JP4924302B2 - Structure of entrance and exit of closed sea area and flow condition control method - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a structure and a flow condition control method for a closed sea area, and more particularly to a closed sea area suitable for improving the flow environment of a closed sea area formed in a coastal area by a past port project. The present invention relates to a structure of a part and a flow condition control method.

  In harbor areas with large metropolitan areas, many highly closed sea areas (closed sea areas) isolated from outside sea areas, for example, in the coastal areas, have been formed by past port projects (land reclamation and breakwater construction). In such a closed sea area, the flow of seawater decreases due to the closed topography, and the exchange of seawater inside and outside the closed sea area decreases. For this reason, the inflow load from the terrestrial area is accumulated excessively, and overnutrition progresses, organic suspensions such as phytoplankton increase (red tide is generated when it grows abnormally), and transparency decreases. Sea area.

  In addition, the organic suspension that has grown up died, and it settles and accumulates in the bottom layer, so that the bottom layer portion becomes sludge and the bottom quality deteriorates. Furthermore, when the bottom layer is excessively sludged, a large amount of dissolved oxygen is consumed during the decomposition, so that the bottom layer becomes hypoxic, organisms and the like living in the bottom layer die, and the ecosystem is remarkably destroyed. In addition, blue tides are generated by the rise of anaerobic water masses in the bottom layer, and even organisms in shallow waters can be killed.

On the other hand, Patent Document 1 discloses an invention related to a breakwater. This breakwater forms the tip of the breakwater facing the entrance / exit where the tidal current flows in and out in a triangular shape or blade shape, thereby spreading the circulation flow generated on the back side of the breakwater over a wide area in the bay. In addition, a strong separation vortex flow is generated on the back side of the breakwater, and this vortex flow generates a large circulation flow in the bay, reducing the stagnation area in the bay, preventing eutrophication in the bay, and improving the flow environment. Yes.
JP-A-10-219650

  However, the breakwater described in Patent Document 1 generates a separation vortex by making the shape of the tip of the breakwater a triangular shape or a blade shape, and uses this separation vortex to generate a large circulating flow in the bay. Therefore, there is no problem when the tidal current is strong, but when the tidal current is weak, the circulation flow cannot be extended to the back of the bay, and the exchange of seawater inside and outside the bay cannot be promoted. The eutrophication in the bay will progress and the fluid environment will deteriorate.

  The present invention has been made in view of the conventional problems as described above, and can promote the exchange of seawater in and out of the closed sea area, and can reach every corner of the closed sea area regardless of the strength of the tidal current. It is an object of the present invention to provide a structure and a flow state control method of an entrance / exit part of a closed sea area that can generate a large circulation flow and thereby improve the flow environment of the closed sea area.

In order to solve the above problems, the present invention employs the following means.
That is, the invention according to claim 1 is a structure of an entrance / exit part of a closed sea area formed in a coastal area, and is provided at an entrance / exit part of the closed sea area, and an opening having a predetermined width is formed in the entrance / exit part. A main levee body, a first sub dam body provided integrally with the main levee body and extending inward of the closed sea area from the main levee body, and the first sub levee to the main levee body A second sub-bank that is integrally provided at a predetermined distance from the body on the opposite side of the opening and that extends from the main bank to the inside of the closed water body and is longer than the first sub-bank It is characterized by comprising a body.

 According to the structure of the entrance / exit part of the closed sea area according to the present invention, when the tidal current passes through the entrance / exit part, the vortex is generated in the vicinity of the tip of the first sub dam body, and this vortex is generated. Moves to the inside of the closed sea area along the second sub-bank body by coming into contact with the second sub-bank body, and reaches the innermost part of the closed sea area while growing gradually. The generation, movement, and growth of such vortices are continuously performed in the closed sea area, and a large circulation flow is generated in the closed sea area, and this circulation flow allows the exchange of seawater inside and outside the closed sea area. And can prevent the formation of stagnant areas in closed waters.

  The invention according to claim 2 is the structure of the entrance / exit of the closed sea area according to claim 1, wherein the first sub levee body is bent in the direction of the second sub dam body. It is characterized by.

  According to the structure of the entrance / exit part of the closed sea area according to the present invention, the vortex generated in the vicinity of the tip of the first sub-bank body when the tidal current passing through the entrance / portion contacts the first sub-bank body is It is guided in the direction of the second sub-bank body by the bent shape of the tip of the body, moves inward of the closed sea area by contacting the second sub-bank body, and gradually grows while deepening the innermost part of the closed sea area Will reach the department.

