Water flow enhancing device based on bubble curtain and dam fishway inlet fish guiding method

Abstract

The invention discloses a water flow enhancing device based on a bubble curtain and a dam fishway inlet fish guiding method. The water flow enhancing device comprises an aeration pipe and an assembly type baffle. The assembled baffle is attached to the aerator pipe along the length direction of the aerator pipe and is vertically arranged in the upstream direction of the aerator pipe, the height of the baffle is smaller than the water depth, and the top water depth is smaller than the thickness of horizontal flow generated by a bubble curtain formed by the aerator pipe. The dam fishway inlet fish guiding method is realized by adopting the water flow enhancing device based on the bubble curtain. The aeration pipe and the assembly type baffle are utilized to enable bubbles to rise to form surface horizontal flow, so that the flow speed of suction flow at the fishway inlet is increased, working parameters of the water flow enhancing device based on the bubble curtain are accurately calculated according to parameters of a dam and the fishway, and specific and expected suction flow is formed at the fishway inlet. The purposes of improving the passability of the fishway inlet, improving the fish passing effect of the fishway and restoring the ecological connectivity of the river are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of ecological protection engineering, and in particular to a water flow enhancement device based on a bubble curtain and a fish attracting method at a dam fishway inlet. Background Art

[0002] Fishways are engineering facilities that help blocked fishes to smoothly go up or down through dams or other obstacles. However, during the upstream season of migratory fish, fishes tend to gather in the tailwater area downstream of the dam and cannot find the entrance of the fishway and smoothly enter the waters upstream of the dam. The main reason is that the downstream flow of the fishway entrance is too small to attract the target fishes. If the downstream flow of the fishway is increased, on the one hand, it will change the hydraulic conditions of the fishway and reduce its fish passing capacity, and on the other hand, it will cause a waste of water resources.

[0003] Currently, there is a lack of effective fish attraction methods for fishway entrances. Summary of the invention

[0004] The present invention provides a bubble curtain flow rate enhancement device which can form a surface horizontal suction flow and increase the flow rate of the suction flow, and a dam fishway inlet fish attracting method using the device to improve the fish passing effect of the fishway, so as to solve the technical problems mentioned in the background technology.

[0005] In order to solve the above technical problems, the technical solution proposed by the present invention is: A water flow enhancement device based on a bubble curtain comprises an aeration tube and a baffle arranged at the bottom of a water body, wherein the aeration tube is used to generate bubbles and form a bubble curtain; the baffle is attached to the aeration tube along the length direction of the aeration tube and is vertically arranged in the upstream direction of the aeration tube, the height of the baffle is less than the depth of the water body, the water depth at the top of the baffle is less than the thickness of the horizontal flow generated by the bubble curtain formed by the aeration tube, and the single-width flow above the baffle is less than the single-width flow discharged from the fishway.

[0006] As a further preferred embodiment of the above technical solution, the baffle is an assembled baffle with adjustable height.

[0007] like Figure 1 As shown in the figure, the aeration pipe can generate bubbles and form a bubble curtain. The bubble curtain is an upward plume generated by underwater perforated pipe aeration. The upward plume carries the water body upward. When the plume encounters the water surface, it will form an outward horizontal flow to form a surface horizontal flow. The horizontal flow can attract migratory fish swimming on the surface of the river to the fishway entrance, increase the density of migratory fish at the fishway entrance, increase the number of fish passing through the fishway, and restore the ecological connectivity of the river. The baffles vertically arranged against the aeration pipe can block part of the water flow moving toward the fishway entrance, further increasing the flow rate of the attraction flow. The model is as follows: Thickness The energy flow of a single-width horizontal flow is: (1); in, is the density, for The cube root of the average depth of ; The upward energy flow generated by the bubble curtain is (2); in, is the atmospheric pressure head, For water depth, is the aeration volume of the aeration pipe at atmospheric pressure; No consideration of energy loss (3), It is generally believed that the horizontal flow generated by the bubble curtain decreases uniformly along the depth from the water surface. (4); in, is the maximum velocity on the water surface; then, (5); According to the research results of Schmidt (1941), (6); so (7); In the above two formulas, and All are coefficients.

