Effect of an axial jet on aircraft wake...
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Work performed with the support from EC FP6 – “FAR-Wake” Effect of an axial jet on aircraft wake vortices D. Marles, P. Margaris, I. Gursul University of Bath Department of Mechanical Engineering
Transcript of Effect of an axial jet on aircraft wake...
Work performed with the support from EC FP6 – “FAR-Wake”
Effect of an axial jet on aircraft wake vortices
D. Marles, P. Margaris, I. Gursul
University of BathDepartment of Mechanical Engineering
Outline
• Single vortex / jet interaction• Main parameters:
R ratio of jet to vortex strengthh/dj jet-to-vortex distanceΓ/ν Reynolds numberαj jet inclination (take-off and
landing phases)
• Vortex pair / jet interaction• Effect on vortex merging• Additional parameter: Γt/ Γf
• Pulsed jets• Simulation of pulsed engine jets • Small flow control jets
Experiments in Fluids 2008
Physics of Fluids 2008
Single vortex / jet interaction
Laser Unit- PIV (Nd-YAG)- Flow Vis. (Argon Ion)
U∞
Laser Sheet(Cross-flow)
Experimental Rig - Wing- Jet
Water tunnel
PIV Camera
PIV Laser Unit(Nd-Yag)
Laser Sheet(Cross-Flow)
U∞
Experimental Rig- Wing- Jet
Wind tunnel
• Wind and water tunnel
• Generic wings and nozzles
• PIV and flow visualization
2
)(Γ
−= ∞
ρρ jjjj AUUU
R
• jet-to-vortex distance (h/dj)
• ratio of jet to vortex strength (R)
Main Parameters
cruise R ≅ 1T-O R ≅ 4 – 6
h/dj
R
0 2 4 6 8 10 120
1
2
3
4
5
6
7
8
9
10Water TunnelLarge Wind TunnelOpen Jet Wind TunnelA330-300B737-500Brunet, Garnier & JacquinWang & ZamanJacquin & Garnier
C
C
Single vortex / jet interaction
• jet inclination (αj)
• Reynolds number (Γ/ν)
x/b = 0.35 x/b = 1.75
h/dj = 6.7 h/dj = 6.7
Flow Visualization
only jet visualised
h/dj = 4 h/dj = 4
Jet wrapped around the vortex
Jet ingested into the vortex
Effect of jet-to-vortex distance (x/b=0.35)
y/dj
z/d j
-8 -6 -4 -2 0 2 4 6-8
-6
-4
-2
0
2
4
6
y/dj
z/d j
-8 -6 -4 -2 0 2 4 6-8
-6
-4
-2
0
2
4
6
y/dj
z/d j
-8 -6 -4 -2 0 2 4 6-8
-6
-4
-2
0
2
4
6
std(%)1815129630
h/dj = 6.7 h/dj = 4.0 h/dj = 2.7
PIV Measurements – Turbulence
Downstream evolution (h/dj=4) x/b = 0.35
/d
z/d j
-8 -6 -4 -2 0 2 4 6-8
-6
-4
-2
0
2
4
6
/d
z/d j
-8 -6 -4 -2 0 2 4 6-8
-6
-4
-2
0
2
4
6
/d
z/d j
-8 -6 -4 -2 0 2 4 6-8
-6
-4
-2
0
2
4
6
std(%)1815129630
x/b = 0.70 x/b = 1.05
y/dj
z/d j
-8 -6 -4 -2 0 2 4 6-8
-6
-4
-2
0
2
4
6
y/dj
z/d j
-8 -6 -4 -2 0 2 4 6-8
-6
-4
-2
0
2
4
6
y/dj
z/d j
-8 -6 -4 -2 0 2 4 6-8
-6
-4
-2
0
2
4
6
y/dj
z/d j
-8 -6 -4 -2 0 2 4 6-8
-6
-4
-2
0
2
4
6
|U|/U00.30.250.20.150.10.050
ReΓ = 5,500h/dj = 4x/b = 1.05
Effect of R: cross-flow velocity magnitude
Uj = 0
R = 0.34
R = 0.13
R = 0.78
PIV Measurements – Time-averaged flow
|U|/U∞
Effect of wandering?
Single vortex / jet interaction
y/dj
z/d j
-8 -6 -4 -2 0 2 4 6-8
-6
-4
-2
0
2
4
6
y/dj
z/d j
-8 -6 -4 -2 0 2 4 6-8
-6
-4
-2
0
2
4
6y/dj
z/d j
-8 -6 -4 -2 0 2 4 6-8
-6
-4
-2
0
2
4
6
y/dj
z/d j
-8 -6 -4 -2 0 2 4 6-8
-6
-4
-2
0
2
4
6
Time-averaged Instantaneous Vortex wanderingN
o je
tW
ith je
t
Vortex cross-flow velocity decreases (both in time-averaged and instantaneous) while wandering increase.
