Patent Publication Number: US-2012027526-A1

Title: Method and structure for reducing turbulence around and erosion of underwater structures

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     The Present Application claims the benefit of priority from U.S. Provisional Patent Application No. 61/368,883 entitled “METHOD AND STRUCTURE FOR REDUCING TURBULENCE AROUND AND EROSION OF UNDERWATER STRUCTURES” and filed on 29 Jul. 2010, the contents of which are hereby incorporated by reference in their entirety to the extent permitted by law. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to methods and structures for reducing turbulence around and erosion of underwater structures. More specifically, it relates to methods and structures for reducing turbulence around and erosion of underwater structures and reducing scouring of ground supporting and surrounding the underwater structure. 
     BACKGROUND 
     Traditionally, many underwater structures use a cylindrical, square or rectangular design, which are generally not considered aerodynamic. As used herein, an underwater structure is a structure of which at least a portion is immersed for some period of time in a body of water, such as a stream, a river, a lake, or an ocean. At least a portion of the underwater structure is therefore for some period of time under a water line of a body of water. Underwater structures include support structures and abutments. Support structures are meant to include any type of structure that is used to hold up a building, a bridge section, or a walkout for fishing or sight-seeing, and include bridge piers and pillars. An abutment is generally the point where two structures or objects meet, such as an end support of a bridge. 
     Since underwater structures are generally not aerodynamically shaped, the flow of water, and other liquids which flow around an underwater structure, may become a violent flow, such as a vortical flow, a turbulent flow, and a cavitational flow occurring around the underwater structures. There are several types of vortical flows in fluids, some are well defined regular, essentially laminar, rotational flows, some are random, essentially turbulent, rotational flows, and some are a mixture of regular and random flows. Vortical flows can be characterized as being either shed vortices or bound vortices. 
     Shed Vortices are the vortices most commonly encountered on support structures such as piers and pylons and are not as damaging as bound vortices. Shed vortices are essentially those described by Kármán&#39;s vortex laws, in which a well regulated series of vortices are shed from a support structure in the water, for example. One can observe them at any support structure in the water, especially rivers where muddy water allows them to be seen easily. Generally the vortices switch from side to side in the water, but not always, as some simply are always shed from the same side, especially in rivers where the mud content seems to force them to always be on one side. Shed vortices also appear in air, for example on tall chimneys, electric towers, and on electric wires stretched between poles or towers. Sometimes the regular shedding causes a resonance in the towers, chimneys, wires, etc, which can lead to structural damage from large amplitude vibrations. 
     Bound vortices are the most likely vortical flows to cause damage. Bound vortices are especially damaging to support structures and abutments, since they tend to form at a junction between a body of water and a mud line of the body of water, such as a river bed. The constant vortical action of bound vortices causes soil at the mud line to be sucked away and eventually develops into a continuous pattern of soil removal, typically behind the support structure that results in a sizeable hole forming This action at the support structure&#39;s bottom is called scouring. The removal of soil at the junction weakens the support structure&#39;s support, hence weakening the above-water structure being supported. Bound vortices are initially formed at some critical speed of flow, and are initially well defined and almost laminar at least in the vicinity of the support structure. The bound vortices that trail away eventually breakdown into more turbulent flows. As the flow speed is increased above that where the bound vortex is initially formed, even vortices at the support structure starts to show some signs of breakdown or random behavior. Likewise the vortices that trail behind the support structure are increasingly more turbulent which increases the scouring action. 
     Cavitational flows are similar to stall conditions of air flowing over a wing in air, except that they occur in water. Here a nominal laminar flow separates from the surface of an object in water, such as a wing, a propeller, or even a dam surface. This separation is severe, as cavitational flows behave very violently, and generally are random. Dams suffer frequent damage as chunks of concrete may be ripped, out necessitating major repairs. One major wear factor of boat propellers is damage due to cavitational flows, or cavitation. 
     Turbulent flows may add additional stress on the sides of the underwater structure, which may lead to erosion, wear, and a weakening of the underwater structure, and eventually, may lead to a catastrophic failure of the underwater structure. The turbulent flow causes turbulent loading of the support structure which is directly transmitted to the above-water structure being supported. 
