Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 1 Slide 1 For STAR South East Asian Conference 2015 Prediction of noise emission from the NASA SR-2 Propeller 8-9 June 2015 Mr Voo Keng Soon Mr Tan Chun Hern Mr Lim Nee Sheng Winson Dr Siauw Wei Long
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1 Slide 1
For STAR South East Asian Conference 2015
Prediction of noise emission from the NASA SR-2 Propeller
8-9 June 2015 Mr Voo Keng Soon Mr Tan Chun Hern
Mr Lim Nee Sheng Winson Dr Siauw Wei Long
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2 Slide 2
A big thank you to CD-adapco for the provision of technical assistance and advice!
Dr Mark Farrall Dr Fred Mendonça
Dr Amel Boudjir Dr Jason Fernandes
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3 Slide 3
Motivation • Fundamental study of noise emission from flow over propeller • Comparison of the usage of acoustics analogy and direct
measurement method for computational aeroacoustics • Investigate the appropriate usage of Moving Reference Frame
and Rigid Body Motion (sliding mesh) methodologies in the modelling of the propeller
• Study the behaviour of the propeller tip vortices in the presence of a generic wing
• NASA SR-2 propeller selected as validation case due to the availability of open source data
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4 Slide 4
Overview • Propeller Basics • Simulation Methodology • Generation of SR-2 propeller CAD • Differences between CFD Setups • CFD Setup of SR-2 propeller • SR-2: Analysis • Propeller in the Presence of Generic Wing • SR-2 + NACA0010: Analysis • Summary
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5 Slide 5
Propeller Basics • [1] held measured noise level and corresponding
spectral representations on a Cessna 172N (two-blade propeller) while [2] tested the Cessna FR172F (three-blade propeller)
• At high propeller RPM, noise at the blade passing frequency (BPF) is the dominant noise
2400rpm, 80Hz, 93.3dB
2400rpm, 120Hz, 91dB
[1] D.Miljkovic, M.Maletic, M.Obad, 2007. “Comparative Investigation of Aircraft Interior Noise Properties”, 3rd Congress of the Alps-Adria Acoustics Association. [2] D.Miljkovic, J. Ivosevic, T.Bucak, 2012. “Two vs Three Blade Propeller – Cockpit Noise Comparison”, 5th Congress of the Alps-Adria Acoustics Association.
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6 Slide 6
Propeller Basics
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7 Slide 7
[3] J.E. Marte, D.w. Kurtz, 1970. “A Review of Aerodynamic Noise From Propellers, Rotors, and Lift Fans”, NASA CR107568. [4] E.L. Chuan-Tau, J. Roskam, 2008. “Airplane Aerodynamics and Performance”, DARcorporation, USA.
http://static.thisdayinaviation.com
Propeller Basics
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8 Slide 8
http://www.aircav.com
https://www.nas.nasa.gov/SC12/demos/demo1.html
[3] J.E. Marte, D.w. Kurtz, 1970. “A Review of Aerodynamic Noise From Propellers, Rotors, and Lift Fans”, NASA CR107568. [4] E.L. Chuan-Tau, J. Roskam, 2008. “Airplane Aerodynamics and Performance”, DARcorporation, USA.
Propeller Basics
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9 Slide 9
[3] J.E. Marte, D.w. Kurtz, 1970. “A Review of Aerodynamic Noise From Propellers, Rotors, and Lift Fans”, NASA CR107568. [4] E.L. Chuan-Tau, J. Roskam, 2008. “Airplane Aerodynamics and Performance”, DARcorporation, USA.
