Rectifying energy-dissipating and anti-collision facility and design method thereof

Abstract

This invention relates to the field of water conservancy and hydropower engineering technology, specifically to a rectification and energy dissipation anti-scour facility and its design method. The facility is located downstream of a dam or apron section and includes a base plate, a first-height rectification pier, a second-height rectification pier, and a low-lying area, with the three components intersecting in plan. Multiple first-height rectification piers are arranged in continuous rows, with a second-height rectification pier located at the junction of two adjacent piers in each row. The first-height rectification piers are inverted V-shaped, composed of three regular square prisms with side length *a* and height *h*, their axes of symmetry parallel to the water flow. The second-height rectification piers have a base with side length *a* and height *h'*, and one diagonal of their projected square is parallel to the water flow. The low-lying area is a square depression with side length *b*, one diagonal parallel to the water flow. The design method involves using a mathematical model to predict future water level and flow rate, combined with physical model experiments to determine unfavorable operating conditions and parameters. This invention eliminates cascading jumps, adapts to water level changes, requires minimal engineering work, and is used for anti-scour protection of dams, dikes, revetments, bridge piers, wharves, etc.

Description

Technical Field

[0001] This invention relates to the field of water conservancy and hydropower engineering technology, specifically to a rectification energy dissipation and anti-scour facility and its design method. Background Technology

[0002] For dam projects located on soft foundations, especially low-head dam projects where downstream scouring is prone to occur over long river sections, leading to drops in downstream water levels, or low-head dam projects located at tidal estuaries where downstream water levels are significantly affected by tidal fluctuations, the energy dissipation and scour prevention effects of downstream energy dissipation structures are easily affected by downstream water level drops or tidal changes. When the downstream riverbed cuts down, water levels drop, or low tides occur, the original design hydraulic boundary conditions for energy dissipation and scour prevention change, altering the flow regime and causing energy dissipation structures to fail. This leads to scour damage to the energy dissipation and scour prevention facilities, threatening the safety of the dam project. Numerous cases of dam scour damage have exposed the insufficient adaptability of traditional downstream energy dissipation and scour prevention facilities in dealing with downstream riverbed cutting and water level drops.

[0003] In recent years, some studies have proposed measures to address the aforementioned issues, such as deepening and lengthening the stilling basin, lowering the apron elevation, or adopting two or even multiple stilling basins to increase the safety margin of energy dissipation structures. Other designs have proposed replacing masonry aprons with reinforced concrete or concrete frame beams with gabion cages, or adding soft sluice gates after the scour channel to enhance the scour resistance of the energy dissipation structure. While these measures can ensure energy dissipation and scour prevention safety to a certain extent, they obviously increase the amount of engineering work and investment significantly. Furthermore, simply increasing the strength of the apron structure or adding soft sluice gates after the scour channel cannot eliminate excess energy; the downstream riverbed still faces a high risk of scour. Therefore, the ideal approach is to install auxiliary rectifying energy dissipation and scour prevention facilities downstream of the dam project to adapt to the effects of downstream riverbed erosion and water level drops or tidal fluctuations, thereby improving the resilience of the energy dissipation and scour prevention facilities and ensuring project safety.

[0004] This invention addresses the problems caused by river channel erosion, water level drops, or tidal fluctuations altering the original design hydraulic boundary conditions for energy dissipation and scour prevention in dam projects. These changes alter the downstream flow regime, leading to energy dissipation failure and consequently, downstream scour and threats to project safety. The invention proposes auxiliary rectification energy dissipation and scour prevention facilities suitable for placement in the downstream apron area of ​​the dam's downstream opening or the downstream stilling basin's apron section. These facilities adapt to low water level changes downstream of the dam, adjust unfavorable flow regimes, enhance the energy dissipation and scour prevention effects and scour resistance of the dam project, improve its resilience, and ensure project safety. Summary of the Invention

[0005] (1) Technical solution

[0006] To solve the above-mentioned technical problems, the present invention provides a rectification energy dissipation and anti-scour facility, which is arranged in the apron or seawall section downstream of the dam, including: a base plate, a first height rectification pier, a second height rectification pier and a low-lying area formed by the exposed base plate, wherein the first height rectification pier, the second height rectification pier and the low-lying area are arranged in an alternating manner in the plane.

