Improving Automotive Fuel Efficiency with Deturbulator Tape
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2007-01-3458
Improving Automotive Fuel Efficiency with Deturbulator Tape
Sumon K. Sinha and Sumontro L. Sinha
Sinhatech
Copyright © 2007 SAE International
ABSTRACT constant speed on highways, even a modest reduction
in CD can have a measurable impact on fuel
A new method for reducing aerodynamic drag of trucks consumption. This is also true for many light trucks and
and vans has been developed. It uses Deturbulator tape sport-utility-vehicles.
to transform separated turbulent wakes into stagnant
virtually solid streamlining extensions attached to the As per the current mandate of the U.S. Federal
vehicle. Constrained mode flow-induced surface government, 8.1% increase in miles per gallon for SUVs
oscillations of the 100-Pm thick, passive, flexible-surface and light trucks is called for the 2008-2011 model years.
Deturbulator tape attenuates turbulent mixing by driving The U.S. DOE has also undertaken a multi-year study
the turbulence to a pre-selected high frequency in the involving the major truck manufacturers in the U.S. to
dissipation range. Wind tunnel tests indicated 80% drag reduce the aerodynamic drag of large tractor trailers and
reduction. Road tests on a minivan and pickup truck semi-trailers by 20% in order to improve fuel efficiency
showed 15-20% increased highway fuel economy due by about 10% through practical techniques and devices
to reduced drag. 6% reduction in overall fuel which can be implemented immediately (Clarke, 2006).
consumption was obtained for an operational Class-8 These recognize the fact that aggressive streamlining of
tractor-semitrailer. trucks, trailers and SUVs is not possible to preserve the
utility of these vehicles. Manufacturers typically
INTRODUCTION streamline vehicle shapes as far as possible. Spoilers
and wind deflectors are then added to make the vehicle
Cars and trucks use about 2/3 of the oil imported by the appear more streamlined than its basic geometry
U.S. They are also the largest users of petroleum suggests. Additional reductions in aerodynamic drag
products worldwide and the largest non-stationary require methods for reducing CD which do not impose
source of greenhouse gases across the world. Simple further alterations to a vehicle’s shape or form.
and effective means of motor vehicle fuel economy
increase are therefore extremely important for the Form or pressure drag resulting from large separated
continued viability of our planet. wakes is the primary contributor towards a vehicle’s CD.
Hence, most add-on aerodynamic drag reduction
As per the U.S. Federal Government’s website methods use strakes and active/passive vortex
www.fueleconomy.gov (posted by DOE and EPA), only generation to reduce the size of the wake. These
12.6% of the energy available in the gasoline fuel is methods enhance mixing in the shear layer separating
typically available at the drive wheels of a vehicle. the wake from the freestream. Drag is reduced as the
Aerodynamic losses reduce the 12.6% energy available mean momentum deficit in the wake is lowered.
at the drive wheels by 21% (or 2.6% of the energy in the However, the power lost through increased turbulence
gasoline) at speeds around 70 km/h (45-mph; i.e., FTP75 arising from vigorous mixing across the shear layer
EPA-City driving mode), while inertia followed by braking ultimately limits the reduction in drag.
consumes 46% (www.fueleconomy.gov). 33% is lost due
to rolling resistance. Aerodynamic drag accounts for The present work focused on developing a simple to
about 50% of the total energy delivered to the wheels of apply method that does not have this shortcoming. The
a vehicle traveling at a constant speed of about 88 km/h method relies on reducing mixing across the shear layer
(55 mph) on a level road. This increases to about 75% at by using a patent pending microstructured flexible-
typical highway speeds of 110 km/h (70 mph) and is surface composite tape known as the “Deturbulator” or
65% even for loaded class-8 tractor trailer trucks. This is FCSD (Sinha, 2003, Sinha and Sinha, 2006). Turbulent
because the drag force FD is proportional to CD.V2, eddy viscosity is responsible for transferring motion
where the coefficient of drag CD remains approximately efficiently from the freestream flow to the large-scale
constant as the velocity of the air relative to the vehicle vortices in a separated wake. Attenuating mixing
(V) increases. For vehicles, such as long distance suppresses this mechanism, transforming the wake to a
tractor-trailer trucks which spend most time traveling at virtual solid extension of the vehicle body. If this
transformed wake resembles a tapering boat tail (Fig 1)the air sees the vehicle as a streamlined shape. frequency band (Sinha and Ravande, 2006b). The
Consequently the drag should reduce. resulting customized turbulent aerodynamic boundary
layer, which remains marginally separated, displays
superior resistance to separation as compared to a
Turbulent Eddies
FLOW WITHOUT TREATMENT laminar boundary layer while exhibiting lower skin-
friction induced losses compared to either “naturally
occurring” or artificially tripped turbulent boundary
layers. This results in a reduction in wing profile drag.
