Symmetrical backwash type underflow energy dissipation structure

Abstract

The application discloses a symmetric type backwash type bottom flow energy dissipation structure, which comprises a stilling basin and a water release pipe; the water inlet ends of the stilling basin and the water release pipe are communicated with the water recession structure of the water discharge building respectively, the water release pipe is provided with at least two water release pipe water outlet ends, the water release pipe water outlet ends are arranged at the water outlet ends of the stilling basin and are located at the symmetric positions of the left and right sides of the cross section of the water outlet ends of the stilling basin, the water flow directions of the water release pipe water outlet ends are opposite to the water flow directions of the water outlet ends of the stilling basin, and the water release pipe water outlet ends are used for forming the opposite flow with the water flow of the stilling basin. The above scheme can solve the problems that the flow speed is too large and the energy dissipation effect is poor due to the large single-width flow caused by the fact that the stilling basin cannot be widened under the condition that the engineering terrain condition is limited, and the problems of complicated and difficult later maintenance caused by the increase of the auxiliary energy dissipation work.

Description

Technical Field

[0001] This invention relates to the field of flood discharge and energy dissipation technology in water conservancy and hydropower projects, and particularly to a symmetrical backwash bottom flow energy dissipation structure. Background Technology

[0002] In hydropower projects, the high-speed water flow carrying enormous kinetic energy during the discharge process of spillway structures can adversely affect the downstream river environment if it is not effectively dissipated. Therefore, to prevent the water flow from the spillway from causing severe scouring of the downstream river channel due to its enormous energy, affecting slope stability and the safe operation of the structure itself, energy dissipation measures are generally adopted in engineering to dissipate or disperse the excess energy during the discharge process as much as possible. This is also a key point and challenge in the construction of the project. Furthermore, the rationality of the layout of the spillway energy dissipation structure is directly related to the stability of the downstream riverbed and the safety of the entire hydropower project.

[0003] The dam sites of large-scale water conservancy and hydropower projects today are mostly high mountains and canyons. The terrain downstream of the spillway is often a narrow, deep canyon with a deep "V" shape, which gradually narrows downstream and the terrain on both sides is asymmetrical. Such conditions of narrow river channels, high water head and large discharge volume bring great challenges and difficulties to the conventional layout of spillway energy dissipation structures.

[0004] Currently, commonly used energy dissipation methods can be divided into bottom flow energy dissipation, jet flow energy dissipation, and surface flow energy dissipation. Among them, jet flow energy dissipation is the most widely used due to fewer limiting factors, but it has high requirements for the geological conditions of the downstream scour zone. Bottom flow energy dissipation, as a conventional form of energy dissipation, creates a hydraulic jump in the downstream stilling basin through discharge, utilizing the swirling and intense turbulence generated by the hydraulic jump to eliminate residual energy. It features stable inflow into the stilling basin, high energy dissipation rate, and minimal atomization of the discharged water, and is widely used in high-head, large-unit-width flow projects. Simultaneously, to improve energy dissipation efficiency and reduce engineering workload, bottom flow energy dissipation often incorporates auxiliary energy dissipation structures such as stilling blocks and stilling teeth within the stilling basin for combined energy dissipation. These auxiliary structures can improve energy dissipation efficiency and generally reduce dredging depth and shorten the stilling basin length.

[0005] However, existing bottom flow energy dissipation still has many shortcomings. In particular, when engineering terrain conditions are limited, the width of the stilling basin cannot be further widened, resulting in large flow rates per unit width, large water level fluctuations, and turbulent flow patterns. Without the installation of complex auxiliary energy dissipation structures, it becomes more difficult to reduce water depth, reduce fluctuations, and stabilize the flow pattern. Furthermore, under high-speed water flow conditions, cavitation erosion is prone to occur at the front of the energy dissipation structure. In addition, in river channels with floating debris or bedload, auxiliary energy dissipation structures are often damaged by impacts, which increases the difficulty and pressure on the maintenance of hydraulic structures during operation. Summary of the Invention

[0006] This invention discloses a symmetrical backwash type underflow energy dissipation structure to solve the problems of poor energy dissipation effect caused by the inability to widen the stilling pool due to limited engineering terrain conditions, as well as the cumbersome and difficult maintenance caused by the addition of auxiliary energy dissipation works.

