Inventor: GUIGE JACQUES / DAVIDSON RON
A drag reducing device for use on transport vehicles includes
a delta wing having variable height and irregularly spaced
undulations on an upper surface of each side of the wing. A
length of each side of the delta wing is different than the
length of the other wing side thereof.
BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The invention relates generally to the field of drag
reducing devices used with transport vehicles. More
particularly the invention relates to specialized shapes for
such devices that have greater efficiency in drag reduction.
 2. Background Art
 It is well understood in the art of physics of fluid
flow control over surfaces that an adverse pressure gradient
exists when low static and high static pressure regions
interact. As a fluid boundary layer flows across a flow
control surface there tends to be a blocking boundary formed
which can block the flow and even reverse the motion of fluid
flow locally. This may in turn separate the fluid with a
resulting rise in drag. It is again well understood in the art
that generating stream-wise vortices, generally using
so-called vortex generators, can create conditions of mixing
which may prevent a separation of the flow. There are many
types of vortex generators primarily embodied as devices with
vanes that protrude above the boundary layer, such as
described by Stephens in U.S. Pat. No. 2,800,291.
Limitations of the device described in the '291 patent include
that the boundary is regulated with increased conditions of
drag. Other approaches have been discussed in Kluethe, U.S.
Pat. Nos. 3,578,264 and 3,741,285 primarily exhibiting
internal boundary vortices when a fluid encounters and is made
to flow over a concave surface; in effect forcing the boundary
layer between adjacent wings to transfer a vortex into the
boundary layer and cause mixing. The results of such devices
while of academic merit have inefficiencies due to out of
scale issues leading to excess drag.
 Wheeler, in U.S. Pat. No. 4,455,045 describes in detail
that a strong vortex is formed along the leading edges of
delta wings at high angles of attack. In the disclosed device
in the '045 patent, submerged channels are molded to have a
nominally triangular plan form shape permanently formed onto a
flow surface. The channels as described in the '045 patent
have sharp upper edges for effective vortex formation,
divergent sidewalls essentially normal to the flow-control
surface, and floor contours arranged to immediately conduct
the stream-wise vortices below the level of the local flow
control surface. Basically, the principles described in the
'045 patent are that placing a series of submerged channels to
be nested together in a properly overlapping manner creates a
stream-wise cascade, thereby reducing the drag and at the same
time controlling the boundary flow.
 There exists a need for improved drag reducing devices
for use on long transport vehicles.
SUMMARY OF THE INVENTION
 A drag reducing device for use on transport vehicles
according to one aspect of the invention includes a delta wing
having variable height and irregularly spaced undulations on
an upper surface of each side of the wing. A length of each
side of the delta wing is different than the length of the
other wing side thereof.
 Other aspects and advantages of the invention will be
apparent from the following description and the appended
BRIEF DESCRIPTION OF THE DRAWINGS
 FIG. 1A shows an example implementation of a drag
reducing device according to the invention.
 FIG. 1B shows another implementation of a
drag reducing device according to the invention.
 FIG. 2 shows simulated air flow over a
prior art drag reduction device having a smooth surface.
 FIG. 3 shows simulated air flow over an
example drag reduction device according to the invention.
 FIG. 2A shows simulated air flow over an
example drag reduction device according to the invention to
show micro eddies formed by the irregular surface.
 FIG. 3A shows a direct comparison of air
flow over a smooth surface drag reduction device and a drag
reduction device according to the invention.
 FIG. 4 shows an example installation of
drag reducing devices according to the invention on a
tractor of a tractor trailer combination truck.
 FIGS. 5 and 6 show, respectively, line
arrays of drag reducing devices according to the invention
disposed on the top and side(s) of a railroad car.
 The present invention augments the
effectiveness of vortex generator drag reducing devices known
in the art by including a plurality of random sized, but
critically varying vortices to be steadily generated
downstream of the device. This function is performed by
substituting the sharp, smooth, linear leading edges on delta
wings or submerged channel wall edges as described in the
Wheeler '045 patent referred to in the Background section
herein with randomly undulating leading structural edge
members having irregularly spaced, multi-wavelength in depth,
cascading forms on the forward edge of a delta wing. The
overall lengths of the leading edges may be different from
each other, and in practice are elongated by several meters to
allow for continuous stream-wise varying sized vortices to
effectively be maintained even when in adverse changing
pressure gradients such as observed under windy conditions.
Using the delta wing edge design of the invention, drag is
reduced under varying conditions of pressure such as observed
when wind gusts occur across long, streamlined transport
trucks and trains. With vortex generator drag reducing devices
known in the art prior to the present invention, the resulting
flow of air as moved by these prior art add on devices cannot
fill the massive wake behind a moving linear vehicle body.
