report to technical working group 4-5 december 2007 5 ... · nch aren needed to see this picture. 2...

Preliminary Investigation of Curved Preliminary Investigation of Curved Liner Sample in the NASA LaRC Curved Duct Test Rig Curved Duct Test Rig

Presented by Carl H. Gerhold

Curved Duct TeamMartha C. Brown Michael G. Jones

Brian M. Howerton Ana F. Tinetti Christal L. Kellam

NASA Langley Research Center, Hampton, VA

Report to Technical Working Group4-5 December 2007

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Curved Duct Test Rig NASA AcousticsAeroacoustics Branch at NASA LaRC

4 5 December, 2007

https://ntrs.nasa.gov/search.jsp?R=20080002269 2020-05-05T06:55:23+00:00Z

Outline

• Background• Aerodynamic Results

Fl M 0 275– Flow on M = 0.275• Acoustic Results

Fl ff– Flow off– Flow on

• Summary• Summary

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Purpose of the Curved Duct Test Rig

Develop capability to investigate acoustic and aerodynamic properties i d tin ducts

- Large scale- Flow rate to M = 0.275

Hi h d d l- Higher order mode control- Curved flow path- Adaptable test section

Flexible test configurations- Flexible test configurations

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Development

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Curved Duct Test Rig

Flow

Sound Source

Liner Test Section

Diffuser/ Termination

Conditioning

Downstream

Upstream microphones

Downstream microphones

microphones

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Curved Duct Test Rig (CDTR)

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Test liner samples

Flow

• Liner Test Section– 6 inch (H) x 15 inch (V) x 36 inch (A)

Straight liner sample (L02S) Curved liner sample (1 duct width offset) (L04S)

• Liner Characteristics– Core depth-0.75 inch– Perforate - 8.7% open area– Perforate thickness - 0.025 inch

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– Manufactured by Goodrich Aerostructures

Aerodynamic measurements

• Measure properties at inlet and outlet of liner test sectionsection

• Data acquired– Mean axial flow across duct – Boundary layer mean flowBoundary layer mean flow– Turbulence intensity– Flow angularity *

• Liner Configurations– Straight, hard wall (calibration duct) (L00H)– Straight, treated both sides (L02S)– Curved, 1D offset, treated both sides (L04S)

* not reported here8


* - not reported here

Local Mach number contoursInlet Outlet

15 15 15

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y, in

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y, in

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y, i

5 0 x, inch

5 0

5 0

0 0 0

• Curvature thickens boundary layer and increases core flow slightly

Straight, hard wall (L00H) Straight, treated (L02S) Curved -1D offset, treated (L04S)x, inch x, inch x, inch

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flow slightly

Boundary Layer - test section outlet6

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( ) Y 0 833 i h (b tt ll)

0 0.1 0.2 0.3measured mach number

0 0.1 0.2 0.3measured mach number

0 0

• Curvature promotes development of secondary flow near corners

Y = 7.5 inch (mid duct) Y = 0.833 inch (bottom wall)

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Turbulence Intensity-test section outlet

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5

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2

1

x, in

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y, i

Across duct width at y = 7 5 inch Across duct height at x = 3 0 inch

0 00 5 10 15

axial turbulence intensity, %0 5 10 15

axial turbulence intensity, %

• Turbulence content not affected by wall acoustic treatment or duct curvature

Across duct width at y = 7.5 inch Across duct height at x = 3.0 inch

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Acoustic testing configurations• Purpose of tests

– Evaluate effect of curvature– Evaluate effect of flow

C id t t d t b th id t t d

Flow Liner Code M = 0.000 M = 0.275

– Compare one side treated to both sides treated

Calibration Duct L00H F PStraight, In-house Hardwall Liner L06H F Straight Goodrich Liner-Both Sides Treated L02S F P Straight Goodrich Liner-Right Side Treated L02R F Pg gStraight Goodrich Liner-Left Side Treated L02F P 1D Offset, In-house Hardwall Liner L05H F P 1D Offset Goodrich Liner-Both Sides Treated L04S F P 1D Offset Goodrich Liner Right Side Treated L04R P P1D Offset Goodrich Liner-Right Side Treated L04R P P1D Offset Goodrich Liner-Left Side Treated L04F P P

