ZA201102296B

ZA201102296B - Breakwater structure

Info

Publication number: ZA201102296B
Application number: ZA2011/02296A
Authority: ZA
Inventors: Phillip Jordaan Peter
Original assignee: Phillip Jordaan Peter
Priority date: 2010-03-30
Filing date: 2011-03-29
Publication date: 2011-11-30
Also published as: MA34181B1; AP2012006541A0; AU2011235846A1; WO2011123870A1

Description

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FIELD OF THE INVENTION

THIS invention relates to a breakwater structure. More specifically, the invention relates to a breakwater structure having a compound parabolic ramp surface capable of dissipating the energy of a wave by directing the wave against the force of gravity and by way of reflection.

BACKGROUND OF THE INVENTION it is well known that waves are caused by the transfer of energy from winds to a body of water. Furthermore, it is well known that the energy stored in waves is capable of causing significant damage to and eventual erosion of coastal structures and/or shorelines if not dissipated prior to impact with the structures and/or shoreline.

A number of different devices have been developed and used to protect coastal structures and/or shorelines One such device is called a Dolos, which is an unusually- shaped concrete block weighing between 20 and 40 tons. Large numbers of Dolosse (typically in excess of 1000 per 1 kilometre stretch of shoreline) are required to erect an interlocking porous wall of Dolosse, which will act as protection against the crashing waves. Although effective, the weight of each Dolos makes erection of these walls very time consuming and tedious Furthermore, and as a result of the constant pounding of the waves thereon, the Dolos wear out and need to be replaced from time to time

Other such concrete block devices include:

“ bs { 9011/07286 -3- - the pierced-pyramid block, having four equilateral triangles joined edge to edge; - the A-Jacks block, used commercially in both open channel and coastal applications and consisting of three long cement stakes joined centrally to form a six-legged structure; - the Akmon block, which is a multi-tonne concrete block used for breakwater and seawall armouring; and - the Tetrapod block, which is a four-legged concrete structure used extensively in coastal engineering, and designed to allow the waves to flow around it rather than against it.

Many wall-type structures for dissipating the energy of waves are also well known. For example, the structure described in United States patent 201/0215435 are also known.

The disadvantage of these structures is that they are typically land-based and furthermore, cause the wave to crash or break, leading to the eventual destruction and/or erosion of the structure.

The known prior art is designed to protect the coast at the shoreline. None are designed to be constructed within the body of water thereby creating a safe calm body of water behind the structure for the purposes of a harbour, dam or other facility. As such, there remains a need for a low cost structure that efficiently diffuses or dissipates wave energy, without compromising on the aesthetics of the shoreline to be protected.

Accordingly, it is an object of the present invention to address the needs of the prior art.

SUMMARY OF THE INVENTION

According to the invention there is provided a breakwater structure having a ramp with an operatively lower end, an operatively upper end and a compound parabolic surface extending between the operatively lower and upper ends, the compound parabolic surface being defined by a portion of a first parabola having a first axis of symmetry and by a portion of a second parabola having a second axis of symmetry, wherein the first and second axes of symmetry are out of phase with respect to one another, and x 9011/082290 further wherein the compound parabolic surface of the ramp acts to reduce the possibility of a wave, coming into contact with the ramp, from breaking, thereby dissipating the energy of the wave with minimal damage to the breakwater structure.

Preferably, the first and second axes of symmetry of the first and second parabolas are out of phase with respect to one another by an angle of between about 45 and 135 degrees. More preferably, the first and second axes of symmetry of the first and second parabolas are substantially perpendicular with respect to one another.

Typically, the first and second parabolas intersect at a point located between the : operatively lower and upper ends. The relevant portion of the first parabola defines a lower section of the compound parabolic surface running between the point of intersection and the operatively lower end of the ramp, while the relevant portion of the second parabola defines a upper section of the compound parabolic surface running between the point of intersection and the operatively upper end of the ramp. .

Generally, the breakwater structure is positionable in a body of water so that the compound parabolic surface faces the waves to be dissipated. The energy of the waves are dissipated in use by directing the wave upwardly along the ramp and against the force of gravity such that, at the stage of the gravitational force overcoming the energy of the wave, the wave is directed downwardly along the parabolic surface of the ramp. Preferably, the breakwater structure is positionable in the body of water such that the ramp 1s in use perpendicular with the prevailing wave flow direction.

