NEAR WALL MEASUREMENTS IN A SEPARATING TURBULENT … 3/S3_Le… · •Laser Doppler Velocimetry...
Transcript of NEAR WALL MEASUREMENTS IN A SEPARATING TURBULENT … 3/S3_Le… · •Laser Doppler Velocimetry...
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
NEAR WALL MEASUREMENTS IN A SEPARATING TURBULENT BOUNDARY LAYER WITH AND WITHOUT
PASSIVE FLOW CONTROL
Davide Lengani, Daniele Simoni, Marina Ubaldi, Pietro ZuninoUniversità degli Studi di Genova (Italy)
Dipartimento di Macchine, Sistemi Energetici e Trasporti
Aerodynamics and Turbomachinery Laboratory
Francesco BertiniAVIO S.p.A.
Torino, Italy
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Objectives
•Experimental analysis of a separating turbulent boundary layer developing on a large scale flat plate with prescribed adverse pressure gradient
•Measurements have been performed in the symmetry plane of a linear diffuser for a baseline uncontrolled condition and then repeated with passive control devices: low-profile vortex generators
•Laser Doppler Velocimetry employed to obtain high spatial resolution and accurate statistical analysis of boundary layer velocity and turbulence profiles
•The three-dimensional effects induced by the Vortex Generators have been also investigated in a cross-stream plane
This work is part of the joint European research project Aggressive Intermediate Duct Aerodynamics for Competitive & Environmentally Friendly Jet Engines
Priority 4 Aeronautics & SpaceSpecific Targeted REsearch Project
AST3-CT-2003-502836
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Open-loop wind tunnel with variable pressure discharge
Inlet boundary layer parameters and free-stream turbulence intensity
1%0.0032110001.245.6 mm80 mm
TucfReθH12θδ
Test section
UNIGE-AVIO test rig for boundary layer separation control experiments
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Large scale flat plate boundary layer experimentswith adverse pressure gradients
Flat plate prescribed pressure distributions through variable top wall inclination with boundary layer suction
Test section top wall inclination 16°Ideal acceleration factor
7
01
0120
1016.3)()( −⋅−=
−−
=XXUU
UK ν
x
y
z
first measuring plane
0 1 2 3 4 5x/H0
0
0.2
0.4
0.6
0.8
Cp=
2(p s
-ps0
)/ρu 0
2
No VGsVGs
• Flat plate: 1700 mm long, 400 mm wide • Test section inlet height: 196 mm• Inlet boundary layer suction on lateral
and top walls
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Vortex generators geometry
25°β
23°α
80mmδs
16mm0.2*δc
64mm0.8*δl
16mm0.2*δh
Geometrical parameters
VGs axial position:95 mm upstream of the detachment point (t.e. x=290 mm)
co-rotating pattern
counter-rotating with respect to the center line
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Laser Doppler Velocimetry instrumentation
Four beams LDV main characteristics:DANTEC FlowLite 2D•200 mW 532 nm and 200 mW 488 nm solid state lasers
•one of each pair of beams frequency shifted by a Bragg cell (40 MHz)
Optical probe characteristics• Diameter D=60 mm• Beam separation before expansion d= 38 mm
• Focal length f=300 mm• Beam intersection angle θ = 7.2°• Fringe separation δ= 4.1 μm (green) 3.8 μm (blue)
• Probe volume 0.09x0.09x1.4 mmBurst Processors
• 2 Dantec Enhanced Burst Spectrum Analysers operated in coincidence mode
Probe Traversing Mechanism• Computer controlled 3-axis mechanism with minimum step of 8 μm
Measurements matrix
• 14 traverses normal to the surface • 103 points per traverse• 30000 samples per point or record length in
time of 120 s
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Laser Doppler Velocimetry instrumentation
Measurements matrix
• traverses normal to the surface • 103 points per traverse• 30000 samples per point or record length in
time of 120 s
x [mm]
0
100
200
300
400
500y
[mm
]
0
50
100
150
z [mm]
0
100
x
y
z
first measuring plane
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Mean velocity distribution without VGs
• Streamwise reduction of the freestream velocity (adverse pressure gradient) and progressive boundary layer momentum reduction.
