JP5067658B2 - Vertical mixing promotion equipment - Google Patents

Description

The present invention relates to a seawall environment improvement type revetment structure using natural energy for the purpose of preventing adverse effects on marine organisms and the like due to stratification by promoting water purification in the inner bay area, particularly vertical mixing in the sea area. .

In a closed inner bay, the water stratification develops in the summer, and the bottom layer tends to become hypoxic due to the inhibition of vertical mixing. Hypoxia is thought to be a factor that promotes the elution of nutrient salts and sulfides in the bottom mud and sometimes causes blue tide and explosive phytoplankton growth (red tide).

As a method for reducing deterioration of water quality in the inner bay area, a vertical mixing promotion embankment (Patent Document 1) that uses overtopping, a seawater exchange breakwater, and the like are known. Non-Patent Document 1 describes forced aeration using electric power.
Jun Yamamoto (2006): Water quality improvement effect verification test of microbubble generator in Uranouchi Bay, Ocean Development Papers, Vol. 22, pp. 643-648 JP 2004-218257 A

The method of using overtopping has the disadvantage that it is easily affected by tide level differences. In the inner bay area in the vicinity of a large city in Japan, there is a relatively large tide level difference of 2 to 3 cm. Therefore, a construction method that is not easily affected by the tide level difference is desirable. Further, the sea purification method using electric power has drawbacks such as high maintenance costs and limited effects to local ones.

An object of the present invention is to provide a water purification technology that is not easily affected by a tide level difference and that does not require maintenance costs for utilizing waves that are natural energy.

In order to solve the above problems, the vertical mixing enhancement equipment according to the present invention comprises a hanging plate, and retarding chamber in contact with the hanging plate, and deaths horizontal plate delimiting the bottom of the retarding chamber, Died horizontal plate below the retarding chamber and a vertical water passage formed between the rear surface of the end portion of the shore side and retarding chamber, there is a gap between the lower end and the sinking horizontal plate hanging plate, the lower end of the plate thickness center of the hanging plate The wedge shape is asymmetric with respect to the surface, and a vertical circulation flow is formed below the submerged horizontal plate . Moreover, it is preferable that it is the shape which has the inclination which the lower end surface of a drooping plate becomes high toward the outer side from the inner side of a water retention chamber.

The vertical mixing promotion equipment of the present invention has a water reservoir inside, and the effect of promoting aeration in the sea area and transport / mixing of surface water to the bottom of the water by the piston mode wave resonance in the water reservoir and the accompanying strong vortex flow. Have In addition, there is an effect of reducing reflected waves, which helps to calm the sea area.

The best mode for carrying out the present invention will be described. FIG. 1 is a cross-sectional view illustrating an example of a vertical mixing promoting facility. The vertical mixing promotion equipment 1 in FIG. 1A includes a drooping plate 2 (dripping plate), a reclaimed water chamber 3 in contact with the drooping plate 2, a submerged horizontal plate 4 separating the bottom surface of the reclaimed water chamber 3, and a lower portion of the reclaimed water chamber 3. And a vertical flow channel 5 formed in There is a gap between the lower end of the hanging plate 2 and the submerged horizontal plate 4.

The lower end of the hanging plate 2 has a wedge shape that is asymmetric with respect to the plate pressure center plane. In the example of FIG. 1A, the hanging plate 2 has a shape in which the lower end surface has an inclination that increases from the inner side to the outer side of the drinking water chamber 3. That is, in FIG. 1 (a), the bottom plate 2 is represented in the upper right direction.

A rear surface of the water reserving chamber 3 is provided at a predetermined interval Bc with respect to the hanging plate 2. Although this vertical mixing promotion equipment 1 can be constructed in a floating manner with a float attached, in this case, a rear drooping plate 6 is provided as the rear surface of the water-reserving chamber 3. Moreover, although this vertical mixing acceleration | stimulation equipment 1 can also be fixed and provided in the wall surface of a shore, when there already exists a wall surface, you may utilize this wall surface as a rear surface.

An end of the submerged horizontal plate 4 on the shore side is bent downward, and a vertical flow channel 5 is formed between the rear horizontal plate 4 and the rear surface.

