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CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a divisional of application Ser. No. 11/286,855, filed Nov. 26, 2005 (incorporated herein by reference) now U.S. Pat. No. 7,823,335, which claims the benefit of U.S. provisional application No. 60/636,083, filed Dec. 15, 2004. 
    
    
     SEQUENCE LISTING 
     Non-Applicable. 
     BACKGROUND 
     1. Field of Invention 
     This invention relates to an aerodynamic means that mitigate wind generated vortices and wind loads in the wall edge areas of a building, in a simple, effective, and economical way, applicable for both new constructions and retrofits of existing buildings. 
     2. Discussion of Prior Art 
     Conventional wall construction practices normally result in a wall edge configuration that tends to generate strong edge vortex and subjects the wall edge area to severe outward suction loads and high risk of wind induced damage. Traditionally, structural strengthening methods have been relied upon, to counter this severe suction force and mitigate damage risk. The wall edge vortex suppressor disclosed herein functions to reduce the suction force and thus mitigates wind damage risk, through passive flow control techniques that eliminate or suppress the wall edge vortex, which is the prime cause for the high suction force. 
     SUMMARY OF THE INVENTION 
     This invention discloses an aerodynamic means that mitigate strong vortices and high loads induced by wind on the wall edge area of a building, in a simple, effective, and economical way, applicable and convenient for both new constructions and retrofits of existing buildings. 
     This is achieved by using elongated devices of appropriate configurations mounted along a wall edge, therefore to intervene with the wind flow and suppress edge vortex. Examples of such configurations include wall edge cap, windscreen and wind spoiler. These devices primarily comprise of elongated members mounted to a wall edge and defining a new exterior configuration of a building corner, and appropriate means to attach and secure the elongated member to a building corner. 
     Herein wall edge refers to an edge at which two terminating wall surfaces intersect at an approximately right angle and form a convex corner of a building. Vortex formation and extreme wind load are inherent around a building corner, where abrupt change in wall surface orientation occurs along the flow path such that the accelerated wind flow around a corner severely separates from the downstream wall surface. A wall edge vortex suppressor intervenes and modifies the wind flow around the corner of a building. It mitigates flow separation, prevents vortex formation or suppresses its strength, and ultimately reduces the wind force exerted on the wall area adjacent to the edge where most initial wind damages to a wall system occur. 
     OBJECTS AND ADVANTAGES 
     Several objects and advantages of the present invention are: 
     to provide wall edge devices which suppress edge vortex formation and reduce wind loads on wall cladding in a building corner area; 
     to provide wall edge devices which reduce wind loads generally on a wall system that are transferred from the wall cladding; 
     to provide wall edge devices which stabilize wind flow around wall corners and minimize cyclic loads on wall components resulting from recurring winds, reducing the chances of damage due to material fatigue; 
     to provide wall edge devices which possess the desired aerodynamic performance for a more wind resistant building structure while maintaining aesthetic and waterproofing functionality under both extreme and recurring weather conditions. 
     Further objects or advantages are to provide wall edge devices which protect a wall system from wind and rain damage, and which are still among the simplest, most effective and reliable, and inexpensive to manufacture and convenient to install. These and still further objects and advantages will become apparent from a consideration of the ensuing description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically shows a cross-sectional view for one of the preferred embodiments of wall edge cap, being mounted to both sides of a wall edge. 
         FIG. 2  illustrates an alternative configuration of wall edge caps, being mounted to each side of a wall edge separately. 
         FIG. 3  schematically shows a cross-sectional view for one of the preferred embodiments of wall edge windscreen.  FIG. 3A  is view  3 A from  FIG. 3 , exemplifying face perforation and edge serration of a windscreen. 
         FIG. 4  exemplifies alternative configuration of wall edge windscreens. 
         FIG. 5  schematically shows a cross-sectional view for one of the preferred embodiments of wail edge wind spoiler.  FIG. 5A  is view  5 A from  FIG. 5 , exemplifying an longitudinally continuous support with face perforation for a wind spoiler. 
         FIG. 6  illustrates an alternative configuration of wall edge wind spoilers. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  illustrates a preferred configuration of wall edge cap  10 , in a cross-sectional top view. The wall edge cap&#39;s arch shape, or any other similar shape of gradual slope change or modest curvature, eliminates or reduces the abrupt change in surface orientation along the flow path around a building corner  105  where two exterior wall surfaces  100  intersect. This will mitigate edge vortex formation and result in the reduction of aerodynamic forces, primarily the outward suction force, exerted on the downwind wall areas adjacent to the edge. Multiple straight segments can also be used to approximate an arched exterior shape for a wall edge cap. The exterior surfaces of the wall edge cap can be optionally perforated to enhance the device&#39;s vortex-suppressing effects, as described for edge screens later in this application. 
     Any appropriate means to attach and secure the devices to wall surfaces are allowable if it does not significantly affect or alter the exterior shape of the device in a way that detriments the vortex-suppressing function. For example, a set of cleats and fasteners  80  as illustrated in  FIG. 1  can be used for securing the apparatus. 
