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National Aeronautics and Space Administration
www.nasa.gov
Computational Analysis of a Chevron Nozzle Uniquely Tailored 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 Pao
NASA Langley Research Center
and
Vinod G. Mengle
Boeing 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
May 8, 2006NASA Langley Research Center 3
General PAA Related Effects and Features On Typical Conventional Aircraft
Nacelle-airframe integration e.g. chines, flow distortion, relative angles
Jet-pylon interaction of the PAA T-fan nozzle
Jet-flap impingement
Jet-flap trailing edge interaction
Jet influence on airframe sources: side edges
Jet interaction with horizontal stabilizers
Jet and fan noise scattering from fuselage, wing, flap surfaces
Pylon-slat cutout
QTD2 partnership of Boeing, GE, Goodrich, NASA, and ANA
May 8, 2006NASA Langley Research Center 4
Objectives
• To build a predictive capability to link geometry to noise for complex configurations
• To identify the flow and noise source mechanisms of the PAA T-Fan (quieter at take off than the reference chevron nozzle)
May 8, 2006NASA Langley Research Center 5
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– Lighthill’s Acoustic Analogy in 3D
– Models the jet flow with a fictitious volume distribution of quadrupole sources radiating into a uniform ambient medium
– Uses RANS CFD as input
– Now implemented for structured and unstructured grids (ref AIAA 2006-2597)
May 8, 2006NASA Langley Research Center 6
Sample Grid Plane
• 31 Million Cells for 180o
• PAB3D solution: 33 hours on 44 Columbia CPU’s (Itanium 2)
• Jet3D solution, 10 minutes on Mac
May 8, 2006NASA Langley Research Center 7
Model Scale LSAF PAA Nozzles Analyzed
Four Nozzles Chosen for Analysis:
• Axisymmetric Nozzle (not an experimental nozzle)
• bb conventional nozzles
• RR state-of-the-art azimuthally uniform chevrons on core and fan
• RT PAA T-fan azimuthally varying chevrons on fan and uniform chevrons on core
For more details see Mengle et al. AIAA 06-2467
May 8, 2006NASA Langley Research Center 8
Generic Pylon Effect Understanding - AIAA 05-3083
• Core Flow Induced Off of Jet Axis by Coanda Effect
• Pairs of Large Scale Vortices Created
• TKE and Noise Sources Move Upstream
• Depending on Design Details can Result in Noise Reduction or Increase with Pylon
Refs: AIAA 01-2183, 01-2185, 03-3169, 03-
3212, 04-2827, 05-3083
May 8, 2006NASA Langley Research Center 9
Analysis Procedure
•Start with established facts and work from derived to fundamental quantities to form connections 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
May 8, 2006NASA Langley Research Center 10
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 2006–2467
Tunnel noise
• bb predicted within 1 dB for whole range
• RR over predicted by 1 dB for frequencies < 10 kHz, under predicted by up to 2 dB for high frequencies
• RT predicted within 1 dB for whole range, under predicted high frequencies
Trends predicted correctly increasing confidence of flow and noise source linkage
May 8, 2006NASA Langley Research Center 11
Noise Prediction – CFD Link
• Noise and TKE sources relative to Axi are consistent with previous pylon 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
May 8, 2006NASA Langley Research Center 12
LAA – CFD Correspondence
Axi bb RR RT
• Peak noise sources correspond with peak TKE
•Local noise increased by chevron length
•Cross flow stream lines show shear layer vorticity orientation
May 8, 2006NASA Langley Research Center 13
Beginning Fan/Core Shear Merger
• Noise and TKE peak as layers merge
• RR levels slightly lower than bb
• RT merger delayed, much lower levels
• Axi noise asymmetry due to LAA observer location. TKE is symmetric
• Axial velocity 20 times stronger than cross flow, thus strongest vortex would take about 60D for one revolution
Axi bb RR RT
May 8, 2006NASA Langley Research Center 14
Peak Noise From Shear Merger
• bb, RR peak shown; RT peaks 0.5D later, one contour lower than bb and RR
• Unmerged Axi with lower noise and TKE, but will persist more downstream
Axi bb RR RT
May 8, 2006NASA Langley Research Center 15
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
May 8, 2006NASA Langley Research Center 16
Pylon, Plug, Chevron Interaction
• RT fan vortices more defined on top, less on bottom due to chevron length
• Vertical velocity component shows effect of pylon on cross flow:
• Axi shows Coanda effect on plug
• Pylon cases have expanded downward flow region to get around pylon to fill in plug
• Less downward movement in fan flow for RT
May 8, 2006NASA Langley Research Center 17
Consolidation and Entrainment
• Core and fan shear layer vorticity consolidates to form vortex pair
• RR vortex pair slightly stronger than bb
• RT vortex pair significantly weaker than bb and RR
May 8, 2006NASA Langley Research Center 18
T-Fan Reduces Overall Mixing
• RT local mixing proportional to chevron length
• RT decreases net mixing, extends core by ~ 1/2 D
• RR negligible mixing over bb
QuickTime™ and aPNG decompressor
are needed to see this picture.
