CA1094828A - Floating breakwater - Google Patents
Floating breakwaterInfo
- Publication number
- CA1094828A CA1094828A CA299,264A CA299264A CA1094828A CA 1094828 A CA1094828 A CA 1094828A CA 299264 A CA299264 A CA 299264A CA 1094828 A CA1094828 A CA 1094828A
- Authority
- CA
- Canada
- Prior art keywords
- float body
- breakwater
- floating breakwater
- sway
- wave
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A10/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE at coastal zones; at river basins
- Y02A10/11—Hard structures, e.g. dams, dykes or breakwaters
Landscapes
- Revetment (AREA)
Abstract
FLOATING BREAKWATER
ABSTRACT OF THE DISCLOSURE
A floating breakwater which is of the anchored, pontoon type where the phase differences between the vertical movement of the float body as caused by incoming waves and that of the lateral left-right sway as caused by incoming waves approach each other, so that a floating breakwater with a characteristic left-right sway-reducing tank is obtained.
ABSTRACT OF THE DISCLOSURE
A floating breakwater which is of the anchored, pontoon type where the phase differences between the vertical movement of the float body as caused by incoming waves and that of the lateral left-right sway as caused by incoming waves approach each other, so that a floating breakwater with a characteristic left-right sway-reducing tank is obtained.
Description
FIELD OF THE INV~NTION
This invention concerns a floating breakwater with a pontoon-type float body which is anchored to the sea bottom.
BACKGROUND OF THE INVENTION
(a) Brief Description of Drawinq Related to Prior Art Figure 1 shows a side cross-sectional view of a floating breakwater of past design.
(b) Description of the Prior Art Referring to Fig. 1, the pontoon-type float body (a) was attached to the sea bottom (c) by a rope or a chain (b). When incident or incoming waves (d) struck, the 10at body (a) would bob up and down, or laterally in a left-right direction.
When a wave would pass this breakwater, the incoming wave (d), when it hit the restrained float body (a), would produce wave (e). The movement of the float body (a) would cause wave (f) to be formed. The optimum conditions which would produce no waves transiting the ~ breakwater would be if float body (a)'s lateral, left-right sway phase difference with respect to incoming wave (d) matched the phase difference of the float body's vertical movement caused by incoming wave (d). With these conditions, waves (e) and (f) would cancel each other out and there would be no transiting waves.
However, as Figure 1 shows, a simple pontoon-type of float body (a~ has only its shape to determine its wave-breaking properties and it was an objective to improve upon this floating breakwater by providing a measure by which these properties could be adjusted.
SUMMARY OF THE INVENTION
Therefore, in this invention's sea bottom-anchored, pontoon-type floating breakwater, there is a ., left-right sway-reducing tank in the above-mentioned float body which makes the phase difference of the 8~
vertical motion of the float body from incoming waves, approach that of the lateral, left-right, sway of the float body caused by the same incoming waves.
~ ore particularly, the invention comprehends a floating breakwater including a pontoon type breakwater float body anchored to the sea bottom.
A floating left-right sway reducing tank floats inside the breakwater float body. Th~ phase difference between the vertical movements of the float body and the incoming waves, and that of the lateral, left-right sway and the incoming waves are caused to approach each other by the left-right sway of the sway reducing tank so that the ratio of the transiting wave to the incoming wave is reduced.
In the past, it was necessary to employ ballast water in pontoon type breakwaters to sink them to a specific draft, but with the floating breakwater o this invention, it has the advantage of combining the function of the functional water with that of ballast water, so it is possible to improve the cost efficiency.
:
.
~9~8~3 BRIEF DESCRIPTION OF THE DRAWINGS OF THE INVENTION
Varlous other objects and many of the attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings in which like reference characters designate the same or similar parts throughout all the figures thereof (Fig. l having been previously described with relation to the prior art1, and wherein:
Figures 2 - 5 are all figures representing side cross-sectional views of actual examples of this invention;
Figure 5 shows a side cross-sectional view of the action of the floating breakwater of this invention;
and Figure 7 is a graph which compares the properties of this invention's breakwater with one of past design.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Figures 2 - 5 are all examples of a side cross-sectional view of an actual example of this invention.
In each of these figures of floating breakwaters, the float body (3) is anchored to the sea bottom (l) by a chain ~, or rope (2). It is built to include a left-right sway-reducing tank. The water inside of the tank combines the ballast water function and that of the functional water (4a).
In each of the examples in Figures 2 - 4, the left-right sway-xeducing tank (4) is mounted on the inner plate (3a) of the double-bottom of the pontoon-type float body (3). As E'igure 5 shows, it would also be alright to have a left-right sway-reducing tank inside of a pontoon-type of float body with a single bottom (3) where it would be in direct contact with the functional water.
Also, as Figure 4 shows, because there are holes (5) made in the wall portion of the pontoon-type float body (3), it is alright if water from the outside is allowed to come into contact with the left-right sway-reducing tank.
