PATENT ABSTRACT
An improved method and device for the reduction of aerodynamic drag and for improved performance of vehicles by increasing the pressure on the base of the trailing vehicle or vehicle component by controlling the boundary layer as it exists the vehicle trailing edge. The subject invention consists of a multiple panels located near the base area of a bluff base vehicle. The flow control objectives are accomplished by positioning minimally sized panels comprising the invention in close proximity to the side and top surfaces of the vehicle, where the leading edge of each panel is positioned in close proximity to the trailing edge of the vehicle. The side panels comprising the invention are laterally positioned outboard of the side surface of the vehicle. The top panels are vertically positioned above the top surface of the vehicle.

PATENT DESCRIPTION
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of U.S. Provisional Application No. 61/070,085, filed Mar. 21, 2008, the entire content of which is incorporated herein by reference. 
    
    
     ORIGIN OF THE INVENTION 
     The invention described herein was made by employees of the United States Government, and may be manufactured and used by or for the Government without payment of any royalties thereon or therefor. 
    
    
     FIELD OF INVENTION 
     The invention relates to the reduction of aerodynamic drag for moving ground vehicles; specifically to an improved method and device for the reduction of aerodynamic drag and for improved performance of ground vehicles by increasing the pressure on the base area of a vehicle or vehicle component by controlling the flow in wake of the vehicle or vehicle component. 
     BACKGROUND OF THE INVENTION 
     In the prior art there have been attempts to reduce the aerodynamic drag associated with the bluff base of the trailer of a tractor-trailer truck system. The wake flow emanating from the bluff base trailer is characterized as unsteady and dynamic. The unsteady nature of the wake flow is a result of asymmetric and oscillatory vortex shedding of the side surface and top surface flow at the trailing edge of the top and side surfaces of the vehicle. The boundary-layer flow passing along the top and side surfaces of the vehicle is at a low energy state and is unable to expand around the corner defined by the intersection of the side or top surfaces with the base surface. The boundary-layer flow separates at the trailing edge of the top and side surfaces and forms rotational-flow structures that comprise the bluff-base wake flow. The low energy flow separating at the trailing edges of the side surfaces and top surface of the trailer is unable to energize and stabilize the low energy bluff-base wake flow. The large rotational-flow structures comprising the wake interact with each other imparting an unsteady pressure loading on the vehicle base. The resulting flow interaction in the vehicle wake and unsteady pressure loading on the vehicle base contributes to the low pressures acting on the vehicle base and therefore high drag force. The resulting bluff-base wake-flow structure emanating from the base area of the vehicle is comprised of the vortex structures that are shed from trailing edges of the side surfaces and top surface of the vehicle. Contributing to the low-energy bluff-base wake is the low-energy turbulent flow that exits from the vehicle undercarriage at the base of the vehicle. The unsteady wake flow imparts a low pressure onto the aft facing surface of the trailer base that results in significant aerodynamic drag. Prior art has addressed the bluff base flow phenomena by adding to or installing various devices to the bluff base region. Examples of these devices are: a contoured three-dimensional aerodynamic surface referred to as a boat-tail; bluff base extensions/flaps/fairings/panels/plates which extend rearward from the side, top and/or lower surfaces that create a cavity; three or four surface panels/plates that extend rearward from the bluff base and are aligned approximately parallel to the side, top and/or lower surfaces of the vehicle and are designed to trap vortices shed from the trailing edges. All of these previous devices have geometrically-simple trailing edges and have an upstream edge that abuts the bluff base surface. Prior art also show the forcing the side surface and top surface flow into the base region through the use of turning vanes or jets of air. 
     Prior art has used the aerodynamic boat-tail fairings applied to the trailer base in order to eliminate flow separation and associated drag, see U.S. Pat. Nos. 4,458,936, 4,601,508, 4,006,932, 4,451,074, 6,092,861, 4,741,569, 4,257,641, 4,508,380, 4,978,162 and 2,737,411. These representative aerodynamic boat-tail fairing devices, while successful in eliminating flow separation, are complex devices that are typically comprised of moving parts that require maintenance and add weight to the vehicle. These devices take a variety of form and may be active, passive, rigid, flexible and/or inflatable. These attributes have a negative impact on operational performance and interfere with normal operations of the vehicle. 
     Other concepts as documented in U.S. Pat. Nos. 5,348,366 and 4,682,808 consist of three or four plates/panels that are attached to the base of a trailer or extend from support mechanisms that are attached to the base of a trailer. These devices operate by trapping the separated flow in a preferred position in order to create an effective aerodynamic boat-tail shape. These representative trailer base devices, while successful in reducing the drag due to base flow are complex devices that are typically comprised of moving parts that require maintenance and add weight to the vehicle. All of these devices add significant weight to the vehicle. These attributes have a negative impact on operational performance and interfere with normal operations of the vehicle. 
     U.S. Pat. Nos. 3,010,754, 5,280,990, 2,569,983 and 3,999,797 apply a flow turning vane to the outer perimeter of the trailer base on the sides and top to direct the flow passing over the sides and top of the trailer into the wake in order to minimize the drag penalty of the trailer base flow. These devices provide a drag reduction benefit but they require maintenance and interfere with normal operations of the trailers fitted with swinging doors. These devices also add weight to the vehicle that would have a negative impact on operational performance of the vehicle. 