When a wave is incident from the sea side, the seawater flows into the water reserving chamber 3 from between the lower end of the hanging plate 2 and the submerged horizontal plate 4. As a result, the water surface of the water reserving chamber 3 rises. When the wave is drawn, the seawater in the water chamber 3 flows out between the lower end of the drooping plate 2 and the submerged horizontal plate 4 to the sea side. Here, since the lower end of the drooping plate 2 has a wedge shape asymmetric with respect to the plate pressure center plane, the inflow amount and the outflow amount are different. Therefore, movement of seawater through the vertical flow channel 5 occurs. In the example of FIG. 1A, since the lower end surface of the drooping plate 2 is increased from the inside to the outside of the water chamber 3, the inflow amount passing between the lower end of the drooping plate 2 and the submerged horizontal plate 4 is the outflow amount. It exceeds. Therefore, a flow in which seawater descends through the vertical flow channel 5 is generated.

Here, when the average wavelength L of the sea area, the distance d from the sea surface to the lower end of the drooping plate 2, and the interval Bc between the drooping plate 2 and the rear surface satisfy the relationship of the following equation, The water level in chamber 3 rises the highest.

FIG.1 (b) is sectional drawing which shows the 2nd example of the vertical mixing promotion equipment. In this example, the lower end surface of the drooping plate 2 has a shape that has an inclination that decreases from the inside to the outside of the water chamber 3. That is, in FIG.1 (b), the lower end surface of the drooping plate 2 is represented in the right downward direction.

Next, it will be described in more detail based on examples. FIG. 2 is a conceptual diagram illustrating a test apparatus for a vertical mixing promotion facility. For the test, a two-dimensional wave-making water tank of 30 m × width 1 m × height 1.25 m was used. In the water channel, as shown in FIG. 1, a slope 11 having a gradient of 1:30 is installed, and a horizontal floor 12 is provided so as to be smoothly connected thereto. The horizontal floor 12 is provided with a partition so that the width of the water channel is substantially divided into two. An incident wave is installed in one water channel, and a model 13 of a vertical mixing facilitating facility is installed in the other water channel. Measured simultaneously. At one end of the waterway, a piston-type wave generator 14 is installed, and at the other end, a wave-dissipating work 15 composed of a lower transmission type hetimaron and a crushed stone slope is installed. It has a waterway structure that does not cause as much water level difference between the front and back as much as possible.

In setting the cross section of the vertical mixing facilitating equipment, relatively wave conditions with a period of T = 3 s and a wave height H of about 10-50 cm were targeted, assuming constant waves in a closed inner bay. Then, as shown in FIG. 1 (a), a preliminary experiment is made on the structure of a water reserving chamber that can generate an average flow in the vertical direction using a water reserving chamber type levee body having a water flow portion 5 vertically below the water reserving chamber 3 as a prototype. I examined it. Note that the permeable structure is applied to a floating structure.

Table 1 collectively shows the dimensions of the model 13 of the vertical mixing promoting equipment used in this example. In the example shown in FIG. 1 (a), the lower end surface of the drooping plate 2 has a shape with an inclination that increases from the inner side to the outer side of the water-reserving chamber 3 (hereinafter referred to as a “right-down wedge shape”). The flow of water into the chamber 3 is facilitated, and the flow of water from the lower end of the drooping plate 2 is suppressed, thereby generating an asymmetrical alternating vortex and generating a downward average flow in the vertical water passage 5. Was the goal. This example is TYPE1. In this type, the examples (TYPE3, TYPE4) with different drench depth d of the drooping plate were also examined. On the other hand, in the example shown in FIG. 1 (b), a shape (hereinafter referred to as a “wedge-up wedge shape”) in which the lower end surface of the drooping plate 2 has a slope that decreases from the inside to the outside of the water chamber 3 is employed. In contrast to TYPE1, the goal was to generate an upward average flow in the vertical waterway. The scale of the model here is set to about 1/5 of the actual machine.