[0007] The first height rectifier has an inverted V-shaped structure, consisting of three regular square prism units with a base side length of a and a height of h. Multiple first height rectifiers are arranged in rows continuously along the water flow direction. A second height rectifier is located at the junction of two adjacent first height rectifiers in each row. The axis of symmetry of the first height rectifier is parallel to the water flow direction. The second height rectifier is a regular square prism structure with a side length of a and a height of h' in its planar projection, and one diagonal of its projected square is parallel to the water flow direction. The concave area is a square pit with a side length of b in its planar projection, and one diagonal of its pit is parallel to the water flow direction.

[0008] The base plate is set in the direction of water flow, with a slope of 0 ≤ i ≤ 1 / 20 and a thickness of not less than 0.5m; the side length of the concave area is b = 2a, and the value of a ranges from 0.5m to 1.5m; the height of the first height rectifier is h, the height of the second height rectifier is h', and h' = 1.5~2h; the height h satisfies: h = 1 / 3 H ~ 2 / 3 H, and 0.5m ≤ h ≤ 1m, where H is the minimum water depth downstream of the dam under the most unfavorable energy dissipation and scour prevention conditions; when 1 / 3H > 1m, h is taken as 1m; when 2 / 3H < 0.5m, h is taken as 0.5m; when 0.5m ≤ 1 / 3H ~ 2 / 3H ≤ 1m, h is determined through model tests.

[0009] Preferably, the base plate, the first height rectifier pier, and the second height rectifier pier are constructed using plain concrete, reinforced concrete, or building materials that meet the impact resistance requirements. The first height rectifier pier, the second height rectifier pier, and the base plate are integrally cast in place in one piece, or the base plate is constructed first and then the first height rectifier pier and the second height rectifier pier are cast on the base plate.

[0010] Preferably, the design method of the rectification energy dissipation and anti-collision facility includes the following steps:

[0011] Step 1: Establish a two-dimensional hydrodynamic and sediment mathematical model of the river where the dam project is located, and verify it using measured data;

[0012] The second step is to use a validated mathematical model to perform numerical simulation calculations of flood or tidal dynamics and sediment. Taking into account the combined effects of long-term unfavorable flood and tidal encounters, river dredging, waterway regulation, and river sand mining, the calculations predict and analyze the changes in riverbed scouring and sedimentation downstream of the dam project and the water level-discharge relationship line at the design low water level downstream of the dam.

[0013] Step 3: Establish a partial flume model or an overall hydraulic model of the dam project. The upstream of the model should simulate a maximum head above the weir that is no less than 12 times the length of the river channel and no less than 1 times the width of the river. The downstream of the model should simulate a point no less than 1 times the width of the river downstream of the anti-scour channel.

[0014] Step 4: Conduct energy dissipation verification tests under the original design energy dissipation and scour prevention scheme of the dam project. Carry out energy dissipation tests corresponding to the original design water level-flow relationship and energy dissipation tests corresponding to the future downstream water level-flow relationship line of the dam obtained from the prediction analysis in Step 2. Analyze the response and adaptability of the original design energy dissipation and scour prevention scheme to future downstream water level changes. By observing the downstream flow velocity and the range and severity of adverse flow states such as drop, hydraulic jump, and water surface fluctuation under different opening conditions, identify the unfavorable energy dissipation conditions under future downstream water level drops and determine the minimum downstream water depth H under this condition.

[0015] Step 5: Based on the most unfavorable energy dissipation condition and the minimum downstream water depth H determined in Step 4, the height h of the first height rectification pier is initially determined according to the rule h=1 / 3H~2 / 3H and 0.5m≤h≤1m. The side length a is selected, and then the model of the rectification energy dissipation and anti-scour facility is arranged in the apron or seawall section of the physical model.