-D Offset Goodrich Liner-Both Sides Treated L03S P

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F ll

Acoustic test matrix

Propagating mode (V,H) Frequency (0,0) (1,0) (2,0) (0,1) (1,1) (3,0) (2,1) (3,1) (4,0) (4,1) (0,2) (5,0) (1,2)

300 400

Full

500 600 700 800 900 1000 1100 1200 1300 1400 15001500 1600 1700 1800 1900 2000 2100 2200 2300 2400

Note: Cut on frequencies based on 6Óx15Ó cross sectional area at 70oF 124 points

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Note: Cut-on frequencies based on 6Óx15Ó cross sectional area at 70F. 124 points.

Acoustic test matrix

Propagating mode (V,H) Frequency (0,0) (1,0) (2,0) (0,1) (1,1) (3,0) (2,1) (3,1) (4,0) (4,1) (0,2) (5,0) (1,2)

300 400

Partial

500 600 700 800 900 1000 1100 1200 1300 1400 15001500 1600 1700 1800 1900 2000 2100 2200 2300 2400

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Effect of curvature-right wall lined

• Curvature has minimal effect on attenuation of plane wave generated in duct at no flow

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wave generated in duct at no flow

Mode scatteringU tUpstream Downstream

• Plane wave source, straight liner section, right wall treated (L02R)

re 90 dB

treated (L02R)• Plane wave amplitude reduced by as much as 18 dB by

liner• Horizontal 0-order mode scatters to horizontal 1-order

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o o ta 0 o de ode scatte s to o o ta o demode

Mode scattering-continued

re 90 dB

• Horizontal order 1 modes scatter to lower energy state

Mode distribution downstream, (0,1) mode generated in duct with curved liner, no flow

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Effect of curvature-both walls treated

• Plane wave incident

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• Curvature does not have large impact on attenuation

Mode Scattering-both sides treated

re 90 dB

• Mode scattering for plane wave incident is eliminated when both sides are lined

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Effect of flow- right side treated (L04R)

• Flow increases attenuation of plane wave by curved liner• Peak shifted slightly toward higher frequency

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• Peak shifted slightly toward higher frequency• Similar result for straight liner (L02R)

Effect of flow-both sides treated

• Attenuation of plane wave generated in duct with Goodrich straight liner, both sides (L02S)

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straight liner, both sides (L02S)• Similar results for curved liner (L04S)

Summary

• Liner has minimal effect on turbulence or Liner has minimal effect on turbulence or boundary layer growth in duct

• Curved duct sample attenuation is affected b d iby mode scattering

CDTR is valid tool for aerodynamic and acoustic evaluation of duct

t t ttreatment

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Thank youThank you

Questions, Comments

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Supplementary

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Duct offset-1 D

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CDTR cut on frequencies

n 0 1 2

“Horizontal” order

m 0 0 1128 2256 1 451 1215 2301 or

der

2 902 1445 2430 3 1354 1762 4 1805 2128“V

ertic

al”

o

4 1805 2128 5 2256 2522

“

• Flow speed: 0.00• Temperature: 70°(F)

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Mode Isolation in CDTR

W)

(dB

re 1

0-12

Pow

er L

evel

So

und

P

• Generally greater than 20 dB mode separation from

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target mode

Mode scattering-higher vertical mode

Mode distribution downstream, (2,0) mode generated in duct with curved liner

• Horizontal 0-order mode scatters to horizontal 1-order mode

, ( , ) g

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report to technical working group 4-5 december 2007 5 ... · nch aren needed to see this picture. 2...

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