• Jet turbulence can wrap around the vortex or get ingested into the vortex• Turbulence ingestion leads to decreasing cross-flow velocities (both in time-averaged and instantaneous sense)
PIV advantage over point measurements: removes the vortex wandering effect which affects the time-averaged measurements.
• Faster ingestion with decreasing jet-to-vortex distance and increasing jet strength
Potential for flap-edge vortices, due to their small distance from the engine jet.
• No noticeable differences were found within the Reynolds number range tested• The effect is negligible when the jet is blowing at an angle to the freestream
and away from the vortex such as during take-off
Summary
Single vortex / jet interaction
αj > 0: little effect(jet turbulence away from vortex)
αj < 0: maximum vortex velocity decreases(jet turbulence blown into vortex)unrealistic case, but useful for flow control purposes
Vortex pair / jet interaction
ΓTip/ Γ Flap = 0.65, 1.0, 1.54
hv c
s
Water level
Uj
hj
U∞
zy x
h
Flap vortex
Tip vortex
Wing-tip vortex generator
Flap-edge vortex generator
U∞
Experimental Setup
III
II
I
Configuration
Aircraft with 4 engines
Aircraft with 4 engines
Aircraft with 2 engines
Aircraft Configuration
ΓFlap ΓTip
ΓFlap ΓTip
Outboard Engine
ΓFlapΓTip
Outboard Engine
Jet Configurations
Flow Visualisation – Jet Inboard of Flap
Tip
Flap
ΓFlap/ Γ Tip = 1.0
Tip
Flap
Vortex Pair Rotation
Tip
Flap
Increasing Downstream Distance
Jet
x/c = 4 x/c = 12 x/c = 24
Tip
FlapTip
Flap
Flap
Tip
Uj/U
∞=
0U
j/U∞
= 2
Flap
Tip
0.75c0.6c
ΓFlap ΓTip
Tip
Flap
Flow Visualisation – Jet Vertically Below FlapΓFlap/ Γ Tip = 1.0
Tip
Flap
Jet
Uj/U
∞=
0U
j/U∞
= 2
x/c = 4 x/c = 12 x/c = 24
Tip
Flap Tip
Flap
Tip
Flap
Vortex Pair Rotation
Tip
Flap
Increasing Downstream Distance
0.75c
0.6c ΓFlap ΓTip
y/c
z/c
-1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
Effect of Jet Flux – Contours of Vorticity
Uj/U∞ = 0Flap
Tip
y/c
z/c
-1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
Jet Inboard of Flap, x/c = 16
Uj/U∞ = 2.8
Vortex Pair Rotation
y/c
z/c
-1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
y/c
z/c
-1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
Flap
Tip
Jet Vertically Below Flap, x/c = 8
Uj/U∞ = 0
Uj/U∞ = 2.8
Vortex Pair Rotation
Flap
Tip
Tip
Flap
ΓFlap/ Γ Tip = 1.0
x/c
h/h v
0 5 10 15 20 250
0.2
0.4
0.6
0.8
1
1.2
x/c
θ
0 5 10 15 20 250
50
100
150
200
250
300
350
400
450
Reference CaseCμ = 0Cμ = 0.025Cμ = 0.05Cμ = 0.1
MERGER DELAYED
No Nozzle StructureUj/U∞ = 0Uj/U∞ = 2.0Uj/U∞ = 2.8 Uj/U∞ = 4.0
Vort
ex S
epar
atio
n / h
v
Increasing Jet FluxIncreases Vortex
Spacing
Rotation Angle
Effect of Jet Flux – Jet Inboard of Flap
Downstream development of vortex pair
Vortex Separation Distance
Vorte
x Sep
arat
ion
θ
ΓFlap
ΓTip
Increasing Jet FluxReduces Rotation Angle
ΓFlap/ Γ Tip = 1.0
0.75c0.6c
ΓFlap ΓTip
y/c
z/c
-1.6 -1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
24
20
16
12
8
4
0
y/c
z/c
-1.6 -1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
(%)∞U
U std
x/c = 4, Uj/U∞ = 0 x/c = 4, Uj/U∞ = 2.8
Turbulence plot overlaid with streamlinesin rotating reference frame
ΓFlap/ Γ Tip = 1.0
0.75c0.6c
ΓFlap ΓTip
Effect of Jet Flux – Jet Inboard of Flap
x/c
θ
0 5 10 15 20 250
50
100
150
200
250
300
350
400
450
Reference CaseCμ = 0Cμ = 0.025Cμ = 0.05Cμ = 0.1
x/c
h/h
v
0 5 10 15 20 250
0.2
0.4
0.6
0.8
1
1.2Reference CaseCμ = 0Cμ = 0.025Cμ = 0.05Cμ = 0.1
Vort
ex S
epar
atio
n / h
v
Increasing Jet FluxReduces Vortex Spacing
MERGER PROMOTED
No Nozzle StructureUj/U∞ = 0Uj/U∞ = 2.0Uj/U∞ = 2.8 Uj/U∞ = 4.0
