Wave Attenuation Device For Restoration Of Oyster Reefs

Abstract

A wave attenuation device converts rotational wave energy of a water body into directional laminar flow. The wave attenuation device includes one or more semi-flexible panels having a second portion inclined with respect to a first portion and a third portion thereof. The semi-flexible panels are spaced apart with respect to each other in a vertical direction. The wave attenuation device includes a plurality of support pilings for supporting the one or more semi-flexible panels on a concrete bed position at a bottom of the water body. A highest point of the plurality of supports pilings is located at a mean low tide height of the water body. A space between the semi-flexible panels is open to flow of water, to enable delivery of food particles to oyster reefs located in the water body, while preventing sediment accretion.

Claims

1. A wave attenuation device for converting rotational wave energy of a water body into directional laminar flow, the wave attenuation device comprising: one or more semi-flexible panels having a second portion inclined with respect to a first portion and a third portion thereof, the one or more semi-flexible panels being spaced apart with respect to each other in a vertical direction, wherein the one or more semi-flexible panels includes a first portion, a second portion and a third portion, the second portion having a first end inclined with respect to the first portion and a second end inclined with respect to the third portion, the second portion is inclined with respect to the first portion with an inclination angle ranging from 20-40, and the third portion extends from the second portion and is parallel to the first portion; and a plurality of support pilings for supporting the one or more semi-flexible panels on a concrete bed position at a bottom of the water body, a highest point of the plurality of supports pilings being located at a mean low tide height of the water body.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The preferred embodiments of the invention will hereinafter be described in conjunction with the appended drawings provided to illustrate and not to limit the invention, where like designations denote like elements, and in which:

[0031] FIG. 1 presents a schematic representation of a wave attenuation device in accordance with an embodiment of the present invention;

[0032] FIG. 2 presents an exploded representation of the wave attenuation device of FIG. 2;

[0033] FIG. 3 presents a left side perspective view of a wave attenuation device in accordance with an embodiment of the present invention;

[0034] FIG. 4 presents a front perspective view of a wave attenuation device as a wave approaches and makes contact with the device in accordance with an embodiment of the present invention;

[0035] FIG. 5 presents a left side perspective view of a wave attenuation device as a wave encounters the device in accordance with an embodiment of the present invention; and

[0036] FIG. 6 presents a schematic representation of the panels of the wave attenuation as a wave approaches and makes contact with the panels of the device in accordance with an embodiment of the present invention.

[0037] Like reference numerals refer to like parts throughout the several views of the drawings.

DETAILED DESCRIPTION

[0038] The following detailed description is merely exemplary in nature and is not intended to limit the described embodiments or the application and uses of the described embodiments. As used herein, the word exemplary or illustrative means serving as an example, instance, or illustration. Any implementation described herein as exemplary or illustrative is not necessarily to be construed as preferred or advantageous over other implementations. All of the implementations described below are exemplary implementations provided to enable persons skilled in the art to make or use the embodiments of the disclosure and are not intended to limit the scope of the disclosure, which is defined by the claims. For purposes of description herein, the terms upper, lower, left, rear, right, front, vertical, horizontal, and derivatives thereof shall relate to the invention as oriented in FIG. 1.

[0039] Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification, are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise.

[0040] Shown throughout the figures, the present invention is directed toward a wave attenuation device which eliminates circular wave movement present within a water wave, which is detrimental to establishment of an oyster reef, while retaining as much forward water movement as possible using an accelerated surface.

[0041] Referring initially to FIGS. 1-5, a wave attenuation device 100, is illustrated in accordance with an embodiment of the present invention. The wave attenuation device 100 converts rotational wave energy of waves of a water body into directional laminar flow. The wave attenuation device 100 includes three or more semi-flexible panels 102 having a total width as measured perpendicular to a general direction of a wave front of one average wavelength. The panels 102 may be made of a marine board material. The panel 102 may be suspended horizontally in a water column having solid supports pilings 104, with a highest point of the supports pilings 104 positioned at a mean low tide height of the water body. The support pilings 104 are positioned on bottom bed of the water body 106.

