Abstract:
A fish screen is presented having a porous surface made of two or more corrugations (e.g., elongated convex shapes) having an at least partially porous surface. The incorporation of a porous area on the corrugations allows increasing the total porous surface area compared to an underlying diversion area. The porous area is a magnification of an underlying diversion area, which reduces the fluid pressure (e.g., impingement forces) acting on the porous area of the screen. The valley between each pair of corrugations is solid, not porous. The solid valley(s) provide two important functions; they provide multiple small solid surface flow channels over the screen surface. These solid channels protect small or weak swimming aquatic organisms from impingement on the screen. That is, once organisms reach the solid channel, they may move along the solid channel free of impingement until they reach the edge of the screen.

Description:
CROSS REFERENCE 
       [0001]    This application claims the benefit of the filing date of U.S. Provisional Application No. 62/049,554 having a filing date of Sep. 12, 2014, the entire contents of which are incorporated herein by reference. 
     
    
     FIELD 
       [0002]    This disclosure is directed to fish screens. More specifically the disclosure is directed to fish screens having a corrugated surfaces with refugia between some or all of the corrugations to protect young life stages of aquatic species. 
       BACKGROUND 
       [0003]    Screens are often used to filter agricultural, municipal and industrial water/flow diversions. The screens prevent debris from passing into such flow diversions. In such applications, a porous surface (e.g., mesh or fabric) covers a flow diversion allowing water to filter though the porous surface while the porous surface prevents debris from entering the flow diversion. When such screens are used to prevent aquatic species from passing into the flow diversion, the screens are commonly referred to as fish screens. The porous surface of these fish screens is sized to prevent passage of aquatic species through the porous surface into the flow diversion. In addition, it is desirable to prevent entrainment/impingement of aquatic species against the porous surface of the screen. In some areas, fish screens are required by federal and state laws to protect aquatic inhabitants from entrainment and removal from native waters. Fish screens are unique from other industrial screens because they must operate within guidelines set by biological parameters such as organism swimming ability and behavior. Accordingly, it would be desirable to design a fish screen to protect aquatic species/organisms from impingement on the screen and allow such organisms to return to their native waters. 
       SUMMARY 
       [0004]    The present disclosure is directed to a fish screen that has various unique features. 
         [0005]    The porous surface or fabric of the screen is shaped in a corrugated form (e.g., elongated convex shape) to increase screen area compared to a projected flat area (e.g., diversion area). This allows the porous area to be a magnification of the diversion area, which reduces the fluid pressure (e.g., impingement forces) acting on the porous area of the screen. The corrugation of the screen surface also provides for another unique attribute. The valley between each pair of corrugations is solid, not porous. This feature is important and unique for fish screens. The solid screen valleys provide two important functions; they provide multiple small solid surface flow channels over the screen surface. These solid channels protect small or weak swimming aquatic organisms from impingement on the screen. That is, once organisms reach the solid channel, they may move along the solid channel free of impingement until they reach the edge of the screen. The corrugation shapes can be triangular, trapezoidal or curved (e.g., in cross-section) and may be varied on a single screen. 
         [0006]    Typically, the fish screen includes a frame that supports two or more elongated convex surfaces (e.g., corrugations) that extend at least a portion of the distance between first and second edges of the frame. The elongated convex surfaces have an open end the disposed downward. At least a portion of the convex surfaces are porous. In one arrangement, the porous portions of the convex surfaces are formed of a plurality of apertures extending through the convex surface. In another arrangement, the convex surfaces are formed a wire mesh. In any arrangement, the maximum cross-dimension of the pores of the porous surface are sized to prevent passage of debris and/or aquatic species through the porous surface. Disposed between the convex surfaces is a solid surface. In one arrangement, the solid surface is a recessed channel having a solid bottom and first and second lateral edges. The recessed channel may be of any appropriate shape including, for example, square trapezoidal, half circular etc. The lateral edges of the convex surface are connected to or integrally formed with lateral edges of the elongated convex surfaces. In the latter regard, the convex surfaces and recessed channel may be formed from a sheet of metal. In various arrangements, the screen may include a plurality of elongated convex surfaces with a solid surface between each adjacent pair of convex surfaces. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is an isometric rendering of a corrugated fish screen. 
           [0008]      FIG. 2  is a plan view of the corrugated fish screen. 
           [0009]      FIG. 3  is a side view of the fish screen. 
           [0010]      FIG. 4  illustrates an elongated porous corrugation. 
           [0011]      FIG. 5  is a cross-sectional view of Section A-A from  FIG. 2 . 
           [0012]      FIG. 6  is a detail from  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Reference will now be made to the accompanying drawings, which at least assist in illustrating the various pertinent features of the presented inventions. The following description is presented for purposes of illustration and description and is not intended to limit the inventions to the forms disclosed herein. Consequently, variations and modifications commensurate with the following teachings, and skill and knowledge of the relevant art, are within the scope of the presented inventions. The embodiments described herein are further intended to explain the best modes known of practicing the inventions and to enable others skilled in the art to utilize the inventions in such, or other embodiments and with various modifications required by the particular application(s) or use(s) of the presented inventions. 