     Moreover, at the mud line of the body of water in which the underwater structure is anchored, the soil around the underwater structure may become scoured and eroded due to turbulence which may form around the underwater structure at the mud line. As a result, the scouring and erosion at the mud line of an underwater structure may lead to the eventual weakening of the underwater structure at the mud line since soil which is typically used to stabilize the underwater structure is displaced. Often times, to combat this scouring, large concrete blocks or rocks are dropped near the base of the underwater structure around the underwater structure, at the mud line. However, many times these large concrete blocks or rocks just result in an increase of the turbulence around the underwater structure and causes further scouring of the soil around the base of the underwater structure. 
     The scouring and erosion of soil, such as mud, sand, or rocks, at the base of the underwater structure may weaken the underwater structure, potentially leading to erosion of or even catastrophic failure of the underwater structure. In addition to turbulence, cavitation effects in the fluid flow may form around the underwater structure which may also cause erosion of or even catastrophic failure of the underwater structure, and contribute to scouring and erosion of soil around the underwater structure. 
     As a result of stress, wear, and ground erosion around underwater structures due to violent flows, such as turbulence, vortical flows, and cavitation effects formed around the underwater structures, maintenance costs associated with underwater structures is often increased. Additionally, safety inspections of underwater structures may also need to be increased. As a result, it would be desirable to develop and deploy designs for underwater structures that will reduce stress, wear, and ground erosion around underwater structures due to violent flows. 
     SUMMARY OF THE INVENTION 
     The present invention is defined by the following claims, and nothing in this section should be taken as a limitation on those claims. 
     In one aspect, an underwater structure for supporting an above-water structure having an underwater portion immersed for some period of time underneath a water line of a body of water is provided. The underwater structure includes, but is not limited to a turbulence reducing member connected with the underwater portion. 
     In one aspect, a turbulence reducing member connected with an underwater water structure for supporting an above-water structure having an underwater portion immersed for some period of time underneath a water line of a body of water is provided. The turbulence reducing member includes, but is not limited to, a fixed air foil, a vertical fence, a horizontal fence, a curved fillet, a straight fillet, an articulating air foil, or a fluttering air foil. The turbulence reducing member is aerodynamically shaped to break up or reduce the turbulence of a flow of water flowing around the underwater portion. The flow of water is flowing in a first direction towards the underwater structure. 
     In one aspect a method for reducing turbulence around and erosion of an underwater structure for supporting an above-water structure having an underwater portion immersed for some period of time underneath a water line of a body of water is provided. The method includes, but is not limited to, connecting a turbulence reducing member with the underwater portion. The turbulence reducing member is aerodynamically shaped to break up or reduce the turbulence of a flow of water flowing around the underwater portion. The flow of water is flowing in a first direction towards the underwater structure. The method further includes, but is not limited to, aligning the turbulence reducing member with the first direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. 
         FIG. 1  depicts a perspective view of an underwater structure, in accordance with one embodiment of the present invention. 
         FIG. 2A  depicts a perspective view of a turbulence reducing member surrounding an underwater structure, in accordance with one embodiment of the present invention. 
         FIG. 2B  depicts a top cross sectional view taken along line A-A of the turbulence reducing member surrounding the underwater structure of  FIG. 2A , in accordance with one embodiment of the present invention. 
         FIG. 3A  depicts a side view of a movable turbulence reducing member surrounding an underwater structure, in accordance with one embodiment of the present invention. 
         FIG. 3B  depicts a top cross sectional view taken along line B-B of the movable turbulence reducing member surrounding the underwater structure of  FIG. 3A , in accordance with one embodiment of the present invention. 
         FIG. 4A  depicts a side perspective view of a vertical fence used as a turbulence reducing member connected with an underwater structure, in accordance with one embodiment of the present invention. 
         FIG. 4B  depicts a side view of a horizontal fence used as a turbulence reducing member connected with an underwater structure, in accordance with one embodiment of the present invention. 
