JP2650819B2 - Floating breakwater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a floating breakwater moored at a predetermined position on a water surface to dissipate wave energy.

[0002]

2. Description of the Related Art Conventionally, a floating breakwater of this type has a breakwater main body having a rectangular shape in a plan view in which three bottomless tanks are formed along the traveling direction of a wave. The bottomless tanks on both sides of the main body are communicated with each other through an air duct, and the central bottomless tank is communicated with the outside air through an air flow hole penetrating through the top plate.

In the above configuration, when a wave is incident and the incident wave hits the side of the breakwater main body, a part of the incident wave becomes a reflected wave, and the remaining wave becomes a transmitted wave and becomes a transmitted wave. , The water level in each bottomless tank moves up and down by the energy of the transmitted wave, and the air in each bottomless tank flows through the air duct and the air circulation hole, and the damping during the circulation The energy of the waves is dissipated in the tank, and divergent waves symmetrical to each other are generated in the bottomless tank, and divergent waves symmetrical to the incident wave are generated in the central bottomless tank. Then the energy of the waves is dissipated.

[0004]

The above-mentioned conventional floating breakwater is designed to effectively dissipate the energy of waves hitting from a direction perpendicular to the side of the breakwater main body. However, in actual waters, the direction in which the waves hit is not always constant, and waves may hit obliquely to the side of the breakwater main body.In such a case, at both ends of the breakwater main body, There is a disadvantage that waves in the oblique direction can hardly be eliminated.

Further, since the entire upper surface of the breakwater main body is covered with a deck, a large amount of deck members are required, and the weight of the freeboard portion is large, a large floating tank is provided in the breakwater main body. And the construction cost is high.

SUMMARY OF THE INVENTION In view of the above problems, the present invention can effectively eliminate even a wave obliquely hitting an end of a breakwater main body, and can reduce the weight of a freeboard portion to construct a low cost. It aims to provide floating breakwaters.

[0007]

In order to achieve the above-mentioned object, the present invention forms three bottomless tanks inside a breakwater main body along a traveling direction of a wave, and includes an upper part of the bottomless tank on both sides. In the floating breakwater that is communicated with each other through an air duct, the upper surface of the tank without a central bottom is opened, and at both ends of the breakwater main body, a wave indentation opening that opens to the end face of the breakwater main body is provided. It is characterized by having been formed.

[0008]

According to the above construction, when a wave is incident, a part of the incident wave hits the side shell of the breakwater main body and becomes a reflected wave, and the remaining wave passes below the breakwater main body. At that time, the water surface in each bottomless tank is moved up and down by the energy of the wave, so that the propagation motion of the wave is disturbed and attenuated by turbulence such as vortex, etc. An anti-symmetric divergent wave is generated while dissipating energy by damping, and in the central bottomless tank, a symmetric divergent wave is generated with the incident wave, and these divergent waves interfere with each other and are disturbed to dissipate the energy of the wave. Thing,
Thereby, the wave height of the transmitted wave passing under the breakwater main body can be reduced.

When a wave is obliquely incident on the end of the main body of the breakwater, the incident wave in the oblique direction enters the wave penetration concave portion and is reflected by the inner wall surface of the concave portion. The vortex-rotated reflected wave and the incident wave that has entered the wave-entering recess interfere with each other and are disturbed, whereby the energy of the obliquely incident wave is dissipated and the wave height is reduced. Can be reduced.

[0010]

FIG. 1 shows an embodiment of the present invention, in which a breakwater main body 1 is moored to a seabed anchor 3 via a chain 2.

As shown in FIG. 2, the breakwater main body 1 has a pair of vertical frame members 1a and 1b parallel to each other and a pair of horizontal frame members provided on both sides between the vertical frame members 1a and 1b. As shown in FIG. 3, both vertical frame members 1a and 1b include tanks 4 and 5 without bottom on both sides.
Are formed, and both vertical frame members 1a, 1b and both horizontal frame members 1c,
1d, a central bottomless tank 6 having an open upper surface is formed in the portion surrounded by 1d.
Are communicated with each other via air ducts 8 provided on both sides of both the horizontal frame members 1c and 1d and the center of the tank 6 without the center bottom. Both ends of the main floating tanks 7, 7 formed in the two horizontal frame members 1c, 1d are connected to the two vertical frame members 1c, 1d.
a, 1b. In FIG. 1, reference numeral 9 denotes an auxiliary floating tank provided at the bottom of the tanks 4 and 5 without side bottoms, E denotes a traveling direction of waves, L is the sea surface.

In the above configuration, when a wave is incident, a part of the incident wave hits the outer shell 10 of the breakwater main body 1 and becomes a reflected wave, and the remaining wave passes below the breakwater main body 1. In doing so, the water surface in each of the bottomless tanks 4 to 6 is moved up and down by the energy of the wave, so that the propagation motion of the wave is disturbed and attenuated by turbulence such as vortices, and the bottomless tank 4 , 5 alternately reciprocate air inside the air duct 8 and dissipate energy due to air resistance during the air circulation, while generating antisymmetric divergent waves. In the central bottomless tank 6, A divergent wave symmetrical to the incident wave is generated, and these divergent waves interfere with each other and are disturbed to dissipate the energy of the wave, whereby the height of the transmitted wave passing under the breakwater main body 1 is increased. Can be reduced.

