Estimation method of water intake boundary layer for deep water intake structures in power plants

Abstract

The present invention relates to a method for estimating the water intake boundary layer of a deep water intake structure of a power plant, including: establishing a three-dimensional water intake flow field model including the marine environment and the deep water intake structure; verifying the flow field model based on the results of physical model experiments; analyzing the water intake inflow characteristics and flow field of the deep water intake structure; analyzing the water intake boundary layer of the deep water intake structure based on discrete particle tracing; and determining the water intake boundary layer of the deep water intake structure. When using a deep water intake structure to take water, the present invention comprehensively considers multiple factors such as the design characteristics of the water intake structure, the characteristics of the deep water intake inflow, and the changes in the environmental flow field, estimates the water intake boundary layer of the water body affected by the water intake environment, and determines the characteristics of the impact of the deep water intake structure on the environmental water body when taking water. The present invention provides a scientific basis for clarifying the impact range of the water intake operation of the deep water intake structure on the environmental water body and improving the safety of nuclear power water intake.

Description

Technical Field

[0001] This invention relates to a method for estimating the water intake boundary layer of a deep water intake structure in a power plant. It is a hydraulic engineering calculation method used to estimate the range of impact of water intake on the surrounding water body when a power plant uses a deep water intake structure for water intake. Background Technology

[0002] Deep water intake for power plants typically involves constructing intake structures at the bottom of deep riverbeds or seabeds. These structures are connected to the power plant's intake pump house via pipelines or tunnels. This method effectively avoids directly drawing water from the bottom of deeper water bodies, thus controlling and reducing the risks to cold source safety. However, current design codes related to deep water intake are largely based on experience, or are simply compared to regulations from other industries such as hydropower. The determination of key design parameters, such as the water intake submersion depth, relies heavily on experience and lacks theoretical support. Furthermore, design codes and methods fail to comprehensively consider factors such as the large water intake flow rate of nuclear power plants, complex tidal conditions in the surrounding water environment, and the impact of marine life, making it difficult to meet the high requirements for safe and ecological operation of nuclear power plant water intake. To clarify the scope of the impact of nuclear power plant deep water intake structures on environmental water bodies, it is urgent to propose a water intake boundary layer estimation method that comprehensively considers the characteristics of nuclear power plant water intake operation and the characteristics of deep water intake flow. This method will provide technical support for quantifying the impact of deep water intake structure operation on environmental water bodies, identifying key areas for cold source safety control, selecting deep water intake structures with minimal impact on environmental water bodies, and ensuring the safety and eco-friendliness of nuclear power plant water intake. Summary of the Invention

[0003] To overcome the problems of existing technologies, this invention proposes a method for estimating the water intake boundary layer of deep water intake structures in power plants. The method introduces the concept of the water intake boundary layer, clarifies the scope of the impact of water intake on environmental water bodies, and comprehensively considers the hydrodynamic characteristics of deep water intake, water intake volume, and the structure of the water intake structure, providing a scientific basis for determining the scope of the impact of deep water intake operation on environmental water bodies.

[0004] The objective of this invention is achieved as follows: a method for estimating the water intake boundary layer of deep water intake structures in power plants, comprising the following steps:

[0005] Step 1: Establish a three-dimensional water intake flow field model including the marine environment and deep water intake structures: Establish a three-dimensional flow field model of the water intake area including deep water intake structures, obtain the topography, environmental water flow conditions, shoreline characteristics of the water intake area, as well as the design dimensions, water intake flow rate, water intake velocity, and water intake depth of the deep water intake structures, establish the water intake flow field model, divide the calculation grid, determine the boundary conditions and initial conditions for the flow field simulation, and select appropriate calculation parameters to simulate the flow field changes including deep water intake structures and the water intake-affected marine area;

[0006] The governing equations for the flow field calculation are as follows:

[0007]

[0008] Where: u is the time-averaged velocity, t is time, p is pressure, ρ is water density, and μ is... eff Let α be the turbulent effective viscosity, k be the turbulent kinetic energy, I be the second-order unit tensor, and α be the turbulent effective viscosity. k Let α be the Prandtl number of turbulent kinetic energy, ε be the turbulent dissipation rate, and α be the turbulent kinetic energy. ε G is the Prandtl number, representing the turbulent dissipation rate. k C represents the turbulent kinetic energy production term caused by the average velocity gradient. 1ε and C 2ε These are constant coefficients, with values ​​of 1.42 and 1.68 respectively;

[0009] Step 2, verify the flow field model based on the experimental results of the physical model: construct a normal scale physical model of the deep water intake structure in an indoor experimental water tank, measure the flow velocity and flow direction of each characteristic section or characteristic point, and compare and verify with the simulation results of the mathematical model to ensure that the calculation results of the flow field model are basically consistent with the experimental results of the physical model, that is, the simulation results of the flow field model can reflect the characteristics of the deep water intake flow field distribution.

[0010] Step 3, Analysis of water intake characteristics and flow field of deep water intake structures: Based on the simulation results of the validated flow field model, conduct an analysis of the water intake characteristics of deep water intake structures and the impact of water intake on the environmental water body, and provide a basis for setting the particle delivery control conditions in Step 4.

[0011] Step 4, Boundary layer analysis of deep water intake structures based on discrete particle tracing:

[0012] Based on the flow field simulation results, discrete particle tracing calculations are performed, and the governing equations for particle motion are as follows:

[0013]

[0014] Where: m is the mass of the particle; v is the velocity of the particle; F is the net force acting on the particle in the flow field; x is the displacement of the particle; in the tracer calculation, the particle is simplified as a moving point mass, that is, the mass of the particle and the resulting force in the flow field are not considered, i.e., m = 0; in the tracer calculation, the following is used When simulating particle motion, the tracer trajectory of a particle can be described as follows:

[0015]

[0016] Where: x(t) is the position of the particle at time t; x(t+Δt) is the position of the particle at time t+Δt; Let Δt be the displacement of the particle during the time interval Δt.

