The turbulent flow over a porous trailing edge of a NACA 0018 airfoil is experimentally investigated to study the link between the hydrodynamic flow field and the acoustic scattering. Four porous trailing edges, obtained from open-cell metal foams, are tested to analyze the effects on far-field noise of the permeability of the material and of the hydrodynamic communication between the two sides of the airfoil. The latter is assessed by filling the symmetry plane of two of the porous trailing edges with a thin layer of adhesive that acts as a solid membrane. Experiments are performed at a zero degree angle of attack. Far-field noise measurements show that the most permeable metal foam reduces noise (up to 10 dB) with respect to the solid trailing edge for Strouhal numbers based on the chord below 16. At higher nondimensional frequencies, a noise increase is measured. The porous inserts with an adhesive layer show no noise abatement in the low frequency range, but only a noise increase at higher frequency. The latter is, therefore, attributed to surface-roughness noise. Flow field measurements, carried out with time-resolved planar particle image velocimetry, reveal correlation of near-wall velocity fluctuations between the two sides of the permeable trailing edges only within the frequency range where noise abatement is reported. This flow communication suggests that permeable treatments abate noise by distributing the impedance jump across the foam in the streamwise direction, promoting noise scattering from different chordwise locations along the inserts. This is further confirmed by noise source maps obtained from acoustic beamforming. For the frequency range where noise reduction is measured, the streamwise position of the main noise emission depends on the permeability of the insert. At higher frequencies, noise is scattered from upstream the trailing edge independently of the test case, in agreement with the roughness-generated noise assumption.
REFERENCES
1.
J. E.
Ffowcs-Williams
and L. H.
Hall
, “Aerodynamic sound generation by turbulent flow in the vicinity of a scattering half plane
,” J. Fluid Mech.
40
(04
), 657
(1970
).2.
M. S.
Howe
, “The influence of vortex shedding on the generation of sound by convected turbulence
,” J. Fluid Mech.
76
(4
), 711
–740
(1976
).3.
S.
Wagner
, R.
Bareiß
, and G.
Guidati
, Wind Turbine Noise
(Springer Berlin Heidelberg
, Berlin, Heidelberg
, 1996
), ISBN: 978-3-642-88712-3.4.
S.
Oerlemans
, P.
Sijtsma
, and B. M.
López
, “Location and quantification of noise sources on a wind turbine
,” J. Sound Vib.
299
, 869
(2007
).5.
E. B.
Tingey
and A.
Ning
, “Trading off sound pressure level and average power production for wind farm layout optimization
,” Renewable Energy
114
, 547
–555
(2017
).6.
M.
Gruber
, P.
Joseph
, and T.
Chong
, “On the mechanisms of serrated airfoil trailing edge noise reduction
,” in 17th AIAA/CEAS Aeroacoustics Conference (32nd AIAA Aeroacoustics Conference), June
(American Institute of Aeronautics and Astronautics
, Reston, Virigina
, 2011
), pp. 1
–23
, ISBN: 978-1-60086-943-3.7.
D. J.
Moreau
and C. J.
Doolan
, “Noise-reduction mechanism of a flat-plate serrated trailing edge
,” AIAA J.
51
(10
), 2513
–2522
(2013
).8.
T. P.
Chong
and A.
Vathylakis
, “On the aeroacoustic and flow structures developed on a flat plate with a serrated sawtooth trailing edge
,” J. Sound Vib.
354
, 65
–90
(2015
).9.
F.
Avallone
, S.
Pröbsting
, and D.
Ragni
, “Three-dimensional flow field over a trailing-edge serration and implications on broadband noise
,” Phys. Fluids
28
(11
), 117101
(2016
).10.
P.
Kholodov
and S.
Moreau
, “Optimization of serrations for broadband trailing-edge noise reduction using an analytical model
,” in 25th AIAA/CEAS Aeroacoustics Conference, May
(American Institute of Aeronautics and Astronautics
, Delft, The Netherlands
, 2019
), pp. 1
–18
, ISBN: 978-1-62410-588-3.11.
F.
Avallone
, W. C. P.
van der Velden
, D.
Ragni
, and D.
Casalino
, “Noise reduction mechanisms of sawtooth and combed-sawtooth trailing-edge serrations
,” J. Fluid Mech.