According to the above configuration, the upper surface of the central bottomless tank 6 is open, and conventionally, the central bottomless tank 6
Since the deck member covering the upper surface of the main floating tank is omitted and the weight of the freeboard portion is reduced accordingly,
In addition, the size of the auxiliary floating tanks 9 can be reduced, so that the construction cost can be reduced.

Further, even if a wave crosses over a freeboard, the overtopping is absorbed in the tank 6 without center bottom, so that the overtopping effect against the overtopping is large. Here, the ratio between the widths b ₁ and b _{2 of the} tanks 4 and 5 on both sides and the width b _{3 of the} tank 6 without the center bottom is 1: 1: 2 (b ₁ : b ₂ : b ₃ = 1: 1). 1: 2),
The cross-sectional area of the air duct 4 is designed to be within 1/60 to 1/100 of the area of the water line in the tanks 4 and 5 without bottom,
Thereby, the wave can be effectively eliminated.

Referring to FIG. 4, the horizontal axis indicates the width B of the breakwater main body 1 with respect to the wavelength λ of the incident wave (λ / B), and the vertical axis indicates the transmittance. C _T (height of incident wave with respect to height Ht of transmitted wave [C _T = Ht / H
i]), and the parameter (auxiliary variable) is the ratio (B / d) of the draft d to the width B of the breakwater main body 1, 3.75 in Example A, and 2.50 in Example B. In Example C, the value is 1.875.

As is apparent from FIG. 4, the wavelength λ of the incident wave
Is short, the transmittance is low, and the wave canceling performance is excellent.
Here, as a specific example, assuming that the wavelength λ of the incident wave is 45 m and the width B of the breakwater main body 1 is 9.5 m, λ / B ≒
When designed at a draft d = 3.8m at 4.75, B / d
From the graph of = 2.50 (Example B), the transmittance C _T is 40% or less until λ = 45 m, and the wave height of 2 m is attenuated to 1 m or less.

As shown in FIG. 1 and FIG.
The vertical frame members 1a, 1b and the horizontal frame members 1c, 1
d, the wave-entry concave portion 1 opening at the end face of the breakwater main body 1
1 and 11 are formed.

According to the above configuration, even if a wave is incident on the end of the breakwater main body 1 from an oblique direction as shown by an arrow F, the incident wave in the oblique direction is reduced by the wave-entering recess 1.
1, 11 and the inner wall surface 11 of the recess 11
a, 11b. The vortex-rotated reflected wave reflected by 11c and the vortex-reflected reflected wave and the incident wave that has entered the wave-entering recesses 11 and 11 interfere with each other and are disturbed. Is dissipated and its wave height can be reduced.

[0019]

According to the present invention, since the wave penetration concave portions are formed at both ends of the breakwater main body, even if a wave is obliquely incident on the end of the breakwater main body, the wave is not oblique. The incident wave in the direction can be drawn into the wave-entering recess to cancel the wave.

Further, the waves incident on the central portion of the breakwater main body can be reliably eliminated by the three bottomless tanks formed inside the breakwater main body as in the conventional case. Furthermore,
The upper surface of the tank without bottom in the center of the breakwater body is open,
Conventionally, the deck member that covered the upper surface of the center bottomless tank was omitted, and the weight of the freeboard portion was reduced accordingly, so that the floating tank provided in the breakwater main body could be made smaller, and, naturally, Costs can be reduced.

Further, even if a wave crosses a freeboard, the overtopping is absorbed in the tank without the center bottom, so that the overtopping effect is large.

[Brief description of the drawings]

FIG. 1 is a perspective view of a floating breakwater according to an embodiment of the present invention.

FIG. 2 is a plan view of the same.

FIG. 3 is a transverse sectional view of the same.

FIG. 4 is a graph showing the wave canceling performance.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Breakwater main body 4,5 Both-side bottomless tank 6 Central bottomless tank 8 Air duct 11 Wave entry recess E Wave traveling direction

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuo Miyagawa 5-3-28 Nishikujo, Konohana-ku, Osaka City, Osaka, Japan Inside Hitachi Zosen Corporation (56) References JP-A-54-99333 (JP, A)

Claims (1)

(57) [Claims] 1. A floating breakwater having three bottomless tanks formed in a main body of a breakwater along a traveling direction of a wave, and upper portions of the bottomless tanks on both sides communicating with each other via an air duct. 2. The floating breakwater according to claim 1, wherein an upper surface of the tank with no central bottom is opened, and a wave indentation recessed at an end face of the breakwater main body is formed at both ends of the breakwater main body.