Acoustics from External Flow-Structure Interactionsfiles.asme.org/Divisions/NCAD/30870.pdf · understanding of “Flow Noise” ASME NCAD ... A History of ASME Noise Control and Acoustics

IMECE 2010

Rayleigh Lecture 2010Vancouver, B.C.

Acoustics fromExternal Flow-Structure Interactions

Theodore M. FarabeeFellow, ASME

Theodore M. FarabeeNaval Surface Warfare CenterCarderock Division, Code 7050 [email protected]

Rayleigh Lecture -

Established by Noise Control and Acoustics Division in 1985

The Rayleigh Lecture

is given at the Society's International Mechanical Engineering Congress and Exposition (IMECE) (formerly the Winter

Annual Meeting) by lecturers selected amongst those who have made pioneering contributions to the sciences and applications of noise control and acoustics

This is the 25th

Anniversary of the Lecture Series

ASME NCAD What is the Rayleigh Lecture

Background:

Who was the person -

Lord Rayleigh

History of the NCAD Rayleigh Lecture Series

Brief History of the Noise Control and Acoustics Division

External Flow-Structure Interactions:

Terminology

for this Lecture

Turbulence as source of sound

Sound due to turbulence-surface interactions

Sound from turbulence-edge interactions

Sound due to turbulent flow past Surface Irregularities

Surface Roughness

Surface Steps

Summary

ASME NCAD Rayleigh Lecture -

Outline

John William Strutt

Born 12 November 1842

Died 30 June 1919 (aged 76)

Eldest son of John James Strutt

Father of 3 sons

eldest became Professor at Imperial College

3rd

Lord Rayleigh

Brief Bio (& other items of interest)

Referred to as an unremarkable student

early in life

1861

entered Trinity College in Cambridge (aged 19)

1865

graduated in the Mathematical Tripos as Senior Wrangler and Smiths Prizeman

1866

became a Fellow of Trinity College

1868

after returning from trip to U.S., purchased equipment and set up experimental laboratory at his fathers country estate

1871

married and resigned Fellowship (Fellowship was only for bachelors)

Soon after getting married, became afflicted with rheumatic fever & as part of cure, took a trip up the Nile during which, it is reported, he worked on his seminal book The Theory of Sound

Lord Rayleigh Who was he?

Brief Bio (& other items of interest), contd 1873

Father dies and he assumes family title of Baron Rayleigh 1877

The Theory of Sound

is published (two-volume)According to biography by Rayleighs son, he wrote the book on the back side of pages turned in by candidates for the Mathematical Tripos in 1876

1876-to-1877-

President of London Mathematical Society (LMS)Interestingly, in 1874 Rayleigh made a generous bequest of 1000and the LMS was thus saved from what could have resulted in its early demise1000 amounts to around $110,000 in todays value

1879

Maxwell dies & Rayleigh replaces him as Cavendish Professor at Cambridge University (holds position for 5 years)

1904

Nobel Prize for Physics (co-discovery of argon, with W. Ramsay)

1905-to-1908

President of Royal Society Authored in excess of 446 scientific papers Many other achievements and accolades

a few of which include Order of Merit; thirteen honorary degrees; five government awards; honorary

membership of five learned societies world-wide

Lord Rayleigh Who was he, contd?

This day in history Lord Rayleigh born 12 November 1842

168 years (and 2 days) ago Jean leRond dAlembert is born in 1717

French mathematician/scientistdAlembertian Operator (related to acoustic wave equation)dAlemberts Paradox (drag on body in inviscid fluid is zero)

14 November 1878

Rayleigh presented Presidential lecture to London Mathematical Society

Lecture titled: On the Instability of Jets

Rayleighs interests in flow noise Interest in subject of Aeloian tones

Extensive citing of the work of Helmholtz and Strouhal Chapter XXI

The Theory of Sound

(Volume Two)Vortex Motion and Sensitive JetsDerivation of criterion for stability of shear layers (Rayleigh Criterion)

Inviscid form of Orr-Sommerfled equationShear layer with inflection point in profile is inviscidly unstable

Lord Rayleigh Other historical notes

http://www-history.mcs.st-andrews.ac.uk/PictDisplay/Rayleigh.html http://www.nobel-winners.com/Physics/john_william_strutt.htmlhttp://en.wikipedia.org/wiki/Lord_Rayleighhttp://nobelprize.org/nobel_prizes/physics/laureates/1904/strutt.htmlhttp://www.lms.ac.uk/contact/lms_history.pdfOptics and Photonics News, Vol. 20, Issue 6, pp. 36-41 (200)

