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Drag reduction of aDrag reduction of a Ahmed body using pulsed jetsInternational Forum of Flow Control (IFFC – 2)
P. JOSEPHInstitut AéroTechnique (IAT)
X. AMANDOLESEAerodynamics Department
J‐L. AIDERPMMH Laboratory
CNAM, Francepierric.joseph@cnam.fr
CNAM, Francexavier.amandolese@cnam.fr
UMR 7636 CNRSESPCI ParisTech, Franceaider@pmmh.espci.fr
Acknowledgements :Acknowledgements :This work was carried out in the framework of a ANR research programme (CARAVAJE) supported by ADEME.
Introduction• CARAVAJE Project :
« Control of the external aerodynamics of automotive– « Control of the external aerodynamics of automotive vehicles by pulsed jets »
– Partnership between seven industrials and laboratoriesPartnership between seven industrials and laboratories– Thematic ANR project financed by ADEME
FLOWDITMicrotechnology and FluidMicrotechnology and Fluid Mechanicswww.flowdit.com
Drag reduction of a Ahmed body using pulsed jets ‐ IFFC‐2 ‐ Pierric JOSEPH 2
Summaryy• Experimental setup
• Experimental measurements
• Reference results
• Pulsed jets actuation
• Control results
• Conclusion
Drag reduction of a Ahmed body using pulsed jets ‐ IFFC‐2 ‐ Pierric JOSEPH 3
Experimental setupp p• Reference Ahmed body model
– Standard dimensions with 25° slant angle.
Drag reduction of a Ahmed body using pulsed jets ‐ IFFC‐2 ‐ Pierric JOSEPH 4
Experimental setupp p• S4 wind tunnel facility, at Institut AéroTechnique
5m x 3m cross section(turbulence ≈ 1% ; wind ‐ speed up to 40 m/s). Raised floor with
airfoil shaped leading edge.
Drag reduction of a Ahmed body using pulsed jets ‐ IFFC‐2 ‐ Pierric JOSEPH 5
Experimental measurementsp• Drag measurements
d d b l– 6 components unsteady aerodynamic balance.– Precision < 0,5 %.
Drag reduction of a Ahmed body using pulsed jets ‐ IFFC‐2 ‐ Pierric JOSEPH 6
Experimental measurementsp• Wall measurements :
– 127 pressures taps.– Surface oil flow visualisation.
Drag reduction of a Ahmed body using pulsed jets ‐ IFFC‐2 ‐ Pierric JOSEPH 7
Experimental measurementsp• Wake measurements :
– 2,5D exploration device.b (h l h l )– Various probes (hot wire, Kiel, 7 holes…).
Drag reduction of a Ahmed body using pulsed jets ‐ IFFC‐2 ‐ Pierric JOSEPH 8
Reference results• Boundary layers measurements – incoming flow
d l f l di d /3,0
Boundary layer ‐ 0,7 m after leading edge ‐ 20 m/s
x = 0,7 m ; Ue = 20 m/s
2,0
2,51/8 th Power law
1,0
1,5y/δ
0,5
1,0
δ = 25 mm H = 1,25
0,0
0,0 0,2 0,4 0,6 0,8 1,0 1,2
u/Ue
Drag reduction of a Ahmed body using pulsed jets ‐ IFFC‐2 ‐ Pierric JOSEPH 9
u/Ue
Reference results• Boundary layers measurements – incoming flow
d l b f l d /3,0
Boundary layer ‐ 0,1 m before slant edge ‐ 20 m/s
x = 0,1 m ; Ue = 20 m/s
2,0
2,51/8 th Power law
1,0
1,5y/δ
0,5
1,0
δ = 24 mm H = 1,21
0,0
0,0 0,2 0,4 0,6 0,8 1,0 1,2
u/Ue
Drag reduction of a Ahmed body using pulsed jets ‐ IFFC‐2 ‐ Pierric JOSEPH 10
u/Ue
Reference results• Drag results
0,335
0,34
0 32
0,325
0,33
C x
0 31
0,315
0,32
0,305
0,31
1,00E+06 1,50E+06 2,00E+06 2,50E+06 3,00E+06
– Significant Reynolds effect.– Consistent with reference results ([Ahmed 1984] : Cx = 0,285 for Re ≈
Re
Drag reduction of a Ahmed body using pulsed jets ‐ IFFC‐2 ‐ Pierric JOSEPH 11
([ ] ,4,2 x 106).
Reference results• Wall pressure and visualisations measurements
Measurements localizationlocalization
– Reynolds effect on the recirculation bubble and surface pressure di t ib ti
Re = 1,4 x 106 Re = 2,1 x 106 Re = 2,8 x 106
Drag reduction of a Ahmed body using pulsed jets ‐ IFFC‐2 ‐ Pierric JOSEPH 12
distribution.
Reference results• Wake measurements Re = 1,4 x 106
144 mm behind model
Position of the
behind model
measurements plan
– Kiel probe measurements.– Flow structure consistent withFlow structure consistent with
classical Ahmed topology [Ahmed 1984].
–
Total pressure loss
With PTA the undisturbed flow total pressure and PTM the wake total pressure.