     Several concepts employ pneumatic concepts to reduce the aerodynamic drag of tractor-trailer truck systems. U.S. Pat. No. 5,908,217 adds a plurality of nozzles to the outer perimeter of the trailer base to control the flow turning from the sides and top of trailer and into the base region. U.S. Pat. No. 6,286,892 adds a porous surface to the trailer base and to the sides and top regions of the trailer abutting the trailer base. These porous surfaces cover a minimum depth plenum that is shared by the sides, top and base regions of the trailer. These two patents provide a drag reduction benefit but as with the other devices discussed previously these devices are complex devices, comprised of moving parts, interfere with normal operations of the truck and add weight to the vehicle. These characteristics of the devices result in a negative impact on the vehicle operational performance. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to eliminate the interaction of naturally occurring large-scale vertical wake flow structures by separating the viscous boundary layer flow from the high-energy free stream flow as it exits the trailing edge of the side and/or top surfaces of a vehicle. The subject invention consists of a multiple panels located near the base area of a bluff base vehicle. The flow control objectives are accomplished by positioning minimally sized panels comprising the invention in close proximity to the side and top surfaces of the vehicle, where the leading edge of each panel is positioned in close proximity to the trailing edge of the vehicle. The side panels comprising the invention are laterally positioned outboard of the side surface of the vehicle. The top panels are vertically positioned above the top surface of the vehicle. The proper placement of the panels allows the side and top surface low velocity boundary layer flow to pass into the gap region located between the vehicle side and top surfaces and the inward facing surfaces of the panels of the subject invention. The high velocity free stream flow outside of the boundary layer is allowed to pass over the outward facing surfaces of the panels comprising the subject invention. The separation of the low velocity boundary layer flow from the high velocity free stream flow reduces the formation of the large eddies that form in the vehicle wake and which impart the low pressures and high drag force on the bluff base region of the vehicle. The use of boundary layer control technologies in the design of a wake stabilization device for a vehicle is dependent upon the vehicle geometry, operational requirements, and maintenance requirements. Controlling the boundary layer flow on the side surfaces is accomplished with vertically orientated panels that extend aft beyond the bluff base a distance that is less than the vehicle width and can be configured with a complex, planar, geometrically shaped trailing edge. Controlling the boundary layer flow on the top surface is accomplished with horizontally orientated panels that extends aft beyond the bluff base a distance that is less than the vehicle width and are configured with a complex, planar, geometrically shaped trailing edge. The control of the boundary layer flow allows the high velocity flow exiting the trailing edge of the panels comprising the invention to expand into the base region and provide drag reduction, increased fuel economy and improved operational performance. The trailing edge geometric shaping of the panels promotes turning of the external flow field thereby increasing the drag reduction benefit of the technology. Aerodynamic drag reduction is created by increasing the average pressure loading on the bluff-base aft-facing surface of the vehicle or vehicle component such as the trailer of a tractor-trailer truck. The invention relates to flow in the base region behind a bluff-base vehicle or vehicle component. The flow in the base region behind a bluff-base vehicle or vehicle component is a function of vehicle geometry, vehicle speed and the free stream flow direction. 
     The device provides improved performance for both the no crosswind condition, in which the air is still, as well as the condition when crosswind flow is present. For all moving vehicles that operate on the ground a crosswind flow is always present due to a combination of atmospheric and environmental factors and the interaction of the naturally occurring wind with stationary geological and manmade structures adjacent to the vehicle path as well as interfering flows from adjacent moving vehicles. The device is designed to reduce aerodynamic drag for the all cross wind conditions for single and multiple-component bluff-base vehicles. The subject device uses boundary layer control to allow the flow passing along the exterior top and side surfaces of a bluff-base ground vehicle to smoothly exit the vehicle at the trailing edge and pass into the wake. The subject device provides reduced aerodynamic drag for all of bluff-base ground vehicles. 
     The present invention is a simple device comprised of multiple panels that attach to the exterior surface of the bluff base of a ground vehicle or vehicle component. The spacing and orientation of the panels, comprising the device, are dependent upon the vehicle geometry and vehicle operating conditions. 
     The present invention pioneers a novel device that is comprised of multiple panels that are attached to the bluff base exterior surfaces of a bluff-base vehicle or vehicle component. The subject panels are located in close proximity to the side surfaces, top surface and rear surface of the vehicle. To maximize the ability of each panel to control the boundary layer the panels are aligned approximately parallel to the air flow direction along the sides and top surfaces of the vehicle. Each of the panels extends aft an equivalent distance. The panels are applied symmetrically to the vehicle about the centerline of the vehicle. Each of the panels may be comprised of multiple elements or segments and/or may be contain local gaps, holes, cutouts, and/or bumps in order to accommodate specific vehicle or vehicle component geometry. 
     For ground vehicles such as tractor-trailer trucks, which have a cross-section shape that is predominately rectangular or square, the panels will be predominately planar, except as required to accommodate vehicle specific geometric features. The flow passing over this class of vehicle is parallel to the vehicle centerline and moving aft along the vehicle surface. Each of the panels may be comprised of various segments that may vary in number, shape, width and orientation that is determined by vehicle geometry. The preferred embodiment of the invention is to have each panel, comprising the invention, extending over the full width and height of the vehicle. The trailing edge shape of each panel shall be similar and is a function of vehicle geometry and operating conditions. Panel trailing edge shape may be either linear and parallel to the vehicle base surface or may be defined as a complex geometric shape such as serrated, notched, curved, or sawtooth shape to stabilize the wake shed from the panel trailing edge. 
     The subject invention is designed to be a maintenance free device that does not interfere with typical operational procedures or add additional operational procedures to ensure successful operation of the device. For ground vehicles, such as tractor-trailer trucks, which typically have a door or doors located on the vehicle base, panels of the subject invention may attach to the side surfaces, top surface, base surface and/or door surface of the vehicle by means of an actuation and/or attachment systems that may consist of various mechanical support systems. The actuation and/or attachment system is designed to position the panels in the preferred orientation and to allow each panel to move to a stowed position as required by the normal operating characteristics of the vehicle. Each panel may be; attached as a rigid member that does not move, attached as a moveable panel that is stowed or deployed manually and locked in the open or closed position, attached as a movable panel that is stowed or deployed in response to the panel impacting another object or by a linkage when the doors are opened and closed, or attached as a movable panel that is stowed and deployed through a powered system linked to a sensor system. 