Propeller Basics
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10 Slide 10
Propeller Basics
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11 Slide 11
Propeller Basics[4][5]
[4] E.L. Chuan-Tau, J. Roskam, 2008. “Airplane Aerodynamics and Performance”, DARcorporation, USA. [5] F.E. Weick, 1930. “Aircraft Propeller Design”, McGraw-Hill Book Company, USA
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12 Slide 12
Simulation Methodology
The following was employed for this aeroacoustics study of the NASA SR-2 propeller 1. Generation of propeller geometry, followed by meshing within the domain 2. Upon completion of volume meshing, simulation is setup to run steady state with Moving Reference Frame (MRF) 3. Converged steady solution is then used to calculate the propeller power coefficient, Cp
4. Calibration of blade angle through a series of steady state simulations at varied propeller blade angle, so as to match the predicted Cp to the experimental Cp
5. Upon calibration of the propeller blade angle, the simulation is then setup to run transiently with rigid body motion (sliding mesh) 6. The transient simulation is allowed to run for at least 10 propeller rotations to transit to a “steady” condition 7. Simulation is subsequently ran for a further 10 propeller rotations in order to record the pressure signal at the receivers 8. Pressure data recorded at the receivers processed to acquire sound pressure levels at the blade passing frequency (BPF)
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13 Slide 13
Simulation Methodology
The following was employed for the physics modelling • Time step of 2.5e-5 seconds utilized to capture propeller rotation rate of 1° per time-step • 10 inner iterations for convergence of time-step
Steady State Simulation Transient Simulation Steady Implicit unsteady
[4] E.L. Chuan-Tau, J. Roskam, 2008. “Airplane Aerodynamics and Performance”, DARcorporation, USA. [7] N.A. Cumpsty, 1989. “Compressor Aerodynamics”, Longman Scientific & Technical, USA [8] D.C. Mikkelson, B.J. Blaha, G.A. Mitchell, J.E. Wikete, 1977. “Design and Performance of Energy Efficient Propellers for Mach 0.8 Cruise”, NASA TM X-73612.
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16 Slide 16
Generation of SR-2 propeller CAD
Fine tuning of digitalized data a) Blade thickness ratio, t/b was fine-tuned, knowing t/b at tip is 2%[8]
b) Blade width ratio, b/D was fine-tuned, knowing blade activity factor AF=203[8][9]
c) Blade design lift coefficient, CLD was fine-tuned, knowing integrated design lift coefficient CLI = 0.081[8][9]
d) Change in blade angle with respect to that at 75% blade radius, Δβ was fine-tuned, knowing Δβ=0 at 0.75 r/R[8][9]
[8] D.C. Mikkelson, B.J. Blaha, G.A. Mitchell, J.E. Wikete, 1977. “Design and Performance of Energy Efficient Propellers for Mach 0.8 Cruise”, NASA TM X-73612. [9] G.L. Stefko, R.J. Jeracki, 1985. “Wind-Tunnel Results of Advanced High-Speed Propellers at Takeoff, Climb, and Landing Mach Numbers”, NASA TM 87030.
Slide 17
Generation of SR-2 propeller CAD
Slide 18
Generation of SR-2 propeller CAD
[9] G.L. Stefko, R.J. Jeracki, 1985. “Wind-Tunnel Results of Advanced High-Speed Propellers at Takeoff, Climb, and Landing Mach Numbers”, NASA TM 87030.
• Geometry generation of area-ruled spinner and turbine sting[9]
• The area-ruled spinner and turbine sting were designed to alleviate blade-root choking and to minimize compressibility drag rise.