848
, 560
–591
(2018
).12.
A.
Finez
, M.
Jacob
, E.
Jondeau
, and M.
Roger
, “Broadband noise reduction with trailing edge brushes
,” in 16th AIAA/CEAS Aeroacoustics Conference
(AIAA
, 2010
), pp. 1
–13
.13.
M.
Herr
and W.
Dobrzynski
, “Experimental investigations in low-noise trailing edge design
,” AIAA J.
43
(6
), 1167
–1175
(2005
).14.
I. A.
Clark
, “Bio-inspired control of roughness and trailing edge noise bio-inspired control of roughness and trailing edge noise
,” Ph.D. thesis, Virginia Polytechnic Institute and State University
, 2017
.15.
T.
Gerhard
, S.
Erbslöh
, and T.
Carolus
, “Reduction of airfoil trailing edge noise by trailing edge blowing
,” J. Phys.: Conf. Ser.
524
(1
), 012123
(2014
).16.
M.
Szoke
, D.
Fiscaletti
, and M.
Azarpeyvand
, “Effect of inclined transverse jets on trailing-edge noise generation
,” Phys. Fluids
30
(8
), 085110
(2018
).17.
T.
Geyer
and E.
Sarradj
, “Noise generation by porous airfoils
,” 13th AIAA/CEAS Aeroacoustics Conference
(AIAA
, 2007
).18.
A.
Vathylakis
, T. P.
Chong
, and P. F.
Joseph
, “Poro-Serrated trailing-edge devices for airfoil self-noise reduction
,” AIAA J.
53
(11
), 3379
–3394
(2015
).19.
S.
Moreau
, P.
Laffay
, A.
Idier
, and N.
Atalla
, “Several noise control of the trailing-edge noise of a controlled-diffusion airfoil
,” in 22nd AIAA/CEAS Aeroacoustics Conference
(AIAA
, 2016
), pp. 1
–13
.20.
T.
Geyer
, E.
Sarradj
, and C.
Fritzsche
, “Measurement of the noise generation at the trailing edge of porous airfoils
,” Exp. Fluids
48
(2
), 291
–308
(2010
).21.
M.
Herr
, K. S.
Rossignol
, J.
Delfs
, N.
Lippitz
, and M.
Moßner
, “Specification of porous materials for low-noise trailing-edge applications
,” in 20th AIAA/CEAS Aeroacoustics Conference
(AIAA
, 2014
), pp. 1
–19
.22.
T.
Geyer
and E.
Sarradj
, “Trailing edge noise of partially porous airfoils
,” in 20th AIAA/CEAS Aeroacoustics Conference
(AIAA
, 2014
).23.
J.
Delfs
, B.
Faßmann
, N.
Lippitz
, M.
Lummer
, M.
Mößner
, L.
Müller
, K.
Rurkowska
, and S.
Uphoff
, “SFB 880: Aeroacoustic research for low noise take-off and landing
,” CEAS Aeronaut. J.
5
(4
), 403
–417
(2014
).24.
A.
Kisil
and L. J.
Ayton
, “Aerodynamic noise from rigid trailing edges with finite porous extensions
,” J. Fluid Mech.
836
, 117
–144
(2018
).25.
T.
Geyer
, E.
Sarradj
, and C.
Fritzsche
, “Porous airfoils: Noise reduction and boundary layer effects
,” Int. J. Aeroacoust.
9
(6
), 787
–820
(2010
).26.
M.
Roger
and S.
Moreau
, “Back-scattering correction and further extensions of Amiet’s trailing-edge noise model. Part 1: Theory
,” J. Sound Vib.
286
(3
), 477
–506
(2005
).27.
M.
Herr
and J.
Reichenberger
, “Search of airworthy trailing-edge noise reduction means
,” in 17th AIAA/CEAS Aeroacoustics Conference, June
(AIAA
, 2011
), pp. 5
–8
, ISBN: 978-1-60086-943-3.28.
A. R.
Carpio
, F.
Avallone
, D.
Ragni
, M.
Snellen
, and S.
van der Zwaag
, “3D-printed perforated trailing edges for broadband noise abatement
,” in 25th AIAA/CEAS Aeroacoustics Conference, May
(AIAA
, 2019
), pp. 1
–13
.29.
J. W.
Jaworski
and N.