     The reduction of aerodynamic drag, improved operational performance and improved stability of multiple component vehicles is obtained by increasing the pressure loading on the bluff base of the vehicle or vehicle component. The pressure loading on the bluff base is increased by eliminating the interaction of the side edge and top edge separated flow structures and facilitate the side and top surface flow to smoothly transition from the vehicle trailing edges and turn into the wake region. The flow control is accomplished by controlling the side surface and top surface boundary layer as it exits the trailing edge of the vehicle. The invention separates the low velocity boundary layer flow from the high velocity free stream flow of the vehicle surfaces thereby allowing the boundary layer flow to pass into the base area and thereby allowing free stream flow to exit the panel trailing edge with minimal viscous effects. More specifically, this invention relates to a device and method for reducing aerodynamic drag utilizing minimum length panels that are specifically shaped, sized, and orientated to inhibit the formation and prohibit the interaction of large separated flow structures in the wake. The invention creates a stabilized vehicle wake, reduced unsteady flow-separation, increased pressures acting on the bluff base area and reduced vehicle aerodynamic drag. The structure and segmentation of the panels, the positioning of the panels, the streamwise extent of the panels, the vertical extent of the panels, and the trailing edge shape of the panels are the primary design variables that are used to determine the drag reduction capability of the device. 
     The invention may be used to reduce the drag of all existing and future ground vehicles (i.e., cars with trailers, tractor-trailer trucks, trains, etc.). 
     OBJECTS AND ADVANTAGES 
     Several objects and advantages of the present invention are:
         (a) to provide a novel process to reduce the aerodynamic drag of vehicles;   (b) to provide a means to use boundary layer flow control to reduce aerodynamic drag;   (c) to provide a means to reduce the aerodynamic drag and improve the operational efficiency of vehicles;   (d) to provide a means to reduce the aerodynamic drag and improve the fuel efficiency of vehicles;   (e) to provide a means to conserve energy and improve the operational efficiency of vehicles;   (f) to provide a means to reduce the aerodynamic drag without a significant geometric modification to existing vehicles;   (g) to provide an aerodynamic drag reduction device that uses a minimum of panels;   (h) to allow the geometric details of each set of panels to be variable to meet the specific needs of the application;   (i) to allow the spacing, location, and orientation of each set of panels to be variable to meet the specific needs of the application;   (j) to create a high pressure and low aerodynamic drag forces on the bluff base of a vehicle to reduce the aerodynamic drag of the subject vehicle;   (k) to allow the device to be fabricated as a number of independent segments and parts that may be applied to an existing vehicle;   (l) to allow the device to be fabricated as a single independent unit that may be applied to an existing vehicle;   (m) to allow the device to be fabricated as an integral part of a vehicle;   (n) to allow for optimal positioning of each panel on the vehicle base surface;   (o) to have minimum weight and require minimum volume within the vehicle;   (p) to have the ability to automatically fold to a stowed position and deploy to a operational position with normal operational of the door system;   (q) to have minimum maintenance requirements;   (r) to have no impact on operational requirements.       

     Further objects and advantages are to provide a device that can be easily and conveniently used to minimize aerodynamic drag on any ground vehicle for the purposes of improving the operational performance of the vehicle. Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a rear perspective view of the aft most portion of a trailer of a tractor-trailer truck system with a non-moveable version of the subject invention installed on the trailer. 
         FIGS. 2   a  and  2   b  is a rear perspective view of the aft most portion of a trailer of a tractor-trailer truck system with a first and second moveable version of the subject invention installed on the trailer. 
         FIG. 3  is a rear perspective view of the aft most portion of a trailer of a tractor-trailer truck system with a third moveable version of the subject invention installed on the trailer. 
         FIG. 4  is a rear perspective view of the aft most portion of a trailer of a tractor-trailer truck system with an alternate embodiment of a non-moveable version of the subject invention installed on the trailer. 
         FIG. 5   a  to  5   d  are side and top views of various ground vehicles with and without the subject invention installed on the vehicles. 
         FIG. 6   a  to  6   d  are side and top views of various ground vehicles with and without an alternate embodiment of the subject invention installed on the vehicles. 
         FIG. 7   a  to  7   c  is a perspective view and horizontal cross section view of a non-movable version of the subject invention installed on the trailer with various base geometries and doors. 
         FIG. 8   a  to  8   c  is a perspective view and vertical cross section view of an alternate embodiment of a non-movable version of the subject invention installed on the trailer with various base geometries and doors. 
         FIG. 9   a  is a perspective view and horizontal cross section view of a movable version of the subject invention installed on the trailer with swing doors. 
         FIG. 9   b  is a perspective view and expanded view of a representative movement mechanism for the movable version of the subject invention installed on the trailer with swing doors. 
         FIG. 9   c  details of a representative manually operated movement mechanism for the movable version of the subject invention installed on the trailer with swing doors. 
         FIG. 9   d  details of a representative automated movement mechanism for the movable version of the subject invention installed on the trailer with swing doors. 
         FIG. 10   a  is a perspective view and horizontal cross section view of the subject invention installed on the trailer with swing doors with a device mounted movement mechanism. 
         FIG. 10   b  is a perspective view and expanded view of a representative device mounted movement mechanism for the movable version of the subject invention installed on the trailer with swing doors. 
