Blade Noise Research at SandiaBlade Noise Research at Sandia National Labs

2010 Blade WorkshopSandia National Laboratories, Albuquerque, NM

21 J l 201021 July, 2010

Matthew Barone and Dale BergWind & Water Power TechnologiesWind & Water Power Technologies

Sandia National Laboratoriesmbarone@sandia.gov, deberg@sandia.gov

Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company,for the United States Department of Energy’s National Nuclear Security Administration

under contract DE-AC04-94AL85000.

Aerodynamic Noise of Wind Turbinesy f

Aerodynamic noise from near the blade tips constrains tip speedspeed• Higher tip speed can lead to lower drive train costs.• Reducing noise while maintaining tip speed relaxes siting

constraints near inhabited areas. Blade noise may limit blade innovation

S l i i d i ( l f• Structural improvements may introduce noise (example of flatback airfoils in this talk).

• Load alleviation strategies may impact noise.Load alleviation strategies may impact noise. Active aerodynamic load control devices Swept blades

Ability to measure and predict blade noise enables innovation in blade design.

Bl d I ti d A d i N iBlade Innovation and Aerodynamic Noise: Flatback Airfoils

Flatback Airfoil Noisef Blade design innovations may impact wind turbine noise generation. Example: Flatback airfoilsp

• Flatback airfoils result in lower blade weight and improved manufacturability.

• An aerodynamic noise source is introduced due to vortex-shedding from the blunt trailing edge.

Relatively low noise intensity due to inboard location of the flatbacks, butthe sound is low-frequency and possibly tonal.

Flatback Airfoil Research at Sandiaf

Wind Tunnel TestsField Tests

Goal: Predict and

Quantify Noise and Drag of

Flatback Airfoils

Computational Modeling

Aeroacoustic Wind Tunnel at Virginia TechgAeroacoustic Test Section with Microphone Array Virginia Tech Stability Wind Tunnel

Virginia Tech Acoustic Wind Tunnel• Aeroacoustic test section with Kevlar side walls

Porous walls largely contain the flow, but with minimal blockage effects.

Allow sound to pass through without attenuation or reflection. Surrounding anechoic chamber allows for accurate noise

measurements.• Noise and aerodynamic measurements for chord Reynolds numbers up y y p

to ~3 million

Flatback Airfoil Wind Tunnel Experimentsf p

SNL tested baseline and flatback versions of the TU-Delft DU97-W-300 airfoil (a 30% thick wind turbine airfoil).W 300 airfoil (a 30% thick wind turbine airfoil).

Noise and aerodynamic measurements were made for several chord Reynolds numbers (1.5 – 3.2 million) and angles of attack.

Measurements were also made for the flatback airfoil with a simple L-bracket splitter plate affixed to the trailing edge.

Flatback Airfoil model Splitter Plate Attachment

Flatback Airfoil Wind Tunnel Experiments: lKey Results

Flatback noise is significantly overpredicted by available semi-empirical noise models (Brooks, Pope, and Marcolini).empirical noise models (Brooks, Pope, and Marcolini).

The splitter plate attachment reduced flatback drag by 50% and noise by 12 dB.

Virginia Tech and SNL worked together to assess and formulate accurate wall interference corrections (both aerodynamic and noise) for the acoustic test sectionnoise) for the acoustic test section.• This wind tunnel is now an industry resource for airfoil noise

and performance testing.

Contacts:Dr. William Devenport, Dept. of Aerospace and Ocean EngineeringDr Ricardo Burdisso Dept of Mechanical EngineeringDr. Ricardo Burdisso, Dept. of Mechanical Engineering

Flatback Rotor Field TestsSandia BSDS rotor employing flatbackairfoils is currently undergoing performance and acoustic testing at theperformance and acoustic testing at the SNL/USDA test site in Bushland, TX.

NREL Microphone Phased Array

Testing Team:SNL J h P tt W l J h M tt BSNL: Josh Paquette, Wesley Johnson, Matt BaroneNREL: Eric Simley, Pat MoriartyUSDA: Byron Neal, Adam Holman

Flatback Blade Trailing Edge Attachmentsg g

Blade-conforming splitter plates have been added to the BSDShave been added to the BSDS rotor.• Plate twist angle follows the

local trailing edge camber line angle.

• Plate length is equal to the• Plate length is equal to the local trailing edge thickness.