[0007] To solve the above problems, the present invention adopts the following technical solution:

[0008] A symmetrical backwash bottom flow energy dissipation structure includes a stilling basin and a discharge pipe. The inlet ends of the stilling basin and the discharge pipe are respectively connected to the drainage structure of the spillway. The discharge pipe is provided with at least two outlet ends, and the outlet ends are all located at the outlet end of the stilling basin and are symmetrically positioned on the left and right sides of the cross-section of the outlet end of the stilling basin. The water flow direction of the outlet ends of the discharge pipes is opposite to the water flow direction of the outlet end of the stilling basin, so as to form a counterflow with the downstream water flow of the stilling basin.

[0009] Optionally, the number of water drain pipes is the same as the number of water outlets of the water drain pipes, and one water outlet of the water drain pipe corresponds to one independent water drain pipe; or, the number of water drain pipes is one, and all water outlets of the water drain pipes share one water drain pipe.

[0010] Optionally, the outlet end of the water pipe has a duckbill-shaped structure that is narrow at the top and bottom and wide at the left and right.

[0011] Optionally, the outlet end of the stilling basin is provided with a stilling sill; the outlet end of the drain pipe passes through the stilling sill and is located on the water-facing side of the stilling sill.

[0012] Optionally, the outlet ends of the two water pipes are located symmetrically on the left and right sides of the center of the water-facing surface of the stilling basin.

[0013] Optionally, the water-facing surface of the stilling basin is a vertical surface, and the outlet end of the drain pipe is flush with the water-facing surface of the stilling basin.

[0014] Optionally, the flow rates of the two drain pipes are equal, and the sum of the flow rates of the two drain pipes is 8.0%-16.09% of the flow rate of the drainage structure.

[0015] Optionally, each of the two drain pipes includes a vertical section and a horizontal section; one end of the vertical section is connected to the drainage structure of the drainage building, and the other end of the vertical section is connected to one end of the horizontal section; the other end of the horizontal section is the outlet end, which is bent 180° and located at the outlet end of the stilling basin to form a water flow that counteracts the downward flow of the stilling basin.

[0016] Optionally, both of the drain pipes are inclined along the slope of the stilling basin. One end of the drain pipe is connected to the drainage structure of the spillway, and the other end of the drain pipe is the outlet end, which is bent 180° and located at the outlet end of the stilling basin to form a water flow that counteracts the downward flow of the stilling basin.

[0017] The technical solution adopted in this invention can achieve the following beneficial effects:

[0018] The symmetrical backwash bottom flow energy dissipation structure disclosed in this invention, through the rational arrangement of multiple symmetrically distributed water outlet pipes, allows the water flow at the outlet ends of these pipes to counteract the downward flow of the stilling basin, resulting in a water flow pattern that exhibits both lateral contraction and longitudinal expansion. This transforms the traditional binary hydraulic jump into a ternary hydraulic jump, significantly reducing the stilling basin length while increasing air entrainment and energy dissipation efficiency. Under conditions equivalent to the original flow characteristics, the stilling basin depth can be reduced or its length shortened, with the stilling basin depth reduced by 8%-1. The length of the stilling basin can be shortened by about 12%-20%, and the length of the basin can be reduced by about 5%. Therefore, this invention can reduce the adverse effects of excessive flow velocity and insufficient energy dissipation caused by large unit width flow rate on the downstream terrain when there are many terrain restrictions and the stilling basin cannot be widened. The maximum scour depth can be reduced by 20%-50%. In addition, by making full use of the flow rate of the discharge pipe, it forms a countercurrent with the main flow at the end of the stilling basin. It can improve the energy dissipation efficiency without the need to provide additional water flow, and avoids the impact and erosion of high-speed water flow on the auxiliary energy dissipation structure. Attached Figure Description

[0019] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0020] Figure 1 This is a schematic diagram of the symmetrical backwash underflow energy dissipation structure disclosed in an embodiment of the present invention;

[0021] Figure 2 This is a top view of one configuration of the discharge pipe of the symmetrical backwash bottom flow energy dissipation structure disclosed in an embodiment of the present invention.