[0017] Calculation process:

[0018] Particle delivery: Uniform, one-time, instantaneous delivery at the characteristic cross-section;

[0019] Based on the characteristics of water intake flow from deep water intake structures and the results of flow field analysis, particle placement control conditions were set, including the initial placement position, placement width, and placement water depth. The initial placement position was set to ensure that the environmental inflow at that location (section) was not affected by the water intake structure, meaning that the particles were evenly distributed at the initial placement moment. The placement width was set to ensure that the cross-sectional width was sufficiently wide, based on the analysis results of the characteristics of water intake flow from deep water intake structures. The placement depth was set to minimize the interval between placement depths to obtain the particle tracer trajectories in both the horizontal and vertical directions.

[0020] Step 5, Determination of the water intake boundary layer for deep water intake structures:

[0021] In the vertical direction of the incoming environmental flow, analyzing the tracer trajectories of the particles, the maximum envelope of the tracer particles that can enter the intake structure is the intake boundary layer of the intake structure under the current condition. Specifically: in the vertical direction of the incoming environmental flow, the maximum width of the tracer particles entering the intake structure is the maximum width of the intake influence; in the vertical direction of the incoming environmental flow, statistically analyzing the deployment depth, the maximum thickness of the tracer particles that can enter the intake structure is the maximum thickness of the intake influence. Where the initial particle position is at the upper edge of the intake structure, the corresponding thickness is the influence thickness above the upper edge of the intake structure, denoted as S. up The initial position of the particles is at the lower edge of the water intake structure, and the corresponding thickness is the influence thickness below the lower edge of the water intake structure, denoted as S. down The height of the inlet window of the water intake structure is denoted as D; the vertical influence thickness of the deep water intake structure is S. total For: S total =S up +D+S down ;

[0022] The boundary layer envelope area of ​​the water intake can characterize the maximum area of ​​the environmental water body affected by a deep water intake structure in the direction perpendicular to the water flow. Its estimation formula is as follows:

[0023]

[0024] In the formula: A is the envelope area of ​​the water intake boundary layer in the direction of the vertical environmental inflow; H is the environmental water depth; h is the particle delivery depth; B' is the envelope width of the corresponding particle delivery depth in the horizontal direction.

[0025] The advantages and beneficial effects of this invention are as follows: When using deep water intake structures for water intake, this invention comprehensively considers multiple factors such as the design characteristics of the intake structure, the characteristics of deep water intake flow, and changes in the environmental flow field. It estimates the water intake boundary layer to determine the impact characteristics of deep water intake structures on the environmental water body, thus identifying the impact characteristics of deep water intake structures on the environmental water body. Existing design specifications are relatively empirical, only proposing empirical estimation methods for design parameters such as the minimum submergence depth of the intake structure, without estimating the water intake boundary layer. This ignores the design of different intake structures, the characteristics of water intake flow, and the environmental flow field, which is clearly unreasonable. This invention comprehensively considers the characteristics of nuclear power plant water intake operation and the inflow characteristics of deep water intake structures, proposing a method for estimating the water intake boundary layer. This provides a scientific basis for clarifying the impact range of deep water intake operation on the environmental water body and improving the safety of nuclear power plant water intake. Attached Figure Description

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0027] Figure 1 This is a schematic diagram of the structural elevation of the funnel-shaped water intake structure on which the method described in the embodiments of the present invention is based;

[0028] Figure 2 This is a schematic plan view of the funnel-shaped water intake structure on which the method described in the embodiments of the present invention is based;

[0029] Figure 3 This is a schematic diagram of the structural elevation of the pier-type water intake structure on which the method described in the embodiments of the present invention is based;

[0030] Figure 4 This is a schematic diagram of the structural plan of the pier-type water intake structure on which the method described in the embodiments of the present invention is based;

[0031] Figure 5 This is a flowchart of the method described in the embodiments of the present invention;

[0032] Figure 6This is a schematic diagram of the water intake boundary layer in the first application example of the present invention, and a schematic diagram of the structural elevation of the funnel-shaped water intake structure;

[0033] Figure 7 This is a schematic diagram of the water intake boundary layer in the second application example of the present invention, and a structural elevation diagram of a pier-type water intake structure. Detailed Implementation

[0034] Example:

[0035] This embodiment describes a method for estimating the water intake boundary layer of a deep water intake structure in a power plant. The deep water intake structure on which this estimation method is based is a funnel-shaped intake structure, such as... Figure 1 , 2 As shown, or pier-type water intake structures, such as Figure 3 , 4 As shown, or other forms of deep water intake structures.

[0036] The aforementioned funnel-shaped water intake structure is a method of water intake along the riverbank. The water intake is at least 1 meter underwater and is arranged along the riverbank or coastline 1. The cross-sectional shape of the water intake 2 is rectangular, and the height of the water intake (i.e., the height of the inflow window) is h1. Figure 1 As shown. The water intake is connected to water intake pipe 3, which is connected to the power plant's cooling water system. Water intake pipe 3 extends towards the land. The water intake direction is (see...) Figure 1 The direction of the middle arrow E) is perpendicular or nearly perpendicular to the direction of the environmental water flow along the coastline or riverbank (see...). Figure 2 The direction of the middle arrow G represents the unidirectional environmental flow of the river. The flow is parallel or nearly parallel to the coastline or riverbank, where rivers are typically unidirectional and ocean currents are usually reciprocating along the coast. The lower edge height h2 of the intake needs to consider bottom sediment control requirements and is generally at least 1 meter higher than the seabed or riverbed. The upper edge height h3 of the intake reaching the water surface should not be less than the minimum inundation depth requirement. Funnel-shaped intake structures are typically excavated along the riverbank or coastline inwards towards the bank foundation, intersecting with the bank slope to form a funnel shape (see...). Figure 2 The intake of a funnel-shaped water intake structure can take various forms. It can be multiple intake pipes arranged horizontally side-by-side, or a box culvert with a relatively large width w1 along the coastline or riverbank (e.g., Figure 2 As shown), this ensures unobstructed water flow into the intake pipe. Funnel-shaped intake structures are typically located on steep riverbanks or coastlines to avoid excessive excavation. The cross-sectional shape of the intake pipe in a funnel-shaped intake structure can be rectangular or circular; in the rectangular case, its height h4 (see...) Figure 1The diameter of the intake pipe should not exceed the height of the outlet culvert. When the cross-sectional shape of the intake pipe is circular, h4 is the diameter of the circular intake pipe. The design has certain requirements for the water flow velocity in the pipeline. The design flow velocity requirement in the intake pipeline is usually high to reduce fouling and biological adhesion. Therefore, the flow velocity in the intake pipeline should be higher than that at the intake point, and the diameter of the intake pipe should be less than or equal to the height of the culvert.

