Patent Document

RELATED APPLICATIONS 
       [0001]    This application claims the benefit of co-pending U.S. Provisional Patent Application Ser. No. 62/000,370, filed May 19, 2014 for WAVE ATTENUATION SYSTEM AND METHOD and co-pending U.S. Provisional Patent application Ser. No. 62/118,173, filed Feb. 19, 2015 for WAVE ATTENUATION SYSTEM AND METHOD, both of which are incorporated herein by reference in their entirety. This application also incorporates by reference U.S. patent application Ser. No. 14/267,612, filed May 1, 2014 for CORROSION-AND-CHAFING-RESISTANT, MOORING SYSTEM AND METHOD, in its entirety. 
     
    
     BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to marine facilities, and more particularly to breakwater systems. 
         [0004]    2. Background Art 
         [0005]    The cyclic forces and motion of wave activity near shorelines has traditionally created problems such as erosion of shorelines, damage of shore-based equipment, navigation problems for small watercraft near reefs, shorelines, and shore-based equipment, and so forth. Waves have a complex motion that includes both cyclical rising and falling of the water level as well as a to-and-fro or ebb-and-flow (actually flow and ebb, respectively) motion of the water as it flows toward shore and recedes away. Typically, wave attenuation systems, or “breakwaters” as they are typically called, have been devised from several mechanisms. 
         [0006]    For example, conventional breakwater systems may include concrete sea walls against which the waves may pound, rock structures, such as rip-rap of rocks, which may or may not be retained within a steel net structure, jetties constructed of large boulders on the order of several feet across each, and some much larger, and so forth. Sometimes, certain floating structures have been used, such as floating logs, rafts, piers, and so forth. Likewise, pilings supporting various structures have also been used as breakwaters. 
         [0007]    What is needed is a system that is resistant to the effects of erosion, suitable for redirecting mass, momentum, energy, and power generated by wave action. Such a system should be effective for cutting down wave height and reducing wave momentum and energy over a long (decades) period of time. Concrete eventually breaks up, fixed constructions such as rock piles, jetties, and the like require considerable construction with commensurate disruption of the sea bed and the marine environment, with the associated time, expense, and labor required. Floating systems are largely ineffective. 
         [0008]    It would be an advance in the art to provide a simplified system that may be towed into place, anchored unobtrusively to the sea bed, and left to effectively operate for decades without significant maintenance, refurbishment, and the like. 
         [0009]    Also, it would be highly desirable to provide a system that is sufficiently robust that it does not even require intense inspections more than every year or every several years during its lifetime. 
       BRIEF SUMMARY OF THE INVENTION 
       [0010]    In view of the foregoing, in accordance with the invention as embodied and broadly described herein, a method and apparatus are disclosed in one embodiment of the present invention as including a breakwater or wave attenuation system includes two horizontally oriented tubes as buoyant members connected to one another and separated by a distance of about two diameters. A ballast tube is spaced from the floating tubes, forming their width an isosceles triangle. The ballast tube rides in the water, perforated to readily permit water to enter and exit. Wave motion is perpendicular to the float tubes, tethered to an anchor at the sea floor. Operation includes rising by a lead float tube in response to an approaching wave. The trailing float tube rises with the wave, but later, due to the separation and distance. The asynchronous rise and fall of the floating tubes causes a rocking of the breakwater system. This results in pivoting or rotating the assembly of tubes and struts (and all three tubes, necessarily at the same time), redirecting and dissipating the original wave momentum, energy, and water volume moving “forward” toward the shore. 
         [0011]    Impact, flow around, and fluid drag on all three tubes and their intermediate struts cause redirection and dissipation of energy and momentum by motion of the tubes in the surrounding water. The circular cross-section of the tubes and struts causes longitudinal, lateral, and vertical dissipation and redirection of water along the length of the breakwater. The rocking causes churning in both the transverse (vertical) and lateral (horizontal) directions. Each is orthogonal to the longitudinal direction of the tubes. Redirection longitudinally is primarily due to the strut geometry. In practice, tremendous dissipation of energy has been effected, providing adequate attenuation of wind-induced waves on enclosed bodies of water as well as near shorelines subject to sea waves. 
         [0012]    In one embodiment of a method in accordance with the invention, the method may include attenuating waves in open water by providing an anchor, securing a tether to the anchor, providing an array of tubes fixed to one another and floating horizontally in water, and securing the array to the anchor by the tether. In providing the array, the array may constitute a triangulated cross-section having vertices defined by first and second tubes at least partially evacuated of water to render them buoyant. A third tube, the ballast tube, may be fixed with respect to the two floating tubes to move in substantially rigid body motion therewith. 
         [0013]    The first and second tubes may extend parallel to one another and the ballast tube and all extend substantially parallel to the surface of the water. The array may further comprise struts extending between the first, second, and third tubes. Typically, the first and second tubes are sealed and the ballast tube is perforated to admit from, and discharge into, a surrounding water environment. The struts may have perforations, which are also admitting and discharging water. 
         [0014]    A sleeve between the array and the tether is effective to reduce chafing or resist chafing between the tether and the array. 
         [0015]    The array further includes a first end wall and a second end wall to each of the first and second tubes at a respective first and second ends thereof, thereby sealing each of the first and second tubes. Flanges on at least one end of the array are mechanically fixed to the first end of each of the first, second, and ballast tubes to secure the array to another array of similar construction. 
         [0016]    A port apparatus extending through the top of a wall of each of the first and second tubes is effective to selectively introduce and remove a quantity of water with inside each of the first and second tubes. This provides a selection of mass and buoyancy for the top tubes (first and second tubes) when sealed. 
         [0017]    Struts extend between adjacent ones of the first, second, and third tubes. The angle of incidence of each strut is selected to engage the respective first, second, and third tubes at approximately a principal stress angle (zero, 45, 90 degrees). 
         [0018]    The apparatus rocks in the water. Rocking, by the array, in a subject body of water is in response to a wave impinging on the first tube as a lead tube, and passing under the second tube as a trailing tube, while the first and second tubes sweep the ballast tube through the water. The first and second tubes redirect water of the wave, transferring energy from the wave. The ballast tube transfers momentum and energy from the first and second tubes into water surrounding the ballast tube. The result is effective to substantially reduce the energy, momentum, and effective height of the wave impinging on the array. 
         [0019]    An apparatus typically comprises a first tube, a second tube fixedly secured to the first tube and spaced away therefrom, a third tube, operating as a ballast tube and fixed to both the first and second tubes, along with a tether secured between an anchor and at least one of the first tube, second tube, and third tube. The anchor is proximate a floor of the sea bed below a water level on which float the first and second tubes. The tether secures the at least one of the first, second, and third tubes to the anchor. The third tube is further provided with access to water surrounding it, in order to permit passage of water through the third tube. 
         [0020]    First struts may be secured between the first and second tubes, with second struts extending between the first and third tubes. Finally, third struts extend between the second and third tubes. All struts may be perforated. At least the second struts and third struts should be perforated to admit water within themselves. 