         FIG. 10   c  details of the representative device mounted manually operated movement mechanism for the movable version of the subject invention installed on the trailer with swing doors. 
         FIG. 11   a  is a perspective view and horizontal cross section view of the subject invention installed on the trailer with swing doors with a device mounted movement mechanism. 
         FIG. 11   b  is a perspective view and expanded view of a representative device mounted movement mechanism for the movable version of the subject invention installed on the trailer with swing doors. 
         FIG. 11   c  details of the representative device mounted manually operated movement mechanism for the movable version of the subject invention installed on the trailer with swing doors. 
         FIG. 12  are planform views of the various panel trailing edge shape concepts. 
         FIG. 13  are cross section views of the various panel cross section shape concepts. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following descriptions are of exemplary embodiments of the invention only, and are not intended to limit the scope, applicability or configuration of the invention in any way. Rather the following description is intended to provide a convenient illustration for implementing various embodiments of the invention. As will become apparent, various changes may be made in the function and arrangement of the elements described herein without departing from the spirit and scope of the invention. For example, though not specifically described, many shapes, widths, leading edge shapes, spacing and orientation of the forward extended plurality of panels, candidate vehicles that can benefit from the device, fabrication means and material, attachments means and material should be understood to fall within the scope of the present invention. 
     Referring now in detail to the drawings, like numerals herein designate like numbered parts in the figures. 
       FIG. 1  is a rear perspective view of the aft portion of a typical trailer  30  of a tractor-trailer truck with the subject invention  40  installed on the trailer  30 . The invention  40  is comprised of panels  41  and attachment hardware  42 . The subject invention is comprised of panels  41  that are attached to the vehicle  30 . The panels  41  are symmetrically positioned about the vehicle vertical plane of symmetry. Each panel  41  may be comprised of multiple elements and/or segments and may contain gaps, holes, cutouts and/or bumps in order to accommodate specific vehicle component geometry or operational features. Each panel has a width W 1  and a length L 1  and is positioned laterally outboard from the vehicle side a distance Y, where Y may be any value less than 25% of the vehicle width. The panel width W 1  is less than the vehicle width. Each panel is positioned longitudinally such that the leading edge of each panel  41  is in close proximity to the vehicle trailing edge. The longitudinal dimension X between the vehicle trailing edge and the panel leading edge is less than 50 percent of the panel width W 1 . The length L 1  of each panel  41  of the invention  40  is equivalent to the full vertical height of the vehicle base  30 . The width W 1  of each panel  41  of the invention  40  is determined by the geometric characteristics of the vehicle  30 , the operational requirements of the vehicle  30  and the maintenance requirements of the vehicle  30 . The type, size and structure of the attachment/actuation hardware  42  of the invention are determined by the geometric characteristics of the vehicle  30 , the operational requirements of the vehicle  30  and the maintenance requirements of the vehicle  30 . 
     The subject invention  40 , comprised of components  41  and  42  provides aerodynamic drag reduction for all free stream flow  100  conditions including crosswind conditions. Aerodynamic drag reduction occurs when vehicle side surface  32  and  33  boundary layer portion of the flow  100  is separated from the free stream portion of the flow  100  at the leading edge of each panel  41  and the boundary layer flow is directed into the base wake region while the high velocity free stream flow continues to flow streamwise along the outer surface of each panel  41 . The free stream portion of the flow  100  leaving each panel  41  trailing edge trailing edge turns into the base area region forming a virtual boattail structure. The effectiveness of the subject invention to reduce drag and thereby increase fuel economy of a vehicle is determined by the panel  41  width W 1 , length L 1 , position X and Y, planform shape as shown in  FIG. 12  and airfoil shape as shown in  FIG. 13 . 
       FIG. 2   a  is a rear perspective view of the aft portion of a typical trailer  30  of a tractor-trailer truck with an alternate embodiment of the subject invention  40  installed on the trailer  30 . The invention  40  is comprised of panels  41  and attachment hardware  42  and actuation hardware  43 .  FIG. 2   a  show the subject invention  40  comprised of panels  41  that are attached to attachment hardware brackets  42  that in turn attach to actuation hardware  43  that in turn attach to the vehicle. The panels  41  are symmetrically positioned about the vehicle vertical plane of symmetry. Each panel has a width W 1  and a length L 1  and is positioned laterally outboard from the vehicle side a distance Y, where Y may be any value less than 25 percent of the vehicle width. The panel width W 1  is less than the vehicle width. Each panel is positioned longitudinally such that the leading edge of each panel  41  is in close proximity to the vehicle trailing edge. The longitudinal dimension X between the vehicle trailing edge and the panel leading edge is less than 50 percent of the panel width W. The length L 1  of each panel  41  of the invention  40  is equivalent to the full vertical height of the vehicle base  30 . The width W 1  of each panel  41  of the invention  40  is determined by the geometric characteristics of the vehicle  30 , the operational requirements of the vehicle  30  and the maintenance requirements of the vehicle  30 . The type, size and structure of the attachment/actuation hardware  42  of the invention are determined by the geometric characteristics of the vehicle  30 , the operational requirements of the vehicle  30  and the maintenance requirements of the vehicle  30 . 
     The subject invention  40 , comprised of components  41 ,  42 ,  43  provides aerodynamic drag reduction for all free stream flow  100  conditions including crosswind conditions. Aerodynamic drag reduction occurs when vehicle side surface  32 ,  33  boundary layer portion of the flow  100  is separated from the free stream portion of the flow  100  at the leading edge of the panel  41  where the boundary layer flow is directed into the base wake region while the high velocity free stream flow continues to flow streamwise along the outer surface of each panel  41 . The free stream portion of the flow  100  leaving each panel  41  trailing edge trailing edge turns into the base area region forming a virtual boattail structure. The effectiveness of the subject invention to reduce drag and thereby increase fuel economy of a vehicle is determined by the panel  41  width W 1 , length L 1 , position X and Y, planform shape as shown in  FIG. 12  and airfoil shape as shown in  FIG. 13 . 