J. Howard, "The Rayleigh Notebooks," Appl. Opt. 3, 1129-1129 (1964)

Lord Rayleigh References for material on Lord Rayleigh

History of the NCAD Rayleigh Lecture Series

Lectures & Lecturers

Lectures addressing topic of Flow Noise

Lecturers who have made contributions to

understanding of Flow Noise

ASME NCAD Rayleigh Lecture Series

NCAD Rayleigh

Lecturers; 1985 -

2009Year Lecturer Lecture Title

2009 Scott Sommerfeldt Global Attenuation of Acoustic Fields Using Energy-Based Active Control Techniques

2008 Martin Pollack A History of ASME Noise Control and Acoustics Division (NCAD)

2007 Robert Schlinker Putting it all Together -

The Technology stages in the Design of Propulsion Systems for Noise

2006 Donald Thompson A Systems Approach to Noise Mitigation Strategies

2005 Robert Clark Structural Acoustics from Macro to Micro

2004 Hafiz M. Atassi Fluid-Structure Interaction and Acoustics

2003 Earl G. Williams Fourier Acoustics: Uncovering the Origins of Sound

2002 Ilene Busch-Vishniac The Big Problems Remaining in Transduction

2001 Jerry H. Ginsberg Variational Solutions: What Rayleigh and Ritz Did Not Tell Us

2000 William K. Blake Quiet Flow: Emerging Design Methods

1999 Adnan Akay Acoustics of Friction

1998 Gary H. Koopmann Designing Quiet Structures -

Virtually

1997 Michael S. Howe Rayleigh Conductivity

1996 Peter A. Nelson Controlled Interference of Acoustic Fields

1995 Maurice M. Sevik Information Extraction from the Scattered Acoustic Field of Waterborne Structures

1994 C. Dan Mote, Jr. Surprises in Axially Moving Material Dynamics

1993 David G. Crighton The High-Speed Many-Bladed Propeller: Asymptotic Theory for its Acoustic Field

1992 Alan D. Pierce Progressive Waves: The Modern Evolution and Refinement of One of

the Most Basic Concepts in Acoustics

1991 David Feit Structural Acoustics from Lord Rayleigh to the Present

1990 David T. Blackstock Nonlinear Acoustics

1989 Sir Michael James Lighthill Biomechanics of Hearing Sensitivity

1988 Allan Powell Elements of Flow Noise from Rayleigh to Today

1987 Miguel C. Junger From the Finite to the Boundless: Acoustics of Very Large Systems

1986 J. E. Ffowcs Williams Computer Aided Silence

1985 K. Uno Ingard Acoustics in Physics and Mechanical Engineering

Rayleigh Lectures Lectures on topic of Flow Noise

Year Lecturer Lecture Title

2007 Robert SchlinkerPutting it all Together The Technology stages in the Design of Propulsion Systems for Noise



1993 David G. CrightonThe High-Speed Many-Bladed Propeller: Asymptotic Theory for its Acoustic Field



Rayleigh Lectures

Year Lecturer Lecture Title2008 Martin Pollack A History of ASME Noise Control and Acoustics Division (NCAD)

2007 Robert SchlinkerPutting it all Together The Technology stages in the Design of Propulsion Systems for Noise

2006 Donald Thompson A Systems Approach to Noise Mitigation Strategies



1997 Michael S. Howe Rayleigh Conductivity

1996 Peter A. Nelson Controlled Interference of Acoustic Fields


1993 David G. Crighton The High-Speed Many-Bladed Propeller: Asymptotic Theory for its Acoustic Field

1989 Sir M. James Lighthill Biomechanics of Hearing Sensitivity



Lecturers who have made contributions to understanding of Flow Noise

(with apologies to anyone who I might have missed)

Rayleigh Lectures (Grandstanding)

Year Lecturer Lecture Title2000 William K. Blake Quiet Flow: Emerging Design Methods


1991 David Feit Structural Acoustics from Lord Rayleigh to the Present

1988 Allan PowellElements of Flow Noise from Rayleigh to Today

(After retiring from NSWC)

Lecturers from my host organizationDavid Taylor Model Basin

DT Naval Ship Research & Development CenterDavid Taylor Research Center

Naval Surface Warfare Center, Carderock Division

Honorable Mention: Naval Research Laboratory

Year Lecturer Lecture Title2003 Earl G. Williams Fourier Acoustics: Uncovering the Origins of Sound

Noise Control and Acoustics Division (and other Historical Notes)

Noise Control and Acoustics Division (NCAD) established in 1979 with formation of the Noise Control and Acoustics (NCA) National Group

National Group -

an ASME probationary group established prior to becoming a DivisionSee the 2004 NCAD Newsletter article by Dr. A. Akay (one of founding members of NCAD)

Division technical structure has changed over the years, but current structure consists of three Technical Committees

Active & Passive Noise Control (A. Smith, Chair)

Structural Acoustics (S. Sung, Chair)

Aero/Hydro Acoustics (B. Paul, Chair)

Notably, NCAD sponsors

Per Bruel Gold Medal -

Society Award

Rayleigh Lecture -

Division Sponsored Lecture Series

Best Paper Award -

Presented at Annual Meeting

Student Paper Competition -

Presented for Best Student Paper given at Annual Meeting

Side Notes

1880 -

ASME is founded

1880 -

Lord Rayleigh published On the stability, or instability, of certain fluid motions, Proc. Lond. Math. Soc.,

11, 57-70

1998

David Taylor Model Basin (DTMB) is recognized by ASME as Mechanical Engineering Landmark -