[0037] A pier-type water intake structure is a hollow structure resembling a bridge pier, built on a riverbed or seabed at a depth of at least 1 meter, located far from the shore.4 Figure 3 The length of the bridge pier is parallel to the direction of the surrounding water flow (see...). Figure 4 (Arrow G direction) Consistent. The term "pier-type" refers to a rectangular box culvert with an inner cavity of length and width w2×w3 along one long side in the direction of water flow on a horizontal cross-section. The two short sides of this rectangular box culvert are set as arcs or triangles, forming an oblong or hexagonal shape. Figure 4 The diagram shows a hexagonal bridge pier shape. The hollow structure in the pier shape has windows on both sides at the top as water intakes 401 (see...). Figure 3 ), forming a double-sided inflow ( Figure 3 , 4 (In the direction of arrow E), a water intake pipe 5 is installed at the bottom, connecting to the power plant's cooling water pool. This water intake pipe is buried in the riverbed or seabed, extending from the water intake culvert to the shore, connecting to the power plant's cooling water pool or water intake pump house, etc. The hollow structure (box culvert) can be divided into one or more spaces. Figure 4 Only one box culvert with a pair of water inlets is shown. Each space is equipped with a water inlet pipe and a pair of opposing water inlet windows, such as... Figure 4 As shown. The cross-sectional shape of the water intake pipe of a bridge pier-type water intake structure can be rectangular or circular. When rectangular, its height d1 (see...) Figure 3 When the cross-sectional shape of the water intake pipe is circular, d1 is the diameter of the circular water intake pipe.

[0038] The steps of the method are as follows, and the process is as follows: Figure 5 As shown:

[0039] Step 1: Establish a three-dimensional water intake flow field model including the marine environment and deep water intake structures: Establish a three-dimensional flow field model of the water intake area including the deep water intake structures, obtain the topography, environmental flow conditions, shoreline characteristics of the water intake area, as well as the design dimensions, water intake flow rate, water intake velocity, and water intake depth of the deep water intake structures, establish the water intake flow field model, divide the computational grid, determine the boundary conditions and initial conditions for the flow field simulation, and select appropriate computational parameters to simulate the flow field changes including the deep water intake structures and the water intake-affected marine area.

[0040] Establish a three-dimensional flow field model of the intake area, including the deep intake structures (the flow field model can be a full three-dimensional flow field model or a layered three-dimensional model; a two-dimensional flow field model cannot be used. The following uses a full three-dimensional flow field model as an example): Simulate the flow field changes of the surrounding environment and the inflow situation of the intake structures. Obtain the topography, tidal conditions, shoreline characteristics, and design dimensions, layout, intake flow rate, average design velocity, and intake depth of the deep intake structures of the power plant in the intake area. Establish a mathematical model of the flow field in the intake area, determine the simulation range, divide the computational grid, determine the boundary conditions and initial conditions of the flow field simulation, select appropriate computational parameters, select the calculation control tidal type, and simulate the flow field changes including the nuclear power plant intake structures and the sea area affected by the intake.

[0041] The governing equations for the flow field calculation are as follows:

[0042]

[0043] Where: u is the time-averaged velocity, m / s; t is time, s; p is pressure, pa; ρ is the density of water, kg / m³. 3 μ eff ρ is the turbulent effective viscosity, Pa·s; k is the turbulent kinetic energy, m. 2 / s 2 I is a second-order unit tensor, α k Let ε be the Prandtl number of turbulent kinetic energy, ε be the turbulent dissipation rate, and m be the turbulent kinetic energy. 2 / s 3 ;α ε G is the Prandtl number, representing the turbulent dissipation rate. k C represents the turbulent kinetic energy production term caused by the average velocity gradient. 1ε and C 2ε C is a constant coefficient. 1ε =1.42, C 2ε =1.68.

[0044] Step 2: Verify the flow field model based on experimental results from the physical model: Construct a normal scale physical model of the deep water intake structure in an indoor experimental water tank. Measure the flow velocity and direction at each characteristic section or point and compare the results with the simulation results of the mathematical model to ensure that the calculated results of the flow field model are basically consistent with the experimental results of the physical model. That is, the simulation results of the flow field model can reflect the distribution characteristics of the deep water intake flow field. The simulated values ​​and the measured values ​​in the model agree well, meaning that the constructed mathematical model can reflect the basic characteristics of the changes in the water intake flow field. Based on this, the characteristics of the water intake flow of the deep water intake structure and the estimation of the water intake boundary layer can be carried out.

[0045] The physical model established in the laboratory must meet the following principles: it must meet the requirements of flow field similarity, and the inlet and outlet sections of the model must have sufficient transition areas to ensure similarity between inlet and outlet flows; the model design should be based on gravity similarity, while also taking into account requirements such as resistance similarity and buoyancy similarity; to ensure that the flow pattern of the model is similar to that of the prototype, the Reynolds number of the model flow must be greater than the critical Reynolds number to ensure that the water in the model enters the self-simulation zone; a large-scale normal physical model of 1:100 is usually used to mainly simulate the environmental flow and the water intake process of water intake structures.

[0046] Step 3, Analysis of water intake characteristics and flow field of deep water intake structures: Based on the simulation results of the validated flow field model, conduct an analysis of the water intake characteristics of deep water intake structures and the impact of water intake on the environmental water body, and provide a basis for setting the particle delivery control conditions in Step 4.

[0047] Deep water intake structures have relatively little impact on the surface or upper layers of water bodies. However, the environmental flow in the middle and lower layers and near the bottom of the water body is affected by the obstruction of the water intake structure and the combined influence of water intake confluence. The environmental flow is prone to varying degrees of deflection and aggregation, and the changes in the environmental flow field are more significant closer to the water intake structure. The flow field distribution around the water intake structure is relatively complex. Direct water intake or inflow is obvious on the upstream inflow surface (i.e., the facing surface) of the inflow window, while the flow field on the downstream inflow surface (i.e., the back surface) is complex. When the average water intake velocity is greater than the environmental velocity, there is obvious inflow on the back surface; when the average water intake velocity is close to the environmental velocity, there is slight inflow on the back surface; and when the average water intake velocity is less than the environmental velocity, there is basically no inflow on the back surface.