For reducing form drag in the separated wake, the
FCSD is typically attached to a portion of the surface of
Vehicle or Bluff
FLOW WITH TREATMENT Body Stagnant Wake
For Virtual
the vehicle where attached flow exists locally (Fig 1).
Deturbulator
Streamlining The flow-FCSD interaction helps reduce turbulent mixing
in the separated shear layers. This slows down the air in
the wake by taking away the energy production
mechanism driving the large eddies. Since these eddies
serve as a conduit for dissipating flow kinetic energy
Fig 1. Drag Reduction from Deturbulating Wake through turbulence, slowing those conserves energy in
the airflow around the vehicle.
The method portrayed here can be seen as an extension
of using spoilers and wind deflectors since they all rely
on virtual shaping. The Deturbulator offers additional
control on turbulent mixing, thereby extending the
degree of morphing possible. Additionally, the
Deturbulator has already demonstrated its efficacy in
improving the lift to drag ratio of sailplane wings by
Fig 3. Schematic of the SINHA Active Flexible Wall
about 20% (Sinha and Ravande, 2006a,b) and this has
recently been verified through independent flight test
evaluations by Johnson (2007).
The current passive FCSD concept evolved by
simplifying an earlier electrically powered Active Flexible
The Deturbulator and its working principles are
Wall (AFW) boundary layer control concept (Fig 3)
described next. This is followed by preliminary wind-
patented by Sumon K. Sinha in 1999. The AFW can
tunnel tests and on-road tests on vehicles demonstrating
sense flow separation (sensor mode) and use the
the efficacy and possibilities of this technique.
sensed signal frequency to electrically drive flexural
oscillations (actuator mode) to control flow separation. It
Boundary Layer High Strips or Ridges has undergone extensive low-speed (M < 0.15) wind
Flow
tunnel testing at the University of Mississippi (Sinha,
Fundamental Flexural
Flexible Membrane a 6Pm thick 2001a,b) primarily for controlling flow separation and
Vibration Mode of Membrane
Shown (Amplitude 0.1 Pm) dynamic stall (Mangla and Sinha, 2004). Unlike earlier
compliant and driven flexible wall devices which were
typically tested on flat-plate zero pressure gradient flow,
50-100Pm
Wing or other
aerodynamic body
S
the AFW and FCSD have been found to work only in
Low Strips as needed to
Substrate Base glued to boundary flows exposed to a streamwise varying
aerodynamic surface
fix flexural damping pressure gradient.
10-50Pm thick Air-Gap
(Membrane Substrate)
To understand the flow-membrane interaction
mechanism the 2-D streamwise u-momentum equation
Fig 2. Schematic of the SINHA Flexible Composite Surface of the flow at the mean equilibrium position (y = 0) of the
surface membrane of the FCSD (or AFW) is considered
first:
THE SINHA DETURBULATOR
v(wu/wy)y=0= (1/U)(wp/wx) + (P/U)(w2u/wy2)y=0
(1)
The SINHA-FCSD is a thin (under 100 Pm) passive (i.e.,
non-powered) device (Fig 2), consisting of a flexible
The streamwise x-component of velocity “u” of the
membrane (typically 30-300 mm wide) stretched across
vibrating membrane (or the velocity of the fluid at the
an array of strips on a substrate, running in the spanwise
points of contact with the membrane) has been assumed
direction. The back of the substrate is bonded to the
to be negligible, while the wall-normal y-component of
surfaces of the wing or stabilizer or a road vehicle. The
velocity “v” of the fluid next to the membrane is clearly
membrane of the FCSD undergoes extremely small
non-zero due to the flexural motion of the membrane.