[0042] The panels 102 may include a first portion 152, a second portion 154 and a third portion 156. A first end of the second portion 154 may be inclined with respect to the first portion 152, with a second end inclined with respect to the third portion 156. The first end of the second portion 154 may be located at 20% of a total width of the panel 102, and the second end of the second portion 154 may be located at 80% of the total width of the panel 102.

[0043] The first portion 152 may include a wave-facing edge 158 which faces the direction of propagation of waves 120 of the water body. The first portion 152 of the panel 102 may be arranged in a horizontal direction. The second portion 154 may be inclined with respect to the first portion 152 with an inclination angle ranging from 20-40. Preferably, the inclination angle is 30. The third portion 156 extending from the second portion 154 may be parallel to the first portion 152. The panel 102 may include as little front-facing area as possible.

[0044] In another embodiment of the invention, the wave attenuation device may include two panels 102 vertically arranged with respect to each other, on the support pilings 104. The panels 102 may be spaced apart with respect to each other in a vertical direction. The space between the top and bottom panels 102 is open to flow of water, to enable delivery of food particles to the oyster reefs located in the water body. To this effect, the waves are allowed to flow through the open spaces between the top and bottom panels 102 which act as shearing plates.

[0045] If more than one of panel 102 are being used, they are arranged to meet the wave with the least possible resistance, so as to efficiently redirect the wave energy into laminar flow 122. In this way, a desired water flow can be maintained, and the floating structure installed over the wave attenuation device is more likely to survive unusual storm events. This requires that the wave attenuation device be self-adapting to both the direction and magnitude of waves and storm surge.

[0046] Waves generally cannot exceed 120 from peak to trough without breaking. Adjusting the wave attenuating device 100 as it intercepts the waves of different heights allows for the limitation of friction between the waves and the panels 102; thus acceleration of the wave is maintained to maximize exit velocity while eliminating orbiting energy.

[0047] In simplified environments with limited fetch, wave equations as provided below describe the physics of the waves the attenuation device 100.

[0048] Equation (1) is a form that, through simplifying assumptions, is relevant to shallow waves. Equation (1) describes wave velocity (C) as:

[00001]$\begin{array}{cc}C=\sqrt{\mathrm{gd}}& \left(1\right)\end{array}$ [0049] where, [0050] C is wave velocity; [0051] g is force of gravity; and [0052] d is depth of water.

[0053] The assumptions yielding simplified form of Equation (1) are reasonable for describing storm waves, where either oyster restoration projects may be suited or where a dock may encounter storm produced wind waves.

[0054] By empirical evidence, wave height cannot be greater than 0.143 (L), at which point it will break and accelerate down the wave front. Here, L denotes wavelength. The property of the wave height is used in the design of the attenuation device 100 to shear an on-coming wave and in aggregate produce an accelerating laminar flow. Equation (2) describes the rate of on-coming wave energy:

[00002]$\begin{array}{cc}\mathrm{Rate}\mathrm{of}\mathrm{wave}\mathrm{energy}\mathrm{delivery}=\frac{H}{L}& \left(2\right)\end{array}$ [0055] where, [0056] H is wave height; and [0057] L is wavelength.

[0058] The total energy over time (and in this way the potential destructiveness) may be predicted by knowing the maximum fetch, i.e., linear distance wind has to work on a water body, sustained wind speed, and the water depth. The maximum and mean wave heights where the fetch can be defined based on fixed parameters. However, these equations do not easily simplify, and wave height values are based on probability. Bottom contour and even small changes in wind speed and direction will affect maximum and mean wave heights. Because of changes, expected wave heights are approximate and based on empirical evidence. Design specifications may include a standard safety factor (H.sub.max) of 1.3.