[0048] Step 4, Boundary layer analysis of deep water intake structures based on discrete particle tracing:

[0049] Based on the flow field simulation results, discrete particle tracing calculations are performed, and the governing equations for particle motion are as follows:

[0050]

[0051] Where m is the mass of the particle (kg); v is the velocity of the particle (m / s); F is the net force acting on the particle in the flow field, including the drag force of the water flow, the gravity of the particle, and buoyancy, etc. (N); and x is the displacement of the particle (m). In the tracer calculation, the particle is simplified to a moving point mass, i.e., the mass of the particle and the resulting forces in the flow field are not considered, i.e., m = 0. The tracer calculation uses... When simulating particle motion, the tracer trajectory of a particle can be described as follows:

[0052]

[0053] Where: x(t) is the position of the particle at time t, in meters; x(t+Δt) is the position of the particle at time t+Δt, in meters; Let be the displacement of the particle during time Δt, in meters (m).

[0054] Calculation process:

[0055] Particle delivery: Uniform, one-time, instantaneous delivery at the characteristic cross-section.

[0056] Based on the characteristics of water intake flow from deep water intake structures and the results of flow field analysis, particle placement control conditions were set, including the initial placement position, placement width, and placement water depth. Initial placement position setting: Based on flow field analysis results, the placement position was set to ensure that the environmental inflow (i.e., the environmental flow field) at that location (section) was not affected by the water intake structure; that is, at the initial placement moment, the particles could be evenly distributed. Placement width setting: Based on the analysis results of the characteristics of water intake flow from deep water intake structures, the placement width was set to ensure that the cross-sectional width was sufficiently wide; that is, the placed particles could completely cover the influence range of the water intake structure in the horizontal width direction. Placement depth: Particles were placed at different water depths with the depth intervals as small as possible, for example, 0.1m, to obtain the particle tracer trajectories in the horizontal (i.e., width) and vertical (i.e., water depth) directions.

[0057] Step 5, Determination of the water intake boundary layer for deep water intake structures:

[0058] In the vertical direction of the incoming environmental flow, analyzing the tracer trajectories of the particles, the maximum envelope of the tracer particles that can enter the intake structure is the intake boundary layer of the intake structure under the current condition. Specifically: in the vertical direction of the incoming environmental flow, the maximum width of the tracer particles entering the intake structure is the maximum width of the intake influence; in the vertical direction of the incoming environmental flow, statistically analyzing the deployment depth, the maximum thickness of the tracer particles that can enter the intake structure is the maximum thickness of the intake influence. Where the initial particle position is at the upper edge of the intake structure (i.e., above the inflow window), the corresponding thickness is the influence thickness above the upper edge of the intake structure, denoted as S. up The initial position of the particles is at the lower edge of the intake structure (i.e., below the inflow window), and the corresponding thickness is the influence thickness below the lower edge of the intake structure, denoted as S. down The height of the inlet window of the water intake structure is denoted as D; the vertical influence thickness of the deep water intake structure is S. total For: S total =S up +D+S down .

[0059] Where S upThe minimum submersion depth is a crucial design parameter for water intake structures. Its engineering significance lies in the fact that the intake of pressurized water diversion projects (water intake projects, such as tunnels) requires a certain submersion depth to prevent air-carrying vortices from entering the intake structure and causing harmful engineering safety issues like cavitation. When the depth of the intake structure above the water surface exceeds the minimum submersion depth, such harmful engineering problems are less likely to occur.

[0060] S total This refers to the height (thickness) of the water layer from which biological or debris sources need to be controlled in the vertical direction for deep water intake structures, i.e., the key control area in the direction of safe water depth for nuclear power cold sources.

[0061] The intake boundary layer characterizes the maximum area of ​​environmental water body affected by a deep water intake structure in the direction perpendicular to the water flow. The intake boundary layer range is drawn based on the maximum envelope of the initial positions of all tracer particles entering the intake structure in the direction perpendicular to the environmental flow, as described in step 5. Its engineering significance lies in the fact that organisms within this envelope are easily affected by water intake and enter the water intake system, thus impacting water intake safety. The intake boundary layer envelope area can characterize the maximum area of ​​environmental water body affected by a deep water intake structure in the direction perpendicular to the water flow; its estimation formula is as follows:

[0062]

[0063] In the formula: A is the area of ​​the water intake boundary layer envelope in the direction perpendicular to the environmental inflow, in m³. 2 H represents the ambient water depth (m); h represents the particle placement depth (m); and B' represents the horizontal envelope width of the corresponding particle placement depth (m). The water intake boundary layer envelope area can be used as an indicator to judge the degree of water intake impact; that is, the smaller the water intake boundary layer envelope area, the smaller the corresponding water intake impact.

[0064] The estimation method described in this embodiment is applicable to the estimation of the water intake boundary layer for deep water intake structures with different topography, tidal currents and different forms. For ease of explanation, the following assumes the same topography, tidal current conditions and the same water intake, and only considers the different forms of deep water intake structures.

[0065] The following two application examples illustrate the method described in this embodiment.

[0066] Environmental currents in the water intake area: Tidal conditions: reciprocating flow along the coast, with an environmental current velocity of 0.3 m / s. Since the water intake structures under study (funnel-shaped deep water intake structures and pier-shaped deep water intake structures) are symmetrical along their central axis, the reciprocating flow causes symmetry in the flow field regardless of whether it is high or low tide. That is, the flow field at high or low tide is symmetrical along the central axis of the water intake structure. Therefore, this application example only calculates the high tide or unidirectional flow situation; Shoreline: straight shoreline; Seabed topography is taken as an example with a water depth of 10 m.

[0067] Application Example 1:

[0068] Estimation of the water intake boundary layer for funnel-shaped deep water intake structures.