(under 0.1-Pm amplitude) flow-induced flexural Key to flow-membrane interaction is the realization that
oscillations, which can neutralize turbulent fluctuations in the wall-normal gradient of the streamwise velocity at
the near-wall boundary layer airflow at all but a narrowthe wall, (wu/wy)y=0, can be extremely large at certain x- precisely matched to the phases of turbulent sweeps
locations. At such locations, even a small oscillation and bursts. This is not required here. Since the
velocity (v 0). The FCSD
also re-energizes oscillations at the control frequency:
f = U/s (1-b)
1 2
Fig 4b. Oil Flow Visualization on Top Surface of a
Freestream Flow
sailplane wing at the 53-inch Span Station (1)
untreated; (2) with Deturbulator shown. (Sinha
Boundary Layer 200 )
Large Small Vortices Small
Vortex created from vortices
Rolling small-
Small
Vortices quickly Fig 4 shows a photograph of a 80-µm thick Deturbulator
wavelength
deflection
Drain Large
Vortex
dissipated
by viscosity
tape mounted on the surface of a 1-m chord sailplane
wing with the surface airflow visualized using oil (Sinha
2007). The oil flow patterns clearly show a modification
of the laminar separation bubble. In this application,
Flexible Skin of Ridges on
Deturbulator Deturbulator
skin-friction drag is lowered (Sinha and Ravande,
2006a,b) by keeping the boundary layer marginally
RED: Large
ANALOGY: Perturbation of large vortex creates separated across the chord (Fig 4b(2)). Apart from
Wavelength deflection
small vortices similar to a tire rolling over rumble
BLUE: Small
Wavelength Deflection
strips on a highway to warn approaching stop. maintaining the correct clearances between the
membrane and ridges on the substrate, locating the
Deturbulator is also critical. In general, the condition of
wp/wx = 0 needs to be relaxed somewhat to account for
Fig 4a. Sketch showing eddy breakdown by Deturbulator boundary layer blockage due to the (~100 µm) thickness
of the Deturbulator tape.
This corresponds to the membrane segments oscillating
in phase with a wave-like disturbance having a
wavelength s and traveling with the freestream. Larger
eddies which energize turbulent fluctuations, impart
longer wavelength traveling waves. These waves are
perturbed by the ridges and subsequently broken down
Cord to
into smaller eddies corresponding to frequency f of measure
equation (1-b). The aforementioned process results in drag force
sustaining fluctuations corresponding to f. Since f is
closer to the dissipation range, the stepwise breakdown
of large-scale eddies through vortex stretching and
bending is eliminated. This attenuates turbulent mixing
without having to damp turbulent fluctuations within the
body or substrate of the flexible wall. This is the most
Fig 5. Cadillac Escalade model in Sinhatech
important difference between the Deturbulator and Wind-Tunnel
the much investigated “compliant wall”. Because
internal damping within the flexible structure is not
needed, the effect (i.e., Deturbulation) can be sustained
over a wide range of flow velocities. In a traditional
compliant wall, the frequencies would need to beMeasured Coeffcient of Drag on Model Car
(Re = 0.4 million)
0.6
0.5
De-turbulator Rear Top
Coefficient of Drag(CD)
0.4 Tape Top Front De-turbulator Top Rear
Tape Top Front
Clean Car
0.3
Fig 7. 2000-Honda Odyssey minivan with
0.2 Deturbulator tape strips
0.1
0 Road Tests:
1 2 3 4 5 6
Test Number
Even though the small-scale wind tunnel tests were
Fig 6. Measured Drag on Wind Tunnel Model of Fig 5 successful it was unclear whether the Deturbulator
with different Deturbulator configurations would work on a full scale vehicle. A 2000-Honda
Odyssey minivan, which has a shape similar to the
Cadillac Escalade was treated with Deturbulator tape as
RESULTS shown in Fig 7. Prior to applying the tape, surface oil
flow visualization was performed to determine regions of
Preliminary Wind Tunnel Drag Measurements: separated flow. Locating the Deturbulator close to these
regions was based on the optimum locations of the
Initial tests were conducted in the Sinhatech low-speed FCSD on the wind-tunnel model.
