Patent Publication Number: US-6669408-B1

Title: Self-orienting piling, fluid-flow reduction device

Description:
STATEMENT OF GOVERNMENT INTEREST 
     The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor. 
     BACKGROUND OF THE INVENTION 
     This invention relates to a device for increasing the survivability of pilings in flowing water. More particularly, this invention provides hydrodynamic structure to reduce the drag load on pilings in flowing water. 
     Many, many commercial and military structures and facilities are located along the coasts of the United States and abroad, and piling supported oilrigs, observation platforms, and anchoring posts are dispersed in offshore waters. In addition, significant numbers of homes and military installations are found along shores, in harbors, and along flowing waterways. Many of these constructions are supported on pilings in order to keep them away from potentially rising floodwaters. 
     Structures built on pilings are designed to withstand the hydrodynamic forces that they are likely to encounter during their life cycle. Often these life cycle and design considerations revolve around what is known as the one-hundred-year flood or one-hundred-year storm. That is, the supporting piling foundation is built such that the protected structure is raised above the potential of the one-hundred-year flood or storm. The piling foundation is also made with sufficient strength to withstand the hydrodynamic forces that accompany rapidly moving water and wind about it. Unfortunately, as has been discovered during recent years, the one-hundred-year storm can strike at any time and can strike during consecutive periods of less than one hundred years. When such events occur, the design and strength of the piling foundations are tested to their limits and quite often fail. 
     The major cause of this failure is due to moving water and the tremendous hydrodynamic forces that this moving water places on the pilings that support various structures. During a hurricane or typhoon, for example, the height of the water may not be sufficient to impact with the raised structure. However, the force of the moving water impinging upon the piling system causes the pilings to shift and move or crack, under the tremendous hydrodynamic drag-load produced by the hydrodynamic flow of water on and around the pilings. To date the only solutions to this problem have been to use larger, longer and more expensive pilings and/or use exotic and expensive piling materials. Lateral bracing between pilings and grading berms across coastal and flood plane constructions have had only minimal success. These are the only known means that have been employed to reduce the hydrodynamic drag load on piling foundations. 
     Thus, in accordance with this inventive concept, a need has been recognized in the state of the art for a cost-effective means utilizing hydrodynamic principles to extend the useful life of pilings in flowing waters. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     An object of the invention is to provide a load reduction device for pilings in flowing fluid. 
     Another object of the invention is to provide devices mounted on pilings and utilizing hydro-dynamic principles to reduce the load imposed by flowing fluid on the pilings. 
     Another object of the invention is to provide a bi-directionally tapered hydrodynamic foil device mounted on pilings to reduce the fluid load created by flowing fluid on the pilings by at least two hundred percent. 
     Another object of the invention is to provide a self-orienting device in flowing fluid requiring no external power source to reduce flow drag on pilings. 
     Another object of the invention is to provide bi-directionally tapered hydrodynamic foil devices capable of being retrofitted on pilings to reduce the load imposed by flowing fluid on the pilings. 
     Another object of the invention is to provide mass-produced, cost-effective, devices mounted on pilings to reduce the load created by flowing fluid. 
     Another object of the invention is to provide cost-effective light-weight, flow-reduction devices mounted on pilings using vane-guide structures as bearing surfaces to eliminate parts and maintenance otherwise required of conventional bearing structures. 
     Another object of the invention is to provide a load reduction device mounted on pilings having non-uniform external surfaces and other shapes than round. 
     Another object of the invention is to provide flow-reduction devices mounted on pilings formed in a variety of shapes, sizes, lengths and colors. 
     These and other objects of the invention will become more readily apparent from the ensuing specification when taken in conjunction with the appended claims. 
     Accordingly, the invention is a device to reduce load created by flowing fluid on a piling. A bi-directionally tapered hydrodynamic foil has a traverse tube sized to fit around a piling in a spaced-apart relationship, and has a tapered leading vane portion located on one side of the traverse tube and extending to diametrically opposed opposite sides of the tube. The hydrodynamic foil additionally is provided with a tapered trailing vane portion located on the opposite side of the traverse tube as the tapered leading vane, and the tapered leading vane portion has a leading edge. The tapered trailing vane portion has an extended tapered shape of greater lateral area than the tapered leading vane portion to orient the leading edge of the tapered leading vane portion into the direction of flow of fluid flowing on the piling. Upper and lower collars engage the piling and contact the traverse tube to support and guide the bi-directionally tapered hydrodynamic foil during rotation around a longitudinal axis of the piling. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric, schematic representation of dynamic load reduction devices of the invention mounted on pilings to reduce the drag loads created by flowing water. 