ASME Historical Landmark #197 (more Grandstanding)

http://divisions.asme.org/NCAD/

Year Location Symposia Sponsored by Aero/Hydro Acoustics Technical Committee

2009 Disney World (Orlando, FL) Flow-Induced Phenomena

2008 Dearborn, MI (w/NoiseCon) Noise from Flow over External Features; Fan Noise

General Mechanisms; Active & Passive Control of Fan Noise

2007 Seattle, WA External Flow Acoustics; Turbomachinery Noise

2006 Chicago, IL Transportation Noise; Flow-Induced Noise

2005 Disney World (Orlando, FL) External Body Flow Noise; Turbomachinery Noise

2004 Anaheim, CA Prediction of Acoustics from Canonical Flows; Acoustic Treatments for Flow Noise

2003 Washington, D.C. Flow Noise Modeling, Measurement & Control

2002 New Orleans, LA 5th

Intern. Symp on Fluid-Structure Interact. (FSI), Aeroelasticity (AE), and Flow-Induced Vibration & Noise (FIV&N)

2001 New York, NY Aero-Hydroacoustic Facilities and Techniques; Validation of Computational Methods

2000 Disney World (Orlando, FL) Pump Unsteady Flow & Acoustics (joint with FED)

1999 Nashville, TN Flow-Induced Vibration and Noise of Thin Materials

1998 Anaheim, CA Flow Noise Modeling, Measurement & Control

1997 Dallas, TX 4th

Intern. Symp. On Fluid-Structure Interactions (FSI), Aeroelasticity (AE), and Flow-Induced Vibration (FIV); Coupling of Acoustic Fields and Flows

1996 Atlanta, GA Vehicle Flow/Structure Noises

1995 San Francisco, CA Flow Noise Modeling, Measurement & Control; Turbomachinery Noise

1994 Chicago, IL Active Control of Vibration & Noise: Active/Passive Control of Flow-Induced Noise & Vibration

1993 New Orleans, LA Flow Noise Modeling, Measurement & Control

1992 Anaheim, CA Flow-Induced Vibration and Noise: Flow-Structure and Flow-Sound Interactions

1991 Atlanta, GA Flow Noise Modeling, Measurement & Control; Hydroacoustic Facilities, Instrumentation & Experimental Techniques

1989 San Francisco, CA Flow-Induced Noise Due to Laminar-Turbulence Transition Process

1988 Chicago, IL Flow Induced Vibration & Noise: Non-Linear Interaction Effects and Chaotic Motions

1987 Boston, MA Developments in Transduction for Flow Induced Noise & Vibration

1986 Anaheim, CA Flow-Induced Noise & Vibrations

1985 Miami, FL Shear Flow/Structural Interactions

1983 Boston, MA Turbulence-Induced Vibrations and Noise of Structures

Symposia/Forums Sponsored by Aero/Hydro Acoustics Technical Committee (listed on Division Webpage)

External Flow-Structure Interactions What is meant by this title

Emphasis on flow-structure interactions due to turbulent flow over a vehicle exterior (Turbulent Boundary Layer

TBL)

Focus on flow-structure interactions that:

Result in production of sound (blocked structure)

Result in excitation of flow surface

Surface vibration

Acoustic radiation from flow-excited vibration

Generate unsteady forces that interfere with system functions

Primary flow-structure configurations of interest are those that occur in marine applications

however there are direct extensions to automotive & aeronautical applications

Fully turbulent flow

Typically a wall bounded shear layer (turbulent boundary layer

TBL)

Low Mach number flow (M

External Flow-Structure Interactions Examples of Flow-Structure Interactions

Examples are taken from Aeroacoustic community who have pioneered to use of phased array measurements for the study of flow noise (airframe noise).

Similar techniques and results for the marine and transportation industries

41st

Aerospace Sciences Meeting & Exhibit, 6-9 January 2003, Reno, NVRobert W. Stoker, Using Microphone Phased Arrays to Enable Low Airframe Noise Design

W.D. Fonseca, S.N.Y. Gerges, and R.P. Dougherty, Pass-by noise measurement using beamforming technique

Internoise 2008

External Flow-Structure Interactions Examples of Flow-Structure Interactions

Interesting images of noise resulting from flow-structure interactionsObtained using phased-arrays

Video from Optinav (B. Dougherty) as placed on YouTubeWind Turbine

Video from Optinav (B. Dougherty) as placed on YouTubeMotorboat

AIAA

Short CoursePhased Array Beamforming

for Aeroacoustics

Sound from Turbulence How to begin?

Theory of Aerodynamically Generated Sound given by Sir James Lighthill Sir James Lighthill (1952)M. James Lighthill. On sound generated aerodynamically I. General theory. Proc. Roy. Soc. A, 211:564-87, 1952. M. James Lighthill. On sound generated aerodynamically II. Turbulence as a Source of Sound. Proc. Roy. Soc. A, 222:1-32, 1954.

Lighthills theory (acoustic analogy) derived by manipulating momentum and

continuity equations to form a wave equation

with turbulence as the (inhomogeneous) source term for the wave equation.- Take divergence of momentum equation- Subtract from it the time derivative of the continuity equation- Subtract from both sides to get Lighthills equation220c

( ) ijjiijji

ij cpvvTwherexx

Tc

t 20

222

02

2

, +=

=

Sir James Lighthill Sir James Lighthill

Rayleigh Lecture 1989Rayleigh Lecture 1989Allan Powell Allan Powell

Rayleigh Lecture 1988Rayleigh Lecture 1988

For flows with constant sound speed and density,(Reynolds stress tensor)

Sound is generated by the unsteady Reynolds stresses (quadrupole

distribution) Note: the equation can be written for the pressure realizing that Further Note: Powell provides and alternative derivation based on vorticity

jiij vvT =

20cp =

Sound from Unbounded Turbulent Flows Slight digression

Lighthills analogy is derived assuming only turbulence sourcesConsider a similar derivation for which;

-

Continuity equation contains a mass-source term (q)-

Momentum equation contains an applied forcePerform same manipulation of the equations and express the wave equation in terms of the pressure -

Consider the multipole

character of the source terms as they appear in the equation

The mass source term has the form of a MonopoleThe applied force term has the form of a DipoleThe Reynolds stresses have the form of a Quadrupole (distribution)

What are the acoustic implications of the multipole nature of the source terms?