wind tunnel (www.sinhatech.com) on a 1/24th scale
Cadillac Escalade (Fig 5). The Eiffel-type Sinhatech The Odyssey normally yielded about 23.5 miles per
wind tunnel has a 12-inches (305-mm) high, 9-inches gallon (9.98 km/liter) for combined city-highway driving
(229-mm) wide, 14-inches (356-mm) long test section around Oxford, Mississippi, during the winter months
and a 4-ft (1.22-m) high 3-ft (0.91-m) wide exponential with 89-octane gasoline and 26 miles per gallon (11.05
profiled bell mouth entrance and a variable speed km/liter) on the highway at speeds between 55-75 mph
suction fan. At the nominal 30-m/s test airspeed, (88-120 km/h). Under the same driving conditions the
turbulence (u-rms/u-mean) in the test section is about FCSD treated Odyssey yielded about 26 miles per
0.8% without screens. The model was placed on free gallon (11.05 km/liter) in combined city/highway driving
rolling wheels on the test section floor and held against and 31 mpg on the highway (Fig 8). These values were
the flow with a cord. The measured tension in the cord obtained by averaging data from several trips and were
provided a direct measure of the drag force and showed found to have a 93% statistical significance level. The
the possibility of 80% drag reduction with a FCSD (Fig gas tank was topped before and after each trip. The trip
6). The best configuration consisted of a 3-mm wide distance and type (i.e., highway or city) were also noted
FCSD on the rear spoiler of the model. since reducing aerodynamic drag is not expected to
improve the city mileage. The measurements revealed
It is interesting to note that at these low Reynolds that city mileage remained essentially unchanged at 18
numbers based on length of the vehicle, a plain duct miles per gallon (7.65 km/liter) even after the FCSD was
tape on the top front reduced drag by about 40%. The applied.
tape encourages the flow to separate, reducing skin
friction (Sinha 2005) by avoiding “surface roughness In order to visually confirm that aerodynamic drag was
like” features (e.g., edges of the sunroof). However, the indeed being reduced by the Deturbulator, the test
separated zone eventually becomes turbulent and Honda Odyssey was coasted down against an identical
increases flow losses. Adding the Deturbulator on the vehicle on a stretch of level 4-lane highway. The gross
rear spoiler reduces these losses by controlling weights of both vehicles with occupants and fuel were
turbulence. Drag is minimized by avoiding blockage of brought within ±5 lbs (mass within ±2.2 kg) and identical
the boundary layer on the top front of the vehicle by tire pressures were applied. The vehicles were brought
removing the plain duct tape. up to 70 mph (110 km/h) in parallel lanes and shifted to
neutral simultaneously. The vehicle with lower
aerodynamic drag was expected to advance during the
coast down period. Without the Deturbulator both
vehicles remained within a car-length while slowing
down to 40 mph (64 km/h). With the Deturbulator the
treated vehicle advanced to about two car lengths,
verifying aerodynamic drag reduction. Even though this
method did not yield accurate quantitative
measurements of fuel economy improvement, it wasfound capable of detecting the effect of small changes in Average Gas Mileages for 1997 Dodge Dakota
treatment. % increase
clean
30 experimental
Miles/Gallon or % mpg
25
20
2000 Honda Odyssey Average Highway
increase
Gas Mileage 15
10
32 experimental
31 5 clean
Control
Miles Per Gallon
30
0
29 % increase
28 Experiment 55
27
65
Miles per Ho
26 ur
25
Experiment
24
23
Fig 9. Measured Fuel Economy of Untreated (clean)
Control
and Deturbulator Treated (experimental) 1997
Dodge Dakota Pickup Truck
2000 Honda Odyssey Overall (Highway
plus City) Gas Mileage Fig 9 shows the miles per gallon before and after
applying the Deturbulator at 55 and 65 miles per hour
26
(88 and 104 km/h). For these tests a single 50-mm wide
Control
25.5 Deturbulator tape was applied on top of the cab guided
Miles per Gallon
25
Experiment by surface oil-flow visualization. The fuel economy
24.5
24 improved 15% at 55 miles per hour and 16% at 65 miles
23.5 Experiment per hour (Fig 9). The data have statistical significance
23
22.5
levels of 99.9% and 96.9% respectively. Actual driving at
22 Control a variety of speeds indicated an increase from 19.9 to
Overall Average
21.8 miles per gallon (8.5 to 9.3 km/liter), or 9.5%
increase due to the Deturbulator. This is comparable to
the 10.6% increase in average city/highway fuel
economy of the Honda Odyssey minivan.