[0022] Figure 3 for Figure 2 Side view;

[0023] Figure 4 This is a side view of another configuration of the discharge pipe of the symmetrical backwash bottom flow energy dissipation structure disclosed in an embodiment of the present invention;

[0024] Figure 5 This is a schematic diagram of the duckbill-shaped structure of the water outlet end of the water pipe disclosed in an embodiment of the present invention.

[0025] Explanation of reference numerals in the attached figures:

[0026] 100 - Drainage structure, 200 - Stilling basin, 210 - Stilling sill, 300 - Water outlet pipe, 301 - Water outlet end of water outlet pipe. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0028] The technical solutions disclosed in the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0029] Example 1

[0030] Please refer to Figures 1 to 5 As shown in the figure, this embodiment of the invention discloses a symmetrical backwash bottom flow energy dissipation structure. The disclosed symmetrical backwash bottom flow energy dissipation structure includes a stilling basin 200 and two discharge pipes 300. The inlet ends of the stilling basin 200 and the two discharge pipes 300 are respectively connected to the drainage structure 100 of the spillway. The outlet ends 301 of the two discharge pipes are both set at the outlet end of the stilling basin 200 and are located symmetrically on the left and right sides of the cross-section of the outlet end of the stilling basin 200. The water flow direction of the outlet ends 301 of the two discharge pipes is opposite to the water flow direction of the outlet end of the stilling basin 200, so as to form a counterflow with the downstream water flow of the stilling basin 200.

[0031] By rationally arranging two water outlet pipes 300, the water flow at their outlet ends is made to counteract the downward flow of the stilling basin 200, so that the water flow has both lateral contraction and longitudinal expansion, thereby transforming the traditional binary hydraulic jump into a ternary hydraulic jump. While increasing aeration and improving energy dissipation rate, the length of the stilling basin 200 is significantly reduced. Under the condition of equivalent water flow characteristics to the original body, the excavation depth of the stilling basin 200 can be reduced or the length of the stilling basin 200 can be shortened. The depth of the stilling basin 200 can be reduced by about 8%-15%, and the length can be shortened by about 12%-20%.

[0032] Therefore, this invention can mitigate the adverse effects of excessive flow velocity and insufficient energy dissipation on downstream terrain caused by large unit width flow rates, even when terrain limitations are significant and the stilling basin 200 cannot be widened. The maximum scour depth can be reduced by 20%-50%. Furthermore, by fully utilizing the flow rate of the discharge pipe 300, it forms a countercurrent with the main flow at the end of the stilling basin 200, achieving improved energy dissipation efficiency without the need for additional water supply, and avoiding the impact and erosion of the auxiliary energy dissipation structure by high-speed water flow. Moreover, compared to a structure where the discharge pipe 300 is only installed on one side of the stilling basin 200, in this embodiment, the outlet ends 301 of the two discharge pipes are symmetrically located on the left and right sides of the outlet end cross-section of the stilling basin 200, allowing for more complete contact between the backwash water flow and the downstream water flow, resulting in less water level rise and better energy dissipation efficiency.

[0033] It is easy to understand that, such as Figure 1 As shown, the two water outlet pipes 300 can be respectively installed on the left and right sides of the stilling basin 200; of course, as another alternative implementation, the two water outlet pipes 300 can also be installed at the bottom of the stilling basin 200.

[0034] Meanwhile, the number of water outlets of the drain pipe 300 can be increased adaptively according to actual construction needs; for example, the number of water outlets of the drain pipe 300 can also be set to three, one of which is located at the vertical center line of the cross-section of the drain end of the stilling basin 200, and the other two are located on the left and right sides of the vertical center line; and the number of drain pipes 300 can be three, with one drain pipe 300 outlet corresponding to one independent drain pipe 300, or the number of drain pipes 300 can also be one, with three drain pipes 300 outlets sharing one drain pipe 300; or the number of drain pipes 300 can be two, with one drain pipe 300 outlet corresponding to one independent drain pipe 300, and the other two drain pipes 300 outlets sharing another drain pipe 300; this embodiment does not limit the arrangement of the drain pipes 300 or the number of drain pipes 300 outlets.