       FIG. 2  shows an alternative configuration of a wall edge cap assembly  20  that functions in a similar fashion as that illustrated in  FIG. 1 . Multiple straight segments can also be used to approximate the curved exterior shape. 
       FIG. 3  illustrates a preferred configuration of wall edge screen  30  in a cross-sectional top view. The perforated face protrudes outwardly from the wall corner  105 , preferably along the axis of symmetry. The wall edge screen employs a venting mechanism to suppress the vortex formation and vortex induced suction force. The perforated face of a wall edge screen generally reduces the flow acceleration around the corner. At the same time it facilitates pressure equalization across the screen face and around the wall corner  105  through a “bleeding” or venting effect, which prevents vortex formation around and behind the outer edge of the windscreen. It also breaks the flow around the corner down to small, random and unorganized eddies, and leads to dissipation of kinetic energy. Optional outer edge serration of the windscreen provides similar effects of flow breakdown and kinetic energy dissipation. View  3 A form  FIG. 3  is shown in  FIG. 3A  to illustrate an example for face perforation and edge serration of a wall edge windscreen. 
       FIG. 4  shows an alternative configuration of a wall edge windscreen assembly  40 . The perforated faces form an approximately symmetrical arrangement, each forming an angle to a wall  100 . Although, the perforated face shown here forms a right angle to a wall surface, the acceptable angles range from the limit case as in  FIG. 3  (aligning with axis of symmetry) to that of about 45° with respect to the wall on the same side. 
       FIG. 5  illustrates a preferred configuration of wall edge wind spoiler  50 , again in a cross-sectional top view. The wind spoiler uses yet another mechanism to mitigate vortex formation around a wall corner  105  of a building. The raised and bent spoiler plate  52  forces the wind flow around the wall corner to conform approximately to the exterior wall surfaces, and thus suppresses flow separation and vortex formation. The resulting effect is the reduction of the wind suction force on the wall area downwind of the wall corner  105 . A plurality of methods is suitable for supporting the raised spoiler plate to the wall corner, as long as the support members do not collectively obstruct the airflow path between the raised spoiler plate and the wall corner. A preferred option is to use significantly perforated, longitudinally continuous, plate-like supports  54  as exemplified in  FIG. 5A , which provide additional effects of flow breakdown and kinetic energy dissipation as described above for edge windscreens. 
       FIG. 6  shows an alternative configuration to form an edge wind spoiler assembly  60 . The raised and bent plates  62  can be configured with multiple straight segments as shown herein or with curved ones. The end segment of the raised plate shall preferably be approximately in parallel with one of the walls  100  secured thereto. The perforated double plates  64  serve as supports to the raised plate segments and as a corner wind screen. 
     The devices can be made of any durable materials that provide mechanical strength and stiffness sufficient to sustain high winds and other weather elements over time. These include, but are not limited to, sheet metal, acrylic, and for the edge cap treated solid wood, etc. Extrusion, or cold form where applicable or other appropriate methods, can be used to manufacture the devices. A generally symmetric shape is preferred for a wall edge vortex-suppressing device in that wind can come from either side of a building corner. However, deviation from a symmetric configuration is allowable for any practical purposes as far as the alteration does not deviate from the spirit of this disclosure for wall edge vortex-suppressing devices. 
     Installation and Operation 
     Any appropriate means to attach and secure the devices to wall surfaces are allowable if it does not significantly affect or alter the exterior shape of the device in a way that detriments the vortex-suppressing function. For example, a set of cleats and fasteners can be used for securing the apparatus to the wall, as illustrated in the above figures. 
     An embodiment of this invention is a passive flow control device for wall edges. Once configured and installed properly, it stays functioning in such a way that it mitigates vortex formation around a wall edge and reduces wind loads on the wall, whenever the wind blows towards a building bearing such wall edge devices, and requires no active operational intervention. 
     CONCLUSION, RAMIFICATIONS, AND SCOPE 
     It is apparent that wall edge vortex suppressors of this invention provide advantageous devices for mitigating wall edge vortex and wall suction, and are still among the simplest, most effective and reliable, inexpensive to manufacture and convenient to install, with little, if any, maintenance required. 
     The present invention provides a simple and unique method for improving building wind resistance, not only suitable for new constructions but also for retrofit on existing buildings. 
     Although the description above contains many specifications, 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. Various changes, modifications, variations can be made therein without departing from the spirit of the invention. Wall edge vortex suppressors can be made of any reasonably durable material with any appropriate means of fabrication as long as a configuration according to the spirit of this invention is accomplished to support the described working mechanism and to provide the associated functionality. Any appropriate conventional or new mounting method can be used to secure a wall edge vortex suppressor to a building corner without departing from the spirit of this invention. Thus the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.

Summary:
An apparatus disposed along and attached to a wall edge to mitigate wind-generated vortices and suction loads on the wall, suitable and convenient for both new constructions and retrofits of existing buildings. Preferred configurations are described and include such types as wall edge cap, wall edge windscreen and wall edge wind spoiler, each utilizing a distinctive primary aerodynamic mechanism, often with optional secondary mechanisms to enhance vortex-suppressing effects.