         FIG. 5A  depicts a side perspective view of a vertical fence used as a turbulence reducing member connected with an underwater structure with fillets, in accordance with one embodiment of the present invention. 
         FIG. 5B  depicts a side perspective view of a turbulence reducing member connected with an underwater structure with curved fillets, in accordance with one embodiment of the present invention. 
         FIG. 5C  depicts a side perspective view of a turbulence reducing member connected with an underwater structure with straight fillets, in accordance with one embodiment of the present invention. 
         FIG. 6A  depicts a side perspective view of a vertical fillet used as a turbulence reducing member connected with an underwater structure, in accordance with one embodiment of the present invention. 
         FIG. 6B  depicts a side perspective view of a vertical fillet and a horizontal fence used as turbulence reducing members connected with an underwater structure, in accordance with one embodiment of the present invention. 
         FIG. 7A  depicts a side view of a fluttering movable turbulence reducing member surrounding an underwater structure, in accordance with one embodiment of the present invention. 
         FIG. 7B  depicts a top cross sectional view taken along line C-C of the fluttering movable turbulence reducing member surrounding the underwater structure of  FIG. 7A , in accordance with one embodiment of the present invention. 
         FIG. 7C  depicts a schematic diagram of a power generating apparatus using a fluttering movable turbulence reducing member surrounding an underwater structure, in accordance with one embodiment of the present invention. 
         FIG. 8A  depicts a perspective view of an underwater structure in which a vortex is generated, in accordance with one embodiment of the present invention. 
         FIG. 8B  depicts a perspective view of a movable turbulence reducing member surrounding the underwater structure of  FIG. 8A , in accordance with one embodiment of the present invention. 
         FIG. 8C  depicts a perspective view of a movable turbulence reducing member surrounding the underwater structure of  FIG. 8A  and forming a muted vortex, in accordance with one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Applicant has discovered that the use of aerodynamically shaped structures, called turbulence reducing members, connected with an underwater structure can reduce turbulent flow, reduce drag, and weaken some of the nominal shed vortices, around the underwater structure. The turbulence reducing members can be connected with the underwater structure at the time the underwater structure is formed, such as by pouring these new turbulence reducing members in concrete when the concrete for the underwater structure is initially poured. The turbulence reducing members may also be later added to an already existing underwater structure. Additionally, Applicant has discovered that movable turbulence reducing members connected with an underwater structure can also be used to reduce turbulent flow, reduce drag, and weaken some of the nominal shed vortices, around the underwater structure. Applicant has also discovered that movable turbulence reducing members may be used to generate energy. 
     Referring to  FIG. 1 , there is shown an underwater structure  100  connected with an above-water structure  110 . Underwater structure  100  is a structure of which at least an underwater portion  108  of underwater structure  100  is immersed for some period of time underneath a water line  116  of a body of water  120 , such as a stream, a river, a lake, or an ocean. Underwater structure  100  may be formed from a variety of rigid materials, such as concrete, wood, steel, and rock. Preferably, the underwater structure  100  is connected to an above-water structure  110 , such as a bridge or walkway, for which the underwater structure  100  provides support. Preferably, another portion  109  of the underwater structure  100  is buried in soil  112  at the bottom of the body of water  120 , beneath a mud line  114  of the body of water  120 . Burying portion  109  beneath the mud line  114  and in the soil  112 , provides additional support to the underwater structure  100 . 
     The underwater structure  100  may have a cross sectional shape, when the cross section is taken along a direction generally parallel to the direction of flow  118 , which is circular (as shown in  FIG. 1 ), square, rectangular, or some combination of circular, square and rectangular, all of which are not very aerodynamic shapes. Flow  118  has a free stream velocity of fluid in the body of water  120  denoted as V. As a result, a turbulent flow  107 , having a velocity V 1 , is induced in and around portion  108  of the underwater structure  100  which is beneath the water line  116 , above the mud line  114 , and in the body of water  120 . 