• Manufactured at SNL using rapid-prototyping machine.

Performance and noise will be compared to the baseline rotorcompared to the baseline rotor case.

Prediction of Wind Turbine Noise

Categories of Airfoil Self-Noiseg f f f

Figure from: Brooks, Pope, and Marcolini, NASA Ref. Pub. 1218, 1989.

Wind Turbine Blade Trailing Edge Noiseg g

Simulation of a turbulent boundary layer interacting with a

Flow

sharp edge to produce sound waves.Sandberg & Sandham, J Fluid Mech 2008

Trailing edge noise is the dominant aeroacoustic noise source on modern utility-scale HAWTs J. Fluid Mech., 2008.utility-scale HAWTs.(S. Oerlemans, Ph.D. Thesis, U. of

Twente, 2009)

Acoustic Modeling Issuesg

Trailing edge noise is difficult to predict using empirical models • Sensitive to airfoil trailing edge shape• Sensitive to boundary layer properties

Direct computation of the trailing edge noise sources using Direct computation of the trailing edge noise sources using high-fidelity CFD methods is possible – if we only focus on small flow regions of interest

Large-Eddy Simulation (LES) of a complete wind turbine and all noise sources not feasible in the near future (especially for design purposes)design purposes)• Must divide the noise modeling problem into sub-parts which

can each be solved in the most efficient way possible

14

Trailing Edge Noise Prediction Tool

In collaboration with Dr. Phil Morris, Dr. Ken Brentner, and Monica Christiansen at Penn State University

FlowChristiansen at Penn State University

Approach is based on the Nonlinear Disturbance Equations (NLDE), solved using Computational Fluid Dynamics (CFD).Hi h d i l h l l i High-order numerical schemes accurately resolve aero-acoustic sources and sound waves.

Step 2.I l bl d

Sound Waves

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Step 1.Full Rotor Simulation to obtain “base flow.”

Isolate blade section for detailed turbulent boundary layer simulation

d iand noise prediction.

NLDE Trailing Edge Prediction Toolg g

RANS Domain

To far-field

NLDE Domain

Turbulence Injection included in NLDE domain To far-

ar-fi

eld

-fieldTo fa

To far-field

Trailing Edge Noise Code Statusg gNLDE flow solver is implemented and coupled with a

RANS “base flow” solver. Basic validation cases complete (circular cylinder flow,

steady airfoil flow)C tl i l ti th d f i t d i Currently implementing method for introducing realistic turbulent boundary layer fluctuations for noise calculations.

N t t lid ti i i f il t ili d iNext step: validation using airfoil trailing edge noise wind tunnel data.

Referencesf• W. Devenport, R. Burdisso, A. Borgoltz, P. Ravetta, and M. Barone, “Aerodynamic and

Acoustic Corrections for a Kevlar-Walled Anechoic Wind Tunnel”, AIAA Paper 2010-p3749, 16th AIAA/CEAS Aeroacoustics Conference, June 2010.

• M. Barone, J. Paquette, E. Simley, and M. Christiansen, “Aeroacoustics and aerodynamic performance of a rotor with flatback airfoils”, Proceedings of the 2010 European Wind Energy Conference April 2010European Wind Energy Conference, April 2010.

• M. Barone, D. Berg, W. Devenport, and R. Burdisso, “Aerodynamic and aeroacoustictests of a flatback version of the DU97-W-300 airfoil”, Sandia Report SAND2009-4185, 2009.

• M. Barone and D. Berg, “Aerodynamic and aeroacoustic properties of a flatback airfoil: an update”, AIAA-2009-271, presented at the ASME Wind Energy Symposium, Orlando,FL, 2009.

• C. Stone, M. Barone, M. Smith, and E. Lynch, “A comparative study of theC. Stone, M. Barone, M. Smith, and E. Lynch, A comparative study of the aerodynamics and aeroacoustics of a flatback airfoil using hybrid RANS-LES”, AIAA-2009-273, presented at the ASME Wind Energy Symposium, Orlando, FL, 2009.

• J. Erwin, P. Morris, and K. Brentner, “Trailing-edge noise prediction using the nonlinear disturbance equations” AIAA 2009 272 presented at the ASME Wind Energydisturbance equations”, AIAA-2009-272, presented at the ASME Wind Energy Symposium, Orlando, FL, 2009.

Thank You