turbine sting
Slide 19
• The generated propeller blades fitted nicely with the spinner • Inboard portion of propeller operates as a cascade rather than isolated blades
Generation of SR-2 propeller CAD
Slide 20
• Differences between earlier and current aeroacoustics studies of the NASA SR-2 propeller • Improved CAD modelling of the propeller blades[4][7][8][9][10] • Obtaining geometry data of spinner and turbine sting[9]
• Revised simulation conditions with inference from new literature[11][12]
• Inclusion of the acoustic plate in the modelling[13]
Differences between CFD Setups
current setup
[10] T.A. Egolf, O.A. Anderson, D.E. Edwards, A.J. Landgrebe, 1988. “An Analysis for High Speed Propeller-Nacelle Aerodynamic Performance Prediction”, NASA-CR-4199. [11] J.H. Dittmar, and P.L. Lasagna, 1982. “A Preliminary Comparison Between the SR-3 Propeller Noise in Flight and in a Wind Tunnel”, NASA-TM-82805. [12] J.H. Dittmar, R.J. Jeracki, and B.J. Blaha, 1979. “Tone Noise of Three Supersonic Helical Tip Speed Propellers in a Wind Tunnel”, NASA-TM-79167. [13] J.H. Dittmar, R.J. Burns, D.J. Leciejewski, 1984. “An Experimental Investigation of the Effect of Boundary Layer Refraction on the Noise From a High-Speed Propeller”, NASA TM 83764.
previous setup
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21 Slide 21
CFD Setup of SR-2 propeller
[13] J.H. Dittmar, R.J. Burns, D.J. Leciejewski, 1984. “An Experimental Investigation of the Effect of Boundary Layer Refraction on the Noise From a High-Speed Propeller”, NASA TM 83764.
Slide 22
• Modelled geometry of plate (holding the installed pressure transducers)[13]
• Patches of 16mm diameter were imprinted on the base of the CAD geometry of the plate to represent the pressure probe points
[13] J.H. Dittmar, R.J. Burns, D.J. Leciejewski, 1984. “An Experimental Investigation of the Effect of Boundary Layer Refraction on the Noise From a High-Speed Propeller”, NASA TM 83764.
CFD Setup of SR-2 propeller
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23 Slide 23
CFD Setup of SR-2 propeller • Trimmed hexahedral mesh
with prism layers • 97.3 million cells • Wall Y+ < 1 at critical areas • Unknown mass flow exiting
from rear of air turbine sting • Tangent ogive cylinder added
to the rear to minimize undesirable noise generation due to abrupt flow separation
(section cut @ Y=0)
Slide 24
[11] J.H. Dittmar, and P.L. Lasagna, 1982. “A Preliminary Comparison Between the SR-3 Propeller Noise in Flight and in a Wind Tunnel”, NASA-TM-82805. [12] J.H. Dittmar, R.J. Jeracki, and B.J. Blaha, 1979. “Tone Noise of Three Supersonic Helical Tip Speed Propellers in a Wind Tunnel”, NASA-TM-79167. [13] J.H. Dittmar, R.J. Burns, D.J. Leciejewski, 1984. “An Experimental Investigation of the Effect of Boundary Layer Refraction on the Noise From a High-Speed Propeller”, NASA TM 83764. [14] J.H. Dittmar, 1989. “Cruise Noise of the SR-2 Propeller Model in a Wind Tunnel”, NASA-TM-101480.
Environmental ConditionsPressure, P (Pa) 90110Temperature, T (K) 279speed of sound (m/s) corresponding to above P & T 334.85air density (kg/m3) corresponding to above P & T 1.1251
Delta blade angle of -0.4° utilized to match experimental Cp of 1.32 [14]
US Standard Atmosphere 1976
SR-2 : Analysis
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25 Slide 25
suction side suction side
pressure side pressure side
SR-2 : Analysis
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26 Slide 26
smaller peak to peak amplitude
[15] J.H. Dittmar, R.J. Jeracki, and B.J. Blaha, 1979. “Tone Noise of Three Supersonic Helical Tip Speed Propellers in a Wind Tunnel”, NASA-TM-79167.