  The invention according to claim 3 is the structure of the entrance / exit part of the closed sea area according to claim 1 or 2, wherein the main levee body is provided on both banks facing the entrance, respectively, The first sub bank body and the second sub bank body are integrally provided on the bank body.

  The invention according to claim 4 is the structure of the entrance / exit part of the closed sea area according to claim 1 or 2, wherein the main levee body is provided on one of both banks facing the entrance / exit part. The body is provided with the first sub-bank body and the second sub-bank body integrally.

  The invention according to claim 5 is a flow state control method for a closed sea area for forming a circulating flow in the closed sea area formed in the coastal area, wherein a main levee body is provided at an entrance / exit part of the closed sea area. An opening having a predetermined width is formed at the entrance and exit, and the main levee body extends from the main levee body to the inside of the closed sea area, and the first sub dam A second auxiliary levee body that is longer than the first auxiliary levee body extending from the main levee body to the inside of the closed sea area at a predetermined interval on the opposite side of the opening from the body, A vortex is generated in the vicinity of the entrance / exit part by receiving the tidal current passing through the entrance / exit part by the first sub-bank body, and the vortex is brought into contact with the second sub-bank body to By moving inward, a circulation flow is formed in the closed sea area.

  According to the closed flow area control method according to the present invention, a vortex is generated in the vicinity of the tip of the first sub-bank body by receiving the tidal current passing through the entrance / exit section by the first sub-bank body, and this vortex is the second It moves inward of the closed sea area along the second sub-bank body by coming into contact with the secondary bank body, and reaches the innermost part of the closed sea area while growing gradually. The generation, movement, and growth of such vortices are continuously performed in the closed sea area, and a large circulation flow is generated in the closed sea area, and the exchange of seawater inside and outside the closed sea area is generated by this circulation flow. Can be prevented, and a stagnation area can be prevented from forming in a closed sea area.

As described above, according to the structure of the entrance / exit part of the closed sea area and the flow condition control method of the present invention, the first sub-bank body generates a vortex near the tip of the first sub-bank body, It is possible to move toward the innermost part of the closed sea area by making it move inward in the closed sea area by the second sub-bank, and to reach the innermost part of the closed sea area while gradually growing. It can be performed continuously in the sea area.
Therefore, regardless of the strength of the tidal current, a large circulation flow can be formed in the closed sea area, so that the exchange of seawater inside and outside the closed sea area can be promoted, and a stagnation area is formed in the closed sea area. Can be prevented, and the flow environment can be improved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 and 2 show an embodiment of the structure of an entrance / exit part of a closed sea area according to the present invention. FIG. 1 is a schematic view showing the entire harbor in which the closed sea area is formed, FIG. Is a partially enlarged view of a closed sea area.

That is, the structure of the entrance / exit part 2 of the closed sea area 1 shown in this embodiment is, for example, as shown in FIG. 1 and FIG. 2, as shown in FIGS. 1 and 2, by the past port business (land reclamation, breakwater construction, etc.) It is effective for improving the flow environment of the highly closed sea area (hereinafter referred to as “closed sea area 1”) formed in the coastal area 20 and isolated from the outer sea area. The main bank body 4 provided in the entrance / exit part 2, and the first sub bank body 6 and the second sub bank body 9 provided integrally with the main bank body 4 are provided.
Here, the “entrance / exit part 2” means a constricted part located at the boundary between the closed sea area 1 and the outer sea area 3. Moreover, in this Embodiment, although the closed sea area 1 formed in the coastal part 20 at the back of the bay of the port 15 is made into object, the closed sea area, the river, the lake, etc. which were formed in the coastal part where a port does not exist It is also possible to target closed water areas.

  The main dam body 4 has a wall shape formed of steel, concrete, or the like, and is disposed so as to face the both banks facing the entrance / exit portion 2 of the closed sea area 1 so as to protrude in the opposite shore direction. The closed sea area 1 is partitioned from the outer sea area 3 by the main dam body 4. In FIG. 2, only one main levee body 4 is shown.

 The pair of main levee bodies 4 is set to a height at which the upper end protrudes upward from the sea level at high tide, and the inner and outer wall surfaces (the wall surface 4a on the closed sea area 1 side and the wall surface 4b on the outer sea area 3 side) are tidal. It is provided on both banks of the entrance / exit part 2 so as to be orthogonal to the moving direction of the tidal current 10 generated by the tidal flow between the closed sea area 1 and the outer sea area 3 between the ends of the pair of main dam bodies 4. An opening 5 having a predetermined width communicating with each other is formed, and the tidal current 10 moves between the outer sea area 3 and the closed sea area 1 through the opening 5.