         [0021]    An anchor secures at least one of the first, second, and third tubes, by the tether, to resist movement away from the anchor within the body of water. Double tethers may extend away from each of the top (first and second) floating tubes in opposite directions. The anchor is effectively fixed proximate the “sea floor” representing the bottom of the body of water in which the first, second, and third tubes are placed and securing the tether. 
         [0022]    The struts are oriented, with respect to a longitudinal direction of the first and second tubes, to extend in a direction corresponding to at least one principal stress direction. End caps provide structural support proximate one or more ends of each of the first, second, and third tubes, as well as sealing for flotation of the first and second tubes. Flanges secured proximate a first end of at least one of the first, second, and third tubes may be fitted with fasteners or other securement mechanisms to extend (e.g., double) the length of the unit of first, second, and third tubes. 
         [0023]    In operation, the two horizontal members (floating tubes) remain buoyant, to an extent that depends on their contained-air-to-water ratio or, alternately, their void fraction (air volume divided by total volume). In contrast, the third member, extending parallel to them and fixed in relation thereto, remains fully submerged in and filled with water from the surrounding environment. 
         [0024]    The anchors, of any suitable type, but well served by a penetrating anchor fully buried below the “sea floor,” are arranged to secure one or more tethers (usually best served by about 5 tethers). The lines, ropes, or other stranded members constituting tethers each extend from the anchor to a member to restrain movement of the assembly of three members connected by struts. 
         [0025]    All members move in effectively rigid body motion, although they may have some deflection due to internal strain. In response to waves impinging on a leading member the assembly rolls about a centerline of rotation parallel to the members. As the wave continues (diminished toward and under the trailing member), the assembly rocks back in the opposition rotational direction. The resultant thrashing of water surrounding the bottom or third member transfers and dissipates momentum and energy from the assembly into the water. To a large extent, the top members (leading and trailing) dissipate and re-direct energy and momentum from the wave by impact against them, movement in translation, consequent rotation, breaking over the members by water of the wave, and so forth. The struts contribute as well to dissipation and redirection of wave momentum and energy to locations elsewhere in the water as well as into localized turbulence that converts to thermal energy. 
         [0026]    The result is substantial attenuation of energy, momentum, water volume, and height of the wave subsequently impinging on a shoreline or shoreward structures to levels below a predetermined fraction thereof initially found in the wave. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    The foregoing features of the present invention will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only typical embodiments of the invention and are, therefore, not to be considered limiting of its scope, the invention will be described with additional specificity and detail through use of the accompanying drawings in which: 
           [0028]      FIG. 1  is top, end perspective view of one embodiment of a breakwater or wave attenuation system in accordance with the invention; 
           [0029]      FIG. 2  is a bottom, end perspective view thereof, absent the tether and anchor; 
           [0030]      FIG. 3  is a top plan view thereof; 
           [0031]      FIG. 4  is a bottom plan view thereof; 
           [0032]      FIG. 5  is a front (windward, seaward) side elevation view thereof; 
           [0033]      FIG. 6  is a rear (windward, seaward) side elevation view thereof; 
           [0034]      FIG. 7  is an end elevation view thereof at the coupled (flanged) end; 
           [0035]      FIG. 8  is an end elevation view thereof from the free end; 
           [0036]      FIG. 9  is a front elevation view of a set of breakwater units secured together to make a single operational unit of double the manufactured length; 
           [0037]      FIG. 10  is a front elevation, cross-sectional view of a top tube or float tube of the breakwater of  FIGS. 1 through 9 , partially cut away to show both ends; 
           [0038]      FIG. 11  is a front elevation view of a breakwater in accordance with the invention, secured to the sea bed by a tether over both top tubes or float tubes; 
           [0039]      FIG. 12  is an end elevation view of an alternative embodiment of a tethering system securing only a leading float tube; 
           [0040]      FIG. 13  is an end elevation view of a breakwater system relying on tethering of the bottom or ballast tube portion thereof; 
           [0041]      FIG. 14  is a perspective view of an installation relying on several breakwater unit assemblies deployed in accordance with the invention by being arrayed across a body of water by such as a bay or harbor; 
           [0042]      FIG. 15  is an end elevation, schematic view of a breakwater in accordance with the invention illustrating the forces acting on the various tubes thereof; and 
           [0043]      FIG. 16  is a schematic diagram of the operational motion of a breakwater in accordance with the invention as it attenuates a wave. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0044]    It will be readily understood that the components of the present invention, as generally described and illustrated in the drawings herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the embodiments of the system and method of the present invention, as represented in the drawings, is not intended to limit the scope of the invention, as claimed, but is merely representative of various embodiments of the invention. The illustrated embodiments of the invention will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. 
         [0045]    Referring to  FIGS. 1 through 10 , while referring generally to  FIGS. 1 through 16 , a wave attenuation system  10  or breakwater  10  may involve several individual units. An individual unit  10  is composed of two floats  12  or float tubes  12  that ride on the surface by the buoyant actions of the water lifting the tubes  12  to the surface thereof, as a result of the contained air therewithin. Two “units” are typically connected end-to-end to make a “unit assembly.” A unit assembly is typically anchored individually as part of an array of such assemblies protecting a length of shoreline, a harbor, a property, or the like. 
         [0046]    Meanwhile, a ballast  14  or ballast tube  14  is fixed to the float tubes  12  to ride therebelow. The ballast tube  14  is provided with several large (one eighth to one quarter diameter) apertures  15 . Typically, the apertures  15  may be about four inches in diameter in a two-foot diameter ballast tube  14 . The float tubes  12  and ballast tube  14  in one embodiment are typically formed of a nominal two-foot-diameter, high-density, polyethylene tubing. The apertures  15  may be spaced at a suitable distance along the length of each of the ballast tubes  14 . Structurally they should not be less than three of their diameters apart. Six is better. Likewise, the apertures  15  may be distributed around the circumference of the ballast tubes  14 , typically being perforated along the bottom, and at 90 degrees thereto along the sides, and opposite thereto along the top center line along the ballast tube  14 . Comparatively larger apertures reduce strength but can increase form drag. 
         [0047]    The tubes  12 ,  14  are secured to one another by struts  16  or braces  16 . Typically, the struts  16  are also long tubes  16  of the same material (e.g., high density polyethylene) as the float tubes  12  and ballast tubes  14 . The struts  16  are typically welded by heat welding to fit with the principal tubes  12 ,  14 . A diameter of a nominal 12 inches for the struts  16  has been found satisfactorily. Certain of the struts  16  extend straight between adjacent tubes  12 ,  14 . Others of the struts  16  extend at an angle, typically at an angle corresponding to principal stresses (about 45 degrees and 90 degrees) with respect to a center line of an associated tube  12 ,  14  supported thereby. 