[0016] Step 6: Based on the future downstream water level-discharge relationship obtained from the prediction and analysis in Step 2 and the unfavorable working conditions determined in Step 4, conduct energy dissipation and scour prevention verification tests on the dam project under different combinations of height and side length of the rectification and energy dissipation facilities. Observe the hydraulic characteristics such as flow velocity, flow pattern, water surface fluctuation, and scour of the scour prevention channel. When the selected combination of height and side length of the rectification and energy dissipation facilities can effectively eliminate unfavorable flow patterns such as drop flow and hydraulic jump, reduce flow velocity, reduce water surface turbulence, and avoid scour of the scour prevention channel area, the height h and side length a of the first-height rectification pier and the height h' and side length b of the second-height rectification pier can be determined.

[0017] Preferably, the first step specifically includes: collecting basic data such as river topography, hydrology, shoreline, important river-related structures and dam engineering design data to establish a two-dimensional hydrodynamic and sediment mathematical model of the river where the dam project is located;

[0018] The hydrodynamic sediment mathematical model was developed using Mike21 software. It is based on the Navier-Stokes equations, which assume incompressibility and uniform distribution of Reynolds values, and is subject to the Boussinesq assumption and the assumption of hydrostatic pressure.

[0019] The two-dimensional non-steady shallow water equations are as follows:

[0020]

[0021]

[0022]

[0023] In the formula: For time; Coordinates are in the Cartesian coordinate system; Water level; The depth of still water; Total water depth; They are respectively Velocity component in the direction; , These are the average flow velocities based on water depth in the x and y directions, respectively; Pa is the local atmospheric pressure. This refers to the density of water under standard temperature and pressure. , They are along Shear stress in the direction; , They are along Undercut stress in the direction; It is the Coriolis force coefficient. , This is the Earth's rotational angular velocity. The latitude is the local latitude. It is the acceleration due to gravity; The density of water; These are the radiation stress components; This is a horizontal viscous stress term. For source and sink items, For the source of the water flow in Flow velocity in the direction.

[0024] Preferably, the hydrodynamic sediment model described in the first step extends from the upstream main stream control hydrological station section of the dam project to the downstream estuary hydrological station or tide level station section of the dam project.

[0025] Preferably, the hydrodynamic sediment mathematical model in the first step adopts an unstructured triangular mesh. The mesh size is determined comprehensively based on the accuracy of the topographic map, the degree of topographic relief, and the size of important river-crossing structures. The mesh size should be comparable to the interval of the elevation measurement points on the topographic map. The local mesh should be densified in areas with drastic topographic relief and important river-crossing structures.

[0026] Preferably, the roughness of the hydrodynamic sediment mathematical model in the first step can be determined based on experience, combined with the river type, riverbed morphology, riverbed composition, distribution of river-related structures, etc., and finally determined through model verification and adjustment.

[0027] The upper boundary of the hydrodynamic sediment mathematical model is set at the starting section of the main stream and tributaries, and the upper boundary is the flow rate. The lower boundary of the model is set at the section where the estuary hydrological station or the estuary tide station is located, and the lower boundary is the water level.

[0028] Preferably, the hydrodynamic sediment mathematical model described in the first step needs to be validated using measured hydrological data. Validation mainly includes flow rate, split ratio, water level, flow velocity, flow direction, riverbed scouring and deposition, and sediment content. This is primarily achieved by adjusting the grid file, model roughness, initial water level field boundary, sediment particle size, thrust-to-suspension ratio, and sediment calculation equations to ensure that the difference between the calculated and measured values ​​meets the error requirements. The error between the calculated and measured values ​​should meet the relevant requirements of the "Technical Specification for Simulation Tests of Water Transport Engineering" (JTS-T 231-2021).

[0029] Preferably, the model described in the third step must be a normal physical model, in accordance with the "Hydraulic Engineering (Conventional) Model Test Procedure" (SL155-2012), following the model similarity law criterion, and satisfying the requirements of geometric similarity, water flow motion similarity, dynamic similarity and Froude number similarity. Considering the scale effect, the scale of the local flume model or the overall hydraulic engineering model shall not be less than 1:30.

[0030] Preferably, the rectification energy dissipation and scour prevention facility is used in the scour protection of dams, dikes, revetments, bridge piers, wharves or groynes.