[0035] In this embodiment, in order to better improve the energy dissipation effect of the bottom flow energy dissipation structure, a simple auxiliary energy dissipation device, such as an energy dissipation sill 210, can be set at the outlet end of the stilling pool 200. This allows the outlet ends 301 of the two water discharge pipes to pass through the energy dissipation sill 210 and be placed on the water-facing side of the energy dissipation sill 210. The combination of the energy dissipation sill 210 and the two water discharge pipes 300 can further improve the energy dissipation effect of the bottom flow energy dissipation structure. Moreover, the energy dissipation sill 210 can also play a good role in fixing the backflow of the two water discharge pipes 300.

[0036] Specifically, such as Figure 2 and Figure 3As shown, the outlet ends 301 of the two water pipes are preferably located symmetrically on the left and right sides of the center of the water-facing surface of the stilling basin 210. This facilitates the full and uniform interaction between the backwash water flow from the outlet ends 301 of the two water pipes and the outflow water flow from the stilling basin 200, ensuring the energy dissipation effect. More preferably, the water-facing surface of the stilling basin 210 is a vertical plane, and the outlet ends 301 of the water pipes are flush with the water-facing surface of the stilling basin 210. This ensures that the water flow direction of the outlet ends 301 of the water pipes is 180° opposite to the outflow water flow direction of the stilling basin 200, thus reducing the adverse impact of the placement of the water pipes 300 on the structural strength of the stilling basin 210.

[0037] Meanwhile, as an implementable structure for the water outlet pipe 300, such as Figure 3 As shown, each of the two drain pipes 300 can include a vertical section and a horizontal section. One end of the vertical section is connected to the drainage structure 100 of the drainage building, and the other end of the vertical section is connected to one end of the horizontal section. The other end of the horizontal section is the outlet end, which is bent 180° and set at the outlet end of the stilling basin 200 to form a water flow that counteracts the downward flow of the stilling basin 200. In this structure, the vertical section design of the drain pipe 300 allows the outlet end of the horizontal section of the drain pipe 300 to be well adapted to the connection and cooperation of the height of the stilling basin 210.

[0038] Another feasible structure for the water outlet pipe 300 is, for example Figure 4 As shown, both water outlet pipes 300 can be inclined along the slope of the stilling basin 200. One end of the water outlet pipe 300 is connected to the drainage structure 100 of the spillway, and the other end of the water outlet pipe 300 is the outlet end, bent 180° at the outlet end of the stilling basin 200, to form a water flow that counteracts the downward flow of the stilling basin 200; this structure is different from the above. Figure 2 Although the structure increases the difficulty of construction and installation of the discharge pipe 300, it reduces the design of elbows and has the advantage of low water flow resistance, thereby ensuring the water flow velocity at the outlet of the discharge pipe 300, which is conducive to improving the energy dissipation effect of the bottom flow energy dissipation structure.

[0039] In the symmetrical backwash bottom flow energy dissipation structure disclosed in this embodiment, in order to better improve the energy dissipation effect, the cross-sectional area of ​​the outlet end 301 of the discharge pipe is smaller than the cross-sectional area of ​​the pipe body of the discharge pipe 300. The outlet end 301 of the discharge pipe forms a structure with a reduced water passage area, thereby increasing the backwash flow velocity at the outlet end 301 of the discharge pipe and further improving the efficiency of the symmetrical backwash bottom flow energy dissipation structure; for example Figure 5As shown, the outlet end 301 of the drain pipe is designed as a duckbill-shaped structure that is narrow at the top and bottom and wide at the left and right. This can increase the backflow velocity of the drain pipe outlet end 301 and reduce the construction and installation elevation of the drain pipe outlet end 301, thus making it suitable for construction situations where the elevation of the stilling basin 210 is lower than that of the end pipe of the drain pipe 300.