[0008] Through the water tank test, it can be estimated and Select five water depths: 0.5m, 1.0m, 1.5m, 2.0m and 2.5m, 15L / min•m -1 、30L / min•m -1 、45L / min•m -1 、60L / min•m -1 and 75L / min•m -1 Five single-width air supply volumes were used as working conditions to measure the average velocity and thickness of the horizontal flow within a range of three times the water depth on both sides of the bubble curtain. According to the test results, and The values ​​are: ,

[0009] Surface currents The velocity at depth is (8); Single width flow rate within this depth for (9).

[0010] Based on the same technical concept, the present invention also provides a method for attracting fish at the entrance of a dam fishway, comprising the following steps: S1. Arranging a water flow enhancement device at the fishway entrance of the dam, wherein the water flow enhancement device is the water flow enhancement device based on the bubble curtain as described in the above technical solution; S2, obtaining the maximum power generation flow of the dam, and estimating the flow of the fishway inlet attraction flow according to the maximum power generation flow; S3, obtaining the width, water depth and downstream flow rate of the fishway inlet, estimating the expected average flow rate of the fishway inlet attraction flow according to the fishway inlet attraction flow rate, fishway inlet width and water depth, and then determining the expected single-width air supply of the bubble curtain enhanced flow rate of the water flow enhancement device according to the expected average flow rate of the fishway inlet attraction flow; determining the single-width downstream flow rate of the fishway according to the downstream flow rate of the fishway; and then determining the baffle height value according to the single-width downstream flow rate of the fishway and the expected single-width air supply of the bubble curtain enhanced flow rate; S5, adjusting the baffle height according to the baffle height value; S6. According to the desired air supply per width for the bubble curtain to enhance the flow rate, the air supply of the water flow enhancement device is controlled so that the surface horizontal flow velocity generated by the water flow enhancement device reaches the desired average flow velocity of the suction flow.

[0011] As a further preferred embodiment of the above technical solution, the flow rate of the fishway inlet suction flow in S1 is estimated to be 3% of the maximum power generation flow rate.

[0012] As a further preferred embodiment of the above technical solution, the expected flow rate of the suction flow in S3 is calculated by the following formula:

[0013] In the formula, Attract flow at the fishway entrance. It's the depth of water. is the fishway width; As a further preferred embodiment of the above technical solution, the expected single-width air supply volume of the bubble curtain enhanced flow in S3 is calculated by the following formula: ; In the formula, To enhance the flow rate of the bubble curtain, the desired single-width air supply volume is is the expected average velocity of the fishway inlet suction flow, is the acceleration due to gravity.

[0014] As a further preferred embodiment of the above technical solution, the height of the baffle in S4 is calculated by the following formula: ; In the formula, is the baffle height, is the water depth at the top of the baffle, It's the water depth.

[0015] In the above scheme, the water depth at the top of the baffle is calculated by the following formula: ; In the formula, is the discharge flow per unit width of the fishway, is the horizontal flow thickness; In the above scheme, the horizontal flow thickness is calculated by the following formula: ; In the formula, is the atmospheric pressure head.

[0016] As a further optimization of the above technical solution, according to the fish attracting effect at the dam fishway entrance and actual needs, a number of bubble curtain-based water flow enhancement devices are arranged in sequence at the fishway entrance and in the downstream direction of the fishway entrance to obtain a larger range of attraction flow.

[0017] As a further preferred embodiment of the above technical solution, the spacing between the plurality of adjacent water flow enhancement devices based on the bubble curtain is three times the depth of the water body.

[0018] As a further preferred embodiment of the above technical solution, the water depth at the fishway entrance is obtained by using a depth sounder.

[0019] The present invention has the following beneficial effects: (1) The water flow enhancement device based on the bubble curtain of the present invention utilizes the specific position combination of the aeration pipe and the height-adjustable baffle to make the bubbles rise to form a surface horizontal flow, thereby increasing the velocity of the suction flow at the fishway inlet, thereby achieving the purpose of improving the passability of the fishway inlet and enhancing the fish passing effect of the fishway; (2) The method for attracting fish at the entrance of a dam fishway of the present invention utilizes the water flow enhancement device based on the bubble curtain of the present invention to accurately calculate the working parameters of the bubble curtain flow velocity enhancement device according to various parameters of the dam and the fishway, and forms a specific and expected attraction flow velocity at the entrance of the fishway, thereby improving the passability of the fishway entrance and the fish passing effect of the fishway.