       FIG. 2   b  is a rear perspective view of the aft portion of a typical trailer  30  of a tractor-trailer truck with an alternate embodiment of the subject invention  40  installed on the trailer  30 . The invention  40  is comprised of panels  41  and attachment hardware  42  and actuation hardware  44 . The subject invention is comprised of panels  41  that are attached to actuation hardware  44  that in turn attach to attachment hardware brackets  42  that in turn attach to the vehicle  30 . The panels  41  are symmetrically positioned about the vehicle vertical plane of symmetry. Each panel has a width W 1  and a length L 1  and is positioned laterally outboard from the vehicle side a distance Y, where Y may be any value less than 25 percent of the vehicle width. The panel width W 1  is less than the vehicle width. Each panel is positioned longitudinally such that the leading edge of each panel  41  is in close proximity to the vehicle trailing edge. The longitudinal dimension X between the vehicle trailing edge and the panel leading edge is less than 50 percent of the panel width W 1 . The length L 1  of each panel  41  of the invention  40  is equivalent to the full vertical height of the vehicle base  35 . The width W 1  of each panel  41  of the invention  40  is determined by the geometric characteristics of the vehicle  30 , the operational requirements of the vehicle  30  and the maintenance requirements of the vehicle  30 . The type, size and structure of the attachment/actuation hardware  42  of the invention are determined by the geometric characteristics of the vehicle  30 , the operational requirements of the vehicle  30  and the maintenance requirements of the vehicle  30 . 
     The subject invention  40 , comprised of components  41 ,  42 , and  43 , provides aerodynamic drag reduction for all free stream flow  100  conditions including crosswind conditions. Aerodynamic drag reduction occurs when vehicle side surface  32 ,  33  boundary layer portion of the flow  100  is separated from the free stream portion of the flow  100  at the leading edge of the panels  41  and the boundary layer flow is directed into the base wake region while the high velocity free stream flow continues to flow streamwise along the outer surface of each panel  41 . The free stream portion of the flow  100  leaving each panel  41  trailing edge trailing edge turns into the base area region forming a virtual boattail structure. The effectiveness of the subject invention to reduce drag and thereby increase fuel economy of a vehicle is determined by the panel  41  width W 1 , length L 1 , position X and Y, planform shape as shown in  FIG. 12  and airfoil shape as shown in  FIG. 13 . 
       FIG. 3  is a rear perspective view of the aft portion of a typical trailer  30  of a tractor-trailer truck with an alternate embodiment of the subject invention  40  installed on the trailer  30 . The invention  40  is comprised of panels  41  and attachment/actuation hardware  47 . The subject invention is comprised of panels  41  that are attached to actuation/attachment hardware  47  that in turn attach to the vehicle  30 . The panels  41  are symmetrically positioned about the vehicle vertical plane of symmetry. Each panel has a width W 1  and a length L 1  and is positioned laterally outboard from the vehicle side a distance Y, where Y may be any value less than 25 percent of the vehicle width. The panel width W 1  is less than the vehicle width. Each panel is positioned longitudinally such that the leading edge of each panel  41  is in close proximity to the vehicle trailing edge. The longitudinal dimension X between the vehicle trailing edge and the panel leading edge is less than 50 percent of the panel width W 1 . The length L 1  of each panel  41  of the invention  40  is equivalent to the full vertical height of the vehicle base  35 . The width W 1  of each panel  41  of the invention  40  is determined by the geometric characteristics of the vehicle  30 , the operational requirements of the vehicle  30  and the maintenance requirements of the vehicle  30 . The type, size and structure of the attachment/actuation hardware  47  of the invention are determined by the geometric characteristics of the vehicle  30 , the operational requirements of the vehicle  30  and the maintenance requirements of the vehicle  30 . 
     The subject invention  40 , comprised of components  41 ,  47  provides aerodynamic drag reduction for all free stream flow  100  conditions including crosswind conditions. Aerodynamic drag reduction occurs when vehicle side surface  32 ,  33  boundary layer portion of the flow  100  is separated from the free stream portion of the flow  100  at the leading edge of the panels  41  and the boundary layer flow is directed into the base wake region while the high velocity free stream flow continues to flow streamwise along the outer surface of each panel  41 . The free stream portion of the flow  100  leaving each panel  41  trailing edge trailing edge turns into the base area region forming a virtual boattail structure. The effectiveness of the subject invention to reduce drag and thereby increase fuel economy of a vehicle is determined by the panel  41  width W 1 , length L 1 , position X and Y, planform shape as shown in  FIG. 12  and airfoil shape as shown in  FIG. 13 . 
