Coefficient Of Drag Vs Reynolds Number – Clean Wing - SinhaTech

Improving Automotive Fuel Efficiency with Deturbulator Tape

SAE Paper: 2007-01- 3458SAE 21st Asia Pacific Automotive Technology Conference, Hollywood, CA, U.S.A.

5th-8th August, 2007

Sumon K. Sinha, Ph.D., P.E,and

Sumontro L. Sinha*

SINHATECH, Oxford, Mississippi

U.S.A.www.sinhatech.com

*Also with Mississippi School of Mathematics & Science, Columbus, MS, U.S.A.

MOTIVATION

Investigate Applicability of DETURBULATOR wing drag reduction

device to bluff bodiesto

Develop a SIMPLE, EFFECTIVE, and PRACTICAL Method of increasing

Automobile and Truck Efficiency Through Aerodynamic Drag Reduction

BACKGROUND

The Deturbulator

ATTENUATING TURBULENT MIXING:SINHA - FLEXIBLE COMPOSITE SURFACE

DETURBULATOR (FCSD)

Membrane Tension

50-100µmS

Boundary Layer Flow

Flexible Membrane ∼ 6µm thick

Substrate Base glued to aerodynamic surface

High Strips or Ridges

Low Strips as needed to fix flexural damping and higher modes

Fundamental Flexural Vibration Mode of MembraneShown (Amplitude < 0.1 µm)

10-50µm thick Air-Gap (Membrane Substrate)

Wing or other aerodynamic body

CLOSE UP OF DETURBULATOR

Substrate Cavity Vents

Flexible Membrane across Ridged Substrate

How Deturbulator Reduces Turbulence

Large Vortex Rolling

Ridges on Deturbulator

Freestream Flow

Flexible Skin of Deturbulator RED: Large Wavelength deflection BLUE: Small Wavelength Deflection

Small Vortices created from small-wavelength deflection

Small Vortices Drain Large Vortex

Boundary Layer

Small vortices quickly dissipated by viscosity

ANALOGY: Perturbation of large vortex creates small vortices similar to a tire rolling over rumble strips on a highway to warn approaching stop.

LARGE VORTICES PRODUCE TURBULENCE FROM MEAN FLOW

DETURBULATOR BREAKS UP LARGE VORTICES

FLOW-FCSD INTERACTION

∂ p/ ∂ x < 0

∂ p/ ∂ x ≅ 0

∂p/∂x > 0

Free stream ∂ U/ ∂ t ≈ v( ∂ u/ ∂ y) y=0

SINHA - FCS (Membrane Oscillation velocity v)

Separation point

Separated Shear Layer (Oscillates due to fluctuations)

Flow of pressure fluctuations

BEST INTERACTION where ∂p/∂x = 0

• FCSD passes oscillation without damping at the Interactionfrequency :

f = U/sAttenuates other frequencies

•This stabilizes the shear layerand mitigates turbulent dissipation

Base Airfoil

Airfoil with Deturbulator

Transition to Turbulent flow

Turbulent Boundary LayerHigh Skin Friction

Laminar Boundary LayerLow Skin Friction

Marginally Separated Boundary Layer Alters “Virtual” Shape of Airfoil; Increases Lift Coefficient

Deturbulator attenuates Turbulent Mixing Keeps separated regions nearly stagnant Almost Zero Skin Friction (Lower than in Laminar Flow)

Thickness of Deturbulator Tape encourages Marginal Separation

Dynamic Flow-Flexible-Surface interaction on Deturbulator maintains nearly stagnant regions of marginal separation

INTEGRATION OF DETURBULATOR WITH AIRFOIL TO INCREASE LIFT AND REDUCE

DRAG

Effect of Deturbulator on Separation bubble

BASE FLOW STRONG LAMINAR SEPARATION BUBBLE w TRANSITION

DETURBULATED FLOW: NO TRANSITION EXTENDED BUBBLE

Smeared Oil: Slip Layer

Full-Span Deturbulator (Tested by Richard Johnson)

