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Page 1 26/03/2012
Esame Finale del Ciclo XXIV Scuola Dottorale di Ingegneria
Sezione di Ingegneria Meccanica e Industriale
Experimental investigation of flow past open and partially covered cylindrical cavities
Francisco Rodriguez Verdugo
Tutor: Prof. Roberto Camussi
Ph.D. Dissertation Defence
Page 2 Contents
Introduction
Examples of flow excited cavities
Aerodynamics proprieties of an open mouth cylindrical cavity
Cavities and flow-acoustic couplings
Experimental set-ups
Open mouth cavity
Partially closed mouth cavity
Main Results
Description of the mean flow in an open mouth cavity
• Shear layer and wake
• The flow inside the cavity
Pressure response to a grazing flow
Acoustic source localization in a partially closed cavity
Conclusion
Page 3
Pressure relief valve of the fuel vents Landing gear wheel wells Aircraft bays Inter-car gap or pantograph recess in trains Pipes and side branches
Flow-excited open mouth cavities
Introduction
Airbus A320
Boeing 737 TVG
Page 4
Blowing over the orifice of a bottle Window buffeting in cars Partially covered aircraft bays Organ pipes
Balasubramanian et al. (2009 AIAA/CEAS conf.)
Numerical simulation of leakage effects on sunroof
buffeting of an idealized generic vehicle
Ma et al. (2009 JFM)
Fluid mechanics of the flow-excited
Helmholtz resonator
Cummings (1973 JSV)
Acoustics of a wine bottle
Flow-excited closed mouth cavities
Lafon et al. (2003 JFS)
Aeroacoustical coupling in a ducted shallow
cavity and fluid/structure effects on a steam line
Introduction
Page 5 Contents
Introduction
Examples of flow excited cavities
Aerodynamics proprieties of an open mouth cylindrical cavity
Cavities and flow-acoustic couplings
Experimental set-ups
Open mouth cavity
Partially closed mouth cavity
Main Results
Description of the mean flow in an open mouth cavity
• Shear layer and wake
• The flow inside the cavity
Pressure response to a grazing flow
Acoustic source localization in a partially closed cavity
Conclusion
Page 6
Open mouth cylindrical cavity: drag
Incremental drag coefficient (Dybenko, 2005)
Friesing (1936)
Pallister (1974)
Savory et al. (1996)
Tillman (1951)
Wieghardt (1942)
Dybenko & Savory (2008)
0,47
0.2
0.4
0.8
0.6
1
0 0.2 0.4 0.6 0.8 1 1.2 0
f
D
c
C
1.4
H/D H
D
Dybenko J, 2005. An experimental investigation of turbulent boundary layer flow over surface-
mounted circular cavities. MESc Thesis, The University of Western Ontario, London, Canada.
Page 7
Open mouth cylindrical cavity: mean flow
x y
z
0°
90° 270°
-0.5
-1
0 0° 90° 180° 270° 360°
y/H
x
z 90°
0°
270°
90°
180°
270°
0°
H/D = 0.47
Introduction Gaudet & Winter (1973). Measurements of the drag of some characteristic aircraft excrescences
immersed in turbulent boundary layers, Tech. Rep. Aero 1538, Royal Aircraft Establishment
Oil-film visualisation
Page 8
H/D = 0.04
H/D = 1.07
Page 9 Contents
Introduction
Examples of flow excited cavities
Aerodynamics proprieties of an open mouth cylindrical cavity
Cavities and flow-acoustic couplings
Experimental set-ups
Open mouth cavity
Partially closed mouth cavity
Main Results
Description of the mean flow in an open mouth cavity
• Shear layer and wake
• The flow inside the cavity
Pressure response to a grazing flow
Acoustic source localization in a partially closed cavity
Conclusion
Page 10
Shear layer hydrodynamic modes
1
M
n
U
LfSt charn
n
n : mode
α : phase delay
M : Mach number
κ : convection velocity ratio
Rossiter’s formula:
Introduction Rossiter (1964). Wind-tunnel experiments on the flow over rectangular cavities at subsonic
and transonic speeds, Tech. Rep. R&M 3438, Aeronautical Research Council.