[0040] It should be noted that, in the symmetrical backwash bottom flow energy dissipation structure disclosed in this embodiment, preferably, the flow rates of the two discharge pipes 300 are equal, thereby ensuring that the backwash water at the outlet end 301 of the two discharge pipes can fully and evenly interact with the downward flow of the stilling basin 200. Furthermore, the sum of the flow rates of the two discharge pipes 300 is 8.0%-16.09% of the flow rate of the drainage structure 100. If this flow rate is less than 8.0% of the flow rate of the drainage structure 100, then the two discharge pipes 300 cannot function effectively. The backwash energy dissipation effect is obvious. If the flow rate is greater than 16.09% of the flow rate of the drainage structure 100, the backwash energy dissipation effect of the two discharge pipes 300 will not be significantly improved. Instead, it will increase the water level of the stilling basin 200. Therefore, the preferred flow rate is 8.0%-16.09% of the flow rate of the drainage structure 100. This ensures that the two discharge pipes 300 have a good backwash energy dissipation effect on the downward flow of water in the stilling basin 200, while also preventing the water level of the stilling basin 200 from rising.

[0041] Of course, other shape designs for the outlet end 301 of the water pipe, such as Figure 2 and Figure 3 As shown, the outlet end 301 of the drain pipe can also be designed as a flared structure with a cross-sectional area larger than that of the pipe body. Although this will reduce the water flow velocity at the outlet end 301 of the drain pipe, thereby reducing the backwash energy dissipation effect, the increased water flow surface can make the backwash force evenly distributed, thus reducing the degree of water level rise.

[0042] Example 2

[0043] This embodiment is a verification embodiment. The water discharge structure is an overflow weir, which discharges water through a drainage tunnel and two discharge pipes 300. The two discharge pipes 300 are symmetrically arranged on the left and right sides of the stilling basin 200. The water inlet ends of the two discharge pipes 300 turn out from the bottom plate of the drainage tunnel and extend obliquely downward along the slope of the stilling basin 200. The water outlet ends 301 of the two discharge pipes turn to the center of the cross section at the outlet section at the end of the stilling basin 200, then turn 180° and merge and penetrate the stilling sill 210. The water outlet ends 301 of the discharge pipes are flush with the vertical plane of the stilling sill 210, forming a countercurrent effect with the downward flow of water from the stilling basin 200.

[0044] The stilling basin 200 is 45m long and 5m wide, with a total flow rate of 197m³ / s. The stilling sill 210 is 5m high. The bottom elevation of the stilling basin 200 is 117m, and the tail sill elevation is 122m. The two discharge pipes 300 are both 1.2m in diameter. The overflow weir crest elevation is 202m, the water level elevation under the check condition is 203.89m, and the water level elevation under the discharge and energy dissipation condition is 203.24m. The flow rate of the drainage tunnel is 175m³ / s-87m³ / s. The flow rates of the two discharge pipes 300 are 7m³ / s under different conditions. The sum of the flow rates of the two discharge pipes 300 accounts for 8.0%-16.09% of the flow rate of the drainage tunnel.

[0045] A systematic hydraulic model test was conducted on the symmetrical backwash bottom flow energy dissipation structure (hereinafter referred to as "this structure") disclosed in the embodiments of the present invention. The model scale was 1:40. The test results were as follows:

[0046] Under design conditions, the upstream reservoir water level is 203.72m, the vertical shaft discharge capacity is 149m³ / s, the sum of the flow rates of the two 300-meter discharge pipes is 14m³ / s, and the water flow velocity before entering the stilling basin is 17m / s.