( )F

222

2 20

1 i ji j

Tp qp Fc t t x x

= +

Sound from Unbounded Turbulent Flows Acoustic Scaling of Multipole Source Terms

( )22

22 20

1 ,i ji j

Tp qp F S y tc t t x x

= + =

The following was covered more thoroughly by Prof. Grace in her 2004 NCA Tutorial Lecture on Computational Methods in Aeroacoustics

( ), rS y ty

xAssuming the source terms occupy a limited region, a general solution to the inhomogeneous wave equation can be obtained for locations in the

far field using the free-space Greens function

For a turbulent flow, it is appropriate to assume the following dimensional scaling:

(Without showing the math) consider the scaling of acoustic power for each term

3

0

0

1( , ) ,4

( ); ;

V

r

Rp x t S y t d yR c

x ywhere t t retarded time and for x y R x

c

=

Velocity ~ v (velocity of turbulence)Length ~ l (eddy size of turbulence); which then givesTime ~ l/v, and thus Frequency ~ v/l, with Volume ~ l3

Sound from Unbounded Turbulent Flows Acoustic Efficiency of Source Terms

( )

( )

2 22

00

3 20

; ,Multipolep Area RAcoustic Power giving p andcc

the turbulent kinetic energy is v l

= =

( )( )( )

4 2 3 20 0 0

0

6 2 3 3 2 30 0 0

8 2 5 3 2 50 0 0

~

~

~

Mono

Dipol

Quad

vv l c v l M M c

v l c v l M

v l c v l M

=

3

5

Mono

Dipole

Quad

M

M

M

With the following definitions and approximations,

The acoustic power for each multipole term is approximated to be:

The acoustic efficiency () for each term can then be expressed as:

Celebrated U8 scaling for jet noise

( ) 2 4~ 0.01 ; ~ 10 40DipleQuadrupole

For low Mach number flow M M dB =

Go back to the Lighthill equation (written on pressure)

and examine the solution obtained using a free-space Greens function

222

2 20

1 i ji j

Tp pc t x x

=

Sound from Turbulence Free-field Turbulence

( )

( )

0

23

23

2 3 20

0

1 1( , ) ,4

1( , ) ,4

; ( ); ;

iji jV rt c

i jij

V

i i i

p x t T y d yr y y

application of chain rule and divergence theorem gives

rrp x t T y d y

c r t

x yr x y t retarded time and for x y r x and r x y

c

=

=

= = =

Sound from Turbulence Effect of Flow Surface

Now, consider the solution when there is the presence of a rigid, stationary surfaceA general solution can be given in terms of a Greens function (G) that provides the proper acoustical boundary conditions

( ) ( )2 3 2, ; , , ; ,( , ) ij j ijV Si j i

j

G x t y G x t yp x t T d yd n p d y d

y y y

n surface outward unit normal

=

Curle (1955) used a free-space Greens function in the above to derive

( )2

3 32 3 2 20 0

1 1( , ) ,4 4

i j i jij j ijs

V

r r r rp x t T y d y n p d y

c r t c r t

+

Now the far-field sound now results from:

Original (quadrupole) Reynolds stresses (Lighthills result), & additionally

Dipole term resulting from turbulence interaction with the surface

Sound from Turbulence Effect of Flow Surface

Large & Small

Curles use of a free-space Greens function in elucidating the production of turbulence noise when a surface is present invoked the requirement that the surface be acoustically compact

d

d

Acoustically Compact Acoustically Non-Compact

For the acoustically non-compact case

for example, very large rigid flat plate

the normal force exerted on the flow vanishes and the dipole terms cancel to produce a less efficient surface quadrupole resulting in the only turbulence quadrupole radiation

However, realistic surfaces may be sufficiently

finite, have curvature, or surface features

resulting in the sound generated from the more efficient surface dipoles being a significant contribution to overall turbulence noise

Sound from Turbulence Finite Surfaces

Half Plane Problem

Ffowcs WilliamsFfowcs Williams

& Hall (1970) addressed the issue of sound generated by turbulent flow passing the edge of a finite plate (half plane) -

turbulent eddy convecting past an edge

Ffowcs WilliamsFfowcs Williams


Approach -

obtain solution to Lighthills equation subject to appropriate Greens function on the half-plane

Appropriate Greens function is one for an infinite rigid plane, but weighted by a

Fresnel integral (magnitude varying from approximately 0 to 1)

Any enhancement

of sound over that for an equivalent free-field condition comes from the derivatives of the Fresnel weighted free-space Greens function

Two regimes identified

Turbulence near the edge; 2kr0

Sound from Turbulence Finite Surfaces

Half Plane Problem

Ffowcs Williams & Hall also considered the case for flow past a pressure release

half-plane and concluded results were essentially the same as for a rigid half-planeCrightonCrighton