For the measurement of wave deformation, six capacitive wave height meters 16 were used and installed as shown in FIG. Of these, two units measure incident waves (front of piston wave generator 14 and incident wave verification channel), two units separate incoming and reflected waves, and measure transmitted waves on the transmission side of the model of the vertical mixing facilitating equipment One wave height meter was installed in the water play room to investigate the appearance of the piston mode in the water play room. The incoming / reflected wave separation estimation method used for the estimation of the reflected wave is as follows. First, two wave height meters installed on the offshore side of the model are used to measure the water surface fluctuation waveform in which the incident wave and the reflected wave are superimposed, and these are subjected to free analysis to obtain the cosine and sine amplitudes. The interval between these two wave height meters is set equal to ¼ of the wavelength of the working wave, and the wave cosine and sine amplitudes obtained by each wave height meter are used to calculate the wave traveling to the shore side. It is possible to separate and analyze the amplitude component (incident wave) and the amplitude component (reflected wave) of the wave traveling offshore. By using the amplitudes of the incident wave and the reflected wave separated and analyzed as described above, the reflectance can be experimentally estimated by the equation: reflectance = reflected wave amplitude / incident wave amplitude.

The flow velocity of the vertical water passage was measured by installing an electromagnetic current meter 17 at the position shown in FIG. 1, extracting about 10 waves from the time waveform of the vertical flow velocity, and calculating the average flow velocity. To measure the average flow velocity at the bottom of the levee body, a Doppler ultrasonic current meter 18 is installed in the lower opening of the submerged horizontal plate 8 as shown in FIG. 1, and the average flow velocity is calculated from the time waveform of the horizontal flow velocity. did

In the test, the water depth h was constant at 64 cm. There are three types of incident waves H, H = 2 cm, 6 cm, and 10 cm (H = 10 cm, 30 cm, and 50 cm in local quantity), and a period T = 0.9 to 2.3 s (T = 2.0 to 5.5 in local quantity). Seven types of regular waves were used within the range of 1 s).

FIG. 3 is a graph showing the change of the reflectance Cr, the transmittance Ct, and the recreational indoor wave height amplification factor Hc / H (Hc; leisure water indoor wave height) according to the period of each vertical mixing promoting facility model. In the figure, L / Bc (wavelength chamber width ratio) was used as a parameter representing the period. The reflectance Cr and transmittance Ct were calculated as follows based on the attenuation wave theory. First, assuming that the structure is a two-dimensional object, a wave boundary value problem around the structure is constructed based on the two-dimensional linear wave theory. Specifically, a linear wave potential problem with the final unknown as a scattered wave potential caused by a cross-sectional object having an arbitrary shape is set and solved by a numerical analysis method. At this time, a fluid having linear attenuation was assumed so that energy dissipation due to flow separation from the acute angle portion of the structure or generation phenomenon of vortex flow can be approximately considered. Here, the linear resistance coefficient was set to about 0.2 with reference to the conventional results. Based on such a numerical analysis method, the wave potential Φr on the reflection side and Φt on the transmission side of the structure were respectively determined, and the ratio with the incident wave potential Φ was determined to calculate the reflectance and transmittance.

Focusing on the reflectance Cr of TYPE 1-3, the correspondence between the test results and the calculation results is generally good, and the local wave period T = 3.0 to 3.5 s (L / Bc = 11.0 to 13.5). ) It exhibits a minimum value in the vicinity, and increases slightly as it moves to the long period side, but it can be confirmed that the reflected wave is reduced, such as Cr <0.4. On the other hand, the test result of the reflectance Cr of TYPE4 shows that the effect of reducing the reflected wave is smaller than that of TYPE1 to 3 such that Cr> 0.4 with respect to the target wave. At this time, there is a difference in the calculation results such as being lower than the test results. This is explained if the wave height gain in the water reservoir is overestimated and the energy loss due to the vortex flow from the bottom of the drooping plate is overestimated. it can.

Focusing on the transmittance Ct, the correspondence between the test result and the calculation result is generally good, and Ct = about 0.2 to 0.4 for the target period.