[0069] The funnel-shaped water intake method is a bottom-level water intake along the shore. One nuclear power plant uses a funnel-shaped water intake structure for water intake. The water inflow method is lateral horizontal flow. The simplified structure and dimensions of the water intake structure are as follows: the length of the funnel opening w1 in the downstream direction is 33 meters (see...). Figure 2 The vertical height h1 of the inlet window is 5 meters, the dimensions of the funnel-shaped inlet culvert are 33×5m, and the height h2 of the lower edge of the inlet from the seabed is 1 meter. The height h4 of the intake pipe (culvert) is 5m. The water intake direction is perpendicular to the environmental flow direction, and the intake flow rate is considered based on one unit's intake flow rate, i.e., 50m³ / h. 3 Based on the existing intake structures of nuclear power plants, the average inflow velocity controlled by the intake structures is 0.3 m / s, and the effective inflow area is approximately 167 m². 2 The uniform inflow effect of the funnel-shaped inlet is generalized by appropriately increasing the depth of the inlet dredging into the solid land on the shore. The inward extension of the funnel depth is taken as 200m (in actual projects, a long pipeline can be used instead). The funnel is designed for water intake close to the shore and is arranged close to the shore. The funnel is dug into the solid land on the shore, with a vertical inlet. The inlet height takes into account bottom sand prevention, and a siltation depth of 1m is set (i.e., the height of the bottom edge of the window above the seabed must be ≥1m). Considering a minimum submergence depth of 0.5m (calculated according to empirical formulas in existing specifications), the upper edge of the funnel inlet window must be ≥0.5m from the water surface, i.e., h3 must be ≥0.5m. In this example, h3 is 4m, and this design meets the requirements. The water intake boundary layer estimation process is as follows (flow process as follows). Figure 5 As shown):

[0070] Step 1: Establish a flow field model of the water intake area, including the marine environment and the funnel-shaped deep water intake structure (taking a full three-dimensional flow field model as an example): simulate the flow field changes including the deep water intake structure and the water intake-affected marine area, as well as the inflow situation of the funnel-shaped water intake structure.

[0071] A mathematical model of the flow field in the water intake area was established. The calculation area at the flare-shaped mouth of the shore was 400×100m. The calculation grid was divided, and the grid size in the near-field area of ​​the flare-shaped mouth was approximately 0.10m.

[0072] The boundary conditions and initial conditions for the flow field simulation are determined as follows: the environmental inflow adopts the velocity inlet boundary condition, the environmental outflow adopts the pressure outlet boundary condition, the seabed and shore wall adopt the no-slip boundary condition, the water surface adopts the free-slip boundary condition, and the funnel-shaped water intake adopts the velocity inlet boundary condition; the initial flow velocity is taken as the upstream inflow velocity, and the flow field simulation is carried out.

[0073] Step 2, verify the flow field model based on the experimental results of the physical model: establish a normal scale physical model of the deep water intake structure in the indoor experimental water tank. The scale is determined according to the experimental purpose and the specific conditions of the laboratory. Here the scale is 1:100.

[0074] The basic principles of physical model design are as follows:

[0075] 1) The similarity requirement of the flow field must be guaranteed;

[0076] 2) The model's inlet and outlet sections need sufficient transition areas to ensure similarity between inlet and outlet flows;

[0077] 3) The experiment was conducted based on a generalized, representative steady flow under conditions of water depth, velocity, and direction.

[0078] Based on the above analysis and in accordance with relevant regulations and standards, this test model must adopt a large-scale normal flume test model. The model design criteria and basic requirements are as follows:

[0079] The model design should primarily focus on gravity similarity, while also considering requirements such as drag similarity and buoyancy similarity.

[0080] Gravitational similarity criterion;

[0081] The buoyancy is similar.

[0082] Based on the above model similarity criteria, the model scale relationship is as follows:

[0083] Flow scale: Q r =L r 52 ;

[0084] Flow velocity scale:

[0085] Meanwhile, to ensure that the model flow pattern is similar to the prototype, the Reynolds number of the model water flow must be greater than the critical Reynolds number to ensure that the model water body enters the self-simulation region.

[0086] Electromagnetic current meters were used to measure the flow velocity and direction at characteristic points of the water intake structure, and the results were compared with those from flow field simulation. The comparison between the numerical model calculation and the flume experiment flow field results showed that the calculated values ​​and the measured values ​​were in good agreement. This indicates that the constructed mathematical model can reflect the basic characteristics of the water intake flow field changes, and can be used to analyze the water intake characteristics of deep water intake structures and estimate the water intake boundary layer.

[0087] Step 3, Intake characteristics and flow field analysis of funnel-shaped deep water intake structures:

[0088] Simulation results show that:

[0089] The ambient current flows uniformly, but due to the suction effect of the funnel-shaped inlet at the bank, the streamlines of different water layers exhibit varying degrees of deflection and aggregation near the funnel. The upper, middle, and bottom water layers are all affected to varying degrees. Concentrated water intake at the funnel results in lateral inflow from the bottom of the water body, leading to a relatively concentrated inflow; water intake has a certain impact on all water layers. In the upper water layer (<4m), the environmental flow is significantly deflected and accelerated near the funnel opening, and some water enters the intake manifold due to the vertical entrainment effect of the funnel opening. In the same water layer (4-9m) at the funnel opening, the streamline upstream of the funnel opening is significantly deflected. Due to the influence of the upstream side structure of the funnel opening, the mainstream is affected by the jet flow and accelerates into the intake manifold, resulting in a relatively concentrated inflow phenomenon in the intake manifold. The mainstream is deflected to the right (measured from the direction of water intake), and there is a certain amount of backflow on the left side. The flow field near the upper and lower edges of the funnel opening is relatively complex. Due to the obstruction of the shoreline, a certain range of weak backflow zone is formed near the surface and bottom layers (i.e., the upper and lower edges of the funnel opening) within the inflow window of the funnel opening.

[0090] Step 4, Boundary layer analysis of deep water intake structures based on discrete particle tracing:

[0091] Perform tracer calculations:

[0092] Particle delivery: Uniform, one-time, instantaneous delivery at the characteristic cross-section.

[0093] Release control conditions: Initial release location setting: Based on flow field analysis results, the release section is set 200m upstream of the water intake. At the initial release moment, the particles can be uniformly distributed, meeting the requirement that the environmental inflow at the release section is not affected by the water intake structure; Release width setting: Based on the analysis results of the water intake characteristics of deep water intake structures, when the release width is 100m, the released particles can completely cover the influence range of the water intake structure in the horizontal width direction; Release depth H d Particles are dropped into different water depths with the intervals between drops being as small as possible, for example, 0.1m, in order to obtain the tracer trajectories of the particles in the horizontal (i.e., width) and vertical (i.e., water depth) directions.