         [0048]    In the illustrated embodiments, the struts  16  are provided with apertures  17  to permit entry of water  37 . The apertures  17  need not be particularly large, and have been found suitable at a dimension of from about one to about three inches. A diameter of from about one to about two inches has been found completely suitable. It has been found advisable to form larger apertures  15  in the ballast tube  14  in order to provide additional fluid drag in the process of operation of the breakwater  10 . 
         [0049]    The wave attenuator system  10  or breakwater  10  is secured by an anchor  18  of any suitable type and a tether  20  running between the anchor  18  and one or more of the tubes  12 ,  14 . U.S. patent application Ser. No. 14/267,612, filed May 1, 2014 for CORROSION-AND-CHAFING-RESISTANT, MOORING SYSTEM AND METHOD is incorporated herein by reference and contains a detailed description of various suitable embodiments for an anchor  18  and tether  20 . 
         [0050]    The cavities  22  in the float tubes  12  operate as air chambers  22  to maintain the floats  12  riding high or at any suitable distance above the surface  36  of the water  37 . As a practical matter, the cavities  23  and the struts  16  are alternately filled and evacuated of water to some extent to increase buoyancy or mass, acting opposite each other. That is, due to the apertures  17  and the struts  16 , water may enter and leave the cavities  23  and the struts  16 . 
         [0051]    The wall  24  around each of the tubes  12 ,  14  may be of any suitable size, but has been found to be adequate at the manufacturing nominal size manufactured in conventional nominal 24 inch high density polyethylene tubing. It has been found suitable to leave the walls  24  as manufactured. Engineering calculations indicate suitable strength, durability, and longevity in service. 
         [0052]    One will note a guard  26 , typically formed of high density polyethylene tubing, such as about an eight inch nominal diameter tubing. The guard  26  is welded to each of the float tubes  12  in order to protect ports  28   a ,  28   b.    
         [0053]    The ports  28   a  are short, penetrating into the wall  24  of a float tube  12  in order to receive air or water therein. Meanwhile, the ports  28   b  are secured to include or communicate with a tube  29  extending down through each of the float tubes  12  toward the bottom surface thereof in order to purge water therefrom. By adding air through the port  28   a , the cavity  22  of each float tube  12  may be filled with air while the stand pipe  29  or tube  29  empties water from within the float tube  12  and passes it outside thereof through the port  28   b . The amount of air or water in each float tube  12  may be selected for best performance. 
         [0054]    Each of the float tubes  12  and ballast tubes  14  is provided with a flange  30  at one end  32   a  thereof. The opposite end  32   b  is simply sealed with an end wall  32   b . As a practical matter, the end walls  32   a ,  32   b  provide stiffening of the cylindrical tubes  12 ,  14 , thus adding structural integrity and stiffness. Meanwhile, the end walls  32   a ,  32   b  on the float tubes  12  seal the tubes  12  in order to render them sealed and buoyant on the surface of the water. 
         [0055]    The tether  20  may be threaded through a sleeve  34  of polyethylene tubing  34  that wraps around one or more of the tubes  12 ,  14 . The sleeve  34  provides chafing protection for the tether  20 . Typically, the tether  20  may be a suitable marine rope of a synthetic polymer (e.g., nylon, polyester, and polypropylene) that has long life when subject to the attack of marine organisms, chemicals, biological activity, and so forth. Accordingly, the sleeve  34  provides a long term chafing protection against the abrasion of the tether  20  on the outer surface of any of the tubes  12 ,  14 , to which the tether  20  may be secured. 
         [0056]    Multiple segments  10  or unit systems  10  may be concatenated or connected. Typically, the systems  10  may be made in units  10  or segments  10  of about 60 feet in length. Two of these  10  may be secured together to make another single longer assembly  10  by securing fasteners  31  through flanges  30  on the ends  32   a  of each of the tubes  12 ,  14 . The effect then is to provide a longer assembly  10  or wave attenuator system  10  of about 120 feet in length, having three tubes  12 ,  14  forming an isosceles triangle. The bottom tube  14  acts as the ballast tube  14  providing damping of motion of the system  10  in response to wave action. 
         [0057]    Referring to  FIGS. 11 through 16 , while continuing to refer generally to  FIGS. 1 through 16 , the system  10  operates by floating on the surface  36  or at the surface level  36  of a body of water  37  defined as extending between the water level  36  on the top thereof and a floor  38  or bed level  38  therebelow. The bed level  38  represents an upper surface  38  of a sea bed  40 . The sea bed  40  or floor  40  may be a concrete bottom, natural rock, soil, or whatever else may underlie a body of water  37 . 
         [0058]    In the illustrated embodiment, an anchor  18  may be fixed near but well below the surface  38  of the bed  40 . Here, the illustration shows an anchor  18  that has been embedded within the sea bed  40  below the floor  38  or bed level  38 . The tether  20  extends continuously from the anchor  18  up through the water  37  to engage one or more of the tubes  12 ,  14  of the breakwater  10 . The tether  20  may secure by a bowline knot, a re-woven loop or the like as understood in the marine arts. 
         [0059]    Referring to  FIGS. 11 through 13 , various embodiments of the tether  20  may engage one or more of the tubes  12 ,  14 . One advantage to the embodiment of  FIG. 1  and that of  FIG. 11  is that the float tubes  12  are both permitted free motion on the surface  36  of the water  37  except to the extent that the tether  20  may restrain them with respect to the anchor  18 . The embodiment of  FIG. 11  would cause more wear between the sheath  34  or sleeve  34  against the tubes  12  as a result of relative motion. 
         [0060]    Typically, the tether  20  will extend at an angle  41  with respect to the floor  38  as a result of action of the waves tending to push the breakwater  10  toward shore. Whether the angle  41  is measured with respect to a vertical direction rising from the floor  38 , or with respect to the floor, is a matter of arbitrary choice. However, the resulting angle  41  that the tether  20  deviates from vertical provides a vector of force on the float tubes  12 . 
         [0061]    For example, when the level  36  of the water  37  rises with a wave, the tether  20  of  FIG. 11  may draw the tubes  12  laterally  11   b  to be more directly over the anchor  18 . The tension in the tether  20  acts as a vector drawing the breakwater  10  toward the anchor  18 . Mathematically, that force vector does not change value substantially, but direction. It is resolved into a component parallel to the surface  36  of the water  37 , and an orthogonal component in a vertical direction  11   a . In  FIG. 1 , the force vectors do not change direction, due to permanent constraint. Force values, however change substantially in operation. Wave action causes pulling by buoyancy forces and lateral  11   b  as well as vertical  11   a  momentum. 
         [0062]    The directions  11  identify various directions  11  with respect to the system  10 . Herein, a trailing letter is a specific instance of a reference number. The direction  11   a  is nominally vertical, while the direction  11   b  is laterally or horizontally orthogonal thereto. Meanwhile, the direction  11   c  is longitudinally orthogonal to both the directions  11   a  and  11   b , and extending along the length or longitudinal axis of the tubes  12 ,  14 . 