Paying attention to the wave height gain Hc / H in the water reserving chamber 3, Hc / H> 1 in a wide range from the vicinity of the period where the reflectance Cr is significantly reduced to the long period side, and the piston mode wave resonance in the water reserving chamber 3 Can be confirmed to occur even when an opening is provided in the submerged horizontal plate 4.

FIG. 4 is a graph obtained by rearranging the reflectivity Cr and the hydrostatic indoor wave height gain Hc / H with respect to the incident wave height H = 6 cm. For any structural type, the reflectance Cr is closely related to the wave height amplification factor Hc / H in the water reserving chamber 3, and it can be confirmed that Cr is reduced as Hc / H increases. This is considered to be due to an increase in the vortex flow generated from the lower end of the drooping plate 2 toward the offshore with an increase in the wave height in the reclaimed water chamber 3.

FIG. 5 is a graph obtained by rearranging the transmittance Ct with respect to the incident wave height H = 6 cm. Ct can be confirmed to be approximately the same for the same period regardless of the structure type, and the effect of the relationship between the installation position of the submerged horizontal plate and the installation depth of the structure is seen rather than the structure of the hanging plate. It is done.

FIG. 6 is a graph showing an example of a flow velocity time waveform (T = 1.35 s, H = 6 cm) measured by an electromagnetic velocimeter in the vertical water passage 5. First, pay attention to the difference in the wedge shape of the hanging plate 2 that affects the vertical flow velocity. It can be confirmed that a downward average flow velocity is generated in the right-down wedge-shaped drooping plate (TYPE 1), and an upward average flow velocity is generated in the right-up wedge shape (TYPE 2). From this, it is recognized that the direction of the average flow velocity in the vertical water passage 5 changes depending on the installation direction of the hanging plate wedge shape.

Next, paying attention to the influence of the inundation depth when fixed to the right-down wedge-shaped drooping plate (TYPE1, 3, 4), it can be seen that the absolute value of the flow velocity amplitude increases as the drooping plate inundation depth becomes shallower. . This can be attributed to the wave height amplification factor of the recreational water chamber shown in FIG. However, there is no significant difference regarding the average flow rate.

FIG. 7 shows a dimensionless flow velocity q * (q * = v / (gH) ^{1 obtained} by dividing the average flow velocity v in the vertical channel 5 by the square root of the product of the gravitational acceleration g and the incident wave height H according to the model of each vertical mixing promoting facility. ^{/ 2} ) and a graph showing the change of the average water level WLc in the recreational water chamber by L / Bc.

Focusing on the dimensionless average flow velocity due to the difference in the wedge shape of the drooping plate, in the right falling wedge drooping plate (TYPE 1), a downward average flow velocity is generated for almost any period band. However, in the wedge type that rises to the right (TYPE2), an upward average flow velocity is generated on the short cycle side, but as it shifts to the long cycle side, it turns to a downward average flow velocity and no flow velocity is generated in a specific direction. .

Focusing on the influence of the drowning depth by fixing to the right-down wedge-shaped drooping plate (TYPE 1, 3, 4), the average downward flow velocity is stably generated regardless of the drooping plate drenching depth. In particular, in the case of TYPE 3 in which the drooping plate inundation depth is shallow, a stable downward average flow velocity is generated from the short cycle side. When the drooping depth of the drooping plate was increased (TYPE1, TYPE4), it was confirmed that a counterclockwise unidirectional flow was formed in the reclaimed water chamber for any periodic zone within the range of this test. Therefore, it is considered that the downward flow velocity accompanying the lowering of the water level in the water reserving chamber 3 is added to the unidirectional flow, and the downward flow velocity component becomes small. On the other hand, when the drooping water is shallow (TYPE 3), no one-way flow is formed in the water reserving chamber 3. For this reason, when the water level is lowered, only a vortex flow in the off-shore direction is formed from the lower end of the drooping plate, and the downward flow velocity including the effect of the drooping right drooping plate shape is unlikely to be disturbed.
From FIG. 3 and FIG. 7, it is found that the downward average flow velocity is increased under the condition that the amount of decrease in the average water level WLc and the wave height gain Hc / H in the recreational water chamber are increased, and vertical mixing is promoted.