     FIG. 2 is an exploded view of a dynamic load reduction device of the invention showing details of upper and lower guide collars and mating halves of the bi-directionally tapered hydrodynamic foil. 
     FIG. 3 is a cross-sectional top view of a dynamic load reduction device of the invention taken generally along line  3 — 3  in FIG. 1 showing details of the interconnection of the halves of the bi-directionally tapered hydrodynamic foil. 
     FIG. 4 is a schematic representation of upper and lower guide collars adapted for tapered support structure. 
     FIG. 5 is a schematic representation of upper and lower guide collars adapted for non-rounded support structure, such as square. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1, several dynamic load reduction devices  10  of this invention are mounted on pilings  80  to reduce the effects of flowing fluid, shown as arrow  90 , such as water  95  that impinges on pilings  80 . Flowing water  90  caused by waves, tidal action, rivers, streams, etc., creates forces, or loads that stress exposed pilings  80  and can eventually cause failure in them. Load reduction devices  10 , shown in two different exemplary sizes, are a cost effective means to dramatically reduce the drag forces imparted to pilings  80  that are exposed to flowing water  90  to increase their survivability and the structures  100  attached to and supported by them. Load reduction devices  10  can reduce the loads on pilings  80  attributed to flowing water by at least two hundred percent for a given set of hydrodynamic flow conditions in the realm of water-flow rates where failure of pilings is likely to occur. 
     Referring additionally to FIGS. 2 and 3, load reduction device  10  has supports  20  including an upper guide collar  30  and lower guide collar  40  connected to piling  80 . Upper guide collar  30  can be made from two semicircular parts  31  and  32  that are connected to an upper part of piling  80  by fasteners  33  such as screws, nails, or the like that extend through holes  34  and into piling  80 . Semicircular parts  31  and  32  that are connected to piling  80  via fasteners  33  form a outwardly facing annular guide surface  36  on upper guide collar  30  and an outwardly extending rim  36   a  that extends radially outwardly from longitudinal axis  85  of piling  80 . Lower guide collar  40  is made from two semicircular parts  41  and  42  that are connected to piling  80  by fasteners  43 , such as screws, nails, etc., that extend through holes  44  and into piling  80 . Semicircular parts  41  and  42  that are connected to piling  80  via fasteners  43  extending through holes  44  form a continuous, upwardly facing annular bearing surface  46  extending radially outwardly on a rim  46   a  from longitudinal axis  85  of piling  80 . 
     A bi-directionally tapered hydrodynamic foil  50  of load reduction device  10  is mounted on guide collars  30  and  40  of supporting section  20  to rotate about longitudinal axis  85  and align load reduction device  10  with flow  90  of ambient water  95 . Bi-directionally tapered hydrodynamic foil  50  includes mating halves  60  and  70  that are connected together with interlocking members  61  and  71 . Interlocking members  61  and  71  can be a wide variety of male and female elements mounted on or cast as part of mating halves  60  and  70 . Interlocking members  61  and  71  are securely connected to each other when they are brought adjacent each other and are forcefully pressed toward one another until they snap together in a mutually engaging relationship, for example. 
     Semi-circular openings  62  and  72  are formed in semi-cylindrical portions  63  and  73  in mating halves  60  and  70 , respectively. When mating halves  60  and  70  are secured together via interlocking members  61  and  71 , mating tongue-and-groove parts  63   a ,  73   a  in semi-cylindrical portions  63  and  73  engage to form an elongate traverse tube  64 . Traverse tube  64  extends from top to bottom of halves  60  and  70  on the inside of hydrodynamic foil  50 . Tube  64  has a diameter  74  larger than the overall diameter of piling  80  including its roughness, irregularities and small protuberances that are routinely found on wooden pilings. The larger diameter  74  maintains a spaced apart relationship with respect to piling  80 . This spaced apart relationship allows unimpeded rotation and alignment with flowing water  90  by bi-directionally tapered hydrodynamic foil  50  on collars  30  and  40  over the often irregularly shaped outer contours on many wooden pilings  80 . 
     Mating halves  60  and  70  have top follower surfaces  65  and  75  located in the inside of the top end of traverse tube  64  to come in contact with and be guided for rotation about piling  80  by outwardly facing annular guide surface  36 . Outwardly extending annular rim  36   a  of upper guide collar  30  extends past tube  64  to prevent bi-directionally  11  tapered hydrodynamic foil  50  from sliding up past upper guide collar  30 . 
     Mating halves  60  and  70  additionally have bottom follower surfaces  66  and  76  located on the bottom end of traverse tube  64  to bear, or rest on upwardly facing annular bearing surface  46  of lower guide collar  40 . The contacts between follower surfaces  65 ,  75  and guide surface  36  and follower surfaces  66 ,  76  and bearing surface  46  are relatively low frictional contacts, and, accordingly, allow rotational sliding displacements in opposite directions between the follower surfaces and the guide and bearing surfaces. As a result, hydrodynamic foil  50  of load reduction device  10  is free to rotate about longitudinal axis  85  on piling  80 . Thus, the relatively narrow, leading edge  53  of tapered leading vane portion  54  of halves  60  and  70  of bi-directionally tapered hydrodynamic foil  50  can be rotated to point into the direction water  95  is coming from. This rotation simultaneously places a trailing edge  55  of a tapered trailing vane portion  56  trailing behind in the direction of flow. Leading edge  53  and tapered leading vane portion  54  are located on one side of tube  64 , and tapered trailing vane portion  56  is located on the opposite side of tube  64  as tapered leading vane portion  54 . Both tapered leading vane portion  54  and tapered trailing vane portion  56  extends to diametrically opposed opposite sides  64   a  and  64   b  of traverse tube  64 . 
     Tapered leading vane portion  54  of bi-directionally tapered hydrodynamic foil  50  is located forward of piling  80  and its relatively narrow leading edge  53  and tapered cross section reduce the force of flowing fluid  90  on piling  80 . By appropriate selection of materials and the thickness of their walls for example, construction of mating halves  60  and  70  is such as to make the masses of tapered leading vane portion  54  and tapered trailing vane portion  56  roughly equal. Tapered leading vane portion  54  is made to have oppositely facing lateral surface areas  54   a ,  54   b  smaller than the oppositely facing lateral areas  56   a ,  56   b  of tapered trailing vane portion  56  rearward of piling  80 . This distribution of lateral areas (or horizontally facing pressure areas)  54   a ,  54   b ,  56   a ,  56   b  creates a weather vane-like effect that places the center of mass forward of the center of horizontal pressure during hydrodynamic flow. In a synergistic manner, this arrangement causes bi-directionally tapered hydrodynamic foil  50  to orient itself with fluid-flow  90  and, therefore, to reduce hydrodynamic drag on piling  80 . 
     Tapered leading vane portion  54  and tapered trailing vane portion  56  of bi-directionally tapered hydrodynamic foil  50  are fabricated in essentially shell-shaped mating halves  60 ,  70 . These mating halves  60 ,  70  have virtually identical mirror-image cross-sectional shapes with respect to their longitudinal axis  57 . Consequently, the flow of flowing fluid  90  is equal about both of the identically shaped mating halves  60 ,  70  to ensure that leading edge  53  of bi-directionally tapered hydrodynamic foil  50  points directly into flowing water  95 . 
     Furthermore, the tapered foil shape of tapered leading vane portion  54  and tapered trailing vane portion  56  has a lower coefficient of drag as compared to the round shaped piling  80  or rectangular shaped piling  80 ″ (see FIG. 5) exposed to flowing fluid  90 . For example, flow studies of air around circular pilings have yielded a drag coefficient of about 0.47. The drag coefficient for load reduction device similar in shape to that disclosed herein has a maximum drag coefficient of around 0.024. The reduction in drag coefficient translates directly into a force reduction of between two hundred and nineteen hundred percent when the shape of load reduction device  10  of this invention is used around a circular piling  80 . The reduced drag force, or load provided by bi-directionally tapered hydrodynamic foil  50  on such pilings increases the survivability of pilings, piling foundations, and the structures they support. The thin leading edge  53  and tapered shapes of both tapered leading vane portion  54  and tapered trailing vane portion  56  being aligned with flowing water  90  synergistically reduce drag. This drag reduction is greater than some contemporary vane structures having blunt or merely rounded frontal surfaces that face into the flow of water and a trailing structure that points downstream, see, for example U.S. Pat. Nos. 4,171,674 and 4,365,574. For a multitude of civilian and military applications the tremendous reductions in load attributed to drag from flowing water on the piling members and the subsequent increase in survivability will be of significant interest to assure survival of piling structures in flood and high-hazard coastal areas worldwide. 