The first axis of symmetry may be substantially horizontal and in use alignable with a line being parallel with a mean still water line of the body of water. The second axis of symmetry may be substantially vertical and in use alignable with a line parallel to the direction in which gravity acts. Typically, the first parabola comprises a first focus point and the second parabola comprises a second focus point. The first and second focus points may be common

In an alternative embodiment, the first parabola comprises a first focus point and the second parabola comprises a second focus point, the first focus point being located

{ ~ OQ s 0114022409 above the second focus point and horizontally closer to the operatively upper end of the ramp than the second focus point.

Preferably, the first and second focus points lie within a common area defined by a horizontal line passing over the operatively upper end of the ramp, a vertical line passing over the operatively lower end of the ramp and the compound parabolic ramp surface. More preferably, the first parabola comprises a first vertex and the second parabola comprises a second vertex, wherein the first and second vertices lie within the common area.

The breakwater structure may include side walls for the purpose of in use containing the waves entering the ramp so as to prevent the waves from overflowing over the sides of the ramp and causing damage to the ramp. Furthermore, the breakwater structure includes a vertical section extending upwardly from the breakwater structure and near the operatively upper end of the ramp for in use directing larger than normal waves. The vertical section may be a fixed section or a movable section that is extendible from and/or retractable into the breakwater structure as required.

The breakwater structure may be constructed in-situ or by modular breakwater structure units to form a barrier in the body of water between a calm body of water and that part of the body of water containing the waves. Preferably, the modular breakwater structure units are buoyant for the purpose of transportation and capable of being sunk into position during construction

Typically, the breakwater structure includes formations on a surface thereof facing in use the calm body of water The formations generally prevent diffraction and/or refraction of any waves in the calm body of water for the purposes of further calming the waters in the calm body of water.

The dimensions of the breakwater structure and the depth at which it is positioned in the body of water are typically functions of the mean still water line of that part of the body of water containing the waves and the desired water level required in the calm body of water. The dimensions of the breakwater structure may be further influenced by the average wave frequency and wave height. The dimensions of the breakwater

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-6- structure may be even further influenced by 100 year and/or 1000 year storm wave frequencies and wave heights.

The calm body of water is from a grouping of calm water bodies including harbours and dams. Where the calm body of water is a dam, the breakwater structure forming the wall of the dam, harbour or other calm body of water may include means to generate power by drainage of water from the dam to that part of the body of water containing the waves. Preferably, the means to generate power are turbines driven by the drainage of water

Typically, the body of water is from a group of bodies of water including the ocean, lakes, dams, rivers and other in-land waters.

The breakwater structure may be a structure from a group of structures including breakwaters, harbour walls, piers and dam walls.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a side view of a breakwater structure in accordance with the present invention (the side walls are not shown),

Figure 2 is a side view of a first alternative embodiment of a breakwater structure in accordance with the present invention,

Figure 3 is a side view of a second alternative embodiment of a breakwater structure in accordance with the present invention;

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Figure 4 is a schematic side view of the breakwater structure of figure 2, illustrating the way in which a wave to be dissipated interacts with the breakwater structure;

Figure 5 is a schematic side view of the breakwater structure of figure 2, illustrating the interaction of a dissipated wave with the breakwater structure;

Figure 6 Is a schematic side view of the breakwater structure of figure 2 in use in one of many application as a harbour wall;

Figure 7 Is a schematic side view of the breakwater structure of figure 2 in use in one of many application as a dam wall for a storage type dam; and

Figure 8 is a schematic side view of the breakwater structure of figure 2 in use in one of many application as a dam wall for a hydroelectric type dam.

DETAILED DESCRIPTION OF THE DRAWINGS

A breakwater structure according to a first preferred embodiment of the invention is designated generally with reference numeral 10 in figure 1. The breakwater structure comprises a ramp 12, an operatively lower end 14 and an operatively upper end 16

The ramp 12 is made up partly from a first parabola 18 and partly from a second parabola 20, intersecting one another at a point of intersection 22 to form a compound parabolic ramp surface. As illustrated in the figure 1, the relevant portion of the first parabola 18 makes up the lower section of the ramp 12, that is, the section between the point of intersection 22 and the operatively lower end 14 of the ramp 12. The relevant portion of the second parabola 20 makes up the upper section of the ramp 12, that is, the section between the point of intersection 22 and the operatively upper end 16 of the ramp 12.