This typically results in very minor benefits in terms of the
energy saved when using such drag reduction vortex generating
devices. In the present invention the randomized, undulating
morphology of the delta wings and their individual uneven
length, enable an order of magnitude increase in the linear
lengths of the sides of the delta wings for certain
applications. That is, a drag reduction device according to
the invention may be made in sizes having wing lengths as
large as the meter scale, whereas prior art drag reduction
devices using the delta wing shape are generally limited to
centimetre scale sizes. The increase in possible useful size
of a drag reduction device according to the invention can
substantially boost the movement of air flow, with more
effective infilling of the wake with continuous regeneration
of vortices as previously formed eddies dissipate. A drag
reduction device according to the invention may provide
effective drag reduction on larger transport vehicles than is
possible using prior art configurations. As an example of a
typical embodiment of the invention in larger sizes, drag
reducing devices may be placed as a linear array of delta
wings along the sides of a train roof and/or along the sides
of a railroad car (FIGS. 5 and 6). As another example of an
embodiment, smaller versions of the delta wings according to
the invention may be used on the air deflector wing and/or on
the sides of a tractor in a tractor trailer truck combination.
 The present invention provides a structure for a drag
reducing device which augments the reduction of energy as
would be required by such slender vehicles as trains and long
transport trucks as they move air by providing a novel means
of effectively redistributing flow in the areas of adverse
pressure gradients as caused by air flow and windy conditions.
The present invention results in measurable reduction of
energy requirements which directly translate into reduced fuel
consumption for very linear long and large moving platforms.
In addition, as a result of placing the invention on the roofs
of transport truck trailers, an increased level of control
would be noted when travelling in high winds, greatly reducing
the events of tipping.
 Referring to FIG. 1A, a first example of a drag
reducing device according to the invention is shown in oblique
view. The drag reducing device 10 is generally shaped as a
delta wing or “wishbone’ having a first side 14 and a second
side 16 with respect to a center of the drag reducing device
10. A surface of the drag reducing device 10 may have a
relatively high angle of attack with respect to the direction
of motion of the vehicle to which the device 10 is placed on
the roof thereof. An example angle of attack may be up to
about sixty degrees. The leading edge of each side 14, 16
includes randomly variable height, depth and spacing
undulations 12. The length of each side 14, 16 may be
different than the length of the other side 16, 14 of the drag
reducing device 10.
 Another example of a drag reducing device according to
the invention is shown in
 FIG. 1B. The example in FIG. 1B may include all the
same features as the example shown in FIG. 1A, only with
different values of the parameters described with reference to
FIG. 1A. A possible result of making a drag reducing device as
explained above is that the device 10 may generate random size
and spacing, counter rotating vortices in the space behind the
 FIG. 2 shows a simulation of air flow across the
surface of a prior art delta wing drag reduction device 10A.
The air flow 40 can be observed generating a single, large
vortex in the air flow behind the drag reduction device 40.
Such vortex can result in decreased drag reduction, that is,
 FIG. 3 shows a simulation of air flow across the
surface of a delta wing drag reduction device according to the
present invention. Air flow 42 over the drag reduction device
10 can be observed as distinctly lacking the single, large
vortex in the air flow behind the drag reduction device 10,
rather, smaller, spaced apart counter rotating vortices are
generated, further reducing resistance to air flow as
contrasted with the device shown in FIG. 2. The foregoing
simulations included capturing at the resultant fluid motion
through simulated smoke lines over typical smooth edge (FIG.
2) and randomized undulating edges (FIG. 3) computed by
solving the Navier-Stokes equations at high definition.
 FIG. 2A shows a simulation of air flow over the surface
of a drag reduction device 10 according to the invention.
Micro eddies in the air flow can be observed above the upper
surface of the drag reduction device 10. A direct comparison
of the air flow over a prior art drag reduction device 10A and
a drag reduction device according to the invention is shown in
FIG. 3A. It can be observed in the figure that the air flow
over the prior art drag reduction device 10A lacks the micro
eddies of the air flow over the drag reduction device 10 of
 FIG. 4 shows an example installation of drag reducing
devices 10 on an air deflector wing 20 and the side 22 of a
tractor 30 of a tractor trailer combination truck. Similar
mounting may be used in other types of transport vehicles.
 FIGS. 5 and 6 show, respectively, line arrays as
described above, of drag reduction devices 10 according to the
invention disposed on the top (FIG. 5) and one side (FIG. 6)
of a railroad car 40. The railroad car 40 can be any or all
cars in a train including the locomotive(s). The side view in
FIG. 6 is applicable to both sides of any railroad car 40.
Direction of motion of the railroad car 40 is indicated by the
arrow at the bottom of FIG. 6.
 A drag reduction device according to the invention may
reduce air flow caused drag on transport vehicles, resulting
in improved efficiency of operation and reduced fuel