U∞
Feedback
Boundary layer
Acoustic waves
Shear layer instabilities
Page 11
Partially covered cavity:
Shear layer hydrodynamic modes
Longitudinal acoustic modes of the cavity
Azimuthal acoustic modes of the cavity
Combination modes (Longitudinal + Azimuthal + Radial)
Open mouth cavity:
Shear layer hydrodynamic modes
Depth acoustic modes (quarter wavelength)
Introduction
Flow-acoustic coupling
Page 12
Partially covered cavity:
Shear layer hydrodynamic modes
Helmholtz resonance:
Periodic compressions and expansions of the
air inside the cavity (mass-spring analogy)
Flow-acoustic coupling
Open mouth cavity:
Shear layer hydrodynamic modes
Depth acoustic modes (quarter wavelength)
Introduction
Page 13 Contents
Introduction
Examples of flow excited cavities
Aerodynamics proprieties of an open mouth cylindrical cavity
Cavities and flow-acoustic couplings
Experimental set-ups
Open mouth cavity
Partially closed mouth cavity
Main Results
Description of the mean flow in an open mouth cavity
• Shear layer and wake
• The flow inside the cavity
Pressure response to a grazing flow
Acoustic source localization in a partially closed cavity
Conclusion
Page 14
Low speed closed circuit wind tunnel
Wind tunnel characteristics:
Velocity range:
U∞ = [0 – 90 m/s]
Test section dimensions:
Lx = 2.5 m, Ly = 0.9 m, Lz = 1.16 m
Cavity Position:
L = 1.78 m
Cylindrical cavity:
Depth:
H = 285 mm
Diameter:
D = 210 mm
Aspect Ratio:
H/D = 1.357
Ly
Lz
Lx
Experimental set-up: wind tunnel ENEA-Roma Tre
Page 15
Hot wire measurements: single component probe
Grid: 2520 points
Upper view
Lateral view
x/D y/D z/D
min 0 0.015 -1.05
max 2.5 0.301 1.05
number 8 7 45
z
x
y
x
Experimental set-up: wind tunnel ENEA-Roma Tre
Page 16
Wall pressure measurements
Microphone: ¼ inch B&K
Wall-mounted
y/H
Lateral wall
Bottom
φ 0° 90° 270° 360° 180°
-0.25
-0.5
0
-0.75
-1
270°
0°
90°
Experimental set-up: wind tunnel ENEA-Roma Tre
Number of measurement
positions: 325
Page 17
Particle Image Velocimetry (PIV)
PIVDEF software developed by the INSEAN (Istituto Nazionale per Studi ed
Esperienze di Architettura Navale)
3 different horizontal planes (y/H = -0.25, -0.50 and -0.75)
Mean velocity field from 600 couple of images
Experimental set-up: wind tunnel ENEA-Roma Tre
Page 18 Contents
Introduction
Examples of flow excited cavities
Aerodynamics proprieties of an open mouth cylindrical cavity
Cavities and flow-acoustic couplings
Experimental set-ups
Open mouth cavity
Partially closed mouth cavity
Main Results
Description of the mean flow in an open mouth cavity
• Shear layer and wake
• The flow inside the cavity
Pressure response to a grazing flow
Acoustic source localization in a partially closed cavity
Conclusion
Page 19
Velocity range: [0 - 53 m/s]
Low speed draw-down wind tunnel
Diffuser
Intake
Test Section
Fan and Motor
Speed Controller
Cavity
Experimental set-up: wind tunnel TCD
Page 20
Experimental techniques
Hot wire anemometry (HWA) in the boundary layer
Velocimetry (PIV) in the shear layer region
16 microphones flush mounted
Dimensions of the rig:
H = 493 mm
D = 238 mm
