National Aeronautics and Space Administration
www.nasa.gov
Computational Analysis of a Chevron Nozzle UniquelyTailored for Propulsion Airframe Aeroacoustics
12th AIAA/CEAS Aeroacoustics ConferenceCambridge, MAMay 8-10, 2006
Steven J. MasseyEagle Aeronautics, Inc.
Alaa A. ElmiliguiAnalytical Services & Materials, Inc.
Craig A. Hunter, Russell H. Thomas, S. Paul PaoNASA Langley Research Center
andVinod G. MengleBoeing Company
May 8, 2006NASA Langley Research Center 2
Outline
Motivation Objectives Numerical Tools Review of Generic Jet-Pylon Effect Axi, bb, RR, RT Nozzle Configurations Analysis Procedure Results Chain from Noise to Geometry Summary Concluding Remarks
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General PAA Related Effects and FeaturesOn Typical Conventional Aircraft
Nacelle-airframe integratione.g. chines, flow distortion,relative angles Jet-pylon
interaction of thePAA T-fan nozzle
Jet-flapimpingement
Jet-flap trailingedge interaction
Jet influence onairframe sources:side edges
Jet interaction withhorizontal stabilizers
Jet and fan noisescattering fromfuselage, wing, flapsurfaces
Pylon-slat cutout
QTD2 partnership ofBoeing, GE, Goodrich,NASA, and ANA
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Objectives
To build a predictive capability to link geometryto noise for complex configurations
To identify the flow and noise sourcemechanisms of the PAA T-Fan (quieter at takeoff than the reference chevron nozzle)
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Numerical Tools
PAB3D 3D RANS upwind code Multi-block structured with general patching Parallel using MPI Mesh sequencing Two-equation k- turbulence models Several algebraic Reynolds stress models
Jet3D Lighthills Acoustic Analogy in 3D
Models the jet flow with a fictitious volume distributionof quadrupole sources radiating into a uniform ambientmedium
Uses RANS CFD as input
Now implemented for structured and unstructuredgrids (ref AIAA 2006-2597)
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Sample Grid Plane
31 Million Cells for 180o
PAB3D solution: 33hours on 44 ColumbiaCPUs (Itanium 2)
Jet3D solution, 10minutes on Mac
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Model Scale LSAF PAA Nozzles Analyzed
Four Nozzles Chosen forAnalysis:
Axisymmetric Nozzle(not an experimentalnozzle)
bb conventional nozzles
RR state-of-the-artazimuthally uniformchevrons on core andfan
RT PAA T-fanazimuthally varyingchevrons on fan anduniform chevrons oncore
For more details seeMengle et al. AIAA 06-2467
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Generic Pylon Effect Understanding - AIAA 05-3083
Core Flow Induced Off of Jet Axis byCoanda Effect
Pairs of Large Scale Vortices Created TKE and Noise Sources Move
Upstream Depending on Design Details can
Result in Noise Reduction or Increasewith Pylon
Refs: AIAA 01-2183, 01-2185, 03-3169, 03-3212, 04-2827, 05-3083
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Analysis Procedure
Start with established facts and work fromderived to fundamental quantities to formconnections to geometry Measured noise data (LSAF) SPL predictions (Jet3D) OASPL noise source histogram (Jet3D) Mass averaged, non-dimensional turbulence intensity
(PAB3D) OASPL noise source maps (Jet3D) Turbulence kinetic energy (PAB3D) Axial vorticity Cross flow streamlines Vertical velocity Total temperature Total temperature centroid Geometry
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Jet3D SPL Predictions with LSAF
*
* Axi case not thrust matched to others
Observer located on a 68.1D radius from the fan nozzle exit at an inlet angle of 88.5 deg. and an azimuthal angle of 180 deg. LSAF data from Mengle et al. AIAA 20062467
Tunnel noise
bb predicted within 1 dB forwhole range
RR over predicted by 1 dB forfrequencies < 10 kHz, underpredicted by up to 2 dB forhigh frequencies
RT predicted within 1 dB forwhole range, under predictedhigh frequencies
Trends predictedcorrectly increasingconfidence of flowand noise sourcelinkage
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Noise Prediction CFD Link
Noise and TKE sources relative to Axi are consistent with previouspylon understanding of mixing
Mass-Avg TKE qualitatively matches noise source histogram bb, RR, RT intersect near x/D = 10 Axi crosses bb, RR at x/D = 12 Axi crosses RT at x/D = 12.75
Jet3D OASPL Histogram PAB3D: Mass-Avg TKE
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LAA CFD Correspondence
Axi bb RR RT
Peak noisesources correspondwith peak TKE
Local noiseincreased bychevron length
Cross flow streamlines show shearlayer vorticityorientation
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Beginning Fan/Core Shear Merger
Noise and TKE peakas layers merge
RR levels slightlylower than bb
RT merger delayed,much lower levels