[0047] Original structure: The water surface fluctuation of stilling basin 200 increases with the increase of the discharge flow. The water depth of stilling basin 200 increases along the flow path, reaching its maximum value at chainage 0+851.000m. The maximum measured water depth of stilling basin 200 is 11.36m under the P=1% condition, corresponding to a water surface elevation of 128.36m. The water level fluctuation of the left and right sidewalls of stilling basin 200 is between 0.88 and 6.44m. The measured bottom flow velocity is between 0.66m / s and 3.37m / s. At the apron behind the tail sill of stilling basin 200, the measured flow velocity is 4.13m / s, which exceeds the downstream scour velocity. The maximum measured bottom pressure is 1. The pressure distribution at the 200-meter tail sill of the stilling basin was normal, with a flow velocity of 4.9 × 9.81 kPa. The flow velocity at the 200-meter tail sill was 3.97 m / s, the pressure at the tail sill was 13.1 kPa, the water level at the tail sill was 128.94 m, the average water level fluctuation was 4.16 m, and the energy dissipation rate was 64.25%. When the flood with a frequency of P=1% was discharged, the flow velocity distribution on the left bank of the river was 0.34 m / s to 2.89 m / s, and the flow velocity distribution on the right bank of the river was 0.17 m / s to 2.29 m / s. The flow velocity did not exceed the scour resistance velocity of 3.5 m / s. When P=1%, the deepest scour pit was 8.68 m, and the deepest point was 10.0 m away from the end of the apron platform.

[0048] In this type of structure: the water depth of stilling basin 200 increases along the course, reaching its maximum value at chainage 0+851.000m. Actual measurements show that the maximum water depth of stilling basin 200 has increased by approximately 17% compared to the original structure. The water level fluctuation on the sidewalls of stilling basin 200 is significantly reduced compared to the original structure, decreasing by more than 50%. The measured bottom velocity is less than 3 m / s, which is lower than the original structure. At the apron behind the tail sill of stilling basin 200, the measured velocity is slightly lower but still slightly greater than 3.5 m / s, exceeding the downstream scour velocity. All velocities are lower than the original structure. The measured maximum pressure at the bottom plate was not significantly different from that of the original structure, and the pressure distribution at the 200mm tail sill of the stilling basin was normal. The flow velocity at the 200mm tail sill of the stilling basin was significantly reduced, about 30% lower than that of the original structure, and lower than the scour resistance velocity. The water level at the tail sill was 130.49m. Due to the increased water depth, the pressure at the tail sill increased slightly, by about 10%. Compared with the original structure, the bottom velocity was significantly reduced, and the outflow velocity was less than the scour resistance velocity of the downstream river channel. The water level increased, resulting in a higher calculated energy dissipation rate. However, due to the significantly reduced bottom velocity, which was less than the scour resistance velocity, the maximum scour depth was only about 40% of that of the original structure.

[0049] Example 3

[0050] In this embodiment, the spillway structure is an overflow weir, which discharges floodwater through a drainage tunnel and two discharge pipes 300. Unlike embodiment 2, the outlet ends 301 of the two discharge pipes do not merge.

[0051] The hydraulic characteristics of this body shape are as follows:

[0052] Under design conditions, the water depth of stilling basin 200 increases along the flow path, reaching its maximum at chainage 0+851.000m. Actual measurements show an increase in the maximum water depth of stilling basin 200, approximately 15% higher than the original design. Water level fluctuations along the sidewalls of stilling basin 200 are significantly reduced compared to the original design, decreasing by over 50%. The measured bottom velocity is less than 3 m / s, a decrease compared to the original design. At the apron behind the tail sill of stilling basin 200, the measured velocity is slightly higher than 3.5 m / s, exceeding the downstream scour velocity. All velocities are lower than the original design. The measured maximum pressure at the bottom plate is not much different from that of the original body, and the pressure distribution at the 200mm tail sill of the stilling basin is normal. The flow velocity at the 200mm tail sill of the stilling basin is significantly reduced, about 30% lower than that of the original body, and lower than the scour resistance velocity. The water level at the tail sill has increased, and due to the increased water depth, the pressure at the tail sill has increased slightly, by about 8%. Compared with the original body, the bottom velocity is significantly reduced, and the outflow velocity is less than the scour resistance velocity of the downstream river channel. The water level has increased, resulting in a higher calculated value for the energy dissipation rate. However, due to the significant reduction in the bottom velocity, which is less than the scour resistance velocity, the maximum scour depth is only about 35% of that of the original body.