The first parabola 18 has a first, substantially horizontal axis of symmetry 24 and a first

) focus point 26. The second parabola 20 has a second, substantially vertical axis of symmetry 28 and a second focus point 30. As such, the first and second axes of symmetry 24,28 are substantially perpendicular with respect to one another. It will be appreciated that the use of the term “substantially” for the purposes of describing the orientations of the axes of symmetry 24,28 with respect to each other, and/or to the vertical and horizontal planes, implies a deviation of between 5 to 10 degrees.

Although the focus points 26,30 of the first and second parabolas may be common (not shown), it is preferable that the first focus point 26 of the first parabola 18 is located, with respect to the prevailing direction “D” of the waves that would in use come into contact with the breakwater structure 10, forwardly and upwardly of the second focus point 30 of the second parabola 20

Referring now to a first alternative embodiment of the invention as illustrated in figure 2, the ramp 12 of the breakwater structure 10 may include a fixed vertical section 32 for directing abnormally high surge waves. In a second alternative embodiment of the invention as illustrated in figure 3, the vertical section 32 of the ramp 12 may be movable to extend upwardly from, or retractable into the breakwater structure 10 as required. The advantage of the second alternative embodiment is that the vertical section 32 can be raised or extending when required, for example during storms, and then retracted so as to prevent the breakwater structure 10 from permanently blocking views.

In use, and with reference now to figure 4, the breakwater structure 10, built in-situ or modularly, is positioned such that the ramp 12 is perpendicular with the direction of the prevailing waves “D”, and such that the first axis of symmetry 24 is substantially parallel with the normal still water line (NSWL) or maximum still water line (MTWL). The normal still water line (NSWL) represents the level of the body of water, under normal conditions, if it were flat without any waves. Similarly, the maximum top water line (MTWL) represents the top level (i.e. the top of the waves) of the body of water, under abnormal conditions as may be encountered in, for example, a 100 year storm. It will be appreciated that the MTWL may or may not include the high or highest astronomical tide. It will be appreciated that the relevant still water level coincides with a level approximately half way between the top of a wave crest and the bottom of a wave

« trough of a given set of waves.

In the aforementioned orientation of the breakwater structure 10, an incoming wave 50, travelling along the prevailing direction “D”, is capable of coming into contact with the lower section of the ramp 12, that is, the section of the ramp 12 defined by the first parabola 18. Contact between the wave 50 and the aforementioned section of the ramp 12 redirects or reflects the water making up the wave 50, as depicted by directional arrows “d+”, towards the first focus point 26 in accordance with generally accepted mathematical methodologies pertaining to parabolas. The redirected water rides upwardly over the ramp 12 into a vertical or near vertical direction “Vy,” by the upper section of the ramp 12, that is the section of the ramp 12 defined by the second parabola 20. For abnormally high waves, the water is further directed the vertical section 32. It will be appreciated that the energy of the waves is opposed and dissipated by the force of gravity during its upward travel along the ramp 12. It will also be appreciated that the forces reflected back by the curvature have a very high correlation to the oncoming waves and therefore a neutralising effect on the oncoming waves thereby having a calming effect inmediately before the structure.

With reference now to figure 5, and at the stage were the energy of the wave has been dissipated, the water making up the wave 50 falls under the force of gravity downwardly, in direction “V4”, to contact that section of the ramp 12 defined by the second parabola 20. Contact between the water making up the wave 50 and the aforementioned section of the ramp 12 redirects or reflects the water, as depicted by directional arrows “d-", towards the second focus point 30. The redirected water rides downwardly on the ramp 12 and back into the body of water from whence the wave 50 originated. It will be appreciated that the water falling downwardly along the ramp 12 forms part of the retraction of the reflected wave and therefore the structure is not subjected to waves breaking on the surface.

As a result, the compound parabolic surface of the ramp 12 acts to reduce the possibility of the wave 50 from breaking, thereby dissipating the energy of the wave 50 with minimal damage to the breakwater structure 10.