Axi noiseasymmetry due toLAA observerlocation. TKE issymmetric
Axial velocity 20times stronger thancross flow, thusstrongest vortexwould take about60D for onerevolution
Axi bb RR RT
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Peak Noise From Shear Merger
bb, RR peak shown;RT peaks 0.5D later,one contour lowerthan bb and RR
Unmerged Axi withlower noise and TKE,but will persist moredownstream
Axi bb RR RT
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Chevrons Add Vorticity
Axi cross flow is symmetric, so axial vorticity = zero bb shows boundary layer vorticity shifted off axis by pylon RT longer chevrons show increased vorticity over RR and
shorter chevrons on bottom show decreases
Plug
Core Cowl
Pylo
n
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Pylon, Plug, Chevron Interaction
RT fan vortices moredefined on top, lesson bottom due tochevron length
Vertical velocitycomponent showseffect of pylon oncross flow:
Axi shows Coandaeffect on plug
Pylon cases haveexpanded downwardflow region to getaround pylon to fillin plug
Less downwardmovement in fanflow for RT
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Consolidation and Entrainment
Core and fan shearlayer vorticityconsolidates to formvortex pair
RR vortex pairslightly strongerthan bb
RT vortex pairsignificantly weakerthan bb and RR
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T-Fan Reduces Overall Mixing
RT local mixingproportional tochevron length
RT decreases netmixing, extends coreby ~ 1/2 D
RR negligible mixingover bb
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Overall Jet Trajectory
bb and RR equivalent symmetric chevron does notinteract with pylon effect
RT showing less downward movement favorableinteraction of asymmetric chevron with pylon effect
Total Temperature Centroid
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Summary
Overall mixing does not vary much between bb, RRand RT and is not indicative of noise in this study
The T-Fan effect: Varies the strength azimuthally of the localized
chevron vorticity Reduces the downstream large scale vorticies
introduced by the pylon Delays the merger of the fan and core shear layers Reduces peak noise and shifts it downstream There is the possibility of a more favorable design
for shear layer merger, which can now be foundcomputationally
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Concluding Remarks
A predictive capability linking geometry to noisehas been demonstrated
The T-Fan benefits from a favorable interactionbetween asymmetric chevrons and the pylon effect
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Discussion, Extra Slides
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Axisymmetric Nozzle
Surfaces colored by temperature
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Baseline Nozzle (bb)
Fan boundarystreamline
Near surface streamlines and temperature
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Reference Chevrons (RR)
Slight upward movement
Near surface streamlines and temperature
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PAA T-Fan Nozzle (RT)
Near surface streamlines and temperature
Further upward movement
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Motivation
Propulsion Airframe Aeroacoustics (PAA)
Definition: Aeroacoustic effects associated with theintegration of the propulsion and airframe systems.
Includes: Integration effects on inlet and exhaust systems Flow interaction and acoustic propagation effects Configurations from conventional to revolutionary
PAA goal is to reduce interaction effects directly oruse integration to reduce net radiated noise.
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PAA on QTD2: Concept to Flight in Two Years
Exploration of Possible PAA Concepts withQTD2 Partners (5/03 4/04)
Extensive PAA CFD/Prediction Work (10/03 8/05)
(AIAA 05-3083, 06-2436)
PAA Experiment at Boeing LSAF9/04
PAA Effects and Noise ReductionTechnologies Studied
AIAA 06-2467, 06-2434, 06-2435PAA on QTD2 8/05
PAA T-Fan ChevronNozzle
PAA EffectsInstrumentation
AIAA 06-2438, 06-2439
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Grid Coarse in Radial Direction
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Grid Cause of Vorticity Lines
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Detailed PAA FlowAnalysis
Begin with Highly ComplexLSAF Jet-Pylon NozzleGeometries
JET3D Noise SourceMap Trends Validatedwith LSAF PhasedArray Measurements
JET3D Validation of SpectraTrend at 90 degrees
Develop Linkages ofcomplex flow and noisesource interactions
Three major effects tounderstand:
Pylon effect Chevron effect PAA T-fan effect and their interaction
PAA Analysis Process to Develop Understanding of PAA T-fanNozzles Flow/Noise Source Mechanisms
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