초록 ▼

An improved method and device for reducing the base drag of bluff bodies, including large boxy highway vehicles such as semi-trailer trucks, which uses low drag vortex generators in combination with either a trailing panel or shortened boattail plates, to provide greater base drag reduction than oth

An improved method and device for reducing the base drag of bluff bodies, including large boxy highway vehicles such as semi-trailer trucks, which uses low drag vortex generators in combination with either a trailing panel or shortened boattail plates, to provide greater base drag reduction than other previously known methods. The preferred embodiment reduces the required length of boattail plates by over half, making it compatible with current U.S. regulations for trailer underride bars, and providing easier access for rear cargo doors. The device is easily installed as an add-on device on both new and existing truck bodies. In an alternate configuration, the shape of one or more sets of shortened boattail plates can be built into the rear body shape of vehicles, to maximize the interior volume for a given total vehicle length.

대표청구항 ▼

1. An apparatus for reducing the fluid-dynamic base drag of a bluff body (20) moving through a fluid (21) and creating, at the rear of the body, a low pressure wake having an outer wake perimeter, which bluff body (20) has a substantially flat rear base surface (25), a pair of opposed side surfaces

1. An apparatus for reducing the fluid-dynamic base drag of a bluff body (20) moving through a fluid (21) and creating, at the rear of the body, a low pressure wake having an outer wake perimeter, which bluff body (20) has a substantially flat rear base surface (25), a pair of opposed side surfaces (22A and 22B), and opposed top and bottom surfaces all joined with said rear base surface at side, top and bottom trailing edges (24), respectively, so as to form a box container (30), said apparatus comprising:V shaped vortex generators in a linear array (40) ahead of the trailing edges (24) of said bluff body (20) for generating counter rotating stream-wise vortices (27) in a fluid boundary layer (23) passing generally along said bluff body and creating from said layer separated shear surfaces (26) which turn sharply inward aft of said trailing edges (24); boattail plates (50) inset and affixed a distance (18) from the top and side trailing edges (24); and rear edges on said boattail plates (50) sized to intercept the separated shear surfaces (26) at the outer perimeter of the low pressure wake, thereby providing maximum fluid-dynamic base drag reduction for said body. 2. The apparatus in accordance with claim 1 wherein the bluff body is a land vehicle.3. The apparatus of claim 2 wherein the vortex generators are positioned with an open end facing toward a forward end of said vehicle; and the pointed end pointed toward the rear of said vehicle.4. The apparatus of claim 2 wherein said land vehicle includes a truck body with a rear opening, and further comprising:boattail plate hinging means allowing said plates to swing clear from said rear opening. 5. The apparatus of claim 2 wherein said truck body has a pair of swinging rear doors (36) vertically divided lengthwise top to bottom at about the center of the base surface, said apparatus further comprising:means dividing the top boattail plate at the point of division of the doors such that opening of the doors allows said boattail plates to separate and travel away with the swinging doors. 6. The apparatus of claim 3, wherein said inset distance is about 8 to 9 percent of the lesser of the height or width of said rear base surface.7. The apparatus of claim 1 wherein the height of said vortex generators is in the range of ¼ to ? of the thickness of said local boundary layer.8. Apparatus for reducing to a minimum the fluid-dynamic base drag of a bluff body moving through a fluid passing generally along said bluff body and creating, at the rear of the body, separated shear surfaces which define a low pressure wake having an outer wake perimeter, which bluff body has a substantially flat rear base surface with given height and width dimensions and a periphery of trailing edges, said apparatus comprising:vortex generator means mounted adjacent to and forward of said periphery for generating counter-rotating stream-wise vortices in said fluid layer, which generators cause the separated shear surfaces to turned sharply inward thereby reducing the size of the low pressure wake; and edge means coupled to said base surface and inset from said trailing edges for intercepting said separated shear surfaces at the outer perimeter of said low pressure wake, namely, at a distance behind said base surface of about ? th to ⅛ th of said given height or width dimension, whichever is less.