Increasing Jet FluxIncreases Rotation
Angle
Vorte
x Sep
arat
ion
θ
ΓFlap
ΓTipDownstream development of vortex pair
Effect of Jet Flux – Jet Vertically Below FlapΓFlap/ Γ Tip = 1.0
Rotation Angle Vortex Separation Distance
0.75c
0.6c ΓFlap ΓTip
y/c
z/c
-1.6 -1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
24
20
16
12
8
4
0
(%)∞U
U std
y/c
z/c
-1.6 -1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4x/c = 4, Uj/U∞ = 0 x/c = 4, Uj/U∞ = 2.8
Turbulence plot overlaid with streamlinesin rotating reference frame
ΓFlap/ Γ Tip = 1.0
0.75c
0.6c ΓFlap ΓTip
Effect of Jet Flux – Jet Vertically Below Flap
Streamlines in a rotating reference frame superimposed with jet turbulence explain the importance of the initial jet configuration.
ΓFlap ΓTip
I
ΓFlap ΓTip
III
ΓFlap ΓTip
II
T
x/c = 4
F
a)
x/c = 4
T
F
b)
x/c = 4c)
Turbulence gets trapped in the outer recirculation region
Uj/U∞
h/h v
0 1 2 3 40
0.2
0.4
0.6
0.8
1
1.2
ΓFlap/ Γ Tip = 1.0hv/c = 1.0 Effect of Jet Flux and Configuration
ΓFlap ΓTip
ΓFlap ΓTip
Jet inboard of Flap
Jet vertically below centre of flap and tip
ΓFlap ΓTip
Jet vertically below flap
Vort
ex S
epar
atio
n / I
nitia
l vor
tex
Spac
ing
Vortex spacing at x/c = 20 as a function of jet exit velocity
Summary
• Depending on the initial position of the jet, vortex merging can either be delayed or promoted:
→Jet Inboard of Flap (Merging Delayed) - jet turbulence trails the flap vortex as the vortices rotate. It alters the streamline pattern in the outer-recirculation region and inhibits the convective merger stage.
→Jet Vertically Below Flap (Merging Promoted) – Jet turbulence rapidly interacts with the flap vortex, causing it to diffuse which aids merging.
→ Streamlines in a rotating reference frame superimposed with jetturbulence explain the effect of the initial jet configuration.
• Different circulation ratios (ΓTip/ΓFlap = 0.65, 1.0, 1.54) and initial vortex spacings (hv/c = 0.75, 1.0) produced similar trends.
Vortex pair / jet interaction
Γ2Γ1Small amplitudes (RMS less than 7%)
Pulsed jets
Simulation of pulsed engine jets
j
jj U
fdSt = Range of optimum frequencies for jets with external flow
(Michalke and Hermann)
• little effect
• additional turbulence generated close to the jet exit decays by the time it interacts with the wake vortices.
y/c
z/c
-1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
y/c
z/c
-1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
Cycles
Uj/U
∞
0 1 2 3 4 5 6 7 8 9 100
2
4
6
8
10
12
14
Jet v
eloc
ity hj
ps
hj/c
a/c
0 0.1 0.2 0.3 0.4 0.50
0.1
0.2
0.3
Reference CaseCμ = 0Cμ = 0.01, No PulsingCμ = 0.025, No PulsingCμ = 0.01, St c = 0.11Cμ = 0.025, St c = 0.11
Small flow control jets
Diffusion of the vortex was observed when the jet was located just outside the vortex core.
Dispersion buffer may damp any perturbations generated within the core.
Conclusions
• Jet turbulence can wrap around the vortex or get ingested into the vortex
• Turbulence ingestion leads to decreasing cross-flow velocities (both in time-averaged and instantaneous sense)
• Important for flap-edge vortices
• Vortex merging can either be delayed or promoted, depending on the jet initial location
• Streamlines in a rotating reference frame superimposed with jet turbulence explain the effect of the initial jet configuration.
• Different circulation ratios and initial vortex spacings produced similar trends.
• Pulsed jets (with small amplitude) have little effect
• Small flow control jets may be useful as an active flow control method