L = 45 mm
W = 125 mm
FLOW
Square Wind
Tunnel
Section
Cylindrical
Cavity
H
D
L
Δ W
Experimental set-up: wind tunnel TCD
Rectangular
Opening
Page 21
Characteristics:
LaVision PIV system
Seeding particles: DEHS (1μm diameter)
Double pulsed Nd:YAG laser NewWave
Digital Flow Master camera with 28mm
focal length lens
1279 × 1023 pixel CCD sensor
Davis 7.2 software
Post-processing method:
Phase averaging of the velocity fields
Particle Image Velocimetry (PIV)
Experimental set-up: wind tunnel TCD
Page 22 Contents
Introduction
Examples of flow excited cavities
Aerodynamics proprieties of an open mouth cylindrical cavity
Cavities and flow-acoustic couplings
Experimental set-ups
Open mouth cavity
Partially closed mouth cavity
Main Results
Description of the mean flow in an open mouth cavity
• Shear layer and wake
• The flow inside the cavity
Pressure response to a grazing flow
Acoustic source localization in a partially closed cavity
Conclusion
Page 23
y/D = 0.015
0.025
0.05
0.1
0.2
x/D = 0 x/D = 0.25 x/D = 0.5
Velocity profiles: /UU hw
z
x
z
x
z
x
Page 24
0.025
0.05
0.1
0.15
y/D = 0.015
Velocity profiles:
x/D = 64 x/D = 1.5 x/D = 2.5
/UU hw
z
x
z
x
z
x
Page 25 z
x
0.015
0.025
0.1
0.2
Mean velocity Velocty fluctuations
Description of the mean flow: downstream edge
/UU hw /Uhw0.05
0.015
0.025
0.05
0.1
0.2
x/D = 0.5
Page 26
Description of the mean flow: wake
Mean velocity
/UU hw
Velocty fluctuations
/Uhw
0.015
0.025
0.05
0.1
0.15
x/D = 1.5 z
x
Page 27
Gaudet & Winter (1973)
X
Z
x/D = 0.5
x/D = 1.5
Description of the mean flow
Oil-film
visualisation
Results: mean flow Gaudet & Winter (1973). Measurements of the drag of some characteristic aircraft excrescences
immersed in turbulent boundary layers, Tech. Rep. Aero 1538, Royal Aircraft Establishment
Page 28 Rodriguez Verdugo, Guitton, Camussi, Di Marco, Grottadaurea (2010). Investigation of the flow and
the acoustics generated by a cylindrical cavity, 16th AIAA/CEAS Aeroacoustics Conference,
Stockholm, Sweden, 07-09 June.
Streamlines and velocity contours over the walls
DES numerical simulation
Tip vortices
Wake vortices
Description of the mean flow: numerical simulation
Page 29 Contents
Introduction
Examples of flow excited cavities
Aerodynamics proprieties of an open mouth cylindrical cavity
Cavities and flow-acoustic couplings
Experimental set-ups
Open mouth cavity
Partially closed mouth cavity
Main Results
Description of the mean flow in an open mouth cavity
• Shear layer and wake
• The flow inside the cavity
Pressure response to a grazing flow
Acoustic source localization in a partially closed cavity
Conclusion
Page 30 Description of the mean flow
z
x
Description of the mean flow: PIV
y
y/H =
-0.25
x
z
Page 31 Description of the mean flow
z
x
Description of the mean flow: PIV
y
y/H =
-0.50
x
z
Page 32 Description of the mean flow
z
x
Description of the mean flow: PIV
y
y/H =
-0.75
x
z
Page 33 Contents
Introduction
Examples of flow excited cavities
Aerodynamics proprieties of an open mouth cylindrical cavity
Cavities and flow-acoustic couplings
Experimental set-ups