         [0063]    Referring to  FIGS. 11 through 16 , and  FIGS. 1 through 16 , generally, the directions  11  may represent up or down, forward or backward directions, as needed. However, one may think of the direction  11   a  as the vertical direction of rise and fall of the apparatus  10  in response to waves, with the lateral direction  11   b  being the back and forth, shoreward and windward, direction with the wave and against the wave that the apparatus  10  may move. 
         [0064]    Similarly, the system  10  may rotate or roll about any of the axes  11   a ,  11   b ,  11   c . Thus, the breakwater  10  will tend to roll in the direction  11   e  as a wave strikes the leading float tube  12   a  and will then counterrotate in the direction  11   d  as the wave passes the float tube  12   a  and lifts the float tube  12   b . Of course, one may speak of the leading float tube  12   a  as that which strikes or receives the wave first, and the trailing float tube  12   b  as that which receives the remainder of the wave thereafter. 
         [0065]    One may see that a float tube  12   a  in rising with a wave  44  on the surface  36  of the water  37  will necessarily rotate the overall structure of tubes  12 ,  14 . As the wave  44  passes the leading tube  12   a  also identified by an L, juxtaposed to the trailing identified by the letter T, a rocking motion will persist forward  11   d  and backward  11   e  with respect to the breakwater  10  facing in its own “forward” direction  11   b  toward the incoming wave  44  advancing “forward”  11   a  in its motion (see  FIG. 1 ). Any time the system  10  tries to lift with a wave  44 , several forces act. Those forces act to redirect energy, momentum, and material (water  37 ) in various directions that randomize the influence of a wave  44 . The result is turning mechanical energy into thermal energy heating (ever so slightly) the water  37  by mixing vigorously. 
         [0066]    One may note that the connection scheme for the tether  20  about the float tubes  12   a ,  12   b  in  FIG. 11  will induce a somewhat different dynamic effect from that of the example of  FIG. 12 . For example, the comparatively lighter of overlying air  42  above the surface  36  of water  37  provides negligible resistance to waves  44 . Waves  44  rise as the floor  38  rises, momentum shifts, and the water  37  finds it easier to move up into the air  42  rather than contend with the resistance of surrounding water  37 . 
         [0067]    In the embodiment of  FIG. 1  and  FIG. 12 , the tube  12   a  will rise first, rotating with respect to the tube  12   b , since a tether  20  is secured about each of both the leading tube  12   a  and trailing tube  12   b . The influence of the ballast tube  14  remains effectively the same. That is, it must move through the water  37  in order for either of the tubes  12   a ,  12   b  to move. To move within the vertical plane (the page) illustrated in  FIG. 12 , the tube  12   a  must lift on the wave  44 . The trailing tube  12   b  does not follow the same magnitude of motion as the wave  44  is redirected. 
         [0068]    Referring to  FIG. 13 , securing a tether  20  about the ballast tube  14  permits rocking or rotating by the ballast  14  and float tubes  12   a ,  12   b . However, if double tethers of  FIG. 12  are used on the ballast tube  14 , to keep it in place, the tether  20  resist the necessary rocking action and fails to operate well. Thus, it has been found suitable to use a configuration of  FIGS. 1 and 12 , although the configurations of  FIGS. 11 and 13  may also be used. 
         [0069]    Alternative configurations may also be used, including securing the tether  20  to the struts  16 , to an anchor point or points along the tubes  12 ,  14 , or the like. However, it has been found effective to minimize tight (comparatively small, on the order of a few radii diameters of the tether  20 ) radii in loops of the tether  20 , and to eliminate metal. 
         [0070]    In the illustrated embodiment, no metal is required within the system  10 . In certain embodiments, the fasteners  31  for securing the flanges  30  together may be formed of metal for expediency. Metal provides substantial strength per unit of cross-sectional area, and may be fabricated from suitable materials, such as stainless steel, that resist corrosion. As the only metallic component, the fasteners  31  cannot set up di-metallic galvanic cell promoting corrosion. 
         [0071]    Referring to  FIG. 14 , a wave  44  may encounter an array  46  of the systems  10  in accordance with the invention. In one manner of speaking, the tubes  12 ,  14  are also configured in an array of three tubes. Likewise, an array  46  may represent several breakwaters  10 , each anchored by suitable tethers  20 , and assembled in pairs secured by intermediate flanges  30 . As a wave  44  approaches, an extensive region of water  37  may be protected by the array  46  of attenuators  10  or breakwaters  10 . Thus, one may speak of a breakwater  10  as the entire array  46 , or a single unit  10 , or some intermediate combination  10  thereof. 
         [0072]    Referring to  FIGS. 15 and 16 , while continuing to refer generally to  FIGS. 1 through 16 , a system  10  in accordance with the invention maintains a very sophisticated and effective pattern of movement. Materials floating on a surface  36  of a body of water  37  are common. Buoys and vessels, from dinghies to ocean-going ships, float on the surface  36  of various bodies of water  37 . Similarly, conventional breakwaters  10  may involve platforms of floating materials, such as logs, or fixed barriers, such as sea walls, rock embankments, and so forth. 
         [0073]    Always the wave energy and momentum (speaking of Newtonian physics and the laws of motion as defined by Newton as understood in the sciences of physics and engineering) demonstrate the transfer of energy and momentum from waves  44  to fixed or moving masses along the surface  36  of water  37 . Redirecting mechanical energy (force times distance) or power (force times velocity) requires redirecting momentum (mast times velocity), which necessarily requires redirection of forces and pressures (force per unit area). Meanwhile, redirection requires structures capable of supporting the tremendous energies and forces of waves  44 . Large forces, large momentum, and large size imply large costs, extensive time, and other artifacts of construction thereof. 
         [0074]    In an apparatus and method in accordance with the invention, a very sophisticated and complex motion occurs in the breakwater  10  based on an almost rudimentary triangular envelope. 
         [0075]    For example, in the illustrated embodiment, a leading tube  12   a  is identified by the letter L while a trailing tube  12   b  is identified by the letter T. A ballast tube  14  identified by a letter B completes the array  10  of tubes  12 ,  14 . The struts  16  have been idealized schematically as straight lines. In the illustrated embodiment, various forces occur. Upon the advance of a wave  44  toward the assembly  10 , the wave  44  effects motions in each of the tubes  12 ,  14 . 
         [0076]    For example, motion  54  in the vertical direction  11   a  results from the swell or the rise of a wave  44  as it advances. Meanwhile, the wave  44  is traveling and therefore contains energy and momentum directed in the direction  11   b . The result is a buoyant force  50   b  tending to lift the tube  12   a  or the leading tube  12   a . Likewise, the tethers  20  each exert a force  50   a  tending to restrain the leading tube  12   a  and trailing tube  12   b  toward their anchors  18 . The forces  50   c ,  50   d  that may exist within the strut  16  between the leading tube  12   a  and the ballast tube  14  also contribute forces restraining the leading tube  12   a  because of fluid drag on the ballast  14  whenever it moves relative to the water  37 . By the same token, forces  50   e ,  50   f  within the struts  16  between the leading tube  12   a  and the trailing tube  12   b  also contribute to the force balance. 