QuickTime™ and aPNG decompressor
are needed to see this picture.
May 8, 2006NASA Langley Research Center 19
Overall Jet Trajectory
• bb and RR equivalent – symmetric chevron does not interact with pylon effect
• RT showing less downward movement – favorable interaction of asymmetric chevron with pylon effect
Total Temperature Centroid
May 8, 2006NASA Langley Research Center 20
Summary
• Overall mixing does not vary much between bb, RR and 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 found computationally
May 8, 2006NASA Langley Research Center 21
Concluding Remarks
• A predictive capability linking geometry to noise has been demonstrated
• The T-Fan benefits from a favorable interaction between asymmetric chevrons and the pylon effect
May 8, 2006NASA Langley Research Center 22
Discussion, Extra Slides…
May 8, 2006NASA Langley Research Center 23
Axisymmetric Nozzle
Surfaces colored by temperature
May 8, 2006NASA Langley Research Center 24
Baseline Nozzle (bb)
Fan boundary streamline
Near surface streamlines and temperature
May 8, 2006NASA Langley Research Center 25
Reference Chevrons (RR)
Slight upward movement
Near surface streamlines and temperature
May 8, 2006NASA Langley Research Center 26
PAA T-Fan Nozzle (RT)
Near surface streamlines and temperature
Further upward movement
May 8, 2006NASA Langley Research Center 27
Motivation
Propulsion Airframe Aeroacoustics (PAA)
• Definition: Aeroacoustic effects associated with the integration 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 or use integration to reduce net radiated noise.
May 8, 2006NASA Langley Research Center 28
PAA on QTD2: Concept to Flight in Two Years
Exploration of Possible PAA Concepts with QTD2 Partners (5/03 – 4/04)
Extensive PAA CFD/Prediction Work (10/03 – 8/05)
(AIAA 05-3083, 06-2436)
PAA Experiment at Boeing LSAF 9/04
PAA Effects and Noise Reduction Technologies Studied
AIAA 06-2467, 06-2434, 06-2435PAA on QTD2 – 8/05
• PAA T-Fan Chevron Nozzle
• PAA Effects Instrumentation
AIAA 06-2438, 06-2439
May 8, 2006NASA Langley Research Center 29
Grid Coarse in Radial Direction
May 8, 2006NASA Langley Research Center 30
Grid Cause of Vorticity Lines
May 8, 2006NASA Langley Research Center 31
Detailed PAA Flow
Analysis
Begin with Highly Complex LSAF Jet-Pylon Nozzle Geometries
JET3D Noise Source Map Trends Validated with LSAF Phased Array Measurements
JET3D Validation of Spectra Trend at 90 degrees
Develop Linkages of complex flow and noise source interactions
Three major effects to understand:
• Pylon effect
• Chevron effect
• PAA T-fan effect
• and their interaction
PAA Analysis Process to Develop Understanding of PAA T-fan Nozzle’s Flow/Noise Source Mechanisms