Fig 8. Measured Fuel Economy of the Honda
Odyssey for Highway (top) and Combined
(bottom) driving for Untreated (Control) and
Wind Tunnel Measurements on Tractor Trailer Trucks:
Deturbulator Treated (Experiment) conditions.
Since long distance tractor-trailer semi trucks spend
more time driving at constant high speeds on the
Tests on a Light Truck highway, they can benefit most from the Deturbulator.
However, the flow over such trucks is more intricate and
Light (pickup) trucks are less streamlined compared to multiple separated zones exist. Hence the effect of the
vans. To determine the effect of treating such vehicles Deturbulator on the Tractor as well as the Tractor-Trailer
with Deturbulator tape, the subsequent tests were combination needed to be understood.
conducted on a 1997 Dodge Dakota pickup truck. This
particular truck was equipped with a fuel economy meter Initial tests were carried out on a 1/48 scale streamlined
that provided instantaneous and average miles per Freightliner Columbia truck with a box trailer. Based on
gallon for each trip. The truck was repeatedly run over a the optimum locations of the FCSD on the model SUV,
level section of highway at a constant speed while the Deturbulator tape was applied on the top rear end of the
instantaneous miles per gallon were recorded at regular tractor cab. A calibrated single-wire hot-wire probe was
intervals. The average of these instantaneous readings used to determine the mean velocities (u-mean) as well
over several runs back and forth (to average effects of as the rms fluctuations (u-rms) behind the vehicle. The
road slope and wind) provided the best estimate of miles results (Fig 10) indicate a reduction in both u-mean and
per gallon at the selected speed. Since the fuel economy u-rms due to Deturbulator treatment behind the cab.
meter was not calibrated, an undetermined bias existed. This also proves that the Deturbulator makes the
However, a comparison of miles per gallon at the same separated wake more stagnant. Prior to this the only
speed before and after treatment is not affected by the anecdotal evidence of wake stagnation was a significant
bias. reduction in splattering of road grime on the rear window
of the Deturbulator treated minivan.MEAN VELOCITIES 1/3-Height BEHIND CAB MODEL
Measured Drag of Truck Model: Effect of FCSD (Deturbulator
1.6 Treatment)
1.4 0.5
Coefficient of Drag (Cd)
0.4 CLEAN
1.2
FCSD-1
0.3
1
FCSD-2
0.2
FCSD-3
Y/h-cab
0.8 0.1 FCSD-4
0
0.6
treatment type
Mean Vel Untreated
0.4
Mean Vel 2 mm s Deturb
0.2
0 Fig 11. Measured Drag on Tractor-Trailer Semi Truck
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
Model in Sinhatech Wind Tunnel for different
U-mean/U-infinity
Deturbulator Treatments
RMS VELOCITY FLUCTUATIONS h/3 BEHIND CAB MODEL
1.6
Mean x-y plane Velocities h/2 Behind Model Tractor-Trailer
1.4 Rms Vel Untreated Truck of height h = 70 mm
rms Vel 2-mm s Deturb
1.2 1.4
Distance From Road Surface (h/h-trailer)
1 1.2
Y/h-cab
0.8 1
0.6 0.8
0.4 0.6
Vmean treated Cab+Trail
0.2 0.4
Vmean UnTreated
0 0.2
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14
0
0 0.2 0.4 0.6 0.8 1 1.2
Mean Velocities (u/u-upstream)
Fig 10. Measured Velocities behind Model of Truck
(Tractor) Cab with and without Deturbulator
treatment. Mean Velocities (top) and RMS-
RMS Velocity Fluctuations Behind Tractor-Trailer Model
fluctuating (bottom)
1.4
1.2
Drag force measurements on the complete tractor-trailer
Height From Floor (h/height-trailer)
model were attempted next similar to measurements on 1
the Cadillac Escalade. However, the rolling friction on 0.8
the 18 smaller diameter tires and wheels was found to
be significant. Hence the actual aerodynamic drag force 0.6
is greater than the measured values. Fig 11 shows the 0.4
V-rms UnTreated
CD values deduced from forces measured on the 1/48 Vrms Treated Cab+Trailer
0.2
scale model at an air speed of 30 m/s. Various FCSD
treatments were attempted on the trailer and tractor. The 0
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2
best treatment indicated 25% drag reduction. Fig 12 RMS Velocity (u-rms/u-upstream)
shows hot-wire measurements of u-mean and u-rms
behind the trailer with and without the aforementioned
“best” Deturbulator treatment. Compared to the wake Fig 12. Measured Mean (top) and RMS-Fluctuating
Velocities (bottom) behind Tractor Trailer Model.