Peake
, “Aerodynamic noise from a poroelastic edge with implications for the silent flight of owls
,” J. Fluid Mech.
723
(2013
), 456
–479
(2013
).30.
J. H. M.
Gooden
, “Experimental low-speed aerodynamic characteristics of the Wortmann FX66-S-196 V1 airfoil
,” in XVI OSTIV Congress
(International Scientific and Technical Soaring Organisation
, Chateauroux, France
, 1978
), pp. 1
–11
.31.
M.
Roger
and S.
Moreau
, “Trailing edge noise measurements and prediction for subsonic loaded fan blades
,” in 8th AIAA/CEAS Aeroacoustics Conference & Exhibit
(AIAA
, 2002
), Vol. 2460, pp. 1
–15
.32.
S.
Moreau
, M.
Henner
, G.
Iaccarino
, M.
Wang
, and M.
Roger
, “Analysis of flow conditions in freejet experiments for studying airfoil self-noise
,” AIAA J.
41
(10
), 1895
–1905
(2003
).33.
A. R.
Carpio
, R.
Merino-Martínez
, F.
Avallone
, D.
Ragni
, M.
Snellen
, and S.
van der Zwaag
, “Experimental characterization of the turbulent boundary layer over a porous trailing edge for noise abatement
,” J. Sound Vib.
443
, 537
–558
(2019
).34.
S.
Luesutthiviboon
, A.
Malgoezar
, M.
Snellen
, P.
Sijtsma
, and D.
Simons
, “Improving source discrimination performance by using an optimized acoustic array and adaptive high-resolution CLEAN-SC beamforming
,” in 7th Berlin Beamforming Conference
, 2018
.35.
P.
Welch
, “The use of fast fourier transform for the estimation of power spectra: A method based on time averaging over short, modified periodograms
,” IEEE Trans. Audio Electroacoust.
15
(2
), 70
–73
(1967
).36.
S.
Oerlemans
and P.
Sijtsma
, “Determination of absolute levels from phased array measurements using spatial source coherence
,” in 8th AIAA/CEAS Aeroacoustics Conference & Exhibit, June
(American Institute of Aeronautics and Astronautics
, Reston, Virigina
, 2002
), pp. 1
–12
, ISBN: 978-1-62410-119-9, URL: http://arc.aiaa.org/doi/abs/10.2514/6.2002-2464.37.
P.
Sijtsma
, “Phased array beamforming applied to wind tunnel and fly-over tests
,” Technical Report NLR-TP-2010-549, NLR
, October 2010
.38.
T. J.
Mueller
, Aeroacoustic Measurements
(Springer
, Berlin, New York
, 2002
), ISBN: 978-3-662-05058-3.39.
Lord Rayleigh
, “Investigations in optics, with special reference to the spectroscope
,” Philos. Mag. Ser.
5
(49
), 8
, 261
–274
(1879
).40.
S.
Oerlemans
and P.
Migliore
, “Aeroacoustic wind tunnel tests of wind turbine airfoils
,” in 10th AIAA/CEAS Aeroacoustics Conference
(AIAA
, 2004
), pp. 1
–18
, ISSN 2229-7928, URL: http://arc.aiaa.org/doi/10.2514/6.2004-3042.41.
E.
Sarradj
, G.
Herold
, P.
Sijtsma
, R. M.
Martinez
, T. F.
Geyer
, C. J.
Bahr
, R.
Porteous
, D.
Moreau
, and C. J.
Doolan
, “A microphone array method benchmarking exercise using synthesized input data
,” in 23rd AIAA/CEAS Aeroacoustics Conference, June
(American Institute of Aeronautics and Astronautics
, 2017
), pp. 1
–16
, ISBN: 978-1-62410-504-3.42.
D.
Ragni
, B. W.
Van Oudheusden
, and F.
Scarano
, “3D pressure imaging of an aircraft propeller blade-tip flow by phase-locked stereoscopic PIV
,” Exp. Fluids
52
(2
), 463
–477
(2012
).43.
R. J.
Adrian
, “Particle-imaging techniques for experimental fluid mechanics
,” Annu. Rev. Fluid Mech.
23
, 261
–304
(1991
).44.
M.
Raffel
, C. E.
Willert
, and J.
Kompenhans
, Particle Image Velocimetry
(Springer Berlin Heidelberg
, 1998
).45.