Drag reduction of a Ahmed body using pulsed jets ‐ IFFC‐2 ‐ Pierric JOSEPH 13
Total pressure loss coefficient (Cpi)
Reference resultsSlantheight
• Unsteady measurements in wake (Kiel and hot wire)
Location Frequency (Hz) – 20 m/s Strouhal (Slant height based) – 20 m/s
32 Hz 0,15
32 Hz 0,15
32 Hz 0,15
140 Hz 0,66
Drag reduction of a Ahmed body using pulsed jets ‐ IFFC‐2 ‐ Pierric JOSEPH 14
Reference results• Unsteady measurements in wake (Kiel probe)
Drag reduction of a Ahmed body using pulsed jets ‐ IFFC‐2 ‐ Pierric JOSEPH 15
Reference results• Unsteady measurements in wake (Kiel probe)
Drag reduction of a Ahmed body using pulsed jets ‐ IFFC‐2 ‐ Pierric JOSEPH 16
Pulsed jets actuationj• Control system description
– Open loop system with solenoid valve :• Frequency from 5 Hz to 300 Hz.• Speed up to 80 m/s – 90 m/s (depends on exhaust geometry).
Drag reduction of a Ahmed body using pulsed jets ‐ IFFC‐2 ‐ Pierric JOSEPH 17
Pulsed jets actuationj• Control system description
Solenoid Valves (Matrix Ltd document).
Component implantation inside Ahmed model.
J h ( l d )
Drag reduction of a Ahmed body using pulsed jets ‐ IFFC‐2 ‐ Pierric JOSEPH 18
Jets exhaust (near slant edge).
Pulsed jets actuationj• Control system location
Continous line Broken line
Winglets
– 2 blowing locations : « roof end » and « slant top edge »– 3 exhaust geometries.
Drag reduction of a Ahmed body using pulsed jets ‐ IFFC‐2 ‐ Pierric JOSEPH 19
Control results• Influence of the forcing parameters on drag
d (m
/s)
d (m
/s)
Broken line – roof end Winglets– roof end
Jets Spe
ed
Jets Spe
ed
s))
Frequency (Hz) Frequency (Hz)
Continious line – slant top edge Broken line – slant top edge
s Spe
ed (m
/s
Speed (m
/s
Jets
Jets
Frequency (Hz) Frequency (Hz)Drag reduction
(%)
Drag reduction of a Ahmed body using pulsed jets ‐ IFFC‐2 ‐ Pierric JOSEPH 20
(%)
Control results• Influence on the local pressure – slant surface
Drag Upper slant surface pressure
(m/s)
Broken line – roof end Winglets– roof end
(m/s)
(m/s)
m/s)
Broken line – roof end Winglets– roof end
Drag Upper slant surface pressure
Jets Spe
ed
Jets Spe
ed
Jets Spe
ed (
Jets Spe
ed (m
Frequency (Hz)
Continious line – slant top edge Broken line – slant top edge
Frequency (Hz) Frequency (Hz) Frequency (Hz)
Continious line – slant top edge Broken line – slant top edge
Speed (m
/s)
Speed (m
/s)
peed
(m/s)
Speed (m
/s)
Jets S
Jets
Jets Sp
Jets S
Frequency (Hz) Frequency (Hz) Frequency (Hz) Frequency (Hz)
Drag reduction of a Ahmed body using pulsed jets ‐ IFFC‐2 ‐ Pierric JOSEPH 21
Drag reduction (%)
Pressure variation (%)
Control results• Influence on the local pressure – vertical surface
Drag Vertical surface pressure
(m/s)
Broken line – roof end Winglets– roof end
(m/s)
(m/s)
m/s)
Broken line – roof end Winglets– roof end
Drag Vertical surface pressure
Jets Spe
ed
Jets Spe
ed
Jets Spe
ed (
Jets Spe
ed (m
Frequency (Hz)
Continious line – slant top edge Broken line – slant top edge
Frequency (Hz) Frequency (Hz) Frequency (Hz)
Continious line – slant top edge Broken line – slant top edge
Speed (m
/s)
Speed (m
/s)
peed
(m/s)
Speed (m
/s)
Jets S
Jets
Jets Sp
Jets S
Frequency (Hz) Frequency (Hz) Frequency (Hz) Frequency (Hz)
Drag reduction of a Ahmed body using pulsed jets ‐ IFFC‐2 ‐ Pierric JOSEPH 22
Drag reduction (%)
Pressure variation (%)
Conclusion• Effective experimental setup.Si ifi d d i• Significants drag reduction.
SetupDrag reduction Frequency St. Jet Speed
Setup(%) (Hz) (slant height based) (m/s)
Broken line – roof 7,8 140 0,66 77
l l d 7 5 75 0 3 22Continious line – slant edge 7,5 75 0,35 22
Broken line – slant edge 6,3 260 1,22 41
Winglets – roof 6,9 240 1,13 75
• Begining of comprehension of Cx reduction mecanisms.
Drag reduction of a Ahmed body using pulsed jets ‐ IFFC‐2 ‐ Pierric JOSEPH 23
Perspectivesp• Extensive parametric study : position, exhaust geometry forcing parametersgeometry, forcing parameters
• Highlight the fluid ‐mechanisms involved by• Highlight the fluid ‐mechanisms involved by unsteady pression and flow analysis
• Tests of MEMS actuators for better performance and• Tests of MEMS actuators for better performance and efficiency.
Drag reduction of a Ahmed body using pulsed jets ‐ IFFC‐2 ‐ Pierric JOSEPH 24
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