With reference still to figure 4 and figure 5, the design of a required breakwater

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Rw 9011/022% 6 structure 10 depends on the application and other factors such as. o the level of the normal still water line (NSWL) and maximum top water line (MTWL); + the average and maximum wave heights; ¢ the average and maximum wave frequencies; and o the depth of the water at which the structure is to be erected.

For maximum performance, the breakwater structure must be erected such that the first axis of symmetry 24 of the first parabola lies at a level higher than the NSWL and

MTWL.

It is envisaged by the inventor that the breakwater structure 10 may be used in many different applications. For example: - as protection to coastal structures, existing or under construction; - as a wall for a harbour, a dam, a dry dock, etc. or as protection thereto; - as protection to a beach, dyke or shoreline; - as protection against flooding caused by regular storms and/or as a result of climate change, - as protection to the entrances of harbours; - as a bridge between two land masses thereby to create a calm body of water behind the structure; and - as a normal breakwater structure.

With reference to list of possible applications above, figure 6 shows the breakwater structure 10 acting as a harbour wall protecting piers 60 and ships 70 alike from the waves 50. In the illustrated application, the breakwater structure 10 is constructed at sea to form a calm body of water 80 between the breakwater structure 10 and a landmass 90. It will be appreciated that the pier structure can be constructed in many different formations behind the structure to manage diffraction, refraction and reflection of wave forces surrounding and resulting from the structure to further calm and stabilise the body of water immediately behind the structure and to allow entrance and exit to the harbour behind the breakwater structure. With the harbour entrance open to the

Ww ama i0272 0 11- EVA RE sea, it will be appreciated that the level of the calm body of water will be the same as the level of the prevailing still water line of the sea.

Figure 7 illustrates the breakwater structure 10 as a dam wall for storing a volume of water 100 between the breakwater structure 10 and a landmass 90. It will be appreciated that the volume of water 100 is isolated from the body of water in which the waves 50 are present. As such, the depth of the volume of water 100 is limited only by the heights of the landmass 90 and breakwater structure 10.

Figure 8 illustrates a breakwater structure 10 acting as a dam wall for a power generating storage dam. It will be appreciated that this application requires the vertical section 32 to be significantly higher than in previously described embodiments so as to provide sufficient head to drive the power generating turbines 110. Water 100 stored in dam is released from the dam into the ocean 50 through the turbines 110, which in turn are driven to produce power.

Although the invention has been described above with reference to preferred embodiments, it will be appreciated that many modifications or variations of the invention are possible without departing from the spirit or scope of the invention. For example, the breakwater structure 10 may include side walls (not shown) for the purpose of in use containing the waves entering the ramp so as to prevent the waves from overflowing over the sides of the ramp and causing damage to the ramp.

Claims

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1. A breakwater structure having a ramp with an operatively lower end, an operatively upper end and a compound parabolic surface extending between the operatively lower and upper ends, the compound parabolic surface being defined by a portion of a first parabola having a first axis of symmetry and by a portion of a second parabola having a second axis of symmetry, wherein the first and second axes of symmetry are out of phase with respect one another, and further wherein the compound parabolic surface of the ramp acts to reduce the possibility of a wave, coming into contact with the ramp, from breaking, thereby dissipating the energy of the wave with minimal damage to the breakwater structure.

2. A breakwater structure according to claim 1, wherein the first and second axes of symmetry of the first and second parabolas are out of phase with respect to one another by an angle of between about 45 and 135 degrees.

3. A breakwater structure according to claim 1 or clam 2, wherein the first and second axes of symmetry of the first and second parabolas are substantially perpendicular with respect to one another.

4. A breakwater structure according to claim 1, claim 2 or claim 3, wherein the first and second parabolas intersect at a point located between the operatively lower and upper ends, wherein the relevant portion of the first parabola defines a lower section of the compound parabolic surface running between the point of Intersection and the operatively lower end of the ramp, and wherein the relevant portion of the second parabola defines a upper section of the compound parabolic surface running between the point of intersection and the operatively upper end of the ramp.

5. A breakwater structure according to any one of claims 1 to 4, wherein the breakwater structure is positionable in a body of water so that the compound parabolic surface faces the waves to be dissipated, the energy of the waves being dissipated in use by directing the wave upwardly along the ramp and against the force of gravity such that, at the stage of the gravitational force overcoming the

Nom yD -13- 7) } | 1 / UZ SL energy of the wave, the wave is directed downwardly along the parabolic surface of the ramp.