Open mouth cavity
Partially closed mouth cavity
Main Results
Description of the mean flow in an open mouth cavity
• Shear layer and wake
• The flow inside the cavity
Pressure response to a grazing flow
Acoustic source localization in a partially closed cavity
Conclusion
Page 34
Unsteady pressure response to a grazing flow
Open mouth cavity Partially closed mouth cavity
Page 35 Results: mean flow
Shear layer hydrodynamic modes
1
M
n
U
LfSt charn
n
n : mode
α : phase delay
M : Mach number
κ : convection velocity ratio
Rossiter’s formula:
α = 0
κ = 0.46
α = 0
κ = 0.53
Unsteady pressure response to a grazing flow
Page 36 Results: mean flow
Shear layer hydrodynamic modes
Acoustic modes
Unsteady pressure response to a grazing flow
Page 37
Acoustic modes: numerical simulation
Experimental set-up: wind tunnel TCD
max min
Comsol Multiphysics
Wave Expansion Method (WEM)
Page 38 Results: mean flow
Shear layer hydrodynamic modes
Acoustic modes
Fluid-acoustic coupling
Unsteady pressure response to a grazing flow
Page 39
Unsteady pressure response to a grazing flow
253 Hz 241 Hz
226 Hz
215 Hz
199 Hz
Page 40 Results: mean flow
Unsteady pressure response to a grazing flow
256 Hz 246 Hz 236 Hz
224 Hz
212 Hz
197 Hz
Page 41
Unsteady pressure response to a grazing flow
258 Hz 249 Hz
244 Hz
232 Hz
225 Hz
250 Hz
Page 42
Unsteady pressure response to a grazing flow
H1 H1AZ1 H3
HW1
Helmholtz
resonance
Page 43 Contents
Introduction
Examples of flow excited cavities
Aerodynamics proprieties of an open mouth cylindrical cavity
Cavities and flow-acoustic couplings
Experimental set-ups
Open mouth cavity
Partially closed mouth cavity
Main Results
Description of the mean flow in an open mouth cavity
• Shear layer and wake
• The flow inside the cavity
Pressure response to a grazing flow
Acoustic source localization in a partially closed cavity
Conclusion
Page 44
Vortex-sound theory: analogy of Howe*
Acoustic power generated by vortices:
V
acoustdVuv
0
Acoustic power *Howe (1975), Contributions to the theory of aerodynamic sound with application to excess jet noise
and the theory of the flute. Journal of Fluid Mechanics 71, pp. 625–673.
acoustu
v
PIV
Velocity Vorticity Acoustic particle velocity
How to apply to experimental data?
Acoustic simulation
+
Experimental Pressure
Page 45
v
90°
180°
0°
270 °
Page 46
Page 47
Page 48
Page 49
Vortex-sound theory: analogy of Howe
Acoustic power generated by vortices:
Acoustic power
V
acoustdVuv
0
acoustu
v
PIV
Velocity Vorticity Acoustic particle velocity
Acoustic simulation
+
Experimental Pressure
How to apply to experimental data?
Page 50
90°
180°
0°
270 °
yacoustu ,
acoustu
Acoustic particle velocity
Acoustic simulation
+
Experimental Pressure
Acoustic particle velocity
WEM
acoust
acoustacoust P
f
tfcstu
2
2cos
Page 51
Acoustic particle velocity
H1 AZ1H1 H3
Page 52
Vortex-sound theory: analogy of Howe
Acoustic power generated by vortices:
acoustu
v
PIV
Velocity Vorticity Acoustic particle velocity
Acoustic simulation
+
Experimental Pressure
Acoustic power
V
acoustdVuv
0
How to apply to experimental data?