Pressure-time trace (probe on tunnel wall) • Sinusoidal waveform observed in CFD • Sinusoidal waveform observed in wind
tunnel data (SR-2, M0.6, J3.06)[15]
• Steep fronted wave (approaches classic N wave shock pattern) observed in wind tunnel data (SR-2, M0.8, J3.07)[15]
• The latter is a good indication on the presence of sharp pressure rises normally associated with supersonic helical tip speed
Helical tip mach 0.857 Helical tip mach 1.14
SR-2 : Analysis
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27 Slide 27
Comparison with previous setup (using direct measurement)
current setup previous setup
• With the updated geometries, the current setup exhibited a closer match in the sound pressure level @BPF when compared to the experimental data
• A delta of 1.173 dB at probe 6 (@ X=0.3in) as compared to experimental data
• Pre-processing is important! Whenever possible, usage of b e t t e r g e o m e t r y C A D representation will lead to peace of mind
SR-2 : Analysis
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28 Slide 28
Comparison with previous setup (using FW-H Impermeable) • Measurement locations are too close to
source, noise does not necessarily meet farfield conditions[11]
• Ffowcs Williams-Hawkings (FW-H) method is a form of acoustic analogy applied to reduce aeroacoustics sound sources to simple emitter type
• Such methods rely on near-field information gathered over surface(s) enclosing as much as possible the noise sources
• These methods propagate noise from source to receiver via analytical solution of the wave equation
• In the far field, sound behaves as in open air without reflecting surfaces to interfere with its propagation
• The near field is the area very close to the noise source where the sound pressure level may vary significantly with a small change in position
• Advantage of FW-H: Only require CFD solution around source, not expensive
• Disadvantage of FW-H: Cannot account for reflection[16]
• Acoustic analogy not recommended for this CFD setup [11] J.H. Dittmar, and P.L. Lasagna, 1982. “A Preliminary Comparison Between the SR-3 Propeller Noise in Flight and in a Wind Tunnel”, NASA-TM-82805. [16] A. Zinoviev, 2002. “Application of Ffowcs Williams and Hawkings Equation to Sound Radiation by Vibrating Solid Objects in a Viscous Fluid: Inconsistencies and the Correct Solution”, ISBN 0-909882-19-3@2002 AAS
Near Field acoustic receiver
FW-H (solve wave equation)
CFD (solve Navier-Stokes)
Far Field
Noise Sources
SR-2 : Analysis
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30 Slide 30
SR-2 + NACA0010 : Analysis
Comparison with and without NACA10 wing (using direct measurement)
SR-2 SR-2 + NACA10
Addition of NACA10 wing • Slightly reduced dB at probe 5-6 • Reduced dB from probe 3 to 11 • Increased dB at Probe 1,2, 12 Propeller + Airfoil = …
less noise?!?
perhaps only at the BPF???
drop of 0.66dB
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31 Slide 31
Addition of NACA10 wing • Slightly reduced dB at probe 5-6 • Reduced dB from probe 3 to 11 • Increased dB at Probe 1,2, 12
Comparison with and without NACA10 wing (using direct measurement)
Propeller + Airfoil = … generally lesser noise at probes near to propeller!
why???
SR-2 + NACA0010 : Analysis
SR-2 SR-2 + NACA10
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32 Slide 32 [17] L.L.M. Veldhuis, 2005. “Propeller Wing Aerodynamic Interference”, Delft University of Technology.
Pressure coefficient contour plots • Sections of blades coloured blue shows area of suction • Areas coloured red shows high pressure stagnation • Presence of wing causes significant reduction in rotation (swirl velocity)[17]
• Viewing from front, the propeller is rotating clockwise • Viewing from front, wing to the left of propeller experienced positive local
angle of angle, leading to higher lift force • Viewing from front, wing to the right of propeller experienced negative
local angle of attack, leading to lower lift force
SR-2 + NACA0010 : Analysis
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33 Slide 33
SR-2
SR-2 + NACA10 http://www.aip.org
SR-2 + NACA0010 : Analysis
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34 Slide 34
SR-2
SR-2 + NACA10
http://www.flickr.com
[18] M.M. Hand, 2001. “Unsteady Aerodynamics Experiment Phase VI: Wind Tunnel Test Configurations and Available Data Campaigns”, NREL/TP-500-29955.
http://www.flickr.com
SR-2 + NACA0010 : Analysis
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35 Slide 35
SR-2 + NACA0010 : Analysis
[19] R.T. Johnston, J.P. Sullivan, 1993. “Unsteady Wing Surface Pressures in the Wake of a Propeller”, Journal of Aircraft Vol. 30, No. 5. [20] A.D. Thom, 2011. “Analysis of Vortex-Lifting Surface Interactions”, University of Glasgow.