& Leppington (1970) evaluated flow-noise scattering from a semi-

infinite compliant plate and reached a somewhat differing conclusion

Crighton Crighton


Addressed problem by replacing eddies with volume distribution of quadrupoles

use of reciprocal theorem to transform quadrupole scattering problem into one of the diffraction of plane acoustic wave (solved via Wiener-Hopf technique)

Amplitude of scattered wave (sound) from quadrupoles near the edge are a function of the fluid loading parameter

()

For small

(little fluid loading) the plate is relatively rigid and the results of Ffowcs Williams & Hall are obtained -

sound scales as U5

For high fluid loading the plate appears limp

and strength of scattering is diminished resulting in sound scaling as U6

For aeronautical applications

is small and hence surface is effectively rigid

resulting in scattered sound scaling as U5

For marine applications

can be large (order 1) and hence surface is not effectively rigid

-

resulting in scattered sound scaling as U6

densityareaplateismscalelengthncorrelatioturbulenceisl

densityfluidiswhereml

,

,;2

0

000 =

Flow Noise on Surfaces Turbulent Boundary Layer (TBL)

Infinite Plane

What is the nature of the stresses (forces) generated on an infinite flat surface over which turbulence passes?

Flow configuration is typically a high Reynolds number Turbulent

Boundary Layer which develops over an infinite flat plate

Stresses that are of interest are:Normal stress or pressureShear stress

From an engineering interest, these stresses are:

Source of surface excitation

leading to unwanted vibration & noise

Noise field for surface mounted sensors (fathometers, etc.)

A general solution for the pressure at a wall is given by

Recall Lighthills Equation ( )22

22 20

1 i jij i j

i j

Tp p with T u uc t x x

= =

( )( )2

2

0

1 1,0, ,2

i jSurface

i jV y

Tp x z t d y

x y x x

=

Assuming flow is homogeneous in planes parallel with surface, take surface-time Fourier-Transform to get,( ) ( ),,,, 31 kktzx

22 2 2 2 2

0 1 3 1 1 2 3 320

; ; ;where k k k k k k and d k d and d kc = = = + = = =

( ) ( ) 21 3 1 2 3 20

2, , , , ,i j i ySurface ij

d dP k k T k y k e dy

i

= y2


Infinite Plane

1 3( , , )ijT k y k

y2i ye


Infinite Plane

( ) ( ) 21 3 1 2 3 20

2, , , , ,i j i ySurface ij

d dP k k T k y k e dy

i

=

While the above is easy

to write ---There is currently insufficient information regarding the Reynolds stress term to provide a complete solutionOver the years, numerous models

have been proposed with varying degrees of validation against (also) limited empirical information, for example:

Kraichnan (1956); Corcos (1963); Chase (1980); BlakeBlake (1986); Goody (2004)

Blake Blake


mm-1

k=/c0 k=/Uc(Uc

0.7U0

)

( ),1k

Wills (1971)

k1

p(

k 1,k 3

, )

/c0 /uc

Chase (1980)

k1

()

,0,

31

=

kk

p


Infinite Plane

Sub-ConvectiveWavenumbers:

k0

< k >k0

SupersonicWavenumbers:

k

Consider Lighthills equation (sound from free-field turbulence)

Now, consider the M = 0 limit (c0

), which represents incompressible flow

(Sound)22

22 20

1 i ji j

Tp pc t x x

=

(Pseudo-Sound) (p

satisfies a Poisson equation)

2 22 i j i j

i j i j

T u up

x x x x

= =

Small amplitude, irrotational fluctuations that satisfy the wave

equation

(propagate from disturbance region at speed of sound, c0)

Pressure fluctuations are directly coupled to density fluctuations (p=c2)

No propagation; hydrodynamic pressures are convected by flow

Incompressible (no change in density with pressure change)

Pressures resulting from turbulence activity

Pressures related to velocity by Bernoulli equation

Far-field is composed of only Sound.

Low Mach Number flows are dominantly incompressible and are thus

essentially silent

In vicinity of turbulence pressures are dominantly pseudo-sound

Flow Noise on Surfaces Sound (Acoustics) vs. Pseudo-Sound (Hydrodynamics)

Slight Digression

Stick-man #1 is riding at 60 mph and there is turbulent flow over his head/ears

' 'turbp u vTypically for a turbulent flow the turbulence intensity (TI) ~10% (TI=u/Ux100%)

( )( ) 2' ' 0.1 0.1 0.01turbp u v U U U =360 26.8 / ; 1.3 / ; 20ref in airmph m s kg m p Pa = = =

3 2

10

0.01 (1.3 / ) (26.8 / ) 1020 log ( / ) 113

turb

ref

p x kg m x m s PaSPL x p p dB

= =

60 mph

-

Biker hears

a pressure level equivalent to sound by a rock band

-

Walker hears nothing from flow over stick-man #1s hears

~ 2x10-4

atm

Sound (Acoustics) vs. Pseudo-Sound (Hydrodynamic) Illustrative Example

http://dir.coolclips.com/People/Body_Parts/Ears/Ears_cart1162.htmlhttp://dir.coolclips.com/People/Body_Parts/Ears/Ears_cart1162.html