J.
Westerweel
, “Fundamentals of digital particle image velocimetry
,” Meas. Sci. Technol.
8
(12
), 1379
–1392
(1997
).46.
F.
Scarano
and M.
Riethmuller
, “Advances in iterative multigrid PIV image processing
,” Exp. Fluids
29
, 51
–60
(2000
).47.
J.
Soria
, “Multigrid approach to cross-correlation digital PIV and HPIV analysis
,” in 13th Australasian Fluid Mecanics Conference, December
(Australasian Fluid Mechanics Society
, Melbourne
, 1998
), pp. 381
–384
, ISBN: 0732620449.48.
F.
Scarano
, “Iterative image deformation methods in PIV
,” Meas. Sci. Technol.
13
(1
), R1
–R19
(2001
).49.
J.
Westerweel
and F.
Scarano
, “Universal outlier detection for PIV data
,” Exp. Fluids
39
(6
), 1096
–1100
(2005
).50.
A.
Melling
, “Tracer particles and seeding for particle image velocimetry
,” Meas. Sci. Technol.
8
(12
), 1406
–1416
(1997
).51.
B.
Wieneke
, “PIV uncertainty quantification from correlation statistics
,” Meas. Sci. Technol.
26
(7
), 074002
(2015
).52.
C. A.
León
, R.
Merino-Martínez
, D.
Ragni
, F.
Avallone
, and M.
Snellen
, “Boundary layer characterization and acoustic measurements of flow-aligned trailing edge serrations
,” Exp. Fluids
57
(12
), 182
(2016
).53.
F.
Avallone
, W. C. P.
van der Velden
, and D.
Ragni
, “Benefits of curved serrations on broadband trailing-edge noise reduction
,” J. Sound Vib.
400
, 167
–177
(2017
).54.
D.
Ragni
and C.
Ferreira
, “Effect of 3D stall-cells on the pressure distribution of a laminar NACA64-418 wing
,” Exp. Fluids
57
(8
), 127
(2016
).55.
M.
Drela
, “XFOIL: An analysis and design system for low Reynolds number airfoils
,” in Low Reynolds Number Aerodynamics: Proceedings of the Conference Notre Dame, Indiana, USA, 5–7 June 1989
(Springer Berlin Heidelberg
, Berlin, Heidelberg
, 1989
), pp. 1
–12
, ISBN: 978-3-642-84010-4.56.
R. J.
Moffat
, “Describing the uncertainties in experimental results
,” Exp. Therm. Fluid Sci.
1
(1
), 3
–17
(1988
).57.
P. R.
Spalart
and J. H.
Watmuff
, “Experimental and numerical study of a turbulent boundary layer with pressure gradients
,” J. Fluid Mech.
249
(1
), 337
(1993
).58.
F. H.
Clauser
, “The turbulent boundary layer
,” in Advances in Applied Mechanics
(Elsevier
, 1956
), pp. 1
–51
.59.
H.
Schlichting
and K.
Gersten
, Boundary-Layer Theory
(Springer Berlin Heidelberg
, Berlin, Heidelberg
, 2017
), Vol. 20, ISBN: 978-3-662-52917-1.60.
K. A.
Flack
and M. P.
Schultz
, “Roughness effects on wall-bounded turbulent flows
,” Phys. Fluids
26
(10
), 101305
(2014
).61.
J. B.
Barlow
, W. H.
Rae
, and A.
Pope
, Low-Speed Wind Tunnel Testing
, 3rd ed. (Wiley
, 1999
), ISBN: 0471557749.62.
V.
Patil
, J.
Finn
, X.
He
, R.
Ziazi
, S. V.
Apte
, J. A.
Liburdy
, and B.
Wood
, “Experimental versus computational methods in the study of flow in porous media
,” in Volume 1D, Symposia
(ASME
, 2014
), pp. 1
–9
, ISBN: 978-0-7918-4624-7.63.
J.
Jiménez
, “Coherent structures in wall-bounded turbulence
,” J. Fluid Mech.
842
, P1
(2018
).64.
D. M.
Chase
, “Sound radiated by turbulent flow off a rigid half-plane as obtained from a wavevector spectrum of hydrodynamic pressure
,” J. Acoust. Soc. Am.