6. A breakwater structure according to claim 5, wherein the breakwater structure is positionable in the body of water such that the ramp is in use perpendicular with the prevailing wave flow direction.

7. A breakwater structure according to claim 5 or claim 6, wherein the first axis of symmetry is substantially horizontal and in use alignable with a line being parallel with a mean still water line of the body of water, and the second axis of symmetry is substantially vertical and in use alignable with a line parallel to the direction In which gravity acts.

8. A breakwater structure according to claim 7, wherein the first parabola comprises a first focus point and the second parabola comprises a second focus point, the first and second focus points being common.

9. A breakwater structure according to claim 7, wherein the first parabola comprises a first focus point and the second parabola comprises a second focus point, the first focus point being located above the second focus point and horizontally closer to the operatively upper end of the ramp than the second focus point

10. A breakwater structure according to claim 8 or clam 9, wherein the first and second focus points lie within a common area defined by a horizontal line passing over the operatively upper end of the ramp, a vertical line passing over the operatively lower end of the ramp and the compound parabolic ramp surface.

11. A breakwater structure according to claim 8 or claim 9, wherein the first parabola comprises a first vertex and the second parabola comprises a second vertex, the first and second vertices lying within a common area defined by a horizontal line passing over the operatively upper end of the ramp, a vertical line passing over the operatively lower end of the ramp and the compound parabolic ramp surface.

) 14 ! AY a i: ~ 3 12 A breakwater structure according to claim 10 or clam 11, further including side walls for the purpose of in use containing the waves entering the ramp so as to prevent the waves from overflowing over the sides of the ramp and causing damage.

13. A breakwater structure according to claim 10, claim 11 or claim 12, further including a vertical section extending upwardly from the breakwater structure and near the operatively upper end of the ramp for in use directing larger than normal waves.

14. A breakwater structure according to claim 13, wherein the vertical section is a fixed section or a movable section that is extendible from and/or retractable into the breakwater structure as required.

15. A breakwater structure according to any one of claims 7 to 14, wherein the breakwater structure is constructible in-situ or by modular breakwater structure units, to form a barrier in the body of water between a calm body of water and that part of the body of water containing the waves.

16. A breakwater structure according to claim 15, wherein the modular breakwater structure units are buoyant for the purpose of transportation and capable of being sunk into position during construction.

17 A breakwater structure according to claim 15 or claim 16, wherein a surface of the breakwater structure facing in use the calm body of water comprises formations for preventing diffraction and/or refraction of any waves in the calm body of water for the purposes of further calming the waters in the caim body of water.

18. A breakwater structure according to any one of claims 15 to 17, wherein the dimensions of the breakwater structure and the depth at which it is positioned in the body of water are functions of the mean still water line of that part of the body of water containing the waves and the desired water level required in the calm body of water.

19. A breakwater structure according to claim 18, wherein the dimensions of the breakwater structure are further influenced by the average wave frequency and wave height.

20. A breakwater structure according to claim 18 or claim 19, wherein the dimensions of the breakwater structure are further influenced by 100 year and/or 1000 year storm wave frequencies and wave heights.

21. A breakwater structure according to any one of claims 15 to 20, wherein the calm body of water is from a grouping of calm water bodies including harbours and dams.

22. A breakwater structure according to any one of claims 15 to 20, wherein the calm body of water is a dam and further wherein the breakwater structure forming the wall of the dam includes means to generate power by drainage of water from the dam to that part of the body of water containing the waves.

23. A breakwater structure according to claim 22, wherein the means to generate power are turbines driven by the drainage of water.

24. A breakwater structure according to any one of claims 5 to 23, wherein the body of water is from a group of bodies of water including the ocean, lakes, dams, rivers and other in-land waters.

25. A breakwater structure according to any one of the preceding claims wherein the breakwater structure is a structure from a group of structures including breakwaters, harbour walls, piers and dam walls.

26. A breakwater structure substantially as herein described and illustrated. Dated this 29" da i b> = fl Sibanda & Zantwik \p)e£Z Applicant's Patent Attorney