[0094] Based on the particle tracer trajectory, the number of particles that can enter the water intake system is counted, and the horizontal influence width of the funnel-shaped deep water intake structure is obtained, as shown in Table 1.

[0095] Table 1. Statistics on the impact of funnel-shaped deep water intake structures on water intake.

[0096]

[0097] Step 5: Determination of the water intake boundary layer for deep water intake structures:

[0098] Determination of the boundary layer of deep intake structures: In the direction perpendicular to the environmental inflow, the tracer trajectories of particles are analyzed. The maximum envelope of the tracer particles that can enter the intake structure is the deep intake boundary layer under this design condition. The maximum width of the tracer particles entering the intake structure in the direction perpendicular to the environmental inflow is the maximum width of the intake influence. In the direction perpendicular to the environmental inflow, the maximum thickness of the tracer particles that can enter the intake structure in the deployment depth direction is the maximum thickness of the intake influence. The thickness of particles initially positioned above the upper edge of the intake structure (i.e., above the inflow window) is the influence thickness above the upper edge of the intake structure, denoted as S. up The initial position of the particles is below the lower edge of the intake structure (i.e., below the inflow window), and the corresponding thickness is the influence thickness below the lower edge of the intake structure, denoted as S. down The height of the inlet window is denoted as D; the vertical influence thickness of the deep intake structure is S. total =S up +D+S down .

[0099] Where S up The minimum submersion depth is a crucial design parameter for water intake structures. Its engineering significance lies in the fact that pressurized water intake projects (such as tunnels) require a certain submersion depth at the inlet to prevent air-carrying vortices from entering the intake structure and causing harmful engineering safety issues such as cavitation. When the depth of the intake structure above the water surface exceeds the minimum submersion depth, such harmful engineering problems are less likely to occur.

[0100] In this example, S up =4m; D=5m; S down =1m; S total =S up +D+S down =10m.

[0101] The water intake boundary layer envelope area is 171.54 m². 2 The water boundary layer diagram is shown below. Figure 6 As shown ( Figure 6 The curved line at the front end of the funnel-shaped inlet is the water intake boundary layer envelope line.

[0102] The estimation results show that: S up The minimum flooding depth is 4m. If the cold source control is based on the minimum flooding depth (0.5m) in the water intake design code, it is easy to cause cold source threat events, which in turn will affect the safety and stability of the nuclear power plant's water intake.

[0103] Application Example 2: Estimation of the water intake boundary layer for bridge pier-type deep water intake structures.

[0104] The pier-type water intake method is an offshore bottom water intake. A power plant uses a pier-type deep water intake structure for water intake, with a double-sided intake method. The simplified structure and dimensions of the intake structure are as follows: The pier-type water intake structure has opposing windows (double-sided intake) in the downstream direction; the window length w2 is 17m; the intake structure width w3 is 6m; the intake window height h5 is 5m; the height h6 of the bottom edge of the window above the seabed is 1m; the minimum submersion depth is 0.5m (calculated based on empirical formulas in existing standards); the diameter d1 of the intake pipe (circular cross-section) is 5m. Figure 3 , 4 As shown.

[0105] The water intake area has a topographical depth of 10 meters. Based on the water intake flow rate of one generating unit, the water intake flow rate is 50 m³ / h. 3 / s, double-sided inflow, with the intake structure controlling the average inflow velocity to be 0.3 m / s. The height of the lower edge of the intake window from the seabed is set to account for bottom sand control, with a siltation depth of 1m, meaning the bottom edge of the window must be at least 1m above the seabed. A minimum submergence depth of 0.5m is considered (calculated using empirical formulas in existing standards), meaning the upper edge of the pier-type intake window must be at least 0.5m above the water surface, i.e., h7 must be at least 0.5m. In this example, h7 is 4m, and this design meets the requirements. The water intake boundary layer estimation process is as follows (flow process as follows). Figure 5 As shown):

[0106] Step 1: Establish a flow field model of the water intake area, including the marine environment and the bridge-pier type deep water intake structure (taking a full three-dimensional flow field model as an example): simulate the flow field changes including the deep water intake structure and the water intake-affected marine area, as well as the inflow situation of the bridge-pier type water intake structure.

[0107] A mathematical model of the flow field in the water intake area was established, and the simulation range of the bridge pier-type water intake structure was determined to be 600×200m. The calculation grid was divided, and the grid size inside the bridge pier and in the near zone was about 0.10m.

[0108] Determine the boundary conditions and initial conditions for the flow field simulation: the environmental inflow adopts the velocity inlet boundary condition, the environmental outflow adopts the pressure outlet boundary condition, the seabed bottom and the shore wall adopt the no-slip boundary condition, the water surface adopts the free-slip boundary condition, and the pier-type water intake inlet adopts the velocity inlet boundary condition; initial condition: the initial flow velocity is taken as the upstream inflow velocity, and the flow field simulation begins.

[0109] Step 2: Verify the flow field model based on experimental results from the physical model:

[0110] A normal scale physical model of a deep water intake structure was established in an indoor experimental water tank. The scale was determined according to the experimental purpose and the specific conditions of the laboratory. Here, the scale is 1:100.

[0111] The basic principles of physical model design are as follows:

[0112] 1) The similarity requirement of the flow field must be guaranteed;

[0113] 2) The model's inlet and outlet sections need to have sufficient transition areas to ensure that the inlet and outlet flows are similar.

[0114] 3) The experiment was conducted based on a generalized, representative steady flow under conditions of water depth, velocity, and direction.

[0115] Based on the above analysis and in accordance with relevant regulations and standards, this test model must adopt a large-scale normal flume test model. The model design criteria and basic requirements are as follows:

[0116] The model design should primarily focus on gravity similarity, while also considering requirements such as drag similarity and buoyancy similarity.

[0117] Gravitational similarity criterion;

[0118] The buoyancy is similar.

