Computational Analysis of a Chevron Nozzle Uniquely Tailored for Propulsion Airframe Aeroacoustics

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National Aeronautics and Space Administration
www.nasa.gov
Computational Analysis of a Chevron Nozzle Uniquely
Tailored for Propulsion Airframe Aeroacoustics
12
th

AIAA/CEAS
Aeroacoustics
Conference
Cambridge,
MA
May
8-10,
2006
Steven J. Massey
Eagle Aeronautics, Inc.
Alaa A. Elmiligui
Analytical Services & Materials, Inc.
Craig A. Hunter, Russell H. Thomas, S. Paul Pao
NASA Langley Research Center
and
Vinod

G.
Mengle
Boeing Company
May 8, 2006
NASA 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, 2006
NASA 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
QTD
2

partnership
of
Boeing,
GE,
Goodrich,
NASA,
and
ANA
May 8, 2006
NASA 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, 2006
NASA 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-
ε

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, 2006
NASA Langley Research Center
6
Sample Grid Plane

31 Million Cells for 180
o

PAB3D solution: 33
hours on 44 Columbia
CPU

s (Itanium 2)

Jet3D solution, 10
minutes on Mac
May 8, 2006
NASA 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, 2006
NASA 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, 2006
NASA 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, 2006
NASA 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, 2006
NASA 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, 2006
NASA 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, 2006
NASA 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, 2006
NASA 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, 2006
NASA 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
P
y
l
o
n
May 8, 2006
NASA 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, 2006
NASA 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, 2006
NASA 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
May 8, 2006
NASA 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, 2006
NASA 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, 2006
NASA 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, 2006
NASA Langley Research Center
22
Discussion, Extra Slides

May 8, 2006
NASA Langley Research Center
23
Axisymmetric Nozzle
Surfaces colored
by temperature
May 8, 2006
NASA Langley Research Center
24
Baseline Nozzle (bb)
Fan boundary
streamline
Near surface streamlines
and temperature
May 8, 2006
NASA Langley Research Center
25
Reference Chevrons (RR)
Slight upward
movement
Near surface streamlines
and temperature
May 8, 2006
NASA Langley Research Center
26
PAA T-Fan Nozzle (RT)
Near surface streamlines
and temperature
Further upward
movement
May 8, 2006
NASA 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, 2006
NASA 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,
06-2435
PAA
on
QTD2
– 8/05

PAA
T-Fan
Chevron
Nozzle

PAA Effects
Instrumentation
AIAA
06-2438,
06-2439
May 8, 2006
NASA Langley Research Center
29
Grid Coarse in Radial Direction
May 8, 2006
NASA Langley Research Center
30
Grid Cause of Vorticity Lines
May 8, 2006
NASA 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