Flow Noise on Surfaces Excitation of Surface

Consider turbulent flow (Turbulent Boundary Layer) excitation of

a plate(Chandiramani [1977], Hwang [1990], Hambric [2004], for reference)-

What is the significance of the wavenumber content of the turbulence-

What is the significance of plate boundary conditions

The modal force spectral density

(mn

) response of a structure excited by turbulent flow is given by,

( ) ( ) ( ) ( ) ( )2 2 2, ik xmn p mn mn mnA

k F k d k where F k x e d x

= =

Hwang (1990)The figure displays typical plots of;(a)

the wavenumber response function for large structures typical of marine applications, and

(b)

streamwise TBL pressure spectrum

Of particular note is the mismatch between peak structural response and flow excitation functions

Flow Noise on Surfaces Excitation of Surface

For large structures it is tempting to assume strongest coupling

between flow-and-structure occurs at low wavenumbers where the structure is most responsiveTo evaluate whether this is true consider the high-wavenumber response of a plate for various plate-edge boundary conditions (evaluation of )( )mnF k

Free rectangular panel:

Simply supported rectangular panel:

Clamped rectangular panel:

( ) 22 kkFmn( ) 2 4mnF k k ( ) 2 6mnF k k

Simply supported ClampedFree

For the case considered, largest contribution to vibration for the Simply Supported and Clamped panels comes from the low-wavenumber pressuresFor the Free panel, vibration is dominated by contribution from high-wavenumber pressures -

significance excitation due to turbulence when there are free edges

Hwang (1990)

Flow Noise on Surfaces Surface Irregularities

Not all flow surfaces of engineering interest are smooth flat platesOr, more to the point - the cost and impact of making surfaces smooth is potentially prohibitive

What is acoustic impact of Surface Irregularities?Perturbations to flow resulting in increases in flow turbulence

Increased flow-structure interactionsScattering of turbulence

Scatter convective pressures (high amplitude) to sound

For discussion purposes, two canonical Surface Irregularities will be consideredSurface roughness

Range of roughness types and heights are possibleSurface steps

Simple forward-facing and backward-facing steps

From Wikipedia

Surface Roughness

(with selected modifications/edits)

Surface roughness, often shortened to roughness, is a measure of the texture of a surface. It is quantified by the vertical deviations of a real surface from its

ideal form. If these deviations are large, the surface is rough; if they are small the surface is smooth. Roughness is typically considered to be the high frequency, short wavelength component of a measured surface.

Roughness plays an important role in determining how a real object will interact with its environment. Rough surfaces usually wear more quickly and have higher friction coefficients than smooth surfaces.

Although roughness is usually undesirable, it is difficult and expensive to control in manufacturing. Decreasing the roughness of a surface will usually increase exponentially its manufacturing costs. This often results in a trade-off between the manufacturing cost of a component and its performance in application.

Flow Noise on Surfaces Surface Roughness

yuln

( )u yu

log-law

outer-flow

overlapviscoussublayer

yuy

+ =

5y + 60y +

5

10

0

15

ks

Flow Noise on Surfaces Roughness Scaling

Boundary Layer impact

For boundary layer flows

surface roughness is quantified in terms the viscous length scale

of the flow;

0 5

5 7 0

7 0

s

s

s

k u

k u

k u

>

Hydraulically Smooth

Transitionally Rough

Hydraulically Rough

( )

uklk

lscalelengthviscousu

ss =

=

+

+

http://mae.ucdavis.edu/~wind/facilities/ablwt.html


Modifications to TBL Pressures

How does surface roughness modify TBL pressures?1)

Increases in turbulence and hence surface pressures2)

Scattering (high amplitude) convective pressure (k~/Uc

)

Empirical Approach:-

Assume same scaling as Smooth Wall flows

accounting for changes to flow parameters results from the rough wall (u

& )

-

Adopt scaling similar to Smooth Wall but use roughness-related length scale

-

Or, something different ------

(seems no single approach is fully successful)

However, these approaches do not provide insight to full spectral description (wavenumber & frequency) of pressures:

( ) ( )

( ) ( )

2

2

2 2

p

w

p

w

uouter variable scaling

u

uinner variable scaling

u

=

=

( ) ( )( )2p g g sw g

u kk k

k u

= =

( ),p k



HoweHowe


( ) ( ) ( )0, , ,Rough wall Diffractedk k k = +

HoweHowe proposed an approach to modeling the rough-wall turbulent boundary layer which provides a description at both subconvective

and acoustic

wavenumbersAssumed the high wavenumber-convective portion of the frequency spectrum could be modeled as previously described (modify existing models for TBL pressures by incorporating adjusted rough wall parameters) Include to the above the scattered pressure resulting from diffraction of the near-field pressures convecting over the rough wall ( ),Diffracted k

( )0 ,k

5=U 40

U

= For M=0.005, U=7.5m/s, =5cm

5 ~ 120

40 ~ 960

f HzU

f HzU

=

=

( ) ( ) ( )0 , , , , ,D iffracted R ough w allk k k


Sound

(far-field pressure)

( ) ( ) ( ) ( ) ( ) ( )00

000

0

0 |,|,, xdSn

xxGxpxxGnxpxp h

S

hScattered

=

( ) ( ) ( ) 31212122

0 ,,,,2, dkdkkkkkAhxkx hrmsScattered

=

Glegg & Devenport derived relationships for how sound

is generated by TBL flow over rough surfaces which separates the scaling of the sound from the scaling for the TBLApproach is similar to Howe in that a scattering problem is solvedFollowed Mores & IngardIngards acoustic scattering from a rough surfaceIncident field scattered by surface is the hydrodynamic pressure field of TBL