• Positive normal velocity component in the freestream (top wall inclination, b. l. suction)
• Detachment point (zero mean velocity gradient in y direction at the wall): x = 385 mm
0 1 2 3 4 5x/H0
0
0.2
0.4
0.6
0.8
Cp=
2(p s
-ps0
)/ρu 0
2
No VGsVGs
0 10 20 30u [m/s]
0
40
80
120
y [m
m]
No VGs, x=0mmNo VGs, x=200mmNo VGs, x=350mmNo VGs, x=385mm
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Mean velocity distribution without VGs
• Streamwise reduction of the freestream velocity (adverse pressure gradient) and progressive boundary layer momentum reduction.
• Positive normal velocity component in the freestream (top wall inclination, b. l. suction)
• Detachment point (zero mean velocity gradient in y direction at the wall): x = 385 mm
0 1 2 3 4 5x/H0
0
0.2
0.4
0.6
0.8
Cp=
2(p s
-ps0
)/ρu 0
2
No VGsVGs
0 10 20 30u [m/s]
0
40
80
120
y [m
m]
No VGs, x=0mmNo VGs, x=200mmNo VGs, x=350mmNo VGs, x=385mm
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Mean velocity distribution without VGs
• Streamwise reduction of the freestream velocity (adverse pressure gradient) and progressive boundary layer momentum reduction.
• Positive normal velocity component in the freestream (top wall inclination, b. l. suction)
• Detachment point (zero mean velocity gradient in y direction at the wall): x = 385 mm
0 1 2 3 4 5x/H0
0
0.2
0.4
0.6
0.8
Cp=
2(p s
-ps0
)/ρu 0
2
No VGsVGs
0 10 20 30u [m/s]
0
40
80
120
y [m
m]
No VGs, x=0mmNo VGs, x=200mmNo VGs, x=350mmNo VGs, x=385mm
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Mean velocity distribution without VGs
• Streamwise reduction of the freestream velocity (adverse pressure gradient) and progressive boundary layer momentum reduction.
• Positive normal velocity component in the freestream (top wall inclination, b. l. suction)
• Detachment point (zero mean velocity gradient in y direction at the wall): x = 385 mm
0 1 2 3 4 5x/H0
0
0.2
0.4
0.6
0.8
Cp=
2(p s
-ps0
)/ρu 0
2
No VGsVGs
0 10 20 30u [m/s]
0
40
80
120
y [m
m]
No VGs, x=0mmNo VGs, x=200mmNo VGs, x=350mmNo VGs, x=385mm
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Mean velocity distribution with and without VGs
• Vortex Generators delaying separation thanks to momentum transferred toward the wall
• Higher diffusion of the flow characterizes the controlled condition
0 1 2 3 4 5x/H0
0
0.2
0.4
0.6
0.8
Cp=
2(p s
-ps0
)/ρu 0
2
No VGsVGs
0 10 20 30u [m/s]
0
40
80
120
y [m
m]
VGs x=350mmNo VGs, x=0mmNo VGs, x=200mmNo VGs, x=350mmNo VGs, x=385mm