       FIG. 4  is a rear perspective view of the aft portion of a typical trailer  30  of a tractor-trailer truck with an alternate embodiment of the subject invention  40  installed on the trailer  30 . The invention  40  is comprised of panels  41  and  45  and attachment hardware  42  and  46 . The subject invention is comprised of panels  41  and  45  that are attached to vehicle  30 . The side panels  41  are symmetrically positioned about the vehicle vertical plane of symmetry. Each side panel has a width W 1  and a length L 1  and is positioned laterally outboard from the vehicle side surfaces  32  and  33  a distance Y, where Y may be any value less than 25 percent of the vehicle width. The panel width W 1  is less than the vehicle width. The top panel  45  has a width W 2  and a length L 2  and is positioned vertically above the vehicle upper surface  34  a distance Z, where Z may be any value less than 25 percent of the vehicle width. The panel width W 2  is less than the vehicle width. Each panel is positioned longitudinally such that the leading edge of each panel  41  and  45  is in close proximity to the vehicle trailing edge. The longitudinal dimension X between the vehicle trailing edge and the leading edge of each panel  41  and  45  is less than 50 percent of the panel width W 1  and W 2  respectively. The length L 1  of each panel  41  of the invention  40  is equivalent to the full vertical height of the vehicle base  30 . The length L 2  of panel  45  of the invention  40  is equivalent to the full width of the vehicle base  30 . The width W 1  of each panel  41  and the width W 2  of panel  45  of the invention  40  are determined by the geometric characteristics of the vehicle  30 , the operational requirements of the vehicle  30  and the maintenance requirements of the vehicle  30 . The type, size and structure of the attachment/actuation hardware  42  and  46  of the invention are determined by the geometric characteristics of the vehicle  30 , the operational requirements of the vehicle  30  and the maintenance requirements of the vehicle  30 . 
     The subject invention  40 , comprised of components  41 ,  42 ,  45 ,  46  provides aerodynamic drag reduction for all free stream flow  100  conditions including crosswind conditions. Aerodynamic drag reduction occurs when vehicle top surface  34  and side surface  32 ,  33  boundary layer portion of the flow  100  is separated from the free stream portion of the flow  100  at the leading edge of panels  41  and  45  and the boundary layer flow is directed into the base wake region while the high velocity free stream flow continues to flow streamwise along the outer surface of panels  41  and  45 . The free stream portion of the flow  100  leaving panels  41  and  45  trailing edge turns into the base area region forming a virtual boattail structure. The effectiveness of the subject invention to reduce drag and thereby increase fuel economy of a vehicle is determined by the panels  41  and  45  width W 1 , width W 2 , length L 1 , length L 2 , position X, Y, Z, and planform shape as shown in  FIG. 11  and airfoil shape as shown in  FIG. 12 . 
       FIG. 5   a  through  FIG. 5   d  are side and top views of example ground vehicles with and without the subject invention installed.  FIG. 5   a  shows a typical tractor-trailer truck system  1 , comprised of a powered tractor  10  that pulls a trailer  30 . The tractor  10  is comprised of a cab  11  and an aerodynamic fairing system  20  that may be an integral part of the tractor  10 .  FIG. 5   b  shows the same tractor-trailer truck system  1  as that of  FIG. 5   a  with the subject invention  40  installed on the tractor  10  and trailer  30 . The panels that comprise the invention  40  are symmetrically positioned about the centerline of the trailer  30 .  FIG. 5   c  and  FIG. 5   d  show an automobile  50  pulling a trailer  60  with and without the subject invention  40  installed on both the automobile  50  and trailer  60 . The various vehicles depicted in  FIG. 5  shows a powered vehicle towing/pulling an un-powered towed vehicle. Additionally, other multiple component vehicles may be considered than those depicted. 
       FIG. 6   a  through  FIG. 6   d  are side and top views of example ground vehicles with and without an alternate embodiment of the subject invention installed.  FIG. 6   a  shows a typical tractor-trailer truck system  1 , comprised of a powered tractor  10  that pulls a trailer  30 . The tractor  10  is comprised of a cab  11  and an aerodynamic fairing system  20  that may be an integral part of the tractor  10 .  FIG. 6   b  shows the same tractor-trailer truck system  1  as that of  FIG. 6   a  with the subject invention  40  installed on the tractor  10  and the trailer  30 . The panels  41  and  45  that comprise the invention  40  are symmetrically positioned about the centerline of the tractor  10  and trailer  30 .  FIG. 6   c  and  FIG. 6   d  show an automobile  50  pulling a trailer  60  with and without the subject invention  40  installed on both the automobile  50  and the trailer  60 . The various vehicles depicted in  FIG. 6  shows a powered vehicle towing/pulling an un-powered towed vehicle. Additionally, other multiple component vehicles may be considered than those depicted. 
       FIG. 7   a  through  FIG. 7   c  shows a rear perspective view and a horizontal section cut of the aft portion of a trailer  30  of a tractor-trailer truck configured with a non-movable version of the subject invention  40  installed on the trailer  30 . Shown in  FIG. 7   a  is a typical swing door trailer  30  of a tractor-trailer truck with the subject invention  40  installed on the trailer  30 . The subject invention  40  attaches to the trailer  30  by means of attachment hardware  42 . The panel  41  has width W 1  and length L 1 . The panel  41  is laterally offset from the side surface  32 ,  33  a distance Y and the panel leading edge is positioned in close proximity to the vehicle side surface  32 ,  33  trailing edge at a distance X. 
     Shown in  FIG. 7   b  is a typical roll up door trailer  30  of a tractor-trailer truck with the subject invention  40  installed on the trailer  30 . The subject invention  40  attaches to the trailer  30  by means of attachment hardware  42 . The panel  41  has width W 1  and length L 1 . The panel  41  is laterally offset from the side surface  32 ,  33  a distance Y and the panel leading edge is positioned in close proximity to the vehicle side surface  32 ,  33  trailing edge at a distance X. 
     Shown in  FIG. 7   c  is a typical trailer  30  without a rear door of a tractor-trailer truck with the subject invention  40  installed on the trailer  30 . The subject invention  40  attaches to the trailer  30  by means of attachment hardware  42 . The panel  41  has width W 1  and length L 1 . The panel  41  is laterally offset from the side surface  32 ,  33  a distance Y and the panel leading edge is positioned in close proximity to the vehicle side surface  32 ,  33  trailing edge at a distance X. 