     Underwater structure  100  includes support structures  102  and abutments. Support structures  102  are any type of structure that is used to hold up and support any structure, such as a building, a roadway, a bridge section, or a walkout, and include bridge piers and pillars. An abutment is generally the point where two structures or objects meet, such as an end support of a bridge. In one embodiment, the underwater structure  100  is a support structure  102  with a circular cross sectional shape having a diameter (D). Preferably, the diameter (D) is from 0.15 to 7 meters, and more preferably, from 0.15 to 1.5 meters. 
     Referring to  FIG. 2 , in one embodiment a turbulence reducing member  130  is connected with underwater structure  100  in order to reduce the amount of turbulent flow  107  surrounding the portion  108  of underwater structure  100  beneath the water line  116 . Preferably, the turbulence reducing member  130  is connected with or surrounds portion  108 . Turbulence reducing member  130  may be formed from a variety of rigid materials, such as concrete, wood, steel, fiberglass, carbon fiber, and stone. The turbulence reducing member  130  is aerodynamically shaped to break up or reduce the turbulent flow  107  so that damage from the turbulent flow  107  to the soil  112  through scouring, or damage to the underwater structure  100 , through erosion, wear, or rust, can be minimized or reduced. The turbulence reducing member  130  may any one of a variety of aerodynamic structures, such as an air foil  132 , a vertical fence  134 , a horizontal fence  135 , a curved fillet  136 , a straight fillet  137 , or any combination of aerodynamic structures. 
     The turbulence reducing member  130  can be connected with the underwater structure  100  at the time the underwater structure  100  is formed, such as by pouring the turbulence reducing member  130  in concrete when the underwater structure  100  is poured initially. The turbulence reducing member  130  may also be later added to an already existing underwater structure  100  as a retrofit. If the turbulence reducing member  130  is added as a retrofit, it may be formed of steel wrapped in a non-corrosive skin such as fiberglass, carbon fiber, or rubber. In one embodiment, if added as a retrofit, turbulence reducing member  130  may be formed of primarily of carbon fiber or fiberglass alone, so as to reduce the weight of turbulence reducing member  130  and to prevent corrosion. 
     Referring to  FIGS. 2A and 2B , in one embodiment, turbulence reducing member  130  is a fixed air foil  132  which surrounds portion  108  of underwater structure  100 . Preferably, the fixed air foil  132  is aligned, along a line L 1 -L 2 , to be parallel to or within ±30 degrees, and more preferably within ±20 degrees, and most preferably within ±5 degrees of the direction of flow  118 , as shown in  FIG. 2B . Alignment of the air foil  132  is taken along a line L 1 -L 2  formed from a center point (L 1 ) of a head  133  of the air foil  132  to an end point (L 2 ) of a tail  138  of the air foil  132 . Preferably, the direction of flow  118  is parallel to or within ±30 degrees, and preferably within ±20 degrees, of line L 1 -L 2 . The fixed air foil  132  would be connected with the underwater structure  100  so that an aerodynamic center (A.C.) is at or as close as possible to a center (C.) of the underwater structure  100 , taken along a cross section A-A generally parallel to the direction of flow  118 , as shown in  FIG. 2B . By aligning the Aerodynamic Center (A.C.) at or near a center (C.) of the underwater structure  100 , any moment effect from the air foil  132  onto the underwater structure  100  can be reduced. The moment effect may cause an undesirable twisting effect to occur onto the underwater structure  100 . 
     Preferably, the air foil  132  has a depth (h) to chord (c) ratio, h/c, of at least 1/5. This makes for an air foil  132  with good lift and low drag in a subsonic flow. More preferably, the depth (h) to chord (c) ratio is at least 2/5, which would reduce the chord length and hence the volume of the air foil  132 , thus reducing the amount of material used in forming the air foil  132 , reducing costs as well. Alternative shapes for the air foil  132  may also be used, such as a more fully rounded shape, for example, as used on “Wheels Pants” of light aircraft to reduce turbulence from wheels of fixed landing gears. 
     Referring to  FIGS. 3A and 3B , in one embodiment, the turbulence reducing member  130  is a movable turbulence reducing member  140  such as an articulating air foil  141  which surrounds portion  108  of underwater structure  100 . Movable turbulence reducing member  140  is movably connected with underwater structure  100 , and specifically portion  108  of underwater structure  100 . By using a movable turbulence reducing member  140 , the movable turbulence reducing member  140  can better align with a changing direction of flow  118 , in order to better minimize or reduce turbulent flow  107  around underwater structure  100 . 