[0119] Based on the above model similarity criteria, the model scale relationship is as follows:

[0120] Flow scale: Q r =L r 52

[0121] Flow velocity scale:

[0122] Meanwhile, to ensure that the model flow pattern is similar to the prototype, the Reynolds number of the model water flow must be greater than the critical Reynolds number to ensure that the model water body enters the self-simulation region.

[0123] Electromagnetic current meters were used to measure the flow velocity and direction at characteristic points of bridge-pier type water intake structures, and the results were compared with those from flow field simulation. The comparison between the numerical model calculation and the flume experiment flow field results showed that the calculated values ​​and the measured values ​​were in good agreement. That is, the constructed mathematical model can reflect the basic characteristics of the water intake flow field changes, and can be used to analyze the water intake characteristics of deep water intake structures and estimate the water intake boundary layer.

[0124] Step 3, Analysis of water intake characteristics and flow field of bridge pier-type deep water intake structures:

[0125] Simulation results show that:

[0126] Pier-type water intake involves drawing water from the bottom of the water body, with the intake windows located on both sides of the intake structure. The ambient flow is uniform, but due to the suction effect of the bottom intake, the streamlines of different water layers in the surrounding water body are deflected and concentrated to varying degrees near the intake, affecting the upper, middle, and bottom water layers. Pier-type centralized water intake, with its dual-sided inflow, results in a relatively large intake flow rate, impacting water bodies of different depths, and exhibiting a difference in inflow between the near-shore and offshore sides. In the upper water layer (<4m), the environmental flow tends to deflect and concentrate near the pier-type water intake. Some water enters the water intake window due to the vertical entrainment effect of the water intake. In the same water layer as the water intake window (4-9m, with an inflow window length of 17m), the environmental flow is affected by the upstream pier-type diversion structure. The water flows into the water intake window from both sides. The upper flow field in the water intake cavity is relatively complex. The inflow mainly comes from the middle and lower layers. Vortex structures of different scales are easily formed near the upper edge of the pier water intake cavity and below the offshore inflow window.

[0127] Step 4, Boundary layer analysis of deep water intake structures based on discrete particle tracing:

[0128] Perform tracer calculations:

[0129] Particle delivery: Uniform, one-time, instantaneous delivery at the characteristic cross-section.

[0130] Release control conditions: Initial release location setting: Based on flow field analysis results, the release section is set 300m upstream of the water intake. At the initial release moment, the particles can be uniformly distributed, meeting the requirement that the environmental inflow at the section is not affected by the water intake structure; Release width setting: Based on the analysis results of the water intake characteristics of deep water intake structures, when the release width is 200m, the released particles can completely cover the influence range of the water intake structure in the horizontal width direction; Release depth H d Particles are dropped into different water depths with the intervals between drops being as small as possible, for example, 0.1m, in order to obtain the tracer trajectories of the particles in the horizontal (i.e., width) and vertical (i.e., water depth) directions.

[0131] Based on the particle tracer trajectory, the number of particles that can enter the water intake system is counted, and the horizontal influence width of the water intake of the bridge pier-type deep water intake structure is obtained, as shown in Table 2.

[0132] Table 2. Statistics on the impact of water intake on bridge pier-type deep water intake structures

[0133]

[0134]

[0135] Step 5: Determination of the water intake boundary layer for deep water intake structures:

[0136] In the vertical direction of the incoming environmental flow, analyzing the tracer trajectories of the particles, the maximum envelope of the tracer particles that can enter the intake structure is the deep intake boundary layer under this design condition. The maximum width of the tracer particles entering the intake structure in the vertical direction of the incoming environmental flow is the maximum width of the intake influence. In the vertical direction of the incoming environmental flow, statistically analyzing the deployment depth, the maximum thickness of the tracer particles that can enter the intake structure is the maximum thickness of the intake influence. The thickness of particles initially positioned above the upper edge of the intake structure (i.e., above the inflow window) is the influence thickness above the upper edge of the intake structure, denoted as S. up The initial position of the particles is below the lower edge of the intake structure (i.e., below the inflow window), and the corresponding thickness is the influence thickness below the lower edge of the intake structure, denoted as S. down The height of the inlet window is denoted as D; the vertical influence thickness of the deep intake structure is S. total =S up +D+S down .

[0137] Where S up The minimum submersion depth of the water intake structure is a crucial design parameter. Its engineering significance lies in the fact that pressurized water intake projects (such as tunnels) require a certain submersion depth at the inlet to prevent air-carrying vortices from entering the intake structure and causing harmful engineering safety issues such as cavitation. When the depth of the intake structure above the water surface exceeds the minimum submersion depth, such harmful engineering problems are less likely to occur.

[0138] In this example, S up =2.9m, D=5m, S down =1m, S total =Sup+D+S down =8.9m.

[0139] The water intake boundary layer envelope area is 169.14 m². 2 The water boundary layer diagram is shown below. Figure 7 As shown ( Figure 7 The curves surrounding the intake of the bridge pier type water inlet are the boundary layer envelope lines of the water intake.

[0140] The estimation results show that: S up The minimum flooding depth is 2.9m. If the cold source control is based on the minimum flooding depth (0.5m) in the water intake design code, it is easy to cause cold source threat events, which in turn will affect the safety and stability of the nuclear power plant's water intake.

[0141] Comparing the two types of deep water intake structures, if designed according to existing specifications, the design parameters such as the minimum inundation depth are the same. However, based on the estimated results of the water intake boundary layer, this is obviously unreasonable. The design needs to take into account the inflow characteristics of the water intake structure and the influence range of the water intake boundary layer.

[0142] Characteristics of the intake boundary layer in funnel-shaped water intake structures: Water intake has a certain impact on different water layers, with surface water being relatively less affected and mid-to-bottom water being more significantly affected. The intake boundary layer gradually increases in the horizontal direction with increasing depth, with the maximum horizontal impact occurring at the bottom of the water body. Water intake has a certain impact on surface water, and there is no minimum design submersion depth. During operation, it is necessary to monitor the air intake structure and connected pipes for air vortex phenomena and water aeration. The key control range for cold sources is 0-10m.