[0053] Meanwhile, by using the formulas for the depth and length of the stilling basin 200, under the condition of equivalent water flow characteristics to the original shape, the length and depth of the stilling basin 200 can be reduced, thereby reducing the amount of engineering work; by using the existing calculation method for the theoretical length of the stilling basin 200, it is calculated that compared with the theoretical length of the stilling basin 200, the symmetrical backwash bottom flow energy dissipation structure of the present invention shortens the length of the stilling basin 200 by about 12%-20%; and, it is calculated that the depth of the stilling basin 200 can be reduced by about 8%-15% based on the original shape.

[0054] Based on the comprehensive hydraulic model test results, by utilizing the flow rate of the two discharge pipes 300 symmetrically arranged on both sides of the stilling basin 200 to form a backflow with the downstream mainstream, the water level fluctuation of the stilling basin 200 is significantly reduced, and the downstream flow velocity is significantly reduced, by more than 40% compared to the original structure. The downstream scouring is significantly weakened, and the maximum scour depth is reduced by more than 50% compared to the original structure. Therefore, the novel energy dissipation structure of this invention can be well adapted to situations where the terrain conditions are limited and the stilling basin 200 cannot be widened, resulting in insufficient energy dissipation effect. By reducing water level fluctuation and bottom velocity, the hydraulic characteristics are optimized to better meet the design requirements.

[0055] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A symmetrical backwash-type underflow energy dissipation structure, characterized in that, The system includes a stilling basin and a drain pipe. The inlet ends of the stilling basin and the drain pipe are respectively connected to the drainage structure of the spillway. The drain pipe has at least two outlet ends, which are located at the outlet end of the stilling basin and symmetrically positioned on the left and right sides of the cross-section of the outlet end of the stilling basin. The water flow direction of the outlet ends of the drain pipes is opposite to the water flow direction of the outlet end of the stilling basin, so as to counteract the downward flow of the stilling basin. The outlet end of the stilling basin is provided with a stilling sill. The outlet end of the drain pipe passes through the stilling sill and is located on the water-facing side of the stilling sill. The water-facing side of the stilling sill is a vertical plane, and the outlet end of the drain pipe is flush with the water-facing side of the stilling sill.

2. The symmetrical backwash-type underflow energy dissipation structure according to claim 1, characterized in that, The number of drain pipes is the same as the number of drain pipe outlets, and one drain pipe outlet corresponds to one independent drain pipe; or, the number of drain pipes is one, and all drain pipe outlets share one drain pipe.

3. The symmetrical backwash-type underflow energy dissipation structure according to claim 1, characterized in that, The cross-sectional area of ​​the outlet end of the drain pipe is smaller than the cross-sectional area of ​​the pipe body, and the outlet end of the drain pipe forms a structure with a reduced water passage area.

4. The symmetrical backwash-type underflow energy dissipation structure according to claim 3, characterized in that, The outlet end of the water pipe has a duckbill-shaped structure that is narrow at the top and bottom and wide at the left and right.

5. The symmetrical backwash-type underflow energy dissipation structure according to claims 1 to 4, characterized in that, The outlet ends of the water pipes are located symmetrically on the left and right sides of the center of the water-facing surface of the stilling basin.

6. The symmetrical backwash-type underflow energy dissipation structure according to any one of claims 1 to 4, characterized in that, The flow rates of the two drain pipes are equal, and the sum of the flow rates of the two drain pipes is 8.0%-16.09% of the flow rate of the drainage structure.

7. The symmetrical backwash-type underflow energy dissipation structure according to claim 6, characterized in that, Both of the aforementioned drain pipes include a vertical section and a horizontal section respectively; one end of the vertical section is connected to the drainage structure of the drainage building, and the other end of the vertical section is connected to one end of the horizontal section. The other end of the horizontal section is the outlet end, which is bent 180° and set at the outlet end of the stilling basin to form a water flow that counteracts the downward flow of the stilling basin.

8. The symmetrical backwash-type underflow energy dissipation structure according to claim 7, characterized in that, Both of the drain pipes are inclined along the slope of the stilling basin. One end of the drain pipe is connected to the drainage structure of the spillway, and the other end of the drain pipe is the outlet end, which is bent 180° and set at the outlet end of the stilling basin to form a water flow that counteracts the downward flow of the stilling basin.

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