     Load reduction device  10  can be made to have longer hydrodynamic profiles of greater than ten-to-one, where the numeral one designates the dimension of the diameter of the piling and ten refers to its length. Load reduction device  10  is not dependent on buoyancy to perform effectively, and it has relatively low mass to reduce mass loading and the possibility of destructive changes in momentum that might otherwise pull a piling structure over to collapse. 
     Load reduction device  10  can be mounted on pilings below the high waterline to reduce loading at high tides that might coincide with storm conditions. When load reduction device  10  is used in this way, it can be made to present an ornamental or artistic flair, such as making it in the form and coloration of a flamingo or other appealing object (not shown). In order to retain its load reduction capabilities, the more visually appealing flamingo-shaped bi-directionally tapered hydrodynamic foil  50  would have to have a greater surface area at the tail (tapered trailing vane portion  56  at the rear of a piling) than the head and neck part (tapered leading vane portion  54  forward of the piling). The width profile (taken from a perspective above and looking-down) of the ornamental structure additionally must be balanced and the tail and head-neck parts should weigh about the same. 
     Load reduction device  10  of this invention is particularly adapted to protecting marine pilings. Marine pilings usually are made of wood and have large variations on external diameter throughout their length as well as extreme variability in surface roughness. In addition, adaptations of load reduction device  10  can accommodate pilings that are tapered or square (or other shapes) to provide for highly satisfactory reduction of dynamic flow loads. 
     Referring to FIG. 4, load reduction device  10  can protect tapered pilings  80 ′ from loading imposed by flowing water as well as the essentially cylindrically-shaped conventional pilings  80 . For this application upper guide collar  30 ′ is made to be smaller than lower guide collar  40 ′ to fit about tapered piling  80 ′. Upper guide collar  30 ′ and lower guide collar  40 ′ respectively have an outwardly facing annular guide surface  36   a  and rim  36   b  and upwardly facing annular bearing surface  46 ′ to respectively guide and support bi-directionally tapered hydrodynamic foil  50  as described above. 
     Referring to FIG. 5, load reduction device  10  of this invention can protect square, triangular, etc., pilings  80 ″ from loading imposed by flowing water as well. Upper guide collar  30 ″ and lower guide collar  40 ″ can be made with larger radially outwardly extending parts A and B that fit about square or other shaped pilings  80 ″. Upper guide collar  30 ″ and lower guide collar  40 ″ respectively have a larger outwardly facing annular guide surface  36   aa  and a larger upwardly facing annular bearing surface  46   aa  to respectively guide and support bi-directionally tapered hydrodynamic foil  50 . 
     The materials selected for fabrication of upper and lower guide collars  30  and  40  of supports  20  and mating halves  60  and  70  of bi-directionally tapered hydrodynamic foil  50  are numerous and should not be construed as limiting. For examples, collars  30  and  40  could be made from plastic or aluminum and secured into place about the piling using a number of different fasteners  33 ,  43 . Mating halves  60  and  70  could be shell-shaped and injection molded from a number of high-strength composite thermo-set or thermo-plastic materials in numerous colors and states of translucency. Optionally, collars  30  and  40  each could be made from a suitable length of an elongate strip of a tough, flexible material. As such it could be wrapped about differently sized pilings  80  and nailed or stapled in place to present sufficiently outwardly extending bearing surfaces to guide and support bi-directionally tapered hydrodynamic foil  50 . Obviously, one having ordinary skill in the art to which this invention pertains can select materials having properties of suitable strength and corrosion resistance that are especially suitable for use in the intended marine environment. 
     Having the teachings of this invention in mind, modifications and alternate embodiments of load reduction device  10  may be adapted without departing from the scope of the invention. Its uncomplicated, compact design lends itself to numerous modifications to permit its reliable use in hostile marine environments as well as high wind conditions where such winds are found to affect long-term reliability or otherwise interfere with operational requirements. 
     The disclosed components and their arrangements as disclosed herein, all contribute to the novel features of this invention. Load reduction device  10  is a user friendly tool that can be installed by unskilled workers after minimal instruction to provide a relatively inexpensive yet effective way to extend the useful life of pilings in different environments where water is flowing. Therefore, load reduction device  10 , as disclosed herein is not to be construed as limiting, but rather, is intended to be demonstrative of this inventive concept. 
     It should be readily understood that many modifications and variations of the present invention are possible within the purview of the claimed invention. It is to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.