         [0077]    The net effect is a resultant force  52  that acts to move the leading tube  12   a  into a net effective direction  56  of the leading tube  12   a . Any motion  56  or direction  56  of movement in response to the resultant force  52  on the leading tube  12   a  results in a resistance force  50   c  on the tube  12   a  exerted by water  37  surrounding itself and by the ballast tube  14  and struts  16  being dragged through the water  37 . The leading tube  12   a  cannot ever move without moving the interconnected trailing tube  12   b , ballast tube  14 , and intervening struts  16 . 
         [0078]    One can immediately see that the forces  50   d ,  50   j  on the ballast tube  14 , imposed by the struts  16  extending toward the leading tube  12   a  and trailing tube  12   b , respectively, tend to move the ballast tube  14  against a resistance force  50   k . The resistance force  50   k  is applied as a “form-drag” of the water  37  acting on the ballast tube  14 . Form drag occurs in response to any motion in any direction. Thus, any tendency of the ballast tube  14  to move in the direction  56  with the lead tube  12   a  will be resisted by force  50   k  in the direction illustrated. However, the force  50   k  will be directed opposite any movement through the water  37 . 
         [0079]    Thus, translation vertically in the direction  11   a , horizontally or laterally in the direction  11   b  as well as in rotation  11   d ,  11   e  about any longitudinal axis of any of the tubes  12 ,  14 , or any central axis of the assembly  10  will result in churning of the water  37  and resistance to any movement therethrough by the tubes  12 ,  14 . 
         [0080]    Referring to  FIG. 16 , the progression of motion of the assembly  10  is illustrated through various phases. Progressing from left to right through this schematic illustration, one may envision a system  10  having a leading tube  12   a  and trailing tube  12   b  above a ballast tube  14 . Upon arrival of a wave  44 , the level  36  of the water  37  rises below the leading tube  12   a . The result of the resultant force  52  imposed by a combination of the buoyance of the tube  12  on wave  44 , fluid drag, and the tether  20  is a rising and pulling back against the anchor  18  of the leading tube  12   a . Meanwhile, the lifting of the leading tube  12   a  results in rotating the assembly  10 . Such motion results in necessarily displacing the trailing tube  12   b  sitting at a lower level  36  of the water  37 , and correspondingly displacing the ballast tube  14  against the resistance of surrounding water  37 . 
         [0081]    Thus one sees the net translation motion  54   a  of the center of mass that may be a net result, and the rotation  54   b  about some axis of rotation. As the wave  44  progresses to the right in the schematic illustration, the level  36   a  of the water  37  under the leading tube  12   a  drops as the swell of the wave  44  tends to lift the level  36   b  of the water  37  under the trailing tube  12   b . This motion reverses the direction of a rotation  54   d , and also may result in a rise  54   c . As a practical matter, any lift  54   a ,  54   c  in any rotation  54   b ,  54   d  will necessarily be a result of the vector of all forces  50  operating on the system  10 . 
         [0082]    Eventually, the weight of the system  10  and the receding of the level  36  of the water  37  to a flat and level surface  36  results in the leading tube  12   a  and trailing tube  12   b  once again dropping  54   e  and rotating back  54   f  to their original equilibrium position. At each point of motion, each of the tubes  12   a ,  12   b ,  14  thrashes through water  37  for every motion required therethrough. 
         [0083]    Drag factors may be found in standard textbooks identifying the form drag or fluid drag of various fluids at various densities as they pass over inner or outer surfaces of solid structures. Accordingly, the tubes  12 ,  14  present form drag to the passing wave  44 , churning and thrashing the water  37  in response to their motions  54  resulting from the balance of resultant force  52  on the system  10  in each of its components  12 ,  14 ,  16  passing through the water  37 . 
         [0084]    In experiments, it has been found that an apparatus and method in accordance with the invention is very effective at reducing the momentum, energy, crest height, and deleterious effects of waves  44  progressing toward shore lines and shore-bound structures. 
         [0085]    Referring to  FIGS. 1 through 16 , several principles have been found significant in providing a suitable breakwater  10 . Initially, the size and spacing of the tubes  12 ,  14  appear to be significant. For example, it has been found that the diameter of the floating tubes  12  should be of about the same size or order of magnitude as the typical swells  44  or waves  44 . A wave  44  expected should typically be not more than about two or three tube diameters in height between crest and trough of a wave  44 . This assures that a significant amount of any cresting wave does not pass over the breakwater  10  upon breaking of the wave  44 . 
         [0086]    Another feature is the spacing between the floating tubes  12 . The distance between tubes should also be about two diameters. A greater distance is satisfactory, but changes performance. A lesser distance tends to leave problems with residual water passing over the entire breakwater  10 , interferes with the rocking or rotational component of motion, and reduces the leverage that the ballast tube  14  can exert against the float tubes  12 . 
         [0087]    Also, the fill amount in each of the float tubes  12  has been found to be a significant factor in engagement of the ballast tube  14 . The specific gravity (an engineering and physics term, well understood in the art, and indicating the ratio between the density of a particular material compared to the density of water as the denominator) of the high density polyethylene (HDPE) embodiment of the apparatus  10  is around 0.92 to about 0.95. Typically, it seems to be in the range of about 0.93 to 0.94. This means that the HDPE will actually float in water, but barely. It is slightly less dense than water, but only by less than ten percent. 
         [0088]    The breakwater  10  can still function with the float tubes  12  containing a substantial amount of water. Filling the float tubes  12  with a fraction of water (any amount is feasible) typically from about one third to about two thirds provides good flotation and increases the overall mass of the float tubes  12 . Thus, the tube  12  on a swell  44  or wave  44  does not tend to have as much buoyancy. This results in less force to lift the float tubes  12  with the swell  44 , and to drag with them the ballast tube  14  through the water  37 . This means that the float tubes  12 , themselves, represent an obstruction that must be faced by an oncoming wave  44 . To the extent that the float tubes  12  have a greater fill or fraction of water inside them, they can no longer float as easily upon the top of the rising wave  44 . This results in the breakwater  10  operating more like a rigid emplacement, with less float tube  12  response. 
         [0089]    However, even with water inside the float tubes  12 , greater than one third of the volume thereof, the pushing by the wave  44  or swell  44  against the float tubes  12  still results in rotation or rocking of the assembly  10 . The corresponding churning of the water below the swell  44  arises from being thrashed by the ballast tube  14 . 
         [0090]    The ballast tube  14  operates according to the principles of form drag of a solid object in a fluid. Drag force is proportional to half the density multiplied by the presented area and velocity squared. Constants of proportionality depend on the shape of the body moving in a fluid. They are available as correlations to a value of Reynolds number. To a certain extent, this may be modified by some passage of water through the apertures  15  in the ballast tube  14 . Both can be modeled by principles of fluid mechanics to provide the net fluid form drag on the ballast tube  14 . Drag resists it in response to its need to rock. Rocking occurs in reaction to the driving of the float tubes  12  by oncoming wave  44  or swell  44 . 