Page 53
90°
180°
0°
270 °
V
acoustdVuv
0
Acoustic power
Page 54
Acoustic energy 46.3 m/s: SL1 - H1
fdVuv
fE
V
acoust
acoust
/
/
0
Net acoustic energy generated per cycle
Acoustic power
Page 55
Acoustic energy 48.4 m/s: SL2 - AZ1H1
Acoustic power
Net acoustic energy generated per cycle
fdVuv
fE
V
acoust
acoust
/
/
0
Page 56
Acoustic energy
Acoustic power
Net acoustic energy generated per cycle
fdVuv
fE
V
acoust
acoust
/
/
0
51.5 m/s: SL2 - H3
Page 57 Conclusions
Conclusions 1/2: open mouth cavity
A cavity model has been designed and tested in a closed test section wind
tunnel.
The shear layer hydrodynamics modes were found to be correctly predicted
by the Rossiter formula.
Lock-on between the shear layer modes and the acoustic resonances of the
test section. The common characteristic of the lock-on modes is the quarter
wavelength shape inside the cavity.
The symmetry of the flow, expected for the aspect ration studied, was
confirmed.
The turned down jet was found to generate two vertical symmetric vortices
near the downstream wall.
Page 58 Conclusions
Conclusions 2/2: partially covered mouth cavity
A cavity model has been designed and tested in a closed test section wind
tunnel.
The shear layer hydrodynamics modes were found to be correctly predicted
by the Rossiter formula.
Lock-on between the shear layer modes and the acoustic resonances of the
cavity.
The dominant acoustic mode does not have an influence on the shear layer
morphology.
The vortex sound theory of Howe (1975) was used to quantify the energy
transfer between the acoustic field and the turbulent flow.
The acoustic power pattern has been found to depend exclusively on the
predominant hydrodynamic shear layer stage.
Page 59
Journal Publications
Rodriguez Verdugo F., Guitton A., Camussi R., “Experimental investigation of a cylindrical cavity in a
low Mach number flow”, Journal of Fluids and Structures 28, pp 1-19, 2012.
Conference Proceedings
Rodriguez Verdugo F., Camussi R., Bennett G.J., “Aeroacoustic source characterization technique
applied to a cylindrical Helmholtz resonator”, International Conference on Sound and Vibration, Rio
de Janeiro, 10-14 July 2011.
Rodriguez Verdugo F., Bennett G.J., Stephens D.B., “Dynamics of the shear layer in the orifice of a
cylindrical Helmholtz resonator using PIV”, XVIII A.I.VE.LA. National Meeting, Rome, Italy, 15-16
December 2010.
Bennett G.J., Rodriguez Verdugo F., Stephens D.B., “Shear layer dynamics of a cylindrical cavity for
different acoustic resonance modes”, 15th Int. Symp. Appl. Laser Techn. Fluid Mech., Lisbon,
Portugal, 05-08 July 2010.
Stephens D.B., Rodriguez Verdugo F., Bennett G.J., “Shear layer driven acoustic modes in a
cylindrical cavity”, 16th AIAA/CEAS Aeroacoustics Conference, Stockholm, 07-09 June 2010.
Rodriguez Verdugo F., Guitton A., Camussi R., Di Marco A., Grottadaurea M., “Investigation of the
flow and the acoustics generated by a cylindrical cavity”, 16th AIAA/CEAS Aeroacoustics Conference,
Stockholm, Sweden, 07-09 June 2010.
Rodriguez Verdugo F., Camussi R., Guitton A., “Experimental characterisation of a cylindrical cavity
in a low Mach number flow”, XX AIDAA Congress, Milano, Italy, July 2009.
Rodriguez Verdugo F., Guitton A., Di Marco A., Camussi R., “Aeroacoustic characterization of a
cylindrical cavity”, XVII AIVELA, Ancona, Italy, 26-27 November 2009.
Rodriguez Verdugo F., Guitton A., Camussi R., Grottadaurea M., “Experimental investigation of a
cylindrical cavity”, 15th AIAA/CEAS Aeroacoustics Conference, Miami, USA, 11-13 May 2009.
Page 60
Acknowledgments
Introduction