behind the cab (Fig 10), the velocity profiles indicate
more complicated interaction of shear layers. This is
because it includes downstream signatures of wakes
from the cab, leading edge of the trailer and the trailing Preliminary operational fuel efficiency measurements
edge of the trailer. were conducted on a Freightliner Columbia tractor
matched with the same Wabash 53-ft box trailer
operating with load on the same route everyday, with the
same driver. Deturbulator strips were then applied to the
sides and top of the cab and on top of the trailer, and
additional data acquired over a month. The following
month, additional Deturbulator tape was applied to the
sides and bottom of the trailer. Fig 13 shows trends in
mileage increase with treatment. A Type IV fuel
economy test is planned after the Deturbulator
configuration is finalized. The actual Deturbulator layoutis somewhat different than on the wind-tunnel model regular high-speed driving conditions under a variety of
because flow separation and reattachment points are weather conditions for about six months. Ultimately the
Reynolds number dependent. Also, at certain locations generic edge sealing tape degraded. A tape designed
the Deturbulators may be prone to damage frequently for longer exposure to weather can easily solve this
and therefore not practical from an operational problem and a life of more than a year is possible and
viewpoint. For example, the deturbulators on top of the ongoing tests on the operational Class-8 truck are being
cab and trailer on our test truck were found damaged used to validate this.
due to frequent impact with tree branches and the
results of Fig 14 are with these damages. The damaged More importantly, the prototype Deturbulator used for
Deturbulators have been removed and new data is the work reported here was prone to temporary
currently being acquired without these. degradation due to moisture. This is because the air gap
between the membrane and the ridged substrate needs
to be vented to the local airflow. Otherwise, a reduction
Operational Class-8 Truck Road Test
in local static pressure due to the external airflow causes
6.5 the membrane to “balloon” (i.e. be pushed out). Once
6.4 the membrane loses contact with the ridges it begins to
Overall Miles/Gallon
6.3
undergo all possible modes of oscillation imposed by the
6.2
flow and its selective frequency filtering behavior is lost.
However, moisture from rain and surface condensation
6.1
also wicks through the vents into the air gap. This makes
6
the membrane more rigid and temporarily destroys its
5.9
performance until the moisture evaporates. This has
5.8
Untreated Deturb Cab sides top Deturb Cab sides top
been a cause of great concern for using the Deturbulator
Trailer top Trailer sides,top, on aircraft wings (www.sinhatech.com) where a more
bottom
consistent performance is required. On a truck or van
the only penalty is a temporary reduction of the fuel
Fig 13. Preliminary Road Test Data on operational
efficiency down to the untreated (base) state. The
Class-8 Tractor Semi-Trailer Truck with two
Deturbulator treatments. Cab and trailer Top average fuel economy still surpasses the untreated
Deturbulators damaged from tree branch impact. value as validated through road tests. This also
necessitates acquiring long-term data for meaningful
estimates of fuel economy enhancement.
