Tailored for Propulsion Airframe Aeroacoustics

mustardarchaeologistMechanics

Feb 22, 2014 (3 years and 3 months ago)

152 views

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
-


瑵牢t汥湣l 浯摥汳


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

Pylon

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