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Dissipation mechanisms
⎟⎟⎠
⎞⎜⎜⎝
⎛−
∂∂
∂∂
−⎥⎦
⎤⎢⎣
⎡⎟⎟⎠
⎞⎜⎜⎝
⎛−
∂∂
∂∂
+⎟⎠⎞
⎜⎝⎛ −
∂∂
∂∂
−⎥⎦
⎤⎢⎣
⎡⎟⎠⎞
⎜⎝⎛ −
∂∂
∂∂
+
=∂∂
+∂
∂+
∂
∂
''1''1'1'1
)2()2(
22
22
vuyu
yuvu
yuu
yu
xu
xuu
xuu
x
xpu
y
uv
x
uu
ρμρ
ρμρ
ρμρ
ρμρ
ρ
⎟⎠⎞
⎜⎝⎛ −
∂∂
∂∂
−⎥⎦
⎤⎢⎣
⎡⎟⎠⎞
⎜⎝⎛ −
∂∂
∂∂
+⎟⎟⎠
⎞⎜⎜⎝
⎛−
∂∂
∂∂
−⎥⎦
⎤⎢⎣
⎡⎟⎟⎠
⎞⎜⎜⎝
⎛−
∂∂
∂∂
+
=∂∂
+∂
∂+
∂
∂
''1''1'1'1
)2()2(
22
22
vuxv
xvvu
xvv
xv
yv
yvv
yvv
y
ypv
y
vv
x
vu
ρμρ
ρμρ
ρμρ
ρμρ
ρ
2
)( ⎟⎟⎠
⎞⎜⎜⎝
⎛∂∂
=yuD Lxt μ
yuvuD Txt ∂∂
−= '')( ρxuuD Txn ∂∂
−=2
')( ρ
2
)( ⎟⎠⎞
⎜⎝⎛∂∂
=xuD Lxn μ
yvvD Tyn ∂∂
−=2
')( ρ
2
)( ⎟⎟⎠
⎞⎜⎜⎝
⎛∂∂
=yvD Lyn μ
2
)( ⎟⎠⎞
⎜⎝⎛∂∂
=xvD Lyt μ
xvvuD Tyt ∂∂
−= '')( ρ
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Dissipation mechanisms
⎟⎟⎠
⎞⎜⎜⎝
⎛−
∂∂
∂∂
−⎥⎦
⎤⎢⎣
⎡⎟⎟⎠
⎞⎜⎜⎝
⎛−
∂∂
∂∂
+⎟⎠⎞
⎜⎝⎛ −
∂∂
∂∂
−⎥⎦
⎤⎢⎣
⎡⎟⎠⎞
⎜⎝⎛ −
∂∂
∂∂
+
=∂∂
+∂
∂+
∂
∂
''1''1'1'1
)2()2(
22
22
vuyu
yuvu
yuu
yu
xu
xuu
xuu
x
xpu
y
uv
x
uu
ρμρ
ρμρ
ρμρ
ρμρ
ρ
⎟⎠⎞
⎜⎝⎛ −
∂∂
∂∂
−⎥⎦
⎤⎢⎣
⎡⎟⎠⎞
⎜⎝⎛ −
∂∂
∂∂
+⎟⎟⎠
⎞⎜⎜⎝
⎛−
∂∂
∂∂
−⎥⎦
⎤⎢⎣
⎡⎟⎟⎠
⎞⎜⎜⎝
⎛−
∂∂
∂∂
+
=∂∂
+∂
∂+
∂
∂
''1''1'1'1
)2()2(
22
22
vuxv
xvvu
xvv
xv
yv
yvv
yvv
y
ypv
y
vv
x
vu
ρμρ
ρμρ
ρμρ
ρμρ
ρ
2
)( ⎟⎟⎠
⎞⎜⎜⎝
⎛∂∂
=yuD Lxt μ
yuvuD Txt ∂∂
−= '')( ρxuuD Txn ∂∂
−=2
')( ρ
2
)( ⎟⎠⎞
⎜⎝⎛∂∂
=xuD Lxn μ
yvvD Tyn ∂∂
−=2
')( ρ
2
)( ⎟⎟⎠
⎞⎜⎜⎝
⎛∂∂
=yvD Lyn μ
2
)( ⎟⎠⎞
⎜⎝⎛∂∂
=xvD Lyt μ
xvvuD Tyt ∂∂
−= '')( ρ
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Dissipation mechanisms
⎟⎟⎠
⎞⎜⎜⎝
⎛−
∂∂
∂∂
−⎥⎦
⎤⎢⎣
⎡⎟⎟⎠
⎞⎜⎜⎝
⎛−
∂∂
∂∂
+⎟⎠⎞
⎜⎝⎛ −
∂∂
∂∂
−⎥⎦
⎤⎢⎣
⎡⎟⎠⎞
⎜⎝⎛ −
∂∂
∂∂
+
=∂∂
+∂
∂+
∂
∂
''1''1'1'1
)2()2(
22
22
vuyu
yuvu
yuu
yu
xu
xuu
xuu
x
xpu
y
uv
x
uu
ρμρ
ρμρ
ρμρ
ρμρ
ρ
⎟⎠⎞
⎜⎝⎛ −
∂∂
∂∂
−⎥⎦
⎤⎢⎣
⎡⎟⎠⎞
⎜⎝⎛ −
∂∂
∂∂
+⎟⎟⎠
⎞⎜⎜⎝
⎛−
∂∂
∂∂
−⎥⎦
⎤⎢⎣
⎡⎟⎟⎠
⎞⎜⎜⎝
⎛−
∂∂
∂∂
+
=∂∂
+∂
∂+
∂
∂
''1''1'1'1
)2()2(
22
22
vuxv
xvvu
xvv
xv
yv
yvv
yvv
y
ypv
y
vv
x
vu
ρμρ
ρμρ
ρμρ
ρμρ
ρ
2
)( ⎟⎟⎠
⎞⎜⎜⎝
⎛∂∂
=yuD Lxt μ
yuvuD Txt ∂∂
−= '')( ρxuuD Txn ∂∂
−=2
')( ρ
2
)( ⎟⎠⎞
⎜⎝⎛∂∂
=xuD Lxn μ
yvvD Tyn ∂∂
−=2
')( ρ
2
)( ⎟⎟⎠
⎞⎜⎜⎝
⎛∂∂
=yvD Lyn μ
2
)( ⎟⎠⎞
⎜⎝⎛∂∂
=xvD Lyt μ
xvvuD Tyt ∂∂
−= '')( ρ
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Dissipation mechanisms
⎟⎟⎠
⎞⎜⎜⎝
⎛−
∂∂
∂∂
−⎥⎦
⎤⎢⎣
⎡⎟⎟⎠
⎞⎜⎜⎝
⎛−
∂∂
∂∂
+⎟⎠⎞
⎜⎝⎛ −
∂∂
∂∂
−⎥⎦
⎤⎢⎣
⎡⎟⎠⎞
⎜⎝⎛ −
∂∂
∂∂
+
=∂∂
+∂
∂+
∂
∂
''1''1'1'1
)2()2(
22
22
vuyu
yuvu
yuu
yu
xu
xuu
xuu
x
xpu
y
uv
x
uu
ρμρ
ρμρ
ρμρ
ρμρ
ρ
⎟⎠⎞
⎜⎝⎛ −
∂∂
∂∂
−⎥⎦
⎤⎢⎣
⎡⎟⎠⎞
⎜⎝⎛ −
∂∂
∂∂
+⎟⎟⎠
⎞⎜⎜⎝
⎛−
∂∂
∂∂
−⎥⎦
⎤⎢⎣
⎡⎟⎟⎠
⎞⎜⎜⎝
⎛−
∂∂
∂∂
+
=∂∂
+∂
∂+
∂
∂
''1''1'1'1
)2()2(
22
22
vuxv
xvvu
xvv
xv
yv
yvv
yvv
y
ypv
y
vv
x
vu
ρμρ
ρμρ
ρμρ
ρμρ
ρ
2
)( ⎟⎟⎠
⎞⎜⎜⎝
⎛∂∂
=yuD Lxt μ
yuvuD Txt ∂∂
−= '')( ρxuuD Txn ∂∂
−=2
')( ρ
2
)( ⎟⎠⎞
⎜⎝⎛∂∂