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36 Slide 36
SR-2 + NACA0010 : Analysis
[19] R.T. Johnston, J.P. Sullivan, 1993. “Unsteady Wing Surface Pressures in the Wake of a Propeller”, Journal of Aircraft Vol. 30, No. 5. [20] A.D. Thom, 2011. “Analysis of Vortex-Lifting Surface Interactions”, University of Glasgow.
Y = -R
Y = -R -2cm
Y = -R +2cm
• Local deformation of propeller tip vortex at wing leading edge[19][20]
• As vortex approaches wing, it will be displaced outwards from the turbine sting
Outwards spanwise flow
Inwards spanwise flow
• Bending around the leading edge, vortex moves inwards towards sting
• Vortex leaves trailing edge at different span locations and time, resulting in shearing of propeller wake
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37 Slide 37
[21] S.Oerlemans, P.Sijtsma, B.M. López, 2007. “Location and quantification of noise sources on a wind turbine”, Journal of Sound and Vibration 299.
• Acoustic field measurements carried out in the framework of the European SIROCCO project found that all the array results reveal that besides a minor source at the rotor hub, practically all noise (emitted to the ground) is produced during the downward movement of the blades[21]
SR-2 + NACA0010 : Analysis
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38 Slide 38
• Acoustic plate located above propeller • propeller rotating clockwise (view from
front) • Upward stroke of propeller blades at region
left of spinner (view from front) liable for noise detected by probes on acoustic plate
• Proximity of airfoil wing to the propeller plane affecting the air flow in the vicinity of the propeller
• Presence of wing near the propeller may have shielded some of the propeller acoustic effect recorded on probe 4 to 11
• Probe 12, located further down the airfoil chord, detected a higher noise
• Perhaps a higher noise contribution from airfoil further downstream of Probe 12?
• Literature review on the aeroacoustics impact of tractor configuration with varied test conditions returned ambiguous findings[22][23]
SR-2 + NACA0010 : Analysis
[22] P.J.W. Block, 1986. “Experimental Study of the Effects of Installation on single- and Counter- Rotation Propeller Noise”, NASA-TP-2541. [23] R.P. Woodward, 1987. “Measured Noise of a Scale Model High Speed Propeller at Simulated Takeoff/Approach Conditions”, NASA-TM-88920.
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39 Slide 39
Summary • Aeroacoustics simulation of the SR-2 with updated geometries detected noise at a closer fit
to the experimental data, registering a difference of 1.173dB at probe 6 • One has to recognize that pre-processing is of utmost importance, especially if one intends
to invest in DES or LES • Whenever possible, usage of better geometry CAD representation is recommended • Appropriate modelling of propeller with MRF or rigid body motion (sliding mesh) is vital • Direct measurement of probe points and acoustic analogy serve different purposes • Direct measurement for near field probe points are highly recommended if the probe points
are located within the simulation domain • Acoustic analogy is an effective method to reduce aeroacoustics sound sources to simple
emitter type for detection in the far field • Noise (emitted to ground) is produced during downward stroke of propeller blades[21] • DES simulation of a generic wing aft of the SR-2 propeller at Mach 0.6 had reduced the
noise level recorded on most of the probe points in the near field • Literature review on the aeroacoustics impact of tractor configuration with varied test
conditions returned ambiguous findings[22][23]
• Scientific research findings can be vague at times • One has to keep an open mind and continue one’s research
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