Evaluations by Dick Johnson (Dec 2006)Supported by Dallas Gliding Association

Automotive Fuel Efficiency Enhancement

Reducing Drag in Fully Separated Wakes

FLOW WITHOUT TREATMENT

FLOW WITH TREATMENT

Turbulent Eddies

Vehicle or Bluff Body

Deturbulator

Stagnant WakeFor Virtual Streamlining

DETURBULATOR DRAG REDUCTION ON A VEHICLE

1/24 Scale SUV in Sinhatech Wind Tunnel

Measured Coeffcient of Drag on Model Car (Re = 0.4 million)

0

0.1

0.2

0.3

0.4

0.5

0.6

1 2 3 4 5 6Test Number

Coe

ffici

ent o

f Dra

g(C

D) De-turbulator Rear Top

Tape Top Front De-turbulator Top RearTape Top FrontClean Car

Deturbulator on 2000 Honda Odyssey

Con

trol

Expe

rimen

t

23242526272829303132

Mile

s Pe

r Gal

lon

2000 Honda Odyssey Average Highway Gas Mileage

Control

Experiment

Overall Average

Control

Experiment

2222.5

2323.5

2424.5

2525.5

26

Mile

s pe

r Gal

lon

2000 Honda Odyssey Overall (Highway plus City) Gas Mileage

Control

Experiment

5565

% increase

clean

experimental

0

5

10

15

20

25

30

Mile

s/G

allo

n or

% m

pg

incr

ease

Miles per Hour

Average Gas Mileages for 1997 Dodge Dakota% increasecleanexperimental

Class-8 Tractor-Trailer Truck Fuel/Emissions ReductionDrag Reduction on Connected

Bluff Bodies

Measured Drag of Truck Model: Effect of FCSD (Deturbulator Treatment)

0

0.1

0.2

0.3

0.4

0.5

treatment type

Coef

ficie

nt o

f Dra

g (C

d)

CLEANFCSD-1FCSD-2FCSD-3FCSD-4

l

Cont r ol Ov er a l l mpg

Det ur bula t or Ove r a l l mpg

Cont r ol Highway mpg

Det ur bula t or Highwaympg

5.8

5.9

6

6 .1

6 .2

6 .3

6 .4

6 .5

Fuel Mileage for Freightliner Freight Truck with Trailer

Contr ol Over al l mpg

Detur bulator Over al l mpg

Contr ol Highway mpg

Detur bulator Highway mpg

Operational Class-8 Truck Road Test

5.8

5.9

6

6.1

6.2

6.3

6.4

6.5

Untreated Deturb Cab sidestop Trailer top

Deturb Cab sidestop Trailer

sides,top, bottom

Ove

rall

Mile

s/G

allo

n

Concluding Remarks

DETURBULATOR: Separation without Turbulent Mixingmakes Wake more Stagnant (Tractor Cab Wake)

MEAN VELOCITIES 1/3-Height BEHIND CAB MODEL

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

U-mean/U-infinity

Y/h-

cab

Mean Vel UntreatedMean Vel 0.5 mm s DeturbMean Vel 2 mm s Deturb

Mean x-y plane Velocities h/2 Behind Model Tractor-Trailer Truck of height h = 70 mm

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 0.2 0.4 0.6 0.8 1 1.2

Mean Velocities (u/u-upstream)

Dis

tanc

e Fr

om R

oad

Surf

ace

(h/h

-trai

ler)

Vmean treated Cab+Trail

Vmean UnTreated

Deturbulator Vs. Other Drag Reduction Methods

% Drag Reduction

0% 5% 10% 15% 20% 25% 30% 35% 40%

Deturb Dodge Dakota

Deturb 2000 Odyssey

2006 Honda Odyssey

Tailcone Truck Drag

Trailer Strakes Truck Drag

Under Chasis BlowTruck Drag

Deturb Class-8 truck

Deturb Class-8 truck

% Drag Reduction

ACKNOWLEDGEMENTS

National Science Foundation SBIR Grant: IIP0638157

QUESTIONS ?