[0143] Characteristics of the water intake boundary layer of bridge pier-type water intake structures: The impact of water intake on different water layers varies. Shallow water layers are almost unaffected, near-surface water layers are less affected, and mid-to-bottom water layers are relatively more significantly impacted. The water intake boundary layer gradually increases in the horizontal direction with increasing depth, with the maximum horizontal impact range occurring at the bottom of the water body. The minimum design inundation depth is 2.9m, and the key control range for cold sources is 1.1-10m.

[0144] The area of ​​the water intake boundary layer (i.e., the range of water intake influence) is greater for pier-type water intake than for funnel-type water intake.

[0145] The impact range of water intake level (i.e., the weak point of water intake safety) is less than that of the flared mouth type.

[0146] Both the funnel-shaped and pier-shaped deep water intake methods have a large and dispersed impact range in the water depth direction. The safety of the water intake cold source should take into account the principle of "controlling the entire water depth and focusing on controlling the bottom layer of the water body".

[0147] Current standards only use empirical formulas to estimate the minimum inundation depth, which is only related to the average water intake velocity, the intake height, and its geometry. In the two application examples of this embodiment, the average water intake velocity is 0.3 m / s, the intake height is 5 m, and the intake cross-section is rectangular. Therefore, if the minimum inundation depth calculated by the above formula is 0.5 m, the water intake characteristics analysis of this embodiment reveals that the impact of these two water intake methods on the upper water body is significantly different. The current standards considering only three parameters, including water intake velocity, are unreasonable.

[0148] Finally, it should be noted that the above is only used to illustrate the technical solution of the present invention and not to limit it. Although the present invention has been described in detail with reference to the preferred arrangement, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solution of the present invention (such as the form of the water intake structure, the application of various formulas, the order of steps, etc.) without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for estimating the water intake boundary layer of a deep water intake structure of a power plant, characterized in that: The steps of the method described are as follows: Step 1, establish a three-dimensional water intake flow field model including the marine environment and deep water intake structures: establish a three-dimensional water intake flow field model including deep water intake structures, obtain the water intake marine terrain, environmental water flow conditions, shoreline characteristics, and the design size, water intake flow rate, water intake flow rate, and water intake depth of the deep water intake structure, establish a three-dimensional water intake flow field model, divide the calculation grid, determine the boundary conditions and initial conditions of the flow field simulation, and select appropriate calculation parameters to simulate the flow field changes including the deep water intake structure and the water intake-affected sea area; the flow field calculation control equation is as follows: Where: u is the time-averaged velocity, t is time, p is pressure, ρ is water density, μ eff is the turbulent effective viscosity, k is the turbulent kinetic energy, I is the second-order unit tensor, α k is the turbulent kinetic energy Prandtl number, ε is the turbulent dissipation rate, α ε is the turbulent dissipation rate Prandtl number, G k is the term for turbulent kinetic energy caused by the average velocity gradient, C 1ε and C 2ε is a constant coefficient, and its values ​​are 1.42 and 1.68 respectively; Step 2, verify the flow field model based on the physical model experimental results: construct a normal scale physical model of the deep water intake structure in the indoor experimental water tank, measure the flow velocity and flow direction of each characteristic section or characteristic point, and compare and verify with the simulation results of the mathematical model to ensure that the calculation results of the flow field model are basically consistent with the physical model experimental results, that is, the flow field model simulation results can reflect the distribution characteristics of the deep water intake flow field; Step 3, deep water intake structure water inflow characteristics and flow field analysis: Based on the simulation results of the verified flow field model, conduct a characteristic analysis of the deep water intake structure water inflow characteristics and the impact of water intake on the environmental water body, and provide a basis for setting the particle delivery control conditions in step 4; Step 4: Analysis of the water intake boundary layer of deep water intake structures based on discrete particle tracing: Based on the flow field simulation results, discrete particle tracing calculations are performed, and the control equation for particle motion is: Where: m is the mass of the particle; v is the velocity of the particle; F is the resultant force on the particle in the flow field; x is the displacement of the particle; when performing tracer calculations, the particle is simplified to a moving particle, that is, the mass of the particle and the resulting force in the flow field are not considered, that is, m = 0; when performing tracer calculations, To simulate the particle motion, the tracking trajectory of a particle can be expressed as: Where: x(t) is the position of the particle at time t; x(t+△t) is the position of the particle at time t+△t; The displacement of particles in time; Calculation process: Particle delivery: uniform one-time instant delivery at characteristic sections; The particle placement control conditions are set based on the characteristics of the water inflow of the deep water intake structure and the flow field analysis results, including the initial position of the particle placement, the placement width and the placement water depth; the initial position of the particle placement is set: based on the flow field analysis results, to ensure that the environmental flow at this position is not affected by the water intake structure, that is, at the initial moment of placement, the particles can be evenly distributed; the placement width is set: based on the analysis results of the characteristics of the water inflow of the deep water intake structure, to ensure that the section width is wide enough; the placement depth: the particles are placed at different water depths, and the interval between the water depths is as small as possible to obtain the horizontal and vertical tracking trajectories of the particles; Step 5, determination of the water intake boundary layer of the deep water intake structure: In the direction of vertical environmental flow, the tracer trajectory of the particles is analyzed. The maximum envelope range of the tracer particles that can enter the water intake structure is the water intake boundary layer of the deep water intake structure under the current situation, among which: in the direction of vertical environmental flow, the maximum width of the tracer particles entering the water intake structure is the maximum width of water intake impact; in the direction of vertical environmental flow, the maximum thickness of the tracer particles that can enter the water intake structure in the direction of statistical placement depth is the maximum thickness of water intake impact, among which, the initial position of the particles is at the upper edge of the water intake structure, and the corresponding thickness is the impact thickness above the upper edge of the water intake structure, recorded as S up , the initial position of the particle is at the lower edge of the water intake structure, and the corresponding thickness is the impact thickness below the lower edge of the water intake structure, denoted as S down ; The height of the inflow window of the water intake structure is recorded as D; The vertical influence thickness of the deep water intake structure is S total For: S total =S up +D+S down ; The water intake boundary layer envelope area can characterize the maximum area of ​​the environmental water body affected by the deep water intake structure in the direction perpendicular to the water flow. The estimation formula is: Where: A is the envelope area of ​​the water boundary layer in the direction perpendicular to the environmental flow; H is the environmental water depth; h is the particle placement depth; B' is the envelope width in the horizontal direction corresponding to the particle placement depth.

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