         [0014]    Fish screens are often used to cover water diversions/flow diversions to prevent entry of debris and/or aquatic species into the diversion. When placed over a diversion, the flow of the water though the fish screen can impinge debris and aquatic species against the surface of the screen. Provided herein is a fish screen that reduces the impingement forces present at the surface of the screen and provides escape routes from the interior of the screen to edges of the screen. Such escape routes may have little or no impingement forces allowing aquatic species to readily move from an interior of the screen to an edge of the screen and back to their native waters. 
         [0015]      FIGS. 1 and 2  show isometric and plan views of one embodiment of a fish screen  10  in accordance with various aspects of the presented inventions. As shown, the screen  10  includes a plurality of aligned corrugations  20  that, in the illustrated embodiment extend along a majority of the length of the screen from a forward end  32  (e.g., upstream end) toward a rearward end  34  (e.g., downstream end). The corrugations  20  are designed to be substantially aligned with a flow direction  50 , when the screen  10  is in use. Further, each corrugation includes a porous surface  22  that is sized to allow water to filter through the corrugations while preventing debris and/or aquatic species from passing there through. 
         [0016]      FIG. 3  illustrates the fish screen  10  as applied to water diversion  100 . In the illustrated embodiment, the fish screen  10  is applied over the diversion  100  at the bottom of a water flow  50 . In this illustration, the fish screen  10  is utilized in a horizontal configuration on the bottom of the flow  50 . However, this is not a requirement and it will be appreciated that fish screen  10  may be applied in other orientations (e.g., angled etc.). As shown, the fish screen covers the diversion  100  such that a frame  30  of the fish screen  10  is supported about a periphery of the diversion  100 . When so positioned, the porous surfaces of the corrugations  20  are disposed above the diversion  100 . As water flows past the screen  10 , the water is able to pass into the porous surfaces  22  of the corrugations  20  and into the flow diversion  100  while preventing debris and aquatic species from entering into the diversion  100 . 
         [0017]      FIG. 4  illustrate one embodiment of a portion of a corrugation  20  removed from the fish screen for purposes of illustration. As shown, the corrugation  20  is at least partially formed of a porous surface  22 . Any porous surface may be unitized and may include, without limitation, woven wire surfaces (e.g., Detail A) and solid surfaces with a plurality of apertures/holes formed (e.g., drilled, punched) through the surface (Detail B). In any arrangement, the size of the pores (e.g., spacing between wires, aperture diameter etc.) are selected to permit water to pass through the surface while preventing aquatic species above a predetermined size from passing through. 
         [0018]    As shown, each corrugation  20  is an elongated convex surface that, when disposed on the frame  30  raises, a reference plane of the screen  10  as generally defined by screen frame  30 . See, e.g.  FIG. 1 . To reduce the impingement forces experienced by the porous surfaces of the screen  10 , each corrugation has a total surface area that is a multiple of the projection area/diversion covered by the corrugation. That is, the convex three-dimensional surface formed by the porous areas of each corrugation is larger than the projected diversion area covered by the corrugation. Referring again to  FIG. 4A , the porous surface area of the exemplary angled corrugation is larger than the diversion area  60  covered by the corrugation  20 . Stated otherwise, the porous surface area of the convex corrugation is larger than the area defined by the open end of the convex corrugation. In the illustrated embodiment, the porous surface area is calculated as twice the porous width (Pw) of the corrugation times the porous length (L) of the corrugation. In contrast, the projection area  60  of the porous surface is equal to the width (W) times the porous length of the corrugation (L). That is: 
         [0000]      2 Pw×L&gt;W×L   
         [0000]    Though illustrated with an angled corrugation, will be appreciated that similar calculations can be made for any convex corrugation (e.g., in cross-section) including, without limitation, half-circular, trapezoidal etc. In any arrangement, the porous screen area is a magnification of the flow diversion area covered by the corrugation  20 . In one embodiment, the porous screen area is at least 1.25 times the projection area. In further embodiments, the porous screen area is at least 1.5 times the projection area. In a yet further embodiment, the porous screen area is at least 2.0 times the projection area. Magnification of porous screen area compared to the diversion area covered by the corrugation allows flow passing through the smaller diversion area to pass through a larger porous area. This reduces the impingement force (e.g., fluid pressure) on the porous screen per unit area. Lower impingement forces entrap less debris and aquatic species. 