In order to examine the generation mechanism of the average flow in the vertical direction, the flow conditions around the dam body were visualized by video recording, and the flow velocity data by the Doppler type ultrasonic anemometer installed in the lower opening of the submerged horizontal plate was analyzed. FIG. 8 schematically shows the flow condition around the vertical mixing promoting facility in the wedge-shaped hanging plate with a lower right. By making the hanging plate a right-down wedge-shaped structure, it is easy to flow the water mass into the water reserving chamber, and by suppressing the water mass outflow from the lower end of the dripping plate, an asymmetrical alternating vortex is generated. As a result, it is considered that a downward flow velocity is generated in the vertical water passage 5 and a clockwise circulation flow is generated in the lower opening of the submerged horizontal plate 4 to promote vertical mixing.

FIG. 9 is a graph showing an example of the vertical distribution of the dimensionless average flow velocity per cycle in the lower opening of the submerged horizontal plate 4. The vertical axis represents the water depth h ₂ from the lower surface of the submerged horizontal plate and z / h ₂ made dimensionless by the distance z from the lower surface of the submerged horizontal plate, and the horizontal axis represents the average flow velocity per cycle (U; horizontal, V: (Vertical) is dimensionless in terms of the incident wave, and the wave direction and the vertical upward direction are positive. From this figure, it can be seen that a mean vertical flow occurs at the bottom of the water and shoreward at the bottom of the submerged horizontal plate, and a significant vertical circulation flow is formed.

As described above, the wave deformation characteristics of the vertical mixing facilitating equipment show almost the same transmission characteristics regardless of the shape of the front hanging plate. Further, even if the submerged horizontal plate is provided with an opening, piston mode wave resonance occurs in the water reserving chamber, and an effective reflected wave reduction effect due to the vortex flow can be obtained.

In the right-down wedge-shaped droop type structure, a vertically downward average flow is stably generated regardless of the condition of the action wave. On the other hand, a wedge-shaped structure with a wedge-shaped structure that rises to the right generates a vertical upward average flow in the target periodic zone, but the average flow in a specific direction changes, such as the direction of the vertical average flow changes depending on the periodic conditions. Generation is not seen.

It is sectional drawing which shows the example of a vertical mixing promotion equipment. It is a conceptual diagram which shows the test apparatus of a vertical mixing promotion facility. It is a graph which shows the change by the period of the reflectance, the transmittance | permeability by the model of each vertical mixing promotion equipment, and the wave height amplification factor of a recreational water chamber. It is a graph which shows the relationship between a reflectance and a recreational indoor wave height gain. It is a graph which shows the test result of the transmittance | permeability. It is a graph which shows an example of the flow velocity time waveform in a vertical water passage. It is a graph which shows the average flow velocity of the vertical water channel of the model of each vertical mixing promotion equipment, and an average water level in a recreational water chamber. It is the conceptual diagram which showed typically the flow condition around the vertical mixing acceleration | stimulation equipment in the wedge-shaped hanging board which falls to the right. It is a graph which shows an example of the vertical distribution of the dimensionless average flow velocity per period in a submerged horizontal board lower side opening.

Explanation of symbols

1. Vertical mixing promotion equipment2. Hanging plate (hanging plate)
3. Reservoir room4. 4. Submerged horizontal plate Vertical waterway

Claims (2)

A vertical plate formed between a drooping plate, a water reserving chamber in contact with the drooping plate, a submerged horizontal plate separating the bottom surface of the water reserving chamber, and a shore side end of the submerged horizontal plate below the water reserving chamber and the rear surface of the water reserving chamber And has a gap between the lower end of the drooping plate and the submerged horizontal plate, and the lower end of the drooping plate is an asymmetric wedge shape with respect to the center plane of the plate thickness, and is vertically below the submerged horizontal plate A vertical mixing facilitator that allows circulation to form.
The vertical mixing facilitating equipment according to claim 1, wherein the lower end surface of the drooping plate has a shape with an inclination that increases from the inside to the outside of the water-reservoir chamber.

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