Comparison with other methods of drag reduction:
In order to deter moisture from entering the air gap, a
second generation Deturbulator tape has been
Assuming aerodynamic drag to be 50% of the total drag
developed incorporating a hydrophobic substrate and
on a road vehicle, a drag reduction of 8-40% is needed
membrane and moisture excluding micro-porous vents.
for 4-20% improvement in measured fuel economy. Test
Preliminary tests on the Honda Odyssey have revealed
results on the minivan, pickup truck and Class-8 tractor-
that it recovers within a few seconds (as opposed to
semi-trailer truck are compared to other methods which
hours) after being exposed to heavy rain.
try to reduce the size of the wake (Fig 14). The data of
Fig 13 indicate that class-8 trucks could experience 8%
and 12% reductions in aerodynamic drag, which are CONCLUSIONS
comparable to using strakes and tailcones but lower
than underchasis blowing. If the effect of engine idling is A thin (100µm thick) microstructured flexible surface
included, the reductions due to Deturbulator use will be Deturbulator tape developed for drag reduction on
more. Significantly higher reductions are obtained if the streamlined wings has been successfully used to reduce
Deturbulator is applied to a more streamlined shape, aerodynamic drag of marginally streamlined road
such as a minivan. Hence a synergism exists if the size vehicles.
of the wake is reduced by partial streamlining and the
Deturbulator makes the wake more stagnant. The Deturbulator transforms the turbulent separated
Interestingly, Deturbulator enhancement on the minivan wake behind a vehicle into a region of stagnant air,
and pickup truck already exceeds the 8.1% increase in making the vehicle appear streamlined to the flow.
miles per gallon called for 2008-2011 model years in the
new Federal standards for SUVs and light trucks. The Deturbulator reduced the drag of a model SUV by
80% and that of a model tractor trailer truck by 25%.
Effect of exposure to the external environment:
A single strip of Deturbulator tape increased the fuel
Is the seemingly delicate construction of the economy of a pickup truck by 15-16% at speeds
Deturbulator tape a deterrent to its regular use on the between 55-65 mph (88-104 km/h).
road? The installations on the Honda Odyssey and
Dodge Dakota, which have used generic tape for sealing Deturbulator tape strips on top of a minivan increased its
the edges of the Deturbulator tape, have endured average highway fuel economy by 19%.Preliminary in-operation road tests indicate the 4. Sinha, S.K.; “System for Efficient Control of Flow
possibility of 6% increase in overall fuel economy in a Separation using a Driven Flexible Wall,” U.S.
Deturbulator equipped Class-8 tractor semi-trailer truck. Patent No. 5,961,080, October 5,1999.
5. Sinha, S.K., 2001a “Flow Separation Control with
Based on $3.00/gallon gasoline and $3.00/gallon diesel Microflexural Wall Vibrations,” Journal of Aircraft,
fuel, and a 9.5% increase in combined city/highway fuel (Vol.38, No.3., May-June-2001) pp. 496-503.
economy an average Deturbulator-treated minivan 6. Sinha, S.K., 2001b “Exploring Separating Boundary
driving 15,000 miles/year would save $188/year and an Layers With a Flexible Wall Transducer Array,” Proc.
average Deturbulator treated tractor trailer truck driving ASME FEDSM-01, 2001 ASME Fluids Eng Summer
120,000 miles per year about $3000/year for a 5% Meet, New Orleans, LA, May 29-June 1, 2001.
increase in overall miles per gallon. 7. Sinha, S.K., “System and Method for Using a
Flexible Composite Surface for Pressure-Drop Free
Based on the current number of automobiles in the U.S. Heat Transfer Enhancement and Flow Drag
if every automobile used the Deturbulator, the nation
Reduction,” U.S. Patent Applications 10/355,346,
would save 14-billion gallons or $33 billion per year in
filed Jan 31, 2003.
imported gasoline, and 40 million metric tons of carbon
8. Sinha, S.K., “Optimizing Wing Lift to Drag Ratio
equivalent greenhouse gas emissions.
Enhancement with Flexible-Wall Turbulence
th
Control”, AIAA Paper No. 2007-4425, 25 . AIAA
% Drag Reduction
Applied Aerodynamics Conference, June 25-28,
Deturb Class-8 truck 2007, Miami, FL, U.S.A.