         [0019]    To further reduce the impingement forces experienced by debris and aquatic species contacting the screen, the valleys  24  between adjacent corrugations  20  are solid. This is best illustrated in the plan view of  FIG. 2 , the cross-sectional view of  FIG. 5  and the detail view of  FIG. 6 . As shown, each solid valley  24  extends between the porous surfaces  22  of two adjacent corrugations  20 . In the illustrated embodiment, the solid valley  24  is generally U-shaped or trapezoidal. That is, the solid valley  24  includes a bottom surface  26  (e.g., flat) and two upwardly extending legs  28   a  and  28   b . Such a configuration provides a recessed channel, which further provides a refuge for aquatic species to move toward the edge of the screen. Though the solid valley is illustrated with a recessed channel, it will be appreciated that other configurations are possible. In any embodiment, the solid valley  24  provides a flow channel across the screen from the forward end  32  to the rearward end  34  with no impingement forces that may trap debris or aquatic species against the screen. Rather, when the corrugations  20  and valleys  24  are aligned with a flow direction, the resulting flow through the valleys is directed toward the edge of the screen  10 , which provide an escape route for aquatic species across the screen and helps remove debris from the surface of the screen  10 . In use, young life stages of aquatic species will naturally navigate to the deeper valleys where solid continuous passage is available. Diverted flow will pass through the screen in the porous surfaces  22  of each corrugation  20 . See  FIG. 3 . 
         [0020]    The forward end and/or rearward end of the corrugations  20  may further include optional flow guidance structures. Referring to  FIG. 1 , the forward ends of the corrugations abut against and angled accelerator plate  40 . As shown, the accelerator plate  40  is an angled surface that extends from the forward end of the frame  30  and extends to the peak surfaces of the aligned corrugations  20 . As shown, the accelerator plate covers the open forward ends of the corrugations preventing objects from entering into these open ends. When utilized, the accelerator plate  40  also diverts the flow upward as it passes over the screen  10 . This reduces the fluid pressure on the forward ends of the porous corrugations  20 . That is, the accelerator plate  40  diverts the flow upward as it contacts the screen  10 . This allows the water to drain through the porous surfaces rather than flowing directly into the porous surfaces. Again, this further reduces the impingement force on the porous surface. The embodiment of the screen illustrated in  FIG. 1  also includes a plurality of individual flow guides  42  disposed on the rearward end of the corrugations  20 . These flow guides enclose the rearward open ends of the corrugations  20 . In other embodiments, such flow guides may be disposed on the forward ends of the corrugations (not shown). In such an arrangement, the flow guides direct flow along the screen. 
         [0021]    As illustrated in the side view of  FIG. 3 , the screen may optionally include a number of flow baffles  44  disposed behind/below the screen  10 , which allow for a more equal distribution of fluid flow through the screen. That is, the flow baffles provide resistance to water passing through the screen such that the forward end does not experience significantly higher flow velocities relative to downstream portions of the screen. The number spacing and physical configuration of the baffles may be varied based on expected conditions (e.g., expected flow velocity, etc.). 
         [0022]    The fish screen may be constructed of any appropriate materials. Typically the fish screen is form of corrosion resistant metals. In one embodiment, the corrugations their porous surfaces and the solid valleys between the corrugations are integrally formed from a common sheet of metal. In such an arrangement, the metal sheet may be perforated (e.g., drilled, punched, laser cut, etc.) to for the porous surfaces. At this time, the sheet may be shaped (e.g., bent) to form the corrugations having the solid valleys there between. However, other methods of manufacture are possible and within the scope of the presented inventions. For instances, metal screens (e.g., woven) may be shaped to form the convex corrugations and the lateral edges of the metal screens may be attached (e.g., riveted, spot welded etc.) to, for example, lateral edges of solid channels. The porous corrugations and solid channels may then be attached to a frame. Alternatively, the frame may be integrally formed with the corrugations and solid valleys. The width and length of the screen may be sized based on its intended use. That is, the screen may be manufactured to the dimensions of a particular diversion. 
         [0023]    In summary, the fish screen can be placed in any orientation from vertical, a porous wall which flow passes through, to horizontal, a porous floor with flow passing over and down through the screen. Most typically, the screen corrugations run parallel to the major direction of flow. Water passes through the screen and fish and debris travel along the screen face returning to native water. The three-dimensional screen surface formed by corrugating the screen provides a magnification of screen area compared to a flat screen surface/diversion area of the same area. This allows more flow to be passed through the screen per unit area. A portion of the valleys formed between the corrugations are preferably a solid material such that the screen contains multiple parallel rows of porous screen and solid valley channels. Weak swimming fish and other aquatic organisms will naturally seek the screen valleys where they are protected from impingement as they pass the entire length of the screen. The solid valleys further serve a benefit by passing debris and fine sediment the length of the screen. This reduces cleaning requirements of the screen compared to a similar continuous flat surface screen. 
         [0024]    The foregoing description has been presented for purposes of illustration and description. Furthermore, the description is not intended to limit the inventions and/or aspects of the inventions to the forms disclosed herein. Consequently, variations and modifications commensurate with the above teachings, and skill and knowledge of the relevant art, are within the scope of the presented inventions. The embodiments described hereinabove are further intended to explain best modes known of practicing the inventions and to enable others skilled in the art to utilize the inventions in such, or other embodiments and with various modifications required by the particular application(s) or use(s) of the presented inventions. It is intended that the appended claims be construed to include alternative embodiments to the extent permitted by the prior art.