=xuD Lxn μ
yvvD Tyn ∂∂
−=2
')( ρ
2
)( ⎟⎟⎠
⎞⎜⎜⎝
⎛∂∂
=yvD Lyn μ
2
)( ⎟⎠⎞
⎜⎝⎛∂∂
=xvD Lyt μ
xvvuD Tyt ∂∂
−= '')( ρ
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Dissipation mechanisms: inlet boundary layer
-1000 0 1000 2000 3000Deformation works [W/m3]
0
40
80
120
y [m
m]
NO VGs(Dt)Tx, x=0mm(Dt)Lx, x=0mm
2
)( ⎟⎟⎠
⎞⎜⎜⎝
⎛∂∂
=yuD Lxt μ
yuvuD Txt ∂∂
−= '')( ρ
0 10 20 30u [m/s]
0
40
80
120
y [m
m]
No VGs, x=0mmNo VGs, x=200mmNo VGs, x=350mmNo VGs, x=385mm
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Dissipation mechanisms: x=200 mm
-1000 0 1000 2000 3000Deformation works [W/m3]
0
40
80
120
y [m
m]
NO VGs(Dt)Tx, x=200mm(Dn)Tx, x=200mm
2
)( ⎟⎟⎠
⎞⎜⎜⎝
⎛∂∂
=yuD Lxt μ
yuvuD Txt ∂∂
−= '')( ρ
xuuD Txn ∂∂
−=2
')( ρ
0 10 20 30u [m/s]
0
40
80
120
y [m
m]
No VGs, x=0mmNo VGs, x=200mmNo VGs, x=350mmNo VGs, x=385mm
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Dissipation mechanisms: BL approaching separation
yuvuD Txt ∂∂
−= '')( ρ
xuuD Txn ∂∂
−=2
')( ρ
0 10 20 30u [m/s]
0
40
80
120
y [m
m]
No VGs, x=0mmNo VGs, x=200mmNo VGs, x=350mmNo VGs, x=385mm
-1000 0 1000 2000 3000Deformation works [W/m3]
0
40
80
120
y [m
m]
NO VGs(Dt)Tx, x=200mm(Dn)Tx, x=200mm(Dt)Tx, x=350mm(Dn)Tx, x=350mm
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Dissipation mechanisms: energy re-distribution effect
yuvuD Txt ∂∂
−= '')( ρ
xuuD Txn ∂∂
−=2
')( ρ
yvvD Tyn ∂∂
−=2
')( ρ
0 10 20 30u [m/s]
0
40
80
120
y [m
m]
No VGs, x=0mmNo VGs, x=200mmNo VGs, x=350mmNo VGs, x=385mm
-1000 0 1000 2000 3000Deformation works [W/m3]
0
40
80
120
y [m
m]
NO VGs(Dt)Tx, x=350mm(Dn)Tx, x=350mm(Dn)Ty, x=350mm
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Vortex generators
25°β
23°α
80mmδs
16mm0.2*δc
64mm0.8*δl
16mm0.2*δh
Geometrical parameters
VGs axial position:95 mm upstream of the detachment point (t.e. x=290 mm)
0 10 20 30u [m/s]
0
40
80
120
y [m
m]
VGs x=350mmNo VGs, x=0mmNo VGs, x=200mmNo VGs, x=350mmNo VGs, x=385mm
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Dissipation mechanisms with Vortex Generators
yuvuD Txt ∂∂
−= '')( ρ
xuuD Txn ∂∂
−=2
')( ρ
yvvD Tyn ∂∂
−=2
')( ρ
0 10 20 30u [m/s]
0
40
80
120
y [m
m]
VGs x=350mmNo VGs, x=0mmNo VGs, x=200mmNo VGs, x=350mmNo VGs, x=385mm
-1000 0 1000 2000 3000Deformation works [W/m3]
0
40
80
120
y [m
m]
(Dn)Tx, No VGs(Dn)Tx, VGs
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Dissipation mechanisms with Vortex Generators
yuvuD Txt ∂∂
−= '')( ρ
xuuD Txn ∂∂
−=2
')( ρ
yvvD Tyn ∂∂
−=2
')( ρ
0 10 20 30u [m/s]
0
40
80
120
y [m
m]