Roughness is acoustically compactHydrodynamic pressure field is homogeneous Wall is taken to be the surface of the roughness

IngardIngard


wavenumber spectrum of surface slopehrms

rms

of roughness height

( )1 2, ,k k

For randomly distributed roughness characterized by relatively discontinuous surfacesTypical of sandpaper roughness and wide range of natural and other man-made roughnesses

Giving ( ) ( ) ( )( )2 2 2 2 2 20 0

2 2

,cos cos, pppp hh

xk h k hx C S or C Sx x

= =

( )( )

22

11 2 0 2, , 2

xk k kx

=


Sound


80 grit20 grit 180 grit

Figures from Alexander (2009; MS-thesis, Virginia Tech.)

Note: for 180 grit @ 60 m/s, k+

~ 6Recall that 0< k+


Sound


103

104

105

-110

-100

-90

-80

-70

-60

-50

-40

Frequency [rad/s]

a(

)/ s(

) [dB

re: 1

P

a/H

z]

Cubes

Hemispheres

103 104 105-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

Frequency [rad/s]

a(

)/ s(

) [dB

re: 1

P

a/H

z/N

s/A F

/CD

]

AFF 0.17" Sparse Cuboids

140 fps, 0.17" C92 fps, 0.17" C60 fps, 0.17" C140 fps, 0.17" H92 fps, 0.17" H60 fps, 0.17" H140 fps, 0.118" H92 fps, 0.118" H60 fps, 0.118" H

2

CubesandHemispheresusedasgenericroughnesselements

( )( )

( )22 2 222 2

, cos16

ppD F S

S o

x CC A N

c r

RadiatedRoughnessNoiseasfunction

ofsurfacepressures

( )( )

pressureSurface

Rad

From Anderson, et al., (ASME, IMECE 2009, NCAD 2009)

Scaling for deterministic roughness on roughness element drag coefficient

RadiatedSound

Rayleigh-LikeTurbulence Scattering

More significantfor smaller roughness size

Shed VorticityMore significant

for larger roughness size

Roughness Noise Demonstration

hg

= 3.0 mmh+

u

h/ 200U = 45 m/s

Smooth v. Rough Surface

ForcingFunction

( ) ( ) ( ) ( )2

2 cos cos4 4

= + n n n

nc r r

GreensFunction

Drag -

Force Spectrum

Turbulence ScatteringDrag DipolesShed Vorticity


Sound


AudiofilefromDevenport(VT)

Surface Pressures

( ) ( ) ( ) ( )2

22122

cos', " " '4

= S k k f d

k k k

x

RadiatedSound

Greens Function of Surface Roughness

Flow Noise on Surfaces Surface Irregularities -

Steps

HMCS Victoria; December 2000

What is meant by steps?Pillars on automobilesPlating mismatches in streamwise directionInterfaces between streamwise spaced components (wing flaps, rail cars, etc.)

HMCS Windsor; SSK-877

Wind Noise Applications

A. Lauterbach, et. al.Institute of Aerodynamics and Flow Technology

German Aerospace Center DLRBerlin Beamforming Conference, February 2010

S. Oerlemans and P. SijtsmaNLR-TP-2004-320

Flow Noise on Surfaces Surface Steps

Flow Features

Forward-Facing StepBackward-Facing Step

Scaling factor most significant to flow noise

character of Step Flows is;

( ) ( )[ ]hheighSteptothicknesslayerBoundaryh



Backward-Facing StepFarabeeFarabee & Casarella (ASME, WAM & Journal

1984)

FarabeeFarabee


For case of /h ~ 1

Highest TBL pressures occur at downstream reattachment location

RMS pressures at reattachment ~ 5 greater than for equilibrium TBL

Spectrum of downstream pressures characterized by enhanced low-frequency content

TBL pressure spectrum has not recovered to equilibrium at most downstream location (x/h = 72)



Forward-Facing StepFarabeeFarabee & Casarella (ASME, WAM & Journal

1986)

For case of /h ~ 2.4

Highest TBL pressures occur at reattachment location downstream of step

Highest RMS pressures ~ 10 greater than for equilibrium TBL

Spectrum of downstream pressures characterized by enhanced low-frequency content

TBL pressure spectrum has not recovered to equilibrium at most downstream location (x/h = 36)

Upstream Locations

Downstream Locations


Sound


Forward-Facing StepFarabeeFarabee & Zoccola (ASME, IMECE

1998)Noise radiated from Forward-facing and Backward-facing steps

Measurements made in Anechoic wind tunnelStep geometries similar to those for Surface pressure measurementsRadiated noise measured using directional-dish microphone positioned normal to step-plate in the acoustic far-field

Measurement approach similar to that pioneered by SchlinkerSchlinker

SchlinkerSchlinker


Could not measure noise from Backward-facing step not measured (lower than background noise)Noise from Forward-facing step

Levels similar for two step heights evaluated

Levels scale as ~ U5

Highest levels at approximately location of step

Prior/OnGoingEffortsinFlowNoise(U)

StepNoise(ONRTurbulenceD&I)

( )

hUp

hUcfvs

Uf

mRad

m

Rad

m

62

52

20.