[0059] Equation (3) describes total energy per unit length of a wave front as:

[00003]$\begin{array}{cc}E=\frac{{\mathrm{LH}}^2}{8}& \left(3\right)\end{array}$ [0060] where, [0061] E is total energy per unit length of a wave front; [0062] is mass per unit volume of water; and [0063] H is wave height.

[0064] Those skilled in the art would appreciate that (mass per unit volume of water) may change with temperature and salinity of the water. As H (height) doubles, E (energy) quadruples. This property has implication for the spacing of the lateral shear members of the wave attenuation device 100.

[0065] Oyster reefs are made of oyster shell (CaCO.sub.3) and floating structures, such as docks or walkways, are typically made of wood. Both oyster reefs and wood are not very dense and have relatively high surface areas. Therefore, the oyster reefs and the floating structures are made of materials that may be easily pushed towards a shore of the water body, or into lower energy areas of a water body. Sediment may be transported towards the shore, or lower energy states, from orbital currents (e.g., low steepness waves). Friction may prevent sediment entrained within a wave from completing the orbit, and thus net transport may be shoreward. Therefore, kelvin waves created by boat-waking, do not significantly affect the docks but prevent oyster restorations from surviving. High wave steepness creates high orbital energy that exceeds friction (or holdfast in the case of oysters) and material becomes suspended in the water column, e.g., waves generated by high wind and low fetch. Suspension of material along with high water during a storm surge destroys docks.

[0066] Munch-Petersen equation (4) describes the amount of material moved with a given wave type and size as:

[00004]$\begin{array}{cc}\mathrm{Material}\mathrm{moved}=\frac{{\mathrm{KH}}^{2}L\cos }{8}& \left(4\right)\end{array}$ [0067] where, [0068] H is wave height; [0069] L is wavelength; [0070] is the angle of an average wave at the point of contact; and [0071] K is a coefficient dependent on size, density, friction, and bottom slope characterizing the material being moved.

[0072] As wave height of the water body increases, different parts of a wave encounters parts of the wave attenuation device 100 at different angles. Accordingly, the wave attenuation device 100 may adjust to the wave height, which is a function of fetch, wind speed, and tidal depth. The panels 102 of the wave attenuation device 100 may be provided in a rotatable manner and pivoted within a limited range to adapt to higher or lower flow regimes. The wave attenuation device 100 may be attached to a bottom surface of the floating structure, and may self-adjust during high tide and extreme weather events.

[0073] Oysters do not need protection from natural calamities, but the marine structures attached to the oysters require protection from the calamities. Marine structures like docks may be destroyed during hurricanes due to fixed position above water line and unsupported stranding between wave heights, which creates a pressure differential that the docks are not designed to withstand. Therefore, the wave attenuation device 100 may be used to protect marine structures.

[0074] The wave attenuation device dampens waves into laminar flow while allowing large volumes of water flow through to feed oysters. The laminar flow additionally prevents sediment from being deposited. Water flows below the bottom panel and the open spaces between the top and the bottom panels of the wave attenuation device, which keeps a large volume of water flowing over the oysters without disruption. Having a high volume of water flow is important to ensure oysters receive sufficient nutrients.

[0075] The wave attenuation device 100 is designed to meet the wave with the least possible resistance and redirect the wave energy into directional laminar flow. The wave attenuation device 100 reduces the wave energy hitting oyster reefs while permitting sufficient flow of water which provides nutrients to the sedentary oyster reefs. The wave attenuation device 100 may be used as a specialized cover for protecting the oyster reefs from rotational wave energy of the water body. The wave attenuation device 100 may also be used to protect marinas or other marine structures by significantly reducing wave energy and orbiting energy of the wave particles, to prevent sediment accumulation behind the marine structures.

[0076] Since many modifications, variations, and changes in detail can be made to the described preferred embodiments of the invention, it is intended that all matters in the foregoing description and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense. Thus, the scope of the invention should be determined by the appended claims and their legal equivalents.