[0031] (2) Beneficial effects

[0032] This invention provides a rectification energy dissipation and anti-collision facility and its design method. Compared with the prior art, this invention has the following advantages:

[0033] 1. By employing three different elevation zones (first-height rectifying pier, second-height rectifying pier, and low-lying area) with alternating high and low elevations, and with one diagonal of each square zone parallel to the water flow direction, multiple "inverted V-shaped" first-height rectifying piers are arranged continuously in rows along the water flow direction. A second-height rectifying pier is set at the junction of two adjacent first-height rectifying piers in each row. This effectively eliminates adverse flow patterns such as plunges, hydraulic jumps, and violent water surface fluctuations caused by the drop in water level or tidal changes downstream of the dam, reduces flow velocity, minimizes water surface turbulence, avoids scouring of the anti-scouring channel area, improves the resilience of energy dissipation and anti-scouring facilities, and ensures the safety of the dam project.

[0034] 2. Existing energy dissipation and scour prevention facilities are prone to failure due to changes in hydraulic boundary conditions when the riverbed is eroded or the water level drops. This invention can proactively adapt to the effects of riverbed erosion downstream of the dam and water level drops or tidal fluctuations, adjusting the flow pattern of the outflow from the stilling basin. Without changing the original layout of the stilling basin and the apron, it meets the energy dissipation and scour prevention requirements after water level changes.

[0035] 3. Compared with measures such as deepening and lengthening the stilling basin, setting up secondary or multi-stage stilling basins, using reinforced concrete frame beams with gabion cages for erosion control, or adding soft embankments for erosion control, this invention proposes to construct high and low rectifying piers and low-lying areas in the apron or seawall section by adding plain concrete or other building materials that meet the erosion resistance requirements, forming a rectifying, energy dissipation and erosion control composite structure. The structure is simple, easy to construct, and can save on engineering work and reduce investment.

[0036] 4. This invention predicts the future water level-discharge relationship by establishing a two-dimensional hydrodynamic sediment mathematical model, and verifies and identifies the most unfavorable energy dissipation condition using a normal physical model. Based on the minimum downstream water depth H, the height of the rectifying pier is initially determined according to h = 1 / 3H to 2 / 3H. Furthermore, the dimensions and height of each section are optimized through model experiments. This method is highly targeted, avoids the blindness of experience-based design, and ensures the rectification, energy dissipation, and scour prevention effects. Attached Figure Description

[0037] Figure 1 This is a three-dimensional diagram of the rectification, energy dissipation, and anti-collision facility of the present invention.

[0038] Figure 2 This is a plan view of the rectification, energy dissipation, and anti-collision facilities of the present invention.

[0039] Figure 3 This is a cross-sectional view of the rectification, energy dissipation, and anti-impact facility of the present invention.

[0040] Figure 4 This is a diagram showing the predicted water level-discharge relationship of a dam project under the designed low tide level downstream of the dam in an embodiment of the present invention.

[0041] Figure 5 This is a partial water channel physical model of a dam project according to an embodiment of the present invention.

[0042] Figure 6 This is a plan view of the rectification, energy dissipation and scour prevention facilities deployed in the floodplain of a dam project according to an embodiment of the present invention.

[0043] Figure 7 The diagram shows a comparison of the flow patterns before (a) and after (b) the arrangement of the rectification, energy dissipation and scour prevention facilities in a dam project according to an embodiment of the present invention.

[0044] Figure 8 This is a plan view of the rectification, energy dissipation and scour prevention facilities of a dam project according to an embodiment of the present invention.

[0045] Figure 9This is a cross-sectional view of the rectification, energy dissipation and scour prevention facilities of a dam project according to an embodiment of the present invention.

[0046] The attached diagram is labeled as follows: 1-base plate, 2-first height rectifier pier, 3-second height rectifier pier, 4-lowering area. Detailed Implementation

[0047] The technical solutions in the embodiments of the present invention will be further described clearly and completely below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0048] Example

[0049] Step 1: Establish a two-dimensional hydrodynamic mathematical model of the river where the dam project using the rectification energy dissipation and scour prevention facility technology is located.

[0050] Collect basic data such as river topography, hydrology, shoreline, important river-related structures and dam engineering design data to establish a two-dimensional hydrodynamic and sediment mathematical model of the river where the dam project is located.