VGs x=350mmNo VGs, x=0mmNo VGs, x=200mmNo VGs, x=350mmNo VGs, x=385mm
-1000 0 1000 2000 3000Deformation works [W/m3]
0
40
80
120
y [m
m]
(Dt)Tx, No VGs(Dt)Tx, VGs
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Dissipation mechanisms with Vortex Generators
yuvuD Txt ∂∂
−= '')( ρ
xuuD Txn ∂∂
−=2
')( ρ
yvvD Tyn ∂∂
−=2
')( ρ
0 10 20 30u [m/s]
0
40
80
120
y [m
m]
VGs x=350mmNo VGs, x=0mmNo VGs, x=200mmNo VGs, x=350mmNo VGs, x=385mm
-1000 0 1000 2000 3000Deformation works [W/m3]
0
40
80
120
y [m
m]
(Dn)Ty, No VGs(Dn)Ty, VGs
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Dissipation mechanisms with Vortex Generators
yuvuD Txt ∂∂
−= '')( ρ
xuuD Txn ∂∂
−=2
')( ρ
yvvD Tyn ∂∂
−=2
')( ρ
0 10 20 30u [m/s]
0
40
80
120
y [m
m]
VGs x=350mmNo VGs, x=0mmNo VGs, x=200mmNo VGs, x=350mmNo VGs, x=385mm
-1000 0 1000 2000 3000Deformation works [W/m3]
0
40
80
120
y [m
m]
VGs x=350mm(Dt)Tx
(Dn)Tx
(Dn)Ty
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Dissipation mechanisms: comparison of total contribution (x=350 mm)
-1000 0 1000 2000 3000Deformation works [W/m3]
0
40
80
120
y [m
m]
D'', No VGsD'', VGs
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Vortex generators
25°β
23°α
80mmδs
16mm0.2*δc
64mm0.8*δl
16mm0.2*δh
Geometrical parameters
1 entire pitch investigated in a cross-stream plane downstream the VGs
x [mm]
0
100
200
300
400
500
y[m
m]
0
50
100
150
z [mm]
0
100
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
3D effects of Vortex Generators
z [mm]
y[m
m]
0 20 40 60 800
20
40
60
80
100
120
20.0
17.8
15.6
13.3
11.1
8.9
6.7
4.4
2.2
0.0
u[m/s]
z [mm]
y[m
m]
0 20 40 60 800
20
40
60
80
100
120
4.03.63.32.92.52.11.81.41.00.70.3
rms(u')[m/s]
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
3D effects of Vortex Generators
z [mm]y
[mm
]0 20 40 60 80
0
20
40
60
80
100
120
20.0
17.8
15.6
13.3
11.1
8.9
6.7
4.4
2.2
0.0
u[m/s]
-4 -2 0 2 4u'v' [m2/s2]
0
40
80
120
y [m
m]
No VGsVGs z=0mmVGs z=10mmVGs z=25mmVGs z=70mm
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Conclusions
• In the framework of the European project AIDA on Aggressive Intermediate Duct Aerodynamics experiments on separated and controlled turbulent boundary layerhave been carried out.
• LDV results provide a description of the separating turbulent boundary layer operating under a prescribed adverse pressure gradient
• Different contributions on the dissipation mechanisms have been distinctly analyzed: normal turbulent terms appear the greatest for a separating turbulent boundary layer.