[0020] The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 Schematic diagram of the flow field around the bubble curtain generated by the aeration tube; Figure 2 A schematic diagram of the surrounding flow field and position of the bubble curtain flow velocity enhancement device of Example 1; Figure 3 It is a structural schematic diagram of the assembled baffle of Example 1; Figure 4 The comparison results of the predicted value and the measured value of the average flow velocity of the horizontal flow within a range of 3 times the water depth on both sides of the water flow enhancement device based on the bubble curtain in Example 1; Figure 5 The comparison results of the predicted value and the measured value of the average thickness of the horizontal flow within the range of 3 times the water depth on both sides of the water flow enhancement device based on the bubble curtain in Example 1; Figure 6 This is a flow chart of the method for attracting fish at the dam fishway inlet of Example 1. DETAILED DESCRIPTION

[0022] The embodiments of the present invention are described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0023] Embodiment 1: like Figure 2 As shown, the water flow enhancement device based on the bubble curtain of this embodiment includes an aeration pipe and an assembled baffle ( Figure 2 In the figure, a is the aeration pipe and b is the assembled baffle), such as Figure 3 As shown, the assembled baffle is composed of multiple baffle components spliced ​​up and down, the aeration tube is used to generate bubbles and form a bubble curtain, the bubble curtain rises and drives the water body to form a surface horizontal flow; the baffle is attached to the aeration tube along the length direction of the aeration tube and is vertically arranged in the upstream direction of the aeration tube, the height of the baffle is less than the depth of the water body, the water depth at the top of the baffle is less than the thickness of the horizontal flow generated by the bubble curtain formed by the aeration tube, and the single-width flow above the baffle is less than the single-width flow of the fishway discharge.

[0024] like Figure 6 As shown, the method for attracting fish at the entrance of a dam fishway of this embodiment comprises the following steps: S1. Arrange the water flow enhancement device based on the bubble curtain of this embodiment at the fishway entrance of the dam.

[0025] S2. Obtain the maximum power generation flow of the dam.

[0026] S3. Estimate the suction flow at the fishway inlet at 3% of the maximum power generation flow.

[0027] S4. Obtain the width and downstream flow rate of the fishway inlet.

[0028] S5. Obtain the water depth at the fishway entrance using a depth sounder.

[0029] S6. Estimate the expected average flow rate of the fishway inlet attraction flow. The specific formula is as follows: ; In the formula, Attract flow at the fishway entrance. It's the depth of water. is the fishway width; S7. Determine the expected single-width air supply volume of the bubble curtain enhanced flow rate based on the expected average flow rate of the suction flow. The specific calculation formula is as follows: ; In the formula, The desired single-width air supply volume for bubble curtain flow enhancement, is the expected average velocity of the fishway inlet suction flow, is the acceleration due to gravity.

[0030] S8. Determine the height of the assembled baffle according to the discharge flow of the fishway. The specific calculation formula is as follows: ; In the formula, is the baffle height, is the discharge flow per unit width of the fishway, is the horizontal flow thickness, , It's the depth of water. is the atmospheric pressure head.

[0031] S9. Install and adjust the baffle according to its height.

[0032] S10, according to the desired air supply per width of the bubble curtain flow rate enhancement device, controlling the air supply of the bubble curtain flow rate enhancement device so that the surface horizontal flow velocity generated by the bubble curtain reaches the desired average flow velocity of the suction flow; S11. Determine whether the fish attracting effect meets the actual needs. If not, several water flow enhancement devices based on the bubble curtain of this embodiment can be arranged in sequence at the entrance of the fishway and in its downstream direction to obtain a larger range of attraction flow. The spacing between adjacent water flow enhancement devices based on the bubble curtain is 3 times the water depth.