Based upon the double pendulum theory, by adding the supplementary pendulum in the form of the left-right sway-reducing tank (4), it becomes possible to change the phase lag of the principal pendulum which is the float body t3) itself.
That is, the functional water (4a) which is enclosed within the floating breakwater upon being hit by an incoming wave of short wavelength, moves in a left-right direction as shown in Figure 6. The phase difference in the left-right sway of the float body vis-a-vis the - incoming waves varies with the width Bo of the left-right sway-reducing tank (4) and the depth (h) of the functional water when it is at rest.
The characteristic periodicity (T) of the back-and-forth motion of the functional water (4a) is shown by the following equation.
T = 2~
.., _ ~ Bog tanh Bo Where: -Bo is the width of tihe functional water ' h is the depth of the functional water at rest g is the acceleration of gravity In this manner, if a left-right sway-reducing tank (4) is incorporated, the phase difference between the vertical movement of the float body (3) due to -.
incoming waves and that of the lateral, left-right sway from incoming waves approach each otherO Due to this, the transition wave ratio, HT/HI (that is the ratio of the transiting wave height (HT) and the incoming wave hcight~.
(HI)-can be reduced.
Figure 7 is a graph which compares the experimental properties of this invention's floating breakwater with a left-right sway-reduclng tank and those of former floating breakwaters. In the figure center, curve M shows properties of a former floating breakwater without a left-right sway-reducing tank. Curve N shows data for this invention. As becomes clear from the figure, where the ratio of the wavelength of the incoming wave ~ and the width (B) of the float body (3), ~/Bo is within limits which are smaller than 4,5, the transiting wave ratio, HT/HI maximum height is reduced by about 17%~
As has been explained in detail above, by -the very simple measure of adding a left-right sway-reducing tank to a pontoon-type of floating breakwater, the phase difference in the vertical motion of the float body caused by incoming waves and that of the lateral, left-right sway of the float body caused by incoming waves, can be made to approach each other so that the wave-breaking effectiveness of the breakwater can be increased by a widé margin. One can also have a breakwater with the same wave-breaking effectiveness of a past breakwater which is of smaller size.
Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein;
- , .
~ ~ .
.
This invention concerns a floating breakwater with a pontoon-type float body which is anchored to the sea bottom.
BACKGROUND OF THE INVENTION
(a) Brief Description of Drawinq Related to Prior Art Figure 1 shows a side cross-sectional view of a floating breakwater of past design.
(b) Description of the Prior Art Referring to Fig. 1, the pontoon-type float body (a) was attached to the sea bottom (c) by a rope or a chain (b). When incident or incoming waves (d) struck, the 10at body (a) would bob up and down, or laterally in a left-right direction.
When a wave would pass this breakwater, the incoming wave (d), when it hit the restrained float body (a), would produce wave (e). The movement of the float body (a) would cause wave (f) to be formed. The optimum conditions which would produce no waves transiting the ~ breakwater would be if float body (a)'s lateral, left-right sway phase difference with respect to incoming wave (d) matched the phase difference of the float body's vertical movement caused by incoming wave (d). With these conditions, waves (e) and (f) would cancel each other out and there would be no transiting waves.
However, as Figure 1 shows, a simple pontoon-type of float body (a~ has only its shape to determine its wave-breaking properties and it was an objective to improve upon this floating breakwater by providing a measure by which these properties could be adjusted.
SUMMARY OF THE INVENTION
Therefore, in this invention's sea bottom-anchored, pontoon-type floating breakwater, there is a ., left-right sway-reducing tank in the above-mentioned float body which makes the phase difference of the 8~
vertical motion of the float body from incoming waves, approach that of the lateral, left-right, sway of the float body caused by the same incoming waves.
~ ore particularly, the invention comprehends a floating breakwater including a pontoon type breakwater float body anchored to the sea bottom.
A floating left-right sway reducing tank floats inside the breakwater float body. Th~ phase difference between the vertical movements of the float body and the incoming waves, and that of the lateral, left-right sway and the incoming waves are caused to approach each other by the left-right sway of the sway reducing tank so that the ratio of the transiting wave to the incoming wave is reduced.
In the past, it was necessary to employ ballast water in pontoon type breakwaters to sink them to a specific draft, but with the floating breakwater o this invention, it has the advantage of combining the function of the functional water with that of ballast water, so it is possible to improve the cost efficiency.
:
.
~9~8~3 BRIEF DESCRIPTION OF THE DRAWINGS OF THE INVENTION
Varlous other objects and many of the attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings in which like reference characters designate the same or similar parts throughout all the figures thereof (Fig. l having been previously described with relation to the prior art1, and wherein:
Figures 2 - 5 are all figures representing side cross-sectional views of actual examples of this invention;
Figure 5 shows a side cross-sectional view of the action of the floating breakwater of this invention;
and Figure 7 is a graph which compares the properties of this invention's breakwater with one of past design.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Figures 2 - 5 are all examples of a side cross-sectional view of an actual example of this invention.