     Referring to  FIGS. 3A and 3B , in one embodiment, the movable turbulence reducing member  140  is an articulating air foil  141  which is movably connected with underwater structure  100  through bearings  142 . The articulating air foil  141  is preferably connected with the underwater structure  100  so that an aerodynamic center (A.C.) is behind a center (C.) of the underwater structure  100 , taken along a cross section B-B generally parallel to the direction of flow  118 , as shown in  FIG. 3B . By aligning the Aerodynamic Center (A.C.) behind a center (C.) of the underwater structure  100 , any moment effect from the articulating air foil  141  onto the underwater structure  100  can be used to allow the articulating air foil  141  to weather vane when on-coming flows change their angle relative to the nominal flow (V)  118 . The articulating airfoil  141  is self-aligning and designed to weather-vane, i.e., always turning into the oncoming direction of flow  118 , as do Weather Cocks on farm buildings. Referring to  FIG. 3B , preferably, the articulating air foil  141  is able to weather vane and move an angle ±θ of ±180° around underwater structure  100 . 
     By using a turbulence reducing member  130 ,  140 , the turbulent flow  107  around underwater structure  100  can be better controlled and often reduced. The shape of the turbulence reducing member  130 ,  140  will cause the flow  107  to move past the underwater structure  100  without generating as much turbulence as would the shape of the underwater structure  100  without the turbulence reducing member  130 ,  140 . If turbulence around the underwater structure  100  is reduced, scouring or erosion of the mud, sand and small rocks at the mud line  114  and under the water line  116 , may be reduced. Reducing turbulence around the underwater structure  100  also reduces the erosion of the underwater structure  100 , and reduces the forces from water and other liquids in the body of water  120  on the underwater structure  100 , and hence the above-water structure  110 . 
     Turbulence reducing members  130 ,  140  may be connected with any underwater structure  100 , including support structures  102  and abutments. For abutments, a similar approach as described herein would be considered to try to control the flow  107  past the abutment to reduce turbulence. In one embodiment, a vortex generator is used as a turbulence reducing member  130 ,  140  and connected with an abutment. The vortex generator is a device used to cause low level vortices to be generated that dissipate the overall turbulence in flow  107 . 
     Referring to  FIG. 4A , in one embodiment, turbulence reducing member  130  comprises a vertical fence  134  connected with a front side of underwater structure  100 . The vertical fence  134  is a partial disc-shaped member whose length (L) is generally greater than longer than its thickness (t). Preferably, the vertical fence  134  has a curved leading edge  143  facing into the direction of flow  118 , as shown in  FIG. 4A . This curved leading edge  143  helps to break up the flow  107  and reduce turbulence. In one embodiment, a vertical fence  134 ′ may be positioned on a backside of underwater structure  100 . Preferably, the vertical fence  134 ′ has a curved leading edge  143 ′ facing away from the direction of flow  118 , as shown in  FIG. 4A . 
     Referring to  FIG. 4B , in one embodiment, turbulence reducing member  130  comprises a horizontal fence  135  connected with, and preferably around, a front side of underwater structure  100 . The horizontal fence  135  is a partial or fully disc-shaped member whose length (L) is generally greater than longer than its thickness (t). Preferably, the horizontal fence  134  has a curved leading edge  144  facing into the direction of flow  118 , as shown in  FIG. 4A . This curved leading edge  144  helps to break up the flow  107  and reduce turbulence. In one embodiment, a horizontal fence  135 ′ may be positioned on, and preferably around, a backside of underwater structure  100 . Preferably, the horizontal fence  135 ′ has a curved leading edge  144 ′ facing away from the direction of flow  118 , as shown in  FIG. 4B . 
     Referring to  FIG. 5A , in one embodiment, turbulence reducing member  130  comprises a vertical fence  134  and curved fillets  136  connected with underwater structure  100 . The curved fillets  136  have a curved leading edge  145  facing into the direction of flow  118 . The curved fillets  136  are connected with both the vertical fence  134  and the underwater structure  100  in order to further reduce the amount of turbulence in the flow  107 . Preferably, the curved fillets  136  are vertically oriented, as shown in  FIG. 5A , having a first edge  186  connected with the underwater structure  100  and a second edge  187  connected with the vertical fence  134 . In one embodiment, curved fillets  136 ′ may be positioned on the backside of underwater structure  100 , facing away from the direction of flow  118 , as shown in  FIG. 5A . 
     Referring to  FIG. 5B , in one embodiment, turbulence reducing member  130  comprises air foil  132  and curved fillets  136  connected with underwater structure  100 . The curved fillets  136  have a curved leading edge  145  facing into the direction of flow  118 . The curved fillets  136  are connected with both the air foil  132  and the underwater structure  100  in order to further reduce the amount of turbulence in the flow  107 . Preferably, the curved fillets  136  are vertically oriented, as shown in  FIG. 5B , having a first edge  186  connected with the underwater structure  100  and a second edge  187  connected with the air foil  132 . In one embodiment, curved fillets  136 ′ may be positioned on the backside of underwater structure  100 , facing away from the direction of flow  118 , as shown in  FIG. 5B . 
     Referring to  FIG. 5C , in one embodiment, turbulence reducing member  130  comprises air foil  132  and straight fillets  137  connected with underwater structure  100 . The straight fillets  137  have a straight leading edge  146  facing into the direction of flow  118 . The straight fillets  137  are connected with both the air foil  132  and the underwater structure  100  in order to further reduce the amount of turbulence in the flow  107 . Preferably, the straight fillets  137  are vertically oriented, as shown in  FIG. 5C , having a first edge  188  connected with the underwater structure  100  and a second edge  189  connected with the air foil  132 . In one embodiment, straight fillets  137 ′ may be positioned on the backside of underwater structure  100 , facing away from the direction of flow  118 , as shown in  FIG. 5C . 
     Referring to  FIG. 6A , in one embodiment, turbulence reducing member  130  comprises vertically oriented curved fillets  139  connected with underwater structure  100 . The curved fillets  136  have a curved leading edge  147  facing into the direction of flow  118 . The curved fillets  139  are connected with the underwater structure  100  in order to further reduce the amount of turbulence in the flow  107 . Preferably, a portion of the curved fillets  139  touches or is embedded in the soil  112  below the mud line  114 . The curved fillets  139  are vertically oriented, as shown in  FIG. 6A , having a first edge  190  connected with the underwater structure  100  and a second edge  191  embedded below in or facing the mud line  114 . In one embodiment, curved fillets  139 ′ may be positioned on the backside of underwater structure  100 , facing away from the direction of flow  118 , as shown in  FIG. 6A . 
     Referring to  FIG. 6B , in one embodiment, turbulence reducing member  130  comprises a vertically oriented curved fillet  139  and a vertical fence or a horizontal fence  135  connected with underwater structure  100 . The curved fillet  139  has a curved leading edge  147  facing into the direction of flow  118 . The curved fillet  139  is combined with horizontal fence  135 , both connected with the underwater structure  100 , in order to further reduce the amount of turbulence in the flow  107 . Preferably, a portion of the curved fillet  139  touches or is embedded in the soil  112  below the mud line  114 . The curved fillet  139  is vertically oriented, as shown in  FIG. 6A , having a first edge  190  connected with the underwater structure  100  and a second edge  191  embedded below in or facing the mud line  114 . In one embodiment, curved fillets  139 ′ may be positioned on the backside of underwater structure  100 , facing away from the direction of flow  118 , as shown in  FIG. 6A . In one embodiment a second curved fillet  136  is connected with curved fillet  139  and fence  135 , as shown in  FIG. 6B  to further reduce turbulence. 