52
(3B
), 1011
–1023
(1972
).65.
O.
Stalnov
, P.
Chaitanya
, and P. F.
Joseph
, “Towards a non-empirical trailing edge noise prediction model
,” J. Sound Vib.
372
, 50
–68
(2016
).66.
W. K.
Blake
, Mechanics of Flow-Induced Sound and Vibration
(Elsevier Science Publishing Co, Inc
, 2017
), Vol. 2, ISBN: 9780128092743.67.
R. K.
Amiet
, “Acoustic radiation from an airfoil in a turbulent stream
,” J. Sound Vib.
41
(4
), 407
–420
(1975
).68.
B.
André
, T.
Castelain
, and C.
Bailly
, “Investigation of the mixing layer of underexpanded supersonic jets by particle image velocimetry
,” Int. J. Heat Fluid Flow
50
, 188
–200
(2014
).69.
M.
Kamruzzaman
, T.
Lutz
, A.
Ivanov
, A.
Herrig
, W.
Wuerz
, and E.
Kraemer
, “Evaluation of measured anisotropic turbulent two-point correlation data for the accurate prediction of the turbulence noise sources
,” in 15th AIAA/CEAS Aeroacoustics Conference
(American Institute of Aeronautics and Astronautics
, 2009
).70.
M.
Kamruzzaman
, T.
Lutz
, A.
Herrig
, and E.
Krämer
, “Semi-Empirical modeling of turbulent anisotropy for airfoil self-noise predictions
,” AIAA J.
50
(1
), 46
–60
(2012
).71.
M.
Kamruzzaman
, Th.
Lutz
, W.
Würz
, W. Z.
Shen
, W. J.
Zhu
, M. O. L.
Hansen
, F.
Bertagnolio
, and H. Aa.
Madsen
, “Validations and improvements of airfoil trailing-edge noise prediction models using detailed experimental data
,” Wind Energy
15
(1
), 45
–61
(2012
).72.
L.
Jones
, R.
Sandberg
, and N.
Sandham
, “Investigation and prediction of transitional airfoil self-noise
,” in 15th AIAA/CEAS Aeroacoustics Conference, May
(AIAA
, 2009
), pp. 1
–13
.73.
W. J.
Devenport
, D. L.
Grissom
, W. N.
Alexander
, B. S.
Smith
, and S. A. L.
Glegg
, “Measurements of roughness noise
,” J. Sound Vib.
330
(17
), 4250
–4273
(2011
).74.
P.
Bradshaw
, “‘Inactive’ motion and pressure fluctuations in turbulent boundary layers
,” J. Fluid Mech.
30
(2
), 241
–258
(1967
).75.
S.
Hoyas
and J.
Jiménez
, “Scaling of the velocity fluctuations in turbulent channels up to Reτ = 2003
,” Phys. Fluids
18
(1
), 011702
(2006
).76.
Y.
Wu
and K. T.
Christensen
, “Spatial structure of a turbulent boundary layer with irregular surface roughness
,” J. Fluid Mech.
655
, 380
–418
(2010
).77.
S. A. S.
Ali
, M.
Azarpeyvand
, and C. R. I.
Da Silva
, “Trailing-edge flow and noise control using porous treatments
,” J. Fluid Mech.
850
, 83
–119
(2018
).78.
J. L.
Lage
, “The fundamental theory of flow through permeable media from Darcy to turbulence
,” in Transport Phenomena in Porous Media
(Elsevier
, 1998
), pp. 1
–30
.79.
J.
Hald
and J. J.
Christensen
, “A novel beamformer array design for noise source location from intermediate measurement distances
,” J. Acoust. Soc. Am.
112
(5
), 2448
(2002
).80.
T. F.
Brooks
, D. S.
Pope
, and M. A.
Marcolini
, “Airfoil self-noise and prediction
,” Technical Report NASA RP-1218, NASA Langley Research Center
, 1989
.81.
P. A.
Nelson
, “Noise generated by flow over perforated surfaces
,” J. Sound Vib.
83
(1
), 11
–26
(1982
).82.
J.
Schulze
and J.
Sesterhenn
, “Optimal distribution of porous media to reduce trailing edge noise
,” Comput. Fluids
78
, 41
–53
(2013
).© 2019 Author(s).
2019
Author(s)
You do not currently have access to this content.