  The main levee body 4 is not necessarily provided on both banks of the entrance / exit portion 2 of the closed sea area 1. The main levee body 4 is provided only on one bank of the entrance / exit portion 2, and the main levee body 4 is opposed to the opposite shore. An opening 5 may be formed between the outer sea area 3 and the closed sea area 1. In addition, if there is an existing main body, it may be used.

The first auxiliary levee body 6 has a wall shape formed of steel, concrete or the like, and is an inner part separated from the tip of one main dam body 4 by a predetermined distance (Lx1) in the shore direction of the entrance / exit portion 2. Both wall surfaces 6 a are integrally provided on the wall surface 4 a side so as to be substantially orthogonal to the inner wall surface 4 a of one main levee body 4, and the tip of the closed sea area 1 extends from the inner wall surface 4 a of one main dam body 4. It extends to a predetermined position on the inside.
The first sub levee body 6 has an inner wall surface 4a of the main dam body 4 so that the tip surface of the main dam body 4 facing the opening 5 and the wall surface 6a are flush with each other, that is, Lx1 = 0. It may be provided on the side.

 The first sub levee body 6 is set at a height such that the upper end protrudes above the sea level at high tide, and the tide 10 passing through the opening 5 is closed from the outer sea area 3 without getting over the first sub dam body 6. It is configured to move from the closed sea area 1 to the outer sea area 3.

  The first sub levee body 6 is formed in a straight portion 7 in which the wall surface 6 a is substantially orthogonal to the inner wall surface 4 a of the main dam body 4 from the main dam body 4 to a predetermined position inside the closed sea area 1. In addition, a portion on the tip side from the straight portion 7 is formed in a bent portion 8 bent at a predetermined angle in a direction away from the opening 5 (a direction approaching a second sub-bank body 9 described later). The direction of the second auxiliary dam body 9 described later is a tidal current 10 that moves from the outer sea area 3 through the opening 5 to the closed sea area 1 along the wall surface 6a on the opening 5 side of the straight part 7 and the bent part 8 of the body 6. Led to.

  By providing the first auxiliary dam body 6 integrally with the main dam body 4, the water channel length L of the opening 5 of the inlet / outlet portion 2 is made longer than when the opening 5 of the inlet / outlet portion 2 is constituted only by the main dam body 4. Can take. In the present embodiment, the water channel length L is the length Ly1 of the straight portion 7 of the first auxiliary dam body 6 and the length of the portion facing the opening 5 of the main dam body 4, that is, the length of the main dam body 4 It becomes the length (L = Ly1 + Ly1 ′) plus the thickness Ly1 ′.

  In the present embodiment, the first auxiliary levee body 6 is configured so that the angle θ formed by the wall surface 6a of the bent portion 8 of the first sub levee body 6 and the inner wall surface 4a of the main levee body 4 is about 30 °. The tip is bent. However, the angle θ can be set to an appropriate value according to the shape of the closed sea area 1 and the like.

  The second auxiliary dam body 9 is formed in a wall shape formed of steel, concrete, or the like, and is located on the outer side of the first auxiliary dam body 6 on the inner wall surface 4a side of the tip portion of one main levee body 4. The first auxiliary bank body 6 is provided integrally with the first sub-bank body 6 at a predetermined distance (Lx2) at a part (a part away from the opening 5).

The second auxiliary dam body 9 is integrally provided on the inner wall surface 4a side of the main dam body 4 so that both wall surfaces 9a are substantially orthogonal to the inner wall surface 4a of one main levee body 4, and the tip thereof is the first auxiliary levee body. It is formed longer than the first auxiliary dam body 6 so as to extend inward of the closed sea area 1 rather than the tip of the body 6.
In the present embodiment, the length Ly2 of the second sub-bank body 9 is approximately twice the length Ly1 of the straight section 7 of the first sub-bank body 6 (substantially the width W of the opening 5 of the entrance / exit section 2). Are set to the same length).

  The second sub-bank body 9 is set to have substantially the same height as the first sub-bank body 6 (the upper end is located above the sea level at the time of high tide), and the tidal current 10 passing through the opening 5 is the second. It is configured to move from the outer sea area 3 to the closed sea area 1 or from the closed sea area 1 to the outer sea area 3 without going over the auxiliary dam body 9.