         [0091]    As to the spacing between the float tubes  12 , vigorous wave  44  approaching the point of breaking, as that term is understood in the marine arts, a wave  44  will often be forced to break by the resistance to motion imposed by the leading float tube  12   a . Again, the spacing between the float tubes  12  or top tubes  12  is effective to receive any wash or crest passing over the lead tube  12   a . The trailing tube  12   b  then provides a similar resistance to passage by the water from the crest, thus encouraging it to flow down between the tubes  12 . 
         [0092]    Tethering has been experimented with in several embodiments. In all the illustrated embodiments, a tether  20  is not rigid. That is, for example, the breakwater  10  is not fixed to a wall, rigidly fixed in space by any other superstructure, or the like. The breakwater  10  is always permitted to move in response to oncoming waves  44 . Several embodiments have been experimented with, teaching much about the hydrodynamic response of the breakwater  10  in a body of water  37 . 
         [0093]    The float tubes  12  are urged by the rising water level  36  of an advancing wave  44  to float upward. Moreover, the cyclic flow and ebb of the oncoming wave  44  also encourage a shoreward and windward motion  11   b  or lateral  11   b  motion in addition to the vertical  11   a  rise and fall of the top tubes  12  in sequence. The leading tube  12   a  first rises, followed by the trailing tube  12   b . Meanwhile, the trailing tube  12   b  will typically not respond as dramatically to flotation forces, nor the dynamic impact forces of an oncoming wave  44 . This occurs because the leading tube 3   12   a  already meets the forces, and initially breaks up the direction of flow of the oncoming wave  44 , and redirects the water, forces, momentum, and energy thereof. The trailing tube  12   b  and ballast tube  14  steady the leading tube  12   a  at all times. 
         [0094]    Tethering may be done in one of several ways. The currently contemplated embodiment of  FIG. 1  may involve tethers  20  angling down both shoreward and windward at a modest angle of from about 50 to about 20 degrees. Typically, an angle from about 30 to about 45 degrees from horizontal has been found a reasonable compromise. 
         [0095]    For example, a certain downward resistance force is presented by the tethers  20 , as well as a lateral force. The force component in the vertical direction  11   a  is significant in resisting ready flotation by the top tubes  12 . Likewise, forces in the lateral direction  11   b  also stabilize against the flow and ebb forces of a wave  44 . Thus, if each is to be resisted equally, then a 45 degree angle is most appropriate. On the other hand, additional length of tethering  20  may result in reducing that angle. Herein, that angle is defined with respect to the horizontal direction  11   b , such as a seabed level  38 . 
         [0096]    In most embodiments, the double tethering in both of the lateral directions  11   b  (e.g., ebb and flow, windward and shoreward, or windward and leeward) and the downward direction  11   a  is important on each of the free ends  32   b . However, the typical length of one assembly of a breakwater  10  is about 60 feet. Accordingly, when two are connected together by their flanges  30 , they represent a length of about 120 feet. To avoid bending, it has been found suitable to tether the top tube  12   a  near the flanges  30  with at least one other tether  20  providing resistance or force applied to the top tube  12   a  (leading tube  12   a ) in the windward direction. 
         [0097]    It has been found that the use of a tether  20  made of a twisted or braided polymeric rope, such as nylon, polyester, or the like provides a certain useful amount of elasticity. Other elastic members may be interposed along or as part of the tether  20 . The effect of the elasticity in the tether  20 , from either source (rope, elastic member, mass of system  10 , air, etc.) is an additional resistance that the force and momentum of a wave  44  must work. Thus, the resistance to rocking of the breakwater  10  occurs as a result of the mass of the top tubes  12 , including any enclosed water, the mass of the ballast tube  14 , form drag of fluid over and through the system  10 , and the forces exerted by the tethers  20  in the vertical direction  11   a  as well as the lateral direction  11   b.    
         [0098]    Referring to  FIGS. 1 through 16 , while also focusing on the views of  FIGS. 3 and 4 , one will notice that a void fraction exists as any wave  44  passes in a vertical direction  11   a  through the maze of top tubes  12 , struts  16 , and the ballast tube  14 . Similarly, referring to  FIGS. 5 and 6 , a void fraction and an interference fraction (occupied space) are presented to an oncoming wave  44  approaching from a lateral direction  11   b  or horizontal direction  11   b . The effects are different. 
         [0099]    The effect of encountering a wall around a circular cross-section or a tubular (e.g., right, circular cylinder) shape is that no area is directly presented normal (perpendicular) to the tubes  12 ,  14  and struts  16 . Theoretically, only a line is normal to any direction of approach to the outer surface of a round tube. In every event, the waves  44  must strike obliquely the surface area of the outside surface of any of the tubes  12 ,  14  and struts  16 . This deflects the water mass, momentum, and energy away from its original direction of travel. It immediately induces a new direction and path calculated to cause interference between the various redirected flows. 
         [0100]    As a result, momentum is taken out of the principal directions of the vertical direction  11   a  of the rising swell  44 , and the horizontal direction  11   b  or lateral direction  11   b  of its progress toward the shore behind (beyond) the breakwater  10 . Meanwhile, the net momentum is not completely reversed. In fact, it is hardly reversed at all except for splashing and collisions. 
         [0101]    If the wave  44  were to strike a solid wall, all momentum must be transferred into the wall, and a certain proportion of that momentum that was not dissipated would then be thrust out away from the wall. Here, the momentum is directed obliquely away from the obstructing tubes  12 ,  14  and struts  16 , toward the openings therebetween. 
         [0102]    The void fraction is the fraction of unobstructed area that can be seen passing through the maze of tubes  12 ,  14  and struts  16 . However, considering only void fraction is informative, but not complete. The void fraction will allow the passage of a certain amount of the water  37  from a wave  44 . However, even that water  37  has been influenced, mixed, struck, and redirected by the water  37  flowing around each of the tubes  12 ,  14  and struts  16 . The apertures  17  in the struts  16  are calculated to be comparatively small, and may actually be neglected in any hydrodynamic analysis. 
         [0103]    The apertures  15  in the ballast tube  14  are considerably larger, amounting to approximately one sixth the diameter of that ballast tube  14 . Thus, they may be ignored in some analyses, but may also be accommodated by analyzing their tortuous flow path. However, the resistance to flow, unless apertures  15  are directly opposite one another to permit flow through the ballast tube  14  in a lateral direction  11   b  or even a vertical direction  11   a , will be substantial, and may properly be ignored in a first order analysis of the fluid dynamic drag of the water  37  passing over or around any particular member  12 ,  14 ,  16 . 