[0051] The hydrodynamic sediment mathematical model was developed using Mike21 software. It is based on the Navier-Stokes equations, which assume incompressibility and uniform distribution of Reynolds values, and is subject to the Boussinesq assumption and the assumption of hydrostatic pressure.

[0052] The two-dimensional non-steady shallow water equations are as follows:

[0053]

[0054]

[0055] In the formula: For time; Coordinates are in the Cartesian coordinate system; Water level; The depth of still water; Total water depth; They are respectively Velocity component in the direction; , These are the average flow velocities based on water depth in the x and y directions, respectively; Pa is the local atmospheric pressure. This refers to the density of water under standard temperature and pressure. , They are along Shear stress in the direction; , They are along Undercut stress in the direction; It is the Coriolis force coefficient. , This is the Earth's rotational angular velocity. The latitude is the local latitude. It is the acceleration due to gravity; The density of water; These are the radiation stress components; This is a horizontal viscous stress term. For source and sink items, For the source of the water flow in Flow velocity in the direction.

[0056] The hydrodynamic sediment model ranges from the upstream control hydrological station section of the dam project to the downstream estuary hydrological (level) station or tide level station of the dam project.

[0057] The hydrodynamic sediment mathematical model adopts an unstructured triangular mesh. The mesh size is determined comprehensively based on the accuracy of the topographic map, the degree of topographic relief, and the size of important river-crossing structures. The mesh size should be comparable to the interval of elevation measurement points on the topographic map. The local mesh should be densified in areas with drastic topographic relief and important river-crossing structures.

[0058] The roughness of the hydrodynamic sediment mathematical model can be determined based on experience, taking into account factors such as river type, riverbed morphology, riverbed composition, and distribution of river-related structures, and then finalized through model verification and adjustment.

[0059] The upper boundary of the hydrodynamic sediment mathematical model is set at the starting section of the main stream and tributaries, and the upper boundary is the flow rate. The lower boundary of the model is set at the section where the estuary hydrological (level) station or the estuary tide level station is located, and the lower boundary is the water (tide) level.

[0060] The hydrodynamic sediment mathematical model needs to be validated using measured hydrological data. Validation mainly includes flow rate, diversion ratio (for distributary channels), water (tidal) level, velocity, direction, riverbed scouring and deposition, and sediment content. This is primarily achieved by adjusting the grid file, model roughness, initial water level field boundary, sediment particle size, bedload ratio, and sediment calculation equations to ensure that the difference between the calculated and measured values ​​meets the error requirements. The error between the calculated and measured values ​​should meet the relevant requirements of the "Technical Specification for Simulation Tests of Water Transport Engineering" (JTS-T 231-2021).

[0061] Step 2: Using a validated mathematical model, numerical simulations of flood (tidal) dynamics and sediment are performed. Taking into account the combined effects of prolonged unfavorable flood and tidal conditions, river dredging, waterway improvement, and river sand mining, the future changes in riverbed scouring and sedimentation downstream of the dam project, as well as the water level-discharge relationship at the design low water (tidal) level downstream of the dam, are predicted and analyzed. Considering the effects of prolonged unfavorable floods and future river dredging, the predicted future water level-discharge relationship downstream of a certain dam project is as follows: Figure 4 .

[0062] Step 3: Establish a local flume model or a complete hydraulic model of the dam project. The upstream of the model should simulate a river length no less than 12 times the maximum head above the weir and no less than 1 times the river width. The downstream of the model should simulate a point no less than 1 times the river width downstream of the scour channel. The model must be a normal physical model, conforming to the "Hydraulic Engineering (Conventional) Model Test Procedure" (SL155-2012), following the model similarity law criteria, and satisfying the requirements of geometric similarity, flow motion similarity, dynamic similarity, and Froude number similarity. Considering the scaling effect, the scale of the local flume model or the complete hydraulic model should be no less than 1:30. In this embodiment, a local normal flume model of the dam project is established. The upstream of the model simulates a point 300m above the dam, with a head greater than 12 times the maximum head above the weir and a river width of 1 times the dam site. The downstream of the model simulates a point 300m downstream of the scour channel, also greater than 1 times the river width of the dam site. The model scale is 1:30, satisfying the requirements of geometric similarity, flow motion similarity, dynamic similarity, and Froude number similarity. The local flume model of this embodiment is shown in [link to embodiment]. Figure 5 (Original energy dissipation scheme).

