can provide 40-50x speedup over single core on CPU

CFD Modeling of OSW Turbines and Wake Interactions



Introduction – Turbulence Model Limitations

Near Copenhagen (Wikipedia)

S809 Airfoil, Re = 106

•  Accuracy of design estimates depends on accuracy of airfoil characteristics •  Issues with conventional RANS turbulence models in CFD simulations

•  Over-predict drag for partially laminar boundary layers at low AoA •  Over-predict maximum lift and stall onset angle (incipient separation)

•  Need accurate laminar/turbulent transition; adverse pressure gradient




2-D Airfoil Results on S809 Airfoil at Re = 1,000,000

SA-Transition-APG model combines best of both Predicts the lower drag at lower AoA and earlier stall onset at higher AoA Looking at incorporating surface roughness effects; cross-flow; DDES

Added Laminar/Turbulent Transition & Adverse Pressure Gradient Corrections




Sandia 100m w/ and w/o tubercles – 3-D URANS simulations

Excellent comparison with previous analysis (without tubercles) No detrimental effect on performance to include tubercles

10 m/s

Subdivision and Hamiltonian Paths

University of Maryland College Park

•  Triangular unstructured grid

•  Divide triangle into three quadrilaterals

• Loops constructed by connecting the midpoint of edges

• Loops formed through all triangles connected by a triangular node

• Each face part of only one distinct loop

• Each cell centroid is intersected by loops of different colors

• Makes the algorithms very efficient!!!




Plans •  Continue to validate CFD for Sandia 100-meter all-glass HAWT blade

design (13.2 MW) for offshore wind turbine applications !  Continue improving physical modeling in CFD; CFD/CSD coupling

•  Continue to investigate tubercle shaped leading-edge, but for desensitizing turbines to upstream disturbances !  Complimentary to experiments

•  Investigate slotted tip for reducing tip vortex swirl using CFD tools !  Momentum and turbulence increases vortex diffusion

•  CFD/CSD to aid in studying tailored composite coupling •  Developing Hamiltonian/Strand solver – HAMSTR for DOD

Task 2.4 Advanced Composite Couplings for Passive Fatigue Load Reduction in OSW (UMCP/AGRC: Chopra; Ananthan)



•  Composite tailoring technology: –  Intentional distribution of fiber orientation and layup –  Meet specific structural requirements –  Achieve desired elastic couplings

•  Successful applications in aerospace: –  Forward sweep wing of Grumman X-29 –  Composite tailored couplings on the AgustaWestland AW101 rotor blade

for vibratory loads reduction

•  Potential benefits of composite tailored couplings on wind turbines: –  Blade loads reduction –  Rotor/tower aeromechanical stability improvement –  Tower vibration reduction

Lag Bending

Nose Down Twist

Comprehensive Analysis – AGRC Modeling Features



" Multiple configurations (SMR/TR, Coax, Tilt-Rotor, Wind Turbine)

" Flexible blades with flap, lag, torsion and axial DOF ( Euler-Bernoulli )

" Multibody-type kinematics and rotating reference frames

" Coupled with free wake, panel* method, CFD

"  Modular inclusion of phenomena into dynamics and trim

" All geometric nonlinearities – “large deflections”

" Modal reduction or full nodal DOF analysis

" Composite coupling, gravity loads and material nonlinearities

" FET, harmonic balance, time integration for trim

" Free-flight, wind-tunnel mode for single/multi-rotor configurations

Power Regulation with RPM, Pitch



0o pitch

2.5o pitch

5o pitch

100% RPM

75% RPM

50% RPM

Blade pitch used to limit power at high speeds

RPM reduction used to extract more power at low wind speeds

Power limit to reduce loads

Results – Tip Deflection



Rigid blade

Elastic blade

Tip deflection scales with inverse of bending stiffness Steady out-of-plane deflection = 5 m

Good agreement with AcuSolve predictions (Corson et. al, AIAA 2012)

v/R

50% stiffness

With atm. Boundary layer

50% stiffness

Rigid blade

w/R

Results – Flap Bending Moment



With atm. boundary layer

Rigid blade

Elastic blade

Blade elasticity alleviates root flap bending moment Minor effect from atmospheric boundary layer

Ft-lb 50% stiffness

Less

More

Results – Torsion Moment



With atm. boundary layer

Rigid blade

Elastic blade

Elastic motions introduce torsion loads into the blade through flap bending, chordwise force and dynamic twist

Ft-lb 50% stiffness

Summary



"  Applied multi-body UMARC version to turbines "  Implemented "  Axial elasticity in blade dynamics "  Coupling with Maryland Free Vortex Wake for turbines "  Wind velocity gradient in wake "  Gravity loading on blades