In each of these figures of floating breakwaters, the float body (3) is anchored to the sea bottom (l) by a chain ~, or rope (2). It is built to include a left-right sway-reducing tank. The water inside of the tank combines the ballast water function and that of the functional water (4a).
In each of the examples in Figures 2 - 4, the left-right sway-xeducing tank (4) is mounted on the inner plate (3a) of the double-bottom of the pontoon-type float body (3). As E'igure 5 shows, it would also be alright to have a left-right sway-reducing tank inside of a pontoon-type of float body with a single bottom (3) where it would be in direct contact with the functional water.
Also, as Figure 4 shows, because there are holes (5) made in the wall portion of the pontoon-type float body (3), it is alright if water from the outside is allowed to come into contact with the left-right sway-reducing tank.
Based upon the double pendulum theory, by adding the supplementary pendulum in the form of the left-right sway-reducing tank (4), it becomes possible to change the phase lag of the principal pendulum which is the float body t3) itself.
That is, the functional water (4a) which is enclosed within the floating breakwater upon being hit by an incoming wave of short wavelength, moves in a left-right direction as shown in Figure 6. The phase difference in the left-right sway of the float body vis-a-vis the - incoming waves varies with the width Bo of the left-right sway-reducing tank (4) and the depth (h) of the functional water when it is at rest.
The characteristic periodicity (T) of the back-and-forth motion of the functional water (4a) is shown by the following equation.
T = 2~
.., _ ~ Bog tanh Bo Where: -Bo is the width of tihe functional water ' h is the depth of the functional water at rest g is the acceleration of gravity In this manner, if a left-right sway-reducing tank (4) is incorporated, the phase difference between the vertical movement of the float body (3) due to -.
incoming waves and that of the lateral, left-right sway from incoming waves approach each otherO Due to this, the transition wave ratio, HT/HI (that is the ratio of the transiting wave height (HT) and the incoming wave hcight~.
(HI)-can be reduced.
Figure 7 is a graph which compares the experimental properties of this invention's floating breakwater with a left-right sway-reduclng tank and those of former floating breakwaters. In the figure center, curve M shows properties of a former floating breakwater without a left-right sway-reducing tank. Curve N shows data for this invention. As becomes clear from the figure, where the ratio of the wavelength of the incoming wave ~ and the width (B) of the float body (3), ~/Bo is within limits which are smaller than 4,5, the transiting wave ratio, HT/HI maximum height is reduced by about 17%~
As has been explained in detail above, by -the very simple measure of adding a left-right sway-reducing tank to a pontoon-type of floating breakwater, the phase difference in the vertical motion of the float body caused by incoming waves and that of the lateral, left-right sway of the float body caused by incoming waves, can be made to approach each other so that the wave-breaking effectiveness of the breakwater can be increased by a widé margin. One can also have a breakwater with the same wave-breaking effectiveness of a past breakwater which is of smaller size.
Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein;
- , .
~ ~ .
.
Claims (3)
1. A floating breakwater comprising a pontoon type breakwater float body anchored to the sea bottom; and a left-right sway reducing tank inside the breakwater float body; said tank being of such a size whereby the phase difference between the vertical movements of the float body and the incoming waves, and that of the lateral, left-right sway and the incoming waves are caused to approach each other by the left-right sway of the sway reducing tank so that the ratio of the transiting wave to the incoming wave is reduced.
2. The floating breakwater of Claim 1 wherein said left-right sway reducing tank has a rectangular cross section.
3. The floating breakwater of Claims 1 or 2 wherein the bottom wall of said sway reducing tank comprises a planar plate.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2996877A JPS53115533A (en) | 1977-03-18 | 1977-03-18 | Floating wave dissipation bank |
| JP52/29968 | 1977-03-18 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1094828A true CA1094828A (en) | 1981-02-03 |
Family
ID=12290756
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA299,264A Expired CA1094828A (en) | 1977-03-18 | 1978-03-20 | Floating breakwater |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS53115533A (en) |
| CA (1) | CA1094828A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110761244A (en) * | 2019-11-28 | 2020-02-07 | 交通运输部天津水运工程科学研究所 | Floating breakwater with anti-rolling function |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103215917B (en) * | 2013-04-17 | 2015-02-18 | 河海大学 | Rectangular square box breakwater structure and physical model testing device thereof |
-
1977
- 1977-03-18 JP JP2996877A patent/JPS53115533A/en active Pending
-
1978
- 1978-03-20 CA CA299,264A patent/CA1094828A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110761244A (en) * | 2019-11-28 | 2020-02-07 | 交通运输部天津水运工程科学研究所 | Floating breakwater with anti-rolling function |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS53115533A (en) | 1978-10-09 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |