coefficient of drag vs reynolds number – clean wing - sinhatech
TRANSCRIPT
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
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
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
FLOW WITHOUT TREATMENT
FLOW WITH TREATMENT
Turbulent Eddies
Vehicle or Bluff Body
Deturbulator
Stagnant WakeFor Virtual Streamlining
DETURBULATOR DRAG REDUCTION ON A VEHICLE
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
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
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
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