103

104

-40

-30

-20

-10

0

10

20

30

40

50

freq [Hz]

SPL

[dB

], (d

B re

f. 20

Pa

2 / H

z)

h = 1.5 mmh = 3.0 mmh = 4.6 mmh = 6.1 mmh = 11.7 mmh = 18 mm

Uj = 60 m/s, = 123.5o

103

104

-40

-30

-20

-10

0

10

20

30

40

50

freq [Hz]

SPL

[dB

], (d

B re

f. 20

Pa

2 / H

z)

Uj = 30 m/s

Uj = 45 m/s

Uj = 60 m/s

h = 11.7 mm , = 123.5omU

f

hUc

m52

2

10log10

vs.

Forward Step Far Field Normalization

10-1

100

101

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

f / Um

10*lo

g 10[

c2

/ 2

U m5 h

]

h = 1.5 mmh = 3.0 mmh = 4.6 mmh = 6.1 mmh = 11.7 mmh = 18.0 mm

Uj = 60 m/s, = 123.5o

10-1

100

101

102

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

f / Um

10*lo

g 10[

c2

/ 2

U m5 h

]

Uj = 30 m/s

Uj = 45 m/s

Uj = 60 m/s

h = 11.7 mm, = 123.5o

ScalingonVelocity ScalingonStepHeight


Sound


Forward-Facing StepResults from recent experimental studies of Devenport (VT)

Backward step Forward step

PSD of Greens Function-Weighted Sources


Sound


Forward-Facing Step

Numerical study of noise from Step Flow

Meng (UND; AIAA & JFM)

Y1 ~ velocity potential for potential flow over step


Sound


Forward-Facing Step


Meng (UND; AIAA & JFM)

Backward step Forward step

Backward-step sound is dominated by diffraction

Forward-step sound is due to both source generation and diffraction


Sound


Forward-Facing Step


Slomski (NSWCCD; AIAA)

Uo

surface 1

surface 2

surface 3

surface 4

surface 5

surface 6

surface 7

surface 8

step face

103 10410

20

30

40

50

60

70

Frequency Hz

PSD

dB

re

Pa / H

z at

1 m

CFD DataMeasurement

ASME NCAD Rayleigh Lecture

Thank you for your attention!

Willing to entertain any questions or comments

Very much look forward to seeing everyone at the 50th

Anniversary

of the Rayleigh LectureRayleigh Lecture

at ASMEs IMECE in 2035

Slide Number 1ASME NCADWhat is the Rayleigh LectureASME NCADRayleigh Lecture - OutlineLord RayleighWho was he?Lord RayleighWho was he, contd?Lord RayleighOther historical notesLord RayleighReferences for material on Lord RayleighASME NCADRayleigh Lecture SeriesNCAD Rayleigh Lecturers; 1985 - 2009Rayleigh LecturesLectures on topic of Flow NoiseRayleigh LecturesRayleigh Lectures(Grandstanding)Noise Control and Acoustics Division(and other Historical Notes)Slide Number 14External Flow-Structure InteractionsWhat is meant by this titleExternal Flow-Structure InteractionsExamples of Flow-Structure InteractionsSlide Number 17Slide Number 18Slide Number 19Slide Number 20Slide Number 21Sound from TurbulenceFree-field TurbulenceSound from TurbulenceEffect of Flow SurfaceSound from TurbulenceEffect of Flow Surface Large & SmallSound from TurbulenceFinite Surfaces Half Plane ProblemSound from TurbulenceFinite Surfaces Half Plane ProblemFlow Noise on Surfaces Turbulent Boundary Layer (TBL) Infinite PlaneSlide Number 28Flow Noise on Surfaces Turbulent Boundary Layer (TBL) Infinite PlaneFlow Noise on Surfaces Turbulent Boundary Layer (TBL) Infinite PlaneSlide Number 31Slide Number 32Flow Noise on Surfaces Excitation of SurfaceFlow Noise on Surfaces Excitation of SurfaceFlow Noise on Surfaces Surface IrregularitiesFlow Noise on Surfaces Surface RoughnessFlow Noise on Surfaces Roughness Scaling Boundary Layer impactFlow Noise on Surfaces Surface Roughness Modifications to TBL PressuresFlow Noise on Surfaces Surface Roughness Modifications to TBL PressuresFlow Noise on Surfaces Surface Roughness Sound (far-field pressure)Flow Noise on Surfaces Surface Roughness Sound (far-field pressure)Flow Noise on Surfaces Surface Roughness Sound (far-field pressure)Slide Number 43Flow Noise on Surfaces Surface Irregularities - StepsFlow Noise on Surfaces Surface Steps Flow FeaturesFlow Noise on Surfaces Surface Steps Modifications to TBL PressuresBackward-Facing StepFlow Noise on Surfaces Surface Steps Modifications to TBL PressuresForward-Facing StepSlide Number 48Slide Number 49Slide Number 50Slide Number 51Slide Number 52ASME NCADRayleigh Lecture

Documents

Acoustics from External Flow-Structure Interactionsfiles.asme.org/Divisions/NCAD/30870.pdf · understanding of “Flow Noise” ASME NCAD ... A History of ASME Noise Control and Acoustics