[0033] The actual effect of the water flow enhancement device based on the bubble curtain and the fish attracting method at the dam fishway inlet of this embodiment is verified by establishing a dam and fishway model. The predicted value and the measured value of the average flow velocity and average thickness of the horizontal flow within the range of 3 times the water depth on both sides of the bubble curtain generated by the water flow enhancement device are compared. The results are as follows: Figure 4 and Figure 5 As shown, it can be seen that the actual average flow velocity and average thickness of the horizontal flow in this embodiment are basically consistent with the expected average flow velocity and average thickness, and the water flow enhancement device based on the bubble curtain and the fish attracting method at the dam fishway inlet of this embodiment have achieved the expected effect.

[0034] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. For those skilled in the art, improvements and changes obtained without departing from the technical concept of the present invention should also be regarded as the protection scope of the present invention.

[0035] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A water flow enhancement device based on a bubble curtain, characterized in that: It comprises an aeration tube and a baffle arranged at the bottom of a water body, wherein the aeration tube is used to generate bubbles and form a bubble curtain; the baffle is close to the aeration tube along the length direction of the aeration tube and is vertically arranged in the upstream direction of the aeration tube, the height of the baffle is less than the depth of the water body, the water depth at the top of the baffle is less than the thickness of the horizontal flow generated by the bubble curtain formed by the aeration tube, and the single-width flow above the baffle is less than the single-width flow of the fishway discharge.

2. The water flow enhancement device based on the bubble curtain according to claim 1 is characterized in that: The baffle is an assembled baffle with adjustable height.

3. A method for attracting fish at the entrance of a dam fishway, characterized in that: The following steps are involved: S1. Arrange a water flow enhancement device at the fishway entrance of the dam, wherein the water flow enhancement device is the water flow enhancement device based on the bubble curtain as claimed in claim 1; S2, obtaining the maximum power generation flow of the dam, and estimating the flow of the fishway inlet attraction flow according to the maximum power generation flow; S3, obtaining the width, water depth and downstream flow rate of the fishway inlet, estimating the expected average flow rate of the fishway inlet attraction flow according to the fishway inlet attraction flow rate, fishway inlet width and water depth, and then determining the expected single-width air supply of the bubble curtain enhanced flow rate of the water flow enhancement device according to the expected average flow rate of the fishway inlet attraction flow; determining the single-width downstream flow rate of the fishway according to the downstream flow rate of the fishway; and then determining the baffle height value according to the single-width downstream flow rate of the fishway and the expected single-width air supply of the bubble curtain enhanced flow rate; S5, adjusting the baffle height according to the baffle height value; S6. According to the desired air supply per width for the bubble curtain to enhance the flow rate, the air supply of the water flow enhancement device is controlled so that the surface horizontal flow velocity generated by the water flow enhancement device reaches the desired average flow velocity of the suction flow.

4. The method for attracting fish at the entrance of a dam fishway according to claim 3, characterized in that: The flow rate of the fishway inlet attraction mentioned in S1 is estimated to be 3% of the maximum power generation flow rate.

5. The method for attracting fish at the entrance of a dam fishway according to claim 3, characterized in that: The expected single-width air supply volume for the bubble curtain enhanced flow rate in S3 is calculated by the following formula: ； In the formula, To enhance the flow rate of the bubble curtain, the desired single-width air supply volume is is the expected average velocity of the fishway inlet suction flow, is the acceleration due to gravity.

6. The dam fishway inlet drainage method according to claim 3, characterized in that: The height of the assembled baffle in S4 is calculated by the following formula: ； ； In the formula, is the baffle height, is the discharge flow per unit width of the fishway, is the horizontal flow thickness, It's the depth of water. is the atmospheric pressure head.

7. The method for attracting fish at the entrance of a dam fishway according to any one of claims 3 to 6, characterized in that: According to the fish attracting effect and actual needs of the dam fishway entrance, a number of water flow enhancement devices based on bubble curtains are arranged in sequence at the fishway entrance and in the downstream direction of the fishway entrance to obtain a larger range of attraction flow.

8. The method for attracting fish at the entrance of a dam fishway according to claim 7, characterized in that: The spacing between the plurality of adjacent bubble curtain-based water flow enhancement devices is three times the depth of the water body.

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