  By providing the first auxiliary dam body 6 and the second auxiliary dam body 9 configured as described above on the inner wall surface 4a of one main levee body 4, the tidal current 10 generated by tidal flow is from the outer sea area 3 to the entrance / exit part. 2, the tidal current 10 comes into contact with the wall surface 6 a on the opening 5 side of the first sub-bank body 6, and along the wall surface 6 a of the straight portion 7 of the first sub-bank body 6, The first sub dam body is guided straight inward, and the course is bent in the direction of the second sub dam body 9 along the wall surface 6 a of the bent portion 8, and is peeled off from the tip of the first sub dam body 6. A vortex 11 is generated near the tip of 6.

  At this time, the vortex 11 moves from the vicinity of the tip of the first sub-bank body 6 toward the second sub-bank body 9 due to the bent shape of the bent portion 8 at the tip of the first sub-bank body 6, and the second sub-bank The closed sea area is brought into contact with the wall surface 9a of the body 9 on the first sub-bank body 6 side, guided to the inside of the closed sea area 1 along the wall surface 9a, and peeled off from the tip of the second sub-bank body 9. It moves toward the inside of 1, and reaches the innermost part of the closed sea area 1 while growing gradually.

  The generation of the vortex 11, the movement of the vortex 11, and the growth of the vortex 11 by the cooperation of the first auxiliary levee body 6 and the second auxiliary levee body 9 are continuously performed in the closed sea area 1, A large circulation flow is generated in the closed sea area 1, and this circulation flow promotes the exchange of seawater between the closed sea area 1 and the outer sea area 3 through the opening 5 of the entrance / exit part 2. A stagnation area is prevented from being formed in the inside, and the flow environment of the closed sea area 1 is improved.

  The inventors of the present application verified the structure of the entrance / exit part of the closed sea area according to the present invention configured as described above by numerical analysis. The results are shown below.

(1) Verification Model First, the following verification models (Case 0 to Case 2) were constructed in order to verify the structure of the entrance / exit part of the closed sea area according to the present invention. This verification model is (Study on hydraulics and water quality environment related to seawater purification in closed inner bay area; Minato Giken No.900, 1998, Kazuo Murakami). It refers to the basic model in the hydraulic experiment when the evaluation of the promotion of exchange is carried out.

The basic shape (case 0) of the verification model is shown in FIG.
Here, in FIG. 3, Lx: width of the target water area (closed sea area), Ly: length of the target water area, W: width of the opening at the entrance / exit, L: water channel length, LB: breakwater (main levee body) Based on these, the tidal prism (the amount of seawater exchanged between one tide) and the average flow velocity at the entrance / exit opening (during high and low tides) were calculated and verified.

(2) Verification method FIGS. 4A to 4C show the form of the circulating flow, and FIG. 5 shows the existence region of the circulating flow.
According to the verification using the theory of Kashiwai (Makoto Kashiwai: Studies on Tidal Exchange (1985 Kyoto University Dissertation 1985)), as shown in FIG. 5, the form of the circulation flow is determined by the relationship between L / W and R / W. Is done.
Here, L: water channel length, W: width of the opening of the entrance / exit part, R: a value indicating the amount of the tidal prism in the dimension of length.

  According to the above theory, the form of the circulating flow can be classified into Type 1, Type 2, and Type 3, as shown in FIGS. The effect of promoting the exchange of seawater is high in the order of type 1 → type 2 → type 3, and the exchange of seawater can hardly be expected with type 3. Therefore, in order to promote the exchange of seawater, type 3 may be improved to type 1 or type 2.

  As a method of improving Type 3 to Type 1 or Type 2, for example, when the basic model in FIG. 3 is type 3, as shown in FIG. The form of the circulating flow can be changed to Type 1 or Type 2 by reducing the length or by increasing the length of the water passage at the opening of the entrance / exit. In addition, like the structure of the entrance / exit part of the closed sea area according to the present invention shown in FIG. 2, the form of circulation can be changed to type 1 or type 2 by changing the vortex transport process.

  Based on the above basic model (case 0), as shown in FIGS. 6 to 8, case 0 (basic model), case 1 (large channel length, Ls = W), case 2 (Ls = 1 / 2Ls2, Ls2 = W) was constructed, and each model was verified by numerical analysis. The model of case 2 shown in FIG. 8 corresponds to the structure of the entrance / exit part of the closed sea area according to the present invention.

  In the numerical analysis using the above models (Case 0 to Case 2), a grid model as shown in FIG. 9 (lattice spacing: 120 m, tide level fluctuation: 0.5 m, wall condition: slip, eddy viscosity coefficient: 20 m / s), this grid model was made to correspond to each model (Case 0 to Case 2). Then, as shown in FIG. 10, monitoring was performed under the conditions of water level fluctuation / water quality: OP1, particle tracking: FLT1 to FLT12, and flow velocity: each lattice point.