"  Performance dominated by external geometry (aerodynamics) "  Flap bending loads, blade stiffness and atmospheric boundary layer (oscillatory

forcing) drive oscillations in hub moments "  Implemented basic composite coupling for turbine blades "  Modeling of axial-flap-lag-torsion structural interactions !  Rotor- tower couplings (in progress) !  Targets for Year-2

•  Characterizing cross-section properties #  Fiber orientation $ blade properties (and cross-couplings) #  Validation of composite beam models

•  Blade load reduction with bend-twist, extension twist coupling



Summary •  Assembled a team across five departments at three universities

to support eight faculty members and eight students in research !  Leverages existing expertise at UMERC, ESSIC, CALCE and AGRC !  Significant cost share from UMCP campus !  Research focused on two major thrust areas !  Builds a foundation for long-term OSW research in Maryland

•  Developing facilities and analytical/computational tools !  Many now in place generating preliminary results !  Frostburg and Bowie became more involved this past summer with URA

•  Already presenting results at conferences !  Posters at Offshore EWEA 2013/15; Three papers at NAWEA 2015 !  Papers at AIAA Scitech 32nd ASME Wind Energy Symposium January

2014/15(2-D CFD;Sustainment;Flatback); Several other AIAA; PHM …


Synergistic Activities at UMCP in Wind Energy •  Wind Energy Thrust as part of UMERC •  Three faculty members visited Europe

!  Attended: Offshore EWEA and met with vendors; O&M Conference !  Made contacts with researchers at DTU and OSW industry !  Visited Anholt Offshore Wind Farm

•  Wind Energy Theory Class (ENAE788I) taught last fall and in 2014 !  15 grads and 2 undergrads (3 and 2 this fall); Guest lectures by specialists !  Final exam/project looked at NREL 5MW Offshore Design (2009 – Jonkman) at Buoy St. 44009

•  The Maryland Wind TERPines formed last fall !  Student organization looking at promoting wind energy on campus !  Developing facilities / analysis for participating in DOE Wind Energy Challenge

•  Offshore Wind Energy Seminar Series started last fall !  Continued last spring; brought in faculty from Delaware and Maine this fall

•  Eight UMCP faculty investigating Offshore Wind Energy Issues !  Hope to expand; make long-term; and work with Maryland companies (BizMDOSW)

(a) Surface unstructured mesh (b) Hamiltonian loops on surface

(c) Volume mesh (d) Curved strand grids Fig. 23. Longitudinal slice of the mesh system around the Robin fuselage highlighting the curved strands in regions ofconcave fuselage surface.

Stagnation point

Stagnation point

Flow acceleration

Flow deceleration

Zero velocity on fuselage surface

Flow recirculationInviscid Laminar

TURNS (Inviscid)Panel method

Hamiltonian (Inviscid)TURNS (Laminar)Hamiltonian (Laminar)

All results are computed in third-order

TURNS (Inviscid)Hamiltonian (Inviscid)TURNS (Laminar)Hamiltonian (Laminar)

(a) Mach number contour on surface and longitudinal slice

(b) Surface pressure distribution (c) Convergence histories

Fig. 24. Flow solution over the Robin fuselage at Mach number 0.3 highlighting: (a) Mach contours, (b) Pressure distri-bution over the longitudinal plane, (c) Residual development.

18

Spanwise Wavy Trailing Edge Airfoil 24/ 31 NAWEA 2015

Results and Discussion: Lift vs. Drag Pole

Halfway cut 1/2 flatback

Halfway cut 3/4 flatback

90C cut 3/4 flatback


Wind Turbine Aeromechanics Potential Collaboration •  GPGPU for Aeromechanic Analysis

!  Laminar/Turbulent transition with APG correction and DDES !  Coupling isolated blade with grid motion to FV-W, CSD and multiple GPGPU cards

•  Hamiltonian/Strand Solver !  Unstructured triangles turned into quads that form Hamiltonian chains !  Strands in the third direction !  Can then examine complicated nacelle / tower interactions

•  Large Blades !  Aeroelastic instabilities at extreme scales? !  Individual blade control (using LIDAR for feedback) !  Tubercles, slotted tips to desensitize turbines !  Flatback airfoils with wavy trailing edges

•  The Maryland Wind TERPines !  Examining cyclo-turbine VAWT !  Examining shroud for DAWT •  Quad-Rotor Bi-Plane Tailsitter

wind turbine aeromechanics research at umd · 1.1 offshore wind power resource evaluation and wind...

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