• For the uncontrolled case the normal contribution along the y direction is negativeand tends to re-transfer energy to the mean motion.
• For the controlled case losses are contained thanks to the separation delaying.
• Future activity will be focused on total pressure measurements and loss production mechanism evaluation for baseline and controlled experiment, with three-dimensional losses evaluation for the controlled case.
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Backflow color plot
Detachment point (detected at x=385mm)
The greatest low frequency oscillations appear for BF=0.5
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Distributions of the streamwise momentum transported by the v velocity component downstream of VGs
-40 -20 0 20 40uv [m2/s2]
0
10
20
30
40
y [m
m]
x = 350 mmx = 400 mmx = 450 mmx = 500 mmx = 550 mmx = 600 mm
yvu
yvu
yu
xu
xu
xp
xu
∂∂
−∂∂
−∂
∂+
∂∂
−∂
∂+
∂∂
−=∂
∂ '''1)(2
22
2
22νν
ρ
•Minimum for y = 18 mm (comparable with VGs height) •Maximum negative peak for x = 350 mm (vanishes beyond x = 500 mm)
x-momentum equation for steady 2D incompressible flow:
accelerates the flow in the x direction for y < 18 mm, and decelerates the flow for y > 18 mm
Distortion in the mean velocity profile
0 5 10 15 20 25u [m/s]
0
40
80
120
160
y [m
m]
x = 400 mm
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
x [mm]
y[m
m]
0 100 200 300 400 500 6000
50
100
150
2000 0.003 0.006 0.009 0.012 0.015 0.018 0.021 0.024
Ti [s]
Flow Integral Time Scale
Detachment point (detected at x=385mm)
Free stream structures at wind tunnel test section inlet
Low integral time scale in the region of attached boundary layer
large integral time scale inside the separated flow region
Open Workshop, Lille, April 21-23, 2009
Università di GenovaDipartimento di Macchine, Sistemi Energetici e TrasportiAerodynamics and Turbomachinery Laboratory
Reynolds shear stress distribution with VGs
• Reynolds shear stress transport mechanism not negligible
-4 -2 0 2 4u'v' [m2/s2]
0
40
80
120
160
y [m
m]
• Reynolds shear stress gradient changes its sign as a function of the distance from the wall
−∂(u v)/∂y>0
−∂(u v)/∂y<0
VGs inlet boundary layer uv effect VGs outlet boundary layer
y [mm]
4020
u u u
−∂(u' v')/∂y<0 −∂(u' v')/∂y>04020
y [mm]
u u u
VGs outlet boundary layer Reynolds stress effect Uniformized boundary layer
x = 400 mm• Reynolds shear stress always acts in the sense of making uniform the velocity profile previously distorted by VGseffect
vu ⋅