[0063] Step 4: Conduct energy dissipation verification tests under the original design energy dissipation and scour prevention scheme of the dam project. Energy dissipation tests are carried out according to the original design water level-discharge relationship and the future downstream water level-discharge relationship obtained from the prediction analysis in Step 2. The responsiveness and adaptability of the original design energy dissipation and scour prevention scheme to future downstream water level changes are analyzed. By observing the downstream flow velocity and the range and severity of adverse flow states such as drops, hydraulic jumps, and water surface fluctuations under different opening conditions, unfavorable energy dissipation conditions under future downstream water level drops are identified. In this example, through experiments, the most unfavorable condition was determined to be a reservoir water level of 5.3m, an opening of 0.25m in the 8-gate first-opening section, a discharge flow of 193m³ / s, and a downstream water level of -2.77m.

[0064] Step 5: Based on the shortcomings of the original energy dissipation and scour prevention scheme under unfavorable energy dissipation conditions revealed in Step 4, which exhibits poor adaptability to downstream water level drops, resulting in low efficiency and susceptibility to unfavorable flow patterns, potentially leading to downstream scour damage, an auxiliary rectification energy dissipation and scour prevention facility is proposed and positioned downstream of the dam. In this embodiment, a stilling basin is located downstream of the dam, followed by a seawall section. Therefore, the auxiliary rectification energy dissipation and scour prevention facility is positioned in the seawall section downstream of the stilling basin. (See...) Figure 6 In the embodiment, the rectification, energy dissipation, and anti-surge facilities (see...) Figure 6The elevation of the first-height rectifier 2 is consistent with the original design elevation of the floodplain. The second-height rectifier 3 is h higher than the original design floodplain, and the depression 4 is h lower than the original design floodplain. The rectification, energy dissipation, and scour prevention facilities are integrally cast with plain concrete, the thickness of the base slab 1 is 0.5m, and the slope i of the base slab 1 is 1 / 30. Multiple first-height rectifiers 2 are arranged continuously in rows along the direction of water flow, and a second-height rectifier 3 is set at the junction of two adjacent first-height rectifiers 2 in each row.

[0065] Step 6: Based on the predicted downstream water level-discharge relationship and unfavorable operating conditions, a local flume model was used to conduct energy dissipation and scour prevention verification tests on the dam project under different combinations of height and side lengths of the rectification and energy dissipation facilities. The hydraulic characteristics such as flow velocity, flow pattern, water surface fluctuations, and scour of the scour prevention channel were observed. The tests showed that, for the specific implementation, when h is 0.5m, h' is 1.0m, a is 1m, and b is 2m, the rectification and energy dissipation facilities effectively eliminated adverse flow patterns such as cascades and hydraulic jumps, reduced flow velocity, decreased water surface turbulence, and prevented scour in the scour prevention channel area. The experimental flow patterns are shown in [see figure]. Figure 7 , Figure 7 (a) shows the drop and secondary hydraulic jump that occur in the sea flood section after the stilling basin is installed; (b) shows the disappearance of the drop and hydraulic jump in the sea flood section after the stilling basin is installed, and the flow is good.

[0066] The rectifier energy dissipation and anti-collision facility layout determined in the embodiment is as follows: Figure 8 (The unit labeled in the figure is m), the cross-sectional layout is as follows: Figure 9 (The unit labeled in the figure is m).