  As a result of numerical analysis, as shown in FIGS. 11 to 13, Case 2 corresponding to the structure of the entrance / exit part of the closed sea area of the present invention has a larger flow on the left side than Case 0, and the entrance / exit from the center of the bay. The exchange of seawater inside and outside the closed sea area can be expected by connecting with the circulation flow formed near the opening of the section.

  Moreover, as shown in FIGS. 14-16, about the case 0, the type 3 circulation flow is formed. Furthermore, in case 1 and case 2, the change of the circulation flow formation process is promoted in each case to promote seawater exchange in the back of the bay, and type 3 is improved to type 2. Furthermore, in case 2, the scale of the circulation flow in the left area increases, and the exchange of seawater can be expected to be promoted.

  As described above, as a result of numerical analysis, by using the structure of the entrance and exit of the closed sea area according to the present invention, it is possible to promote the exchange of seawater inside and outside the closed sea area regardless of the magnitude of the tidal current, It is possible to prevent a stagnant area from being formed in the closed sea area, and to improve the flow environment of the closed sea area.

It is the schematic which showed the whole harbor where a closed sea area is formed. It is the schematic which showed one Embodiment of the structure of the entrance-and-exit part of the closed sea area by this invention, Comprising: It is the elements on larger scale of FIG. It is explanatory drawing which showed the basic model used for a numerical analysis. It is explanatory drawing which showed the form of the circulating flow. It is explanatory drawing which showed the existence area | region of the circulation flow. It is explanatory drawing which showed case 0 (basic model). It is explanatory drawing which showed the case 1 model. It is explanatory drawing which showed the case 2 model. It is explanatory drawing which showed the grid model. It is explanatory drawing which showed monitoring. It is explanatory drawing which showed the flow of the buoy of the case 0 model. It is explanatory drawing which showed the flow of the buoy of case 1 model. It is explanatory drawing which showed the flow of the buoy of Case 2 model. It is explanatory drawing which showed the form of the circulation flow of case 0 model. It is explanatory drawing which showed the form of the circulation flow of case 1 model. It is explanatory drawing which showed the form of the circulation flow of case 2 model.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Closed sea area 2 Entrance / exit part 3 Outer sea area 4 Main levee body 4a Inner wall surface 4b Outer wall surface 5 Opening 6 1st sub levee body 6a Wall surface 7 Straight part 8 Bending part 9 2nd sub dam body 9a Wall surface 10 Tidal current 11 Vortex 15 Port 20 coastal area

Claims (5)

It is a structure of the entrance / exit part of the closed sea area formed in the seaside part,
A main levee body provided at an entrance / exit of the closed sea area and forming an opening of a predetermined width at the entrance / exit;
A first sub dam body provided integrally with the main levee body and extending inward of the closed sea area from the main levee body;
The first levee is provided integrally with the main levee body at a predetermined interval from the first sub levee body on a side opposite to the opening, and extends inward of the closed water area from the main dam body. The structure of the entrance / exit part of the closed sea area characterized by including the 2nd sub dam body longer than a sub dam body.   2. The structure of an entrance / exit of a closed sea area according to claim 1, wherein a tip portion of the first sub-bank is bent in a direction of the second sub-bank.   The main levee body is provided on both banks facing the doorway, and the first sub levee body and the second sub levee body are integrally provided on one of the main levee bodies. The structure of the entrance / exit part of the closed sea area of Claim 1 or 2.   The main levee body is provided on one of both banks facing the entrance and exit, and the first sub levee body and the second sub levee body are integrally provided on the main levee body. Item 3. A structure of an entrance / exit of a closed sea area according to item 1 or 2. A closed flow area control method for forming a circulating flow in a closed area formed in a coastal area,
A main bank body is provided at the entrance / exit of the closed sea area, an opening having a predetermined width is formed at the entrance / exit part, and the main bank body extends from the main bank body to the inside of the closed sea area. A first sub-bank, and a first sub-bank that extends from the main bank to the inside of the closed sea area at a predetermined interval from the first sub-bank to the side opposite to the opening. The second sub-bank body that is longer than the body is integrally provided,
A vortex is generated in the vicinity of the entrance / exit portion by receiving the tidal current passing through the entrance / exit portion at the first sub-bank body, and the vortex is brought into contact with the second sub-bank body and moved inward in the closed sea area. A flow current control method for a closed sea area, wherein a circulation flow is formed in the closed sea area.