       FIG. 8   a  through  FIG. 8   c  shows a rear perspective view and a vertical section cut of the aft portion of a trailer  30  of a tractor-trailer truck configured with an alternate embodiment non-movable version of the subject invention  40  installed on the trailer  30 . Shown in  FIG. 8   a  is a typical swing door trailer  30  of a tractor-trailer truck with the subject invention  40  installed on the trailer  30 . The subject panels  41  and  45  of the invention  40  attach to the trailer  30  by means of attachment hardware  42  and  46 . The side panels  41  have width W 1  and length L 1 . The top panel  45  has width W 2  and length L 2 . The panel  41  is laterally offset from the side surface  32 ,  33  a distance Y and the panel  45  is vertically offset from the top surface  34  a distance Z and the leading edges of panels  41  and  45  are positioned in close proximity to the vehicle side surface  32  and  33  and top surface  34  trailing edge at a distance X. 
     Shown in  FIG. 8   b  is a typical roll up door trailer  30  of a tractor-trailer truck with the subject invention  40  installed on the side surface  32  and  33  and top surface  34  of a trailer  30 . The subject panels  41  and  45  of the invention  40  attach to the trailer  30  by means of attachment hardware  42  and  46 . The side panels  41  have width W 1  and length L 1 . The top panel  45  has width W 2  and length L 2 . The panel  41  is laterally offset from the side surface  32 ,  33  a distance Y and the panel  45  is vertically offset from the top surface  34  a distance Z and the leading edges of panels  41  and  45  are positioned in close proximity to the vehicle side surface  32 ,  33  and top surface  34  trailing edge at a distance X. 
     Shown in  FIG. 8   c  is a typical trailer  30  without a rear door of a tractor-trailer truck with the subject invention  40  installed on the trailer  30 . The subject panels  41  and  45  of the invention  40  attach to the trailer  30  by means of attachment hardware  42  and  46 . The side panels  41  have width W 1  and length L 1 . The top panel  45  has width W 2  and length L 2 . The panel  41  is laterally offset from the side surface  32 ,  33  a distance Y and the panel  45  is vertically offset from the top surface  34  a distance Z and the leading edges of panels  41  and  45  are positioned in close proximity to the vehicle side surface  32 ,  33  and top surface  34  trailing edge at a distance X. 
       FIG. 9   a  through  FIG. 9   d  shows a rear perspective view and details of the aft portion of a trailer  30  of a tractor-trailer truck configured with a movable version of the subject invention  40  installed on the trailer  30 . Shown in  FIG. 9   a  is a typical swing door trailer  30  of a tractor-trailer truck with the subject invention  40  installed on the trailer  30 . The subject invention  40  attaches to the trailer  30  by means of attachment hardware  42  and actuation hardware  43 . The panel  41  has width W 1  and length L 1 . The panel  41  is laterally offset from the side surface  32 ,  33  a distance Y and the panel leading edge is positioned in close proximity to the vehicle side surface  32 ,  33  trailing edge at a distance X. The panel  41  attaches to the attachment hardware  42  that in turn attaches to the actuation hardware  43  that in turn attaches to the side surface  32  and  33  of the vehicle. 
     Shown in  FIG. 9   b  is a typical roll up door trailer  30  of a tractor-trailer truck with the subject invention  40  installed on the trailer  30 . Also shown in  FIG. 9   b  is an expanded view of one embodiment of attachment hardware  42  and actuation hardware  43 . The subject invention  40  attaches to the trailer  30  by means of attachment hardware  42  and actuation hardware  43 . The actuation hardware  43  represented in the figure is a sliding mechanism that may be manually operated or powered.  FIG. 9   c  shows additional details of a typical manually operated sliding actuation hardware  43 .  FIG. 9   d  shows additional details of a typical powered sliding actuation hardware  43  that contains a drive mechanism  49  that would be connected to a power supply and sensor or switch device to activate the drive mechanism  49 . 
       FIG. 10   a  through  FIG. 10   c  shows a rear perspective view and details of the aft portion of a trailer  30  of a tractor-trailer truck configured with a movable version of the subject invention  40  installed on the trailer  30 . Shown in  FIG. 10   a  is a typical swing door trailer  30  of a tractor-trailer truck with the subject invention  40  installed on the trailer  30 . The subject invention  40  attaches to the trailer  30  by means of attachment hardware  42  and actuation hardware  44 . The panel  41  has width W 1  and length L 1 . The panel  41  is laterally offset from the side surface  32 ,  33  a distance Y and the panel leading edge is positioned in close proximity to the vehicle side surface  32  and  33  trailing edge at a distance X. The panel  41  attaches to the actuation hardware  44  that in turn attaches to the attachment hardware  43  that in turn attaches to the side surface  32  and  33  of the vehicle. 
     Shown in  FIG. 10   b  is a typical swing door trailer  30  of a tractor-trailer truck with the subject invention  40  installed on the trailer  30 . Also shown in  FIG. 10   b  is an expanded view of one embodiment of attachment hardware  42  and actuation hardware  43 . The subject invention  40  attaches to the trailer  30  by means of attachment hardware  42  and actuation hardware  44 . The actuation hardware  44  represented in the figure is a sliding mechanism that may be manually operated or powered.  FIG. 10   c  shows additional details of a typical sliding actuation hardware  44 . 
       FIG. 11   a  through  FIG. 11   c  shows a rear perspective view and details of the aft portion of a trailer  30  of a tractor-trailer truck configured with a movable version of the subject invention  40  installed on the trailer  30 . Shown in  FIG. 11   a  is a typical swing door trailer  30  of a tractor-trailer truck with the subject invention  40  installed on the trailer  30 . The subject invention  40  attaches to the trailer  30  by means of attachment/actuation hardware  47 . The panel  41  has width W 1  and length L 1 . The panel  41  is laterally offset from the side surface  32  and  33  a distance Y and the panel leading edge is positioned in close proximity to the vehicle side surface  32  and  33  trailing edge at a distance X. The panel  41  attaches to the actuation/attachment hardware  47  that in turn attaches to the vehicle  30 . 
     Shown in  FIG. 11   b  is a typical swing door trailer  30  of a tractor-trailer truck with the subject invention  40  installed on the trailer  30 . Also shown in  FIG. 11   b  is an expanded view of one embodiment of attachment/actuation hardware  47 . The subject invention  40  attaches to the trailer  30  by means of attachment/actuation hardware  47 . The actuation hardware  44  represented in the figure is a hinged mechanism that may be manually operated or powered.  FIG. 11   c  shows additional details of a typical actuation hardware  47 . 
       FIG. 12  show representative planform shapes of panels  41  and  45  of the invention  40 . Panel  41  has width W 1  and length L 1  and panel  45  has width W 2  and length L 2 .  FIG. 12  show four representative panel shapes; Baseline, 1 st  Alternate Embodiment, 2 nd  Alternate Embodiment, and 3 rd  Alternate Embodiment. The Baseline panel planform shape is rectangular. The 1 st  Alternate Embodiment has a straight leading edge and triangular notched trailing edge. The 2 nd  Alternate Embodiment has a straight leading edge and curved notched trailing edge. The 3 rd  Alternate Embodiment is rectangular with rounded corners. The planform shapes shown are representative of possible shapes and are intended to be examples only and are not intended the limit the possible shapes that are used. 
       FIG. 13  show representative airfoil shapes of panels  41  and  45  of the invention  40 . Panel  41  has width W 1  and length L 1  and panel  45  has width W 2  and length L 2 .  FIG. 13  show seven representative panel shapes; Thin Plate, Thick Plate, Rounded Edges, Symmetric Wedge-Slab-Wedge, Asymmetric Wedge-Slab-Wedge, Symmetric Wedge-Wedge, and Asymmetric Wedge-Wedge. The airfoil shapes shown are representative of possible shapes and are intended to be examples only and are not intended the limit the possible shapes that are used. 
     ADVANTAGES 
     From the description provided above, a number of advantages of the outboard wake stabilization plates become evident:
         The invention provides a novel process to reduce the drag of a bluff-base body.   (a) The invention provides a means to use boundary layer separation methods on the side and top surfaces of a bluff-base body to reduce drag.   (b) The invention provides a means to reduce the aerodynamic drag and improve the operational efficiency of bluff-base vehicles.   (c) The invention provides a means to reduce the aerodynamic drag and improve the fuel efficiency of bluff-base vehicles.   (d) The invention provides a means to conserve energy and improve the operational efficiency of bluff-base vehicles.   (e) The invention provides a means to reduce the aerodynamic drag without a significant geometric modification to existing bluff-base vehicles.   (f) The invention may be easily applied to any existing bluff-base vehicle or designed into any new bluff-base vehicle.   (g) The invention allows for the efficient operation of the invention with a limited number of panels.   (h) The invention allows for the matching of complex surface shapes by the shaping and placement of the panels.   (i) Large reductions in drag force can be achieved by diverting the boundary layer.   (j) The structure, placement, and shape of each panel may be adapted to meet specific performance or vehicle integration requirements.   (k) The trailing edge shape of each panel may be linear or complex to meet specific performance or vehicle integration requirements.   (l) The ability to optimally position each panel on the vehicle rear surface.   (m) The ability to minimize weight and volume requirements within the vehicle.   (n) The ability to minimize maintenance requirements.   (o) The ability to minimize the impact on operational and use characteristics of the vehicle door system.   (p) The ability to maximize the safety of vehicle operation.       

     CONCLUSION, RAMIFICATIONS, AND SCOPE 
     Accordingly, the reader will see that the outboard wake stabilization device can be used to easily and conveniently reduce aerodynamic drag on any ground vehicle for the purposes of improving the operational performance of the vehicle. Furthermore, the panels comprising the outboard wake stabilization device has the additional advantages in that:
         it provides a aerodynamic drag reduction force over the base of the vehicle;   it allows the contour of the host surface to be easily matched;   it allows easy application to any existing vehicle or designed into any existing vehicle;   it allows the device to be fabricated as an independent unit that may be applied to an existing surface;   it allows for optimal positioning of each panel on the vehicle;   it allows the design of a system with minimum weight and to require minimum volume within the vehicle;   it allows minimum maintenance requirements;   it allows minimum impact on door operation and use.   it allows for the maximum safety of vehicle operation;       

     Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. For example, the panels can be composed of various planar shapes such as ellipsoid, quadratic, etc.; the thickness and width can vary along the length; the material can be any light-weight and structurally sound material such as wood, plastic, metal, composites, etc.; the substrate can be any metal, wood, plastic, composite, rubber, ceramic, etc.; the application surface can be that of a metal, wood, plastic, composite, rubber, ceramic, etc. The attachment and actuation hardware can be either conventional off the shelf or designed specifically for the subject invention. 
     The invention has been described relative to specific embodiments thereof and relative to specific vehicles, it is not so limited. The invention is considered applicable to any road vehicle including automobiles, trucks, buses, trains, recreational vehicles and campers. The invention is also considered applicable to non-road vehicles such as hovercraft, watercraft, aircraft and components of these vehicles. It is to be understood that various modifications and variation of the specific embodiments described herein will be readily apparent to those skilled in the art in light of the above teachings without departing from the spirit and scope. 
     Thus, the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.