[0067] The embodiments described above are merely preferred embodiments of the present invention, and are described in a relatively specific and detailed manner. However, the present invention is not limited to these embodiments. It should be noted that for those skilled in the art, any modifications made without departing from the spirit of the present invention fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A rectification energy dissipation and anti-collision device, characterized in that, The revetment or seawall section located downstream of the dam includes: a bottom plate, a first height straightening pier, a second height straightening pier set on the upper surface of the bottom plate, and a low-lying area formed by the exposed bottom plate. The first height straightening pier, the second height straightening pier, and the low-lying area are arranged in an alternating manner in the plane. The first height rectifier has an inverted V-shaped structure, consisting of three regular square prism units with a base side length of a and a height of h. Multiple first height rectifiers are arranged in rows continuously along the water flow direction. A second height rectifier is provided at the junction of two adjacent first height rectifiers in each row. The axis of symmetry of the first height rectifier is parallel to the water flow direction. The second height rectifier is a regular square prism structure with a side length of a and a height of h' in its planar projection, and one diagonal of its projected square is parallel to the water flow direction. The concave area is a square pit with a side length of b in its planar projection, and one diagonal of its pit is parallel to the water flow direction. The base plate is set in the direction of water flow, with a slope of 0 ≤ i ≤ 1 / 20 and a thickness of not less than 0.5m; the side length of the concave area is b = 2a, and the value of a ranges from 0.5m to 1.5m; the height of the first height rectifier is h, the height of the second height rectifier is h', and h' = 1.5~2h; the height h satisfies: h = 1 / 3 H ~ 2 / 3 H, and 0.5m ≤ h ≤ 1m, where H is the minimum water depth downstream of the dam under the most unfavorable energy dissipation and scour prevention conditions; when 1 / 3H > 1m, h is taken as 1m; when 2 / 3H < 0.5m, h is taken as 0.5m; when 0.5m ≤ 1 / 3H ~ 2 / 3H ≤ 1m, h is determined through model tests.

2. The rectification energy dissipation and anti-collision device according to claim 1, characterized in that, The base plate, the first height rectifier pier, and the second height rectifier pier are constructed using plain concrete, reinforced concrete, or building materials that meet the requirements for impact resistance. The first height rectifier pier, the second height rectifier pier, and the base plate are integrally cast in place in one piece, or the base plate is constructed first and then the first height rectifier pier and the second height rectifier pier are cast on the base plate.

3. The design method of a rectification energy dissipation and anti-collision facility according to claim 1 or 2, characterized in that, Includes the following steps: Step 1: Establish a two-dimensional hydrodynamic and sediment mathematical model of the river where the dam project is located, and verify it using measured data; The second step is to use a validated mathematical model to perform numerical simulation calculations of flood or tidal dynamics and sediment. Taking into account the combined effects of long-term unfavorable flood and tidal encounters, river dredging, waterway regulation, and river sand mining, the calculations predict and analyze the changes in riverbed scouring and sedimentation downstream of the dam project and the water level-discharge relationship line at the design low water level downstream of the dam. Step 3: Establish a partial flume model or an overall hydraulic model of the dam project. The upstream of the model should simulate a maximum head above the weir that is no less than 12 times the length of the river channel and no less than 1 times the width of the river. The downstream of the model should simulate a point no less than 1 times the width of the river downstream of the anti-scour channel. Step 4: Conduct energy dissipation verification tests under the original design energy dissipation and scour prevention scheme of the dam project. Carry out energy dissipation tests corresponding to the original design water level-flow relationship and energy dissipation tests corresponding to the future downstream water level-flow relationship line of the dam obtained from the prediction analysis in Step 2. Analyze the response and adaptability of the original design energy dissipation and scour prevention scheme to future downstream water level changes. By observing the downstream flow velocity and the range and severity of adverse flow states such as drop, hydraulic jump, and water surface fluctuation under different opening conditions, identify the unfavorable energy dissipation conditions under future downstream water level drops and determine the minimum downstream water depth H under this condition. Step 5: Based on the most unfavorable energy dissipation condition and the minimum downstream water depth H determined in Step 4, the height h of the first height rectification pier is initially determined according to the rule h=1 / 3H~2 / 3H and 0.5m≤h≤1m. The side length a is selected, and then the model of the rectification energy dissipation and anti-scour facility is arranged in the apron or seawall section of the physical model. Step 6: Based on the future downstream water level-discharge relationship obtained from the prediction and analysis in Step 2 and the unfavorable working conditions determined in Step 4, conduct energy dissipation and scour prevention verification tests on the dam project under different combinations of height and side length of the rectification and energy dissipation facilities. Observe the hydraulic characteristics such as flow velocity, flow pattern, water surface fluctuation, and scour of the scour prevention channel. When the selected combination of height and side length of the rectification and energy dissipation facilities can effectively eliminate unfavorable flow patterns such as drop flow and hydraulic jump, reduce flow velocity, reduce water surface turbulence, and avoid scour of the scour prevention channel area, the height h and side length a of the first-height rectification pier and the height h' and side length b of the second-height rectification pier can be determined.