Deturb Class-8 truck
9. Sinha, S.K., and Ravande, S.V., “Sailplane
Under Chasis BlowTruck Drag
Trailer Strakes Truck Drag
Performance Improvement Using a Flexible
Tailcone Truck Drag Composite Surface Deturbulator,” AIAA Paper 2006-
2006 Honda Odyssey 0447, 44th AIAA Aerospace Sciences Meeting,
Deturb 2000 Odyssey
Reno, NV, Jan 9-12, 2006a.
Deturb Dodge Dakota
10. Sinha, S.K., and Ravande, S.V., “Drag Reduction of
0% 5% 10% 15% 20% 25% 30% 35% 40%
Natural Laminar Flow Airfoils with a Flexible Surface
% Drag Reduction
Deturbulator”, AIAA Paper 2006-3030, 3rd. AIAA
Flow Control Conference, San Francisco, CA, June
5-8, 2006b.
Fig 14. Comparison of Present Deturbulator Drag 11. Sinha, S.L., “Can Flow Control Devices Significantly
Reduction with more traditional methods Reduce Drag?” 2005 Intel Science and Engineering
(Underchasis Blowing, Strakes on Trailer, tailcone Fair, Project EN 074, Phoenix, Arizons, May 2005.
extension on trailer (source Clarke, 2006, Wood,
12. Sinha, S., and Sinha, S.K.,, “Method of Reducing
2003), streamlining 2006 model Odyssey by Honda
compared to 2000 model). % Reductions are with
Drag and Increasing Lift due to Flow of a Fluid over
respect to corresponding base untreated vehicles. Solid Objects”, International Patent Application No.:
PCT/US2006/011430, international Publication
Number WO 2006/105174 A2 with an International
Publication Date of 5 October 2006.
13. Wood M. Richard. “Simple and Low Cost
ACKNOWLEDGMENTS
Aerodynamic Reduction Devices for Tractor Trailer
Trucks”, Society of Automotive Engineers, Paper
The authors acknowledge support from The National
SAE 2003-01-0377, 2003.
Science Foundation for providing funded for part of this
work through SBIR Grant No. IIP-0638157. 14. www.fueleconomy.gov (U.S. DOE and EPA)
REFERENCES CONTACT
Dr. Sumon K. Sinha (sumon@sinhatech.com or
1. Clarke, R.M., “Truck Manufacturers Program to
sumonksinha@aol.com), President and founder of
Review Aerodynamic Drag” DOE Heavy Vehicle
Sinhatech (www.sinhatech.com) (Ph.D., M.S., B.Tech
Systems Optimization Merit Review, April 2006.
Mechanical Engineering) is the inventor of the Sinha-
2. Johnson, R.H., “A Flight Test Evaluation of the
Deturbulator and pioneered its use for wing lift/drag ratio
Sinha Wing Performance Enhancing increase.
Deturbulators,” SOARING and Motorgliding
Magazine, The Journal of the Soaring Society Mr. Sumontro L. Sinha, Research Assistant, Sinhatech,
of America Inc., Vol 71., No.5, May 2007, pp. (sinh008@msms.k12.ms.us or
35-41. sumontropsinha@aol.com) pioneered the use of the
3. Mangla, N.L., and Sinha, S.K., 2004, “Controlling Deturbulator for motor vehicles in 2006. He is also a
Dynamic Stall with an Active Flexible Wall” Amer. senior at the Mississippi School of Mathematics and
Soc of AIAA Paper AIAA-2004-2325; 2nd AIAA Flow Sciences, Columbus, MS.
Control Conf, Portland, June 28-July 1, 2004.ADDITIONAL SOURCES IS HIGHWAY GAS MILEAGE REALLY INCREASED?
t-Test: Two-Sample Assuming Unequal Variances
Control Experiment Increase
Variable 1 Variable 2
www.sinhatech.com.: Information regarding further HONDA AVERAGE HIGHWAY
Mean Miles/Gallon 26.40 31.37
in mpg
18.83%
developments and availability of the Deturbulator on Variance
Observations
0.399640501
4
14.85522397
3
Sinhatech’s website. Hypothesized Mean Difference
df
0
2
t Stat -2.211781909
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