         [0104]    The triangulation of the tubes  12 ,  14  in the illustrated embodiment forms an isosceles triangle. It is not required to have an isosceles triangle. However, one must realize that anything other than an isosceles triangle changes the net leverage of any particular tube  12 ,  14  with respect to any other tube  12 ,  14 . For example, if the struts  16  between the top tubes  12  and the ballast tube  14  are longer than those between the float tubes  12 , than the ballast tube  14  has greater leverage in resisting the natural rocking. 
         [0105]    The rocking is important, and is substantial. Even in small, modeled, laboratory experiments, an attempt to apply force to the ballast tube  14  in order to steady it against rocking was completely ineffective. The energy of the wave  44  is applied to every tube  12 ,  14  the breakwater  10 , and the rocking and churning will not be denied. However, that rocking is resisted at all times by the form drag of the surrounding water  37  against all tubes  12 ,  14 ,  16  moving therein. 
         [0106]    The planes defined by the center lines of each set of struts  16 , passes through the center line of each pair of adjacent tubes  12 ,  14 . One will see that even these planes are oblique to the oncoming wave  44 . In addition, only the front most contact line of any tubular member  12 ,  14 ,  16  could ever be normal to the direction of a wave  44 . Thus circular tubes  12 ,  14 ,  16  divide and redirect the water, rather than stopping or reversing it. 
         [0107]    The void fractions or open spaces seen through the maze of members  12 ,  14 ,  16  are not required. However, a solid or uninterrupted surface would defeat several beneficial functions. Tubes  12 ,  14 ,  16  provide redirection of water and form drag against such relative motion. Thus, to balance forces to effective levels, redirected water needs a path that does not reverse. 
         [0108]    In order to obtain the proper operation, it has been found that a diameter of each of the tubes  12 ,  14  should be related to the maximum expected wave height, crest to trough. A range of from about one wave height to about five works, and three wave heights has been found suitable, economical, and effective. Meanwhile, a diameter of each of the struts  16  has been found to be best suited for both mechanical and hydrodynamic purposes at about one quarter to about three quarters of the diameter of the operational tubes  12 ,  14 . 
         [0109]    A diameter of the struts  16  equal to about half the diameter of each of the tubes  12 ,  14  has been found highly suitable, providing a void fraction that provides a workable and effective void fraction, adequate rocking, and excellent effectiveness at breaking waves, while providing structural integrity of the entire breakwater  10 , its structural connections, anchors  18 , and tethers  20 . Decreasing the void fraction can be expected to cause more momentum transfer of “redirection” into the breakwater  10 . Eventually this risks potential damage to tethers  20 , anchors  18 , and structures of the breakwater  10 . 
         [0110]    In the illustrated embodiments, it has been found advisable to provide a one-hundred-percent-coverage welding by thermal welding for all contacts between the tubes  12 ,  14  and the interconnecting struts  16 . This has been cohesive welding based on a melted, thermoplastic polymer substantially identical to the base material of the other members  12 ,  14 ,  16 . 
         [0111]    As a practical matter, it has been found suitable to provide certain struts  16  that pass directly and orthogonally with respect to the longitudinal direction to each of the tubes  12 ,  14 . Initially, these provide inter-tube spacing initially in a straightforward manner, so that the diagonal struts  16  can then be installed. They also provide a certain amount of support by way of tensile and compressive force transfer directly between the tubes  12 ,  14 . They do not provide as good longitudinal support as the diagonal struts  16  in operation. 
         [0112]    In the illustrated embodiment, the system  10  is virtually corrosion proof. No galvanic cells are set up. No differences in metallic constituents are present. It has been found that the flanges  30  are best secured together by fasteners  31  formed of nonreactive, non-corroding, stainless steel. All other connections and members, from the anchor  18  up through the tether  20 , and including all the other structural members  12 ,  14 ,  16 , are formed of polymers. The polymers (such as HDPE) are nonreactive with sea water or normal constituents of fresh water or salt water. 
         [0113]    In the illustrated embodiment, virtually no flow propagated by a wave  44  is allowed escape. The illustrated embodiment was installed in certain locations where the maximum expected wave height was about five feet. The two-foot diameter of the tubes  12 ,  14 , coupled with the eight foot (e.g., greater than one wave height) outer dimension across any base or side of the triangle formed by the tubes  12 ,  14 . This relation assured that the effect of the wave  44  was intercepted directly by at least one of the members  12 ,  14 ,  16 . 
         [0114]    Moreover, even any fraction of flow that may persist below the surface  36  of the water  37  deeper than the position of the ballast tube  14 , is nevertheless affected by the vortices and churning occasioned by movement of the ballast tube  14 . Thus, there is substantially no “free stream” (e.g., unperturbed, distant) flow at the wave velocity in either the vertical direction  11   a  or the horizontal direction  11   b  or lateral direction  11   b  without a system width of (across) the breakwater  10 . Instead, all the surrounding water  37  is subjected to impact, change of direction, mixing, and so forth occasioned by the rocking of the breakwater  10  in the waves  44 . 
         [0115]    As a practical matter, one will notice that forces applied to the breakwater  10  are triangulated by the tubes  12 ,  14  and struts  16 . Thus, the system  10  is very stable. Forces are transferred in tension and compression directly. The wall thicknesses of the materials of the members  12 ,  14 ,  16  may be selected at nominal values for such structures and still provide adequate stiffness, strength, section modulus, and so forth as needed for the mechanical properties thereof. 
         [0116]    The maximum or minimum size at which a breakwater  10  may still successfully operate appears to be within an order of magnitude, and most likely within half an order of magnitude of the wave height. That is, diameters of the tubes  12 ,  14  should typically be within one third to one half an order of magnitude of the maximum wave height from crest to trough. 
         [0117]    A void fraction in the projected area normal to a wave has been found to be adequate in the range of about twenty five percent to about sixty six percent. Higher void fractions will simply reduce the effectiveness at redirecting all of the water from the wave  44 . One function is redirection without having to absorb the momentum and energy into the breakwater  10 . Those properties need to be redirected as randomly as possible. The resulting mechanical energy is thus reduced to heat by “mixing.” 
         [0118]    Smaller void fractions will put greater stress on the anchors  18  and tethers  20 , and may result in more momentum and energy transferred to the breakwater  10 , rather than redirecting the energy and momentum of the waves  44  into a churning effect. The fundamental charter of a breakwater  10  is to reduce the momentum and energy striking the shoreline or shore structures. 
         [0119]    A wave attenuation system (WAS)  10  illustrated in the accompanying  FIGS. 1 through 16  is designed to reduce the amplitude of wind-generated surface waves in marine, sea and fresh water, environments. Wind-generated surface waves  44  have wave periods (time of passage from crest to crest) that range from less than 0.1 seconds to 30 seconds but may range up to 5 minutes. In the areas where WASs  10  are being tested, typical wave amplitudes (height from trough to crest) of wind-generated surface waves  44  vary from mere inches (ripples) upward to amplitudes of 5 to 6 feet. Wavelengths (distance from crest to crest) are from about 25 feet, for small waves on the order of 1-foot high, to 100 feet for 5-ft high waves. The typical installation for a WAS  10  is contemplated to be in the nearshore environment as a means of protecting marinas and boats, shoreline structures, and other human-made floating and shoreline features from wave damage. It functions as an alternative to other types of breakwater systems, such as floating logs and rock, earthen, and concrete berms, and various wood, rock, or concrete sea walls. 