4. The design method of a rectification energy dissipation and anti-collision facility according to claim 3, characterized in that, The first step specifically includes: collecting basic data such as river topography, hydrology, shoreline, important river-related structures and dam engineering design data to establish a two-dimensional hydrodynamic and sediment mathematical model of the river where the dam project is located; The two-dimensional hydrodynamic sediment mathematical model was developed using Mike21 software. It is based on the Navier-Stokes equations, which assume incompressibility and uniform distribution of Reynolds values, and is subject to the Boussinesq assumption and the assumption of hydrostatic pressure. The two-dimensional non-steady shallow water equations are as follows: ； ； ； In the formula: For time; Coordinates are in the Cartesian coordinate system; Water level; The depth of still water; Total water depth; They are respectively Velocity component in the direction; , These are the average flow velocities based on water depth in the x and y directions, respectively; Pa is the local atmospheric pressure. This refers to the density of water under standard temperature and pressure. , They are along Shear stress in the direction; , They are along Undercut stress in the direction; It is the Coriolis force coefficient. , This is the Earth's rotational angular velocity. The latitude is the local latitude. It is the acceleration due to gravity; The density of water; These are the radiation stress components; This is a horizontal viscous stress term. For source and sink items, For the source of the water flow in Flow velocity in the direction.

5. The design method of a rectification energy dissipation and anti-collision facility according to claim 4, characterized in that, The scope of the two-dimensional hydrodynamic sediment mathematical model described in the first step extends from the upstream main stream control hydrological station section of the dam project to the downstream estuary hydrological station or tide gauge station section of the dam project.

6. The design method of a rectification energy dissipation and anti-collision facility according to claim 3, characterized in that, The two-dimensional hydrodynamic sediment mathematical model described in the first step adopts an unstructured triangular mesh. The mesh size is determined comprehensively based on the accuracy of the topographic map, the degree of topographic relief, and the size of important river-crossing structures. The mesh size should be comparable to the interval of elevation measurement points on the topographic map. The local mesh should be densified in areas with drastic topographic relief and important river-crossing structures.

7. The design method of a rectification energy dissipation and anti-collision facility according to claim 3, characterized in that, The roughness of the two-dimensional hydrodynamic sediment mathematical model mentioned in the first step can be determined based on experience, combined with the preliminary values ​​given by river type, riverbed morphology, riverbed composition, and distribution of river-related structures, and finally determined through model verification and adjustment. The upper boundary of the two-dimensional hydrodynamic sediment mathematical model is set at the starting section of the main stream and tributaries, and the upper boundary is the flow rate. The lower boundary of the model is set at the section where the estuary hydrological station or the estuary tide station is located, and the lower boundary is the water level.

8. The design method of a rectification energy dissipation and anti-collision facility according to claim 3, characterized in that, The two-dimensional hydrodynamic sediment mathematical model described in the first step needs to be validated using measured hydrological data. The validation mainly includes flow rate, split ratio, water level, flow velocity, flow direction, riverbed scouring and deposition, and sediment content. This is mainly achieved by adjusting the grid file, model roughness, initial water level field boundary, sediment particle size, thrust-suspension ratio, and sediment calculation equations to ensure that the difference between the calculated and measured values ​​meets the error requirements. The error between the calculated and measured values ​​should meet the relevant requirements of the "Technical Specification for Simulation Test of Water Transport Engineering" (JTS-T 231-2021).

9. The design method of a rectification energy dissipation and anti-collision facility according to claim 3, characterized in that, The model described in the third step must be a normal physical model, in accordance with the "Hydraulic Model Test Procedure" (SL155-2012), following the model similarity law criterion, and satisfying the requirements of geometric similarity, water flow motion similarity, dynamic similarity and Froude number similarity. Considering the scale effect, the scale of the local flume model or the overall hydraulic model shall not be less than 1:

30.

10. The application of a rectification energy dissipation and scour prevention facility according to claim 1 or 2 in scour protection of dams, dikes, revetments, bridge piers, wharves or groynes.

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