     Referring to  FIGS. 7A and 7B , in one embodiment, movable turbulence reducing member  140  is a fluttering air foil  150  which surrounds portion  108  of underwater structure  100 . The fluttering air foil  150  includes a flap  154  which is connected to a main airfoil body  151  via a hinge  156 . The addition of the flap  154  would allow for relocation of the fore-aft position of the fluttering air foil  150  to enhance a stronger flutter at lower speeds of flow (V)  118 . Also, the flap  154  would act as a weathervane effect to control, or actually eliminate, divergence. Preferably, fluttering air foil  150  is movably connected with underwater structure  100 , and specifically portion  108  of underwater structure  100 . By using fluttering air foil  150 , the movable turbulence reducing member  140  can better align with a changing direction of flow  118 , in order to better minimize or reduce turbulent flow  107  around underwater structure  100 . 
     Preferably, the fluttering air foil  150  is movably connected with underwater structure  100  through bearings  142 . Preferably, the fluttering air foil  150  is connected with the underwater structure  100  so that an aerodynamic center (A.C.) is behind a center (C.) of the underwater structure  100 , taken along a cross section C-C generally parallel to the direction of flow  118 , as shown in  FIG. 7B . By aligning the Aerodynamic Center (A.C.) behind a center (C.) of the underwater structure  100 , any moment effect from the fluttering air foil  150  onto the underwater structure  100  can be used to allow the fluttering air foil  150  to weather vane and flutter when on-coming flows change their angle relative to the nominal flow (V)  118 . The fluttering air foil  150  is designed to weather-vane, i.e., always turning into the oncoming direction of flow  118 , quicker than the articulating air foil  132  without a flap  154 . 
     Additionally, since the fluttering air foil  150  moves more than a typical articulating air foil  141 , the fluttering air foil  150  can be used to generate power. Referring to  FIG. 7C , a power generating apparatus  148  is provided which includes a fluttering air foil  150  connected with a generator  160  for generating electricity. The generator  160  is in turn connected with an energy receiving apparatus  162 , such as lights. The lights could serve to illuminate the underwater structure  100  or an above-water structure  110 . A feedback and control mechanism  164  is connected with the energy receiving apparatus  162 , the generator  160 , and the fluttering airfoil  150 , so as to provide feedback and better direct the fluttering air foil  150 . Electrical power generation can be made with oscillating airfoils in air or water. More control and mitigation of the turbulent flow is accomplished via controls  164 . Flutter from the air foil  150  and flap  154  absorbs energy from the flow  107 , thus weakening any shed vortices. Modulation of the absorbed energy from the flow  107  could be used to control any shed vortices. 
     Referring to  FIGS. 8A ,  8 B, and  8 C, in one embodiment, movable turbulence reducing member  140  is an energy wheel  170  which surrounds portion  108  of underwater structure  100 . Energy wheel  170  may be a propeller  170  or turbine. Preferably, energy wheel  170  is movably connected with underwater structure  100  through bearings  174 . Individual blades  171  of energy wheel  170  are caused to rotate around the underwater structure  100  as a result of flow  107 . Preferably, a debris deflector  172 , such as a series of bars, is provided around the energy wheel  170  or between the energy wheel  170  and the direction of flow  118 , as shown in  FIG. 8B . The debris deflector  172  prevents debris such as rocks and soil from damaging or eroding the underwater structure  100 . As shown in  FIG. 8C , the direction of flow  107  as it approaches and enters energy wheel  170  is then altered as the flow  107  exists energy wheel  170 , reducing turbulence in the flow  107  and damage to underwater structure  100 . Additionally, the energy wheel  170  could be used to generate energy, in a similar manner as discussed above for the fluttering air foil  150 . 
     Referring to  FIG. 8C , free stream velocity of fluid in the body of water  120  is denoted as V while velocity induced from the propeller is denoted as V P  and causes a mixed flow to occur where the free stream is deflected upward or downward accordingly. This flow change will reduce the strength of vortex  182  at the mud line  114  surrounding underwater structure  100  through proper design, and reduce any damaging effect of those vortices cause by flow  107 . Preferably, as many as three debris deflectors  172  may be used, orientated at zero degrees from the direction of flow  118 , and at 60 degrees on either side of the underwater structure  100 . 
     The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in various embodiments for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separately claimed subject matter. 
     While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that other embodiments and implementations are possible within the scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.