         [0120]    The WAS  10  in experiments was constructed almost entirely of high-density polyethylene (HDPE) for its high strength-to-density ratio. Its density, 0.93 to 0.97 grams per cubic centimeter, is slightly less than that of water (˜1.0 g/cm3). It has a sufficiently high tensile strength and tends to tear and draw (strain) when it fails or is damaged, rather than brittle fracturing, thus not producing sharp, jagged edges or pieces. It resists corrosion, leaching of chemical constituents and their derivatives into the surrounding waters, and degradation caused by solar radiation, particularly in the ultraviolet wavelengths. The structural components  10 ,  12 ,  14 ,  16 ,  30 ,  32  composing the WAS were joined by thermal welding. 
         [0121]    The operation of the WAS is based on the premise that amplitudes of wind-generated waves can be reduced by disrupting, reflecting, and randomizing the trajectory of the wave energy away from its initial path toward shore. Traditional floating breakwaters function in large part by simply presenting a considerable floating mass extending over a significant fraction of the length of a wave that depresses the crest of waves. 
         [0122]    The shape of each the three tubes  12   a ,  12   b ,  14  and the array of struts  16  as cross members, presents a curved (e.g., a right, circular cylinder) face to approaching waves, virtually regardless of the direction of wave propagation. This causes the wave mass, momentum, and energy contacting the structure to be deflected and redirected away from the individual elements of the structure  10 . The redirected streams are churned or thrashed by each other and subsequent encounters with other elements  12 ,  14 ,  16  of the breakwater  10  and surrounding water  37 . The result is extensive dissipation of momentum and energy. Specular reflection is virtually non existent. 
         [0123]    The top two, buoyant, surface tubes  12  function to maintain the orientation of the WAS in the water. Together, they intercept and redirected surface waves or the water moved by them. Water that does manage to pass over the windward tube  12   a  then encounter, the shoreward tube. Again, the mass is redirected to mix with and slow down with the bulk liquid water in the region. 
         [0124]    The perforated submerged ballast tube  14  weighs little, because of the nearly neutral density of HDPE in the water. It has almost no weight relative to the surrounding water. It has considerable mass and an area that creates substantial form drag resisting passage of water thereacross. This mass, and the resistance force of drag that the tube itself exerts in moving through the water, increase the effectiveness of the two buoyant surface tubes in redirecting water near the crests of passing surface waves. 
         [0125]    Passing waves  44  cause the entire structure  10  to rock in a direction  11   e  perpendicular to the direction  11   b  of wave propagation. As the crest of a wave  44  passes the windward buoyant surface tube  12   a , it exerts an upward lift. This causes the top of the structure  10  to tilt toward the shore, causing the submerged, perforated ballast tube  14  to rock toward the windward direction, opposite to the shoreward direction of the way  44   e.    
         [0126]    As the remaining crest of the wave  44  encounters the shoreward buoyant tube  12   b , the submerged ballast tube  14  swings in pendulum-like fashion, churning through the water  37  toward the shore. As a result, the submerged ballast tube  14  causes the entire structure  10  to resist moving up and down due to form drag and contained mass. It resists rocking back and forth, yet does so, dissipating energy because of the mass, shape, and area of the tube  12 ,  14 ,  16  resistance to moving though the water. Performance of the entire WAS  10  is excellent, dissipating wave energy and momentum by churning and mixing it in a multitude of trajectories around the tubes. Two-foot high wave virtually completely dissipated. More vigorous waves self destruct under more vigorous rocking of the system  10 . 
         [0127]    The arrangement of struts  16  is structurally robust. Arrangement along principal stress lines resists failure of the system  10 . The differences in orientation present a complex structural path to oncoming waves, regardless of the direction of propagation. Thus they further redirect and dissipate wave energy and momentum by providing additional round faces to redirect and collide mass flows of wave energy in a complex array of directions within, through, and around the structure  10 . 
       Example I 
       [0128]    A wave attenuator  10  was constructed with a six foot surface width by eight foot depth. Making the wave attenuator to have a six foot width did not allow for effective diagonal bracing. Therefore, the surface braces were parallel to the wave coming in. The system worked very well. 
         [0129]    The ports  28  were added to add or remove (as required) water to the upper tubes  12 . In the summer water was added to lower the attenuator  10  and make it more massive (added weight of water) and less visible. In the winter water was pumped out, raising the attenuator  10 , making it more buoyant. Two one a half inch diameter pipes were welded into the 24 inch tube  12  (one pipe  29  was 23 inches, the other very short). Air blown into the short pipe (at five psi or less) forced water out through the long pipe  29 . Flotation (buoyancy) can be infinitely adjusted. 
       Example II 
       [0130]    A wave attenuator  10  (of 100 foot length) had an eight foot width across adjacent main float tubes  12  with diagonal, cross-bracing struts  16  worked well, an improvement over the six foot width with struts  16  running straight between. 
       Example III 
       [0131]    Combining the wave attenuator  10  with a dock float system, was tested at a wave testing facility with scaled prototypes for testing. When hooked to pilings or other docks to reduce rocking the wave attenuator system  10  did not function satisfactorily. The attenuator  10  needs to move in response the wave  44 . 
       Example IV 
       [0132]    Prototype wave attenuators  10  in accordance with the invention were constructed to include three 24 inch diameter high-density polyethylene (HDPE) pipes  12 ,  14 . Two of the three pipes, used as flotation tubes  12  with captive air, were on the surface  36  separated at an overall outside distance of eight feet (the first one was six feet). The ballast tube  14  was underwater and separated from the upper tubes  12  by the same distance, eight feet outside measure. These were held together with diagonal 12-inch-diameter HDPE struts  16 . Tubes  12 ,  14  cut 60 feet in length are shippable by common carrier. A width of 8 feet or less is shippable without special highway permits. These flanges  30  connect the 60 foot sections of tubing together. Flanges  30  bolted together on the ends of all three tubes  12 ,  14 . The wave attenuators  10  were held in place by tying rope around the upper 24-inch-diameter tubes  12 . This rope was threaded through sleeves  34  of small HDPE pipe (which is flexible) acting as chafe guard  34 . Therefore, HDPE tubes  12  are rubbing on HDPE pipe and the rope is protected. This rope goes to the seabed  40  where it is attached to an anchor system  18 . 
         [0133]    The present invention may be embodied in other specific forms without departing from its purposes, functions, structures, or operational characteristics. The described embodiments are to be considered in all respects only as illustrative, and not restrictive. The scope of the invention is, therefore, indicated by the appended claims, rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Technology Category: 4