Estimation Method for Intake Boundary Layer and Its Characteristic Values of Mushroom-Type Water Intake Structure in Power Plant

Abstract

The present invention relates to a method for estimating the intake boundary layer and its characteristic values of a mushroom-shaped water intake structure in a power plant, including: establishing a three-dimensional flow field model of the water intake sea area including the mushroom-shaped water intake structure; verifying the flow field model based on the results of physical model experiments; analyzing the intake flow characteristics and flow field of the mushroom-shaped water intake structure; analyzing the boundary layer of the mushroom-shaped water intake structure based on discrete particle tracing; identifying the key factors affecting the intake boundary layer of the mushroom-shaped water intake structure; constructing a rapid estimation formula for the characteristic values and key design parameters of the intake boundary layer of the mushroom-shaped water intake structure. When using the mushroom-shaped deep water intake structure for water intake, the present invention estimates the intake boundary layer for the influence range of the water body in the intake environment, determines the characteristics of the influence of the mushroom-shaped deep water intake structure on the environmental water body, and comprehensively considers multiple factors such as the intake flow characteristics of the mushroom-shaped water intake and the changes in the environmental flow field, providing a basis for the influence range of the mushroom-shaped water intake structure on the water body.

Description

Technical Field

[0001] The present invention relates to a method for estimating the water intake boundary layer and its characteristic values of a mushroom-shaped water intake structure in a power plant, which is a hydraulic calculation method and a method for estimating the influence range of water intake on the surrounding environmental water body when a power plant uses a deep water intake structure for water intake. Background Art

[0002] Deep water intake in a power plant generally refers to building a water intake structure at the bottom of a riverbed or seabed with a relatively large water depth. The water intake structure is connected to the water intake pump house of the power plant through pipelines or diversion tunnels, that is, the water intake structure takes water from the bottom of the water area with a relatively deep water depth. This method can effectively avoid directly taking the surface water with rich organisms and control and reduce the risk of cold source safety at the source. When a power plant adopts the deep water intake method, generally a mushroom head at the bottom layer of the water body is used for water intake, and the water intake mushroom head is connected to the pump house through a diversion tunnel (culvert). This water intake method can generally eliminate the influence of offshore waves through the resistance of the water intake mushroom head and the diversion pipeline (long enough) without additional wave dissipation measures, but the disadvantage of this water intake method is that the head loss is relatively large. Due to the increase in the water intake of power plants and the development of construction technology, in large and medium-sized power plants designed after the 1970s and 1980s, mushroom head water intake is widely used, and the mushroom head water intake method has become a more widely used method in deep water intake.

[0003] However, the current design specifications related to the deep water intake method are relatively empirical, or in the design process, relevant regulations of other industries such as hydropower are compared and implemented. In the design, the key design parameters such as the minimum submerged depth of water intake are proposed empirically and lack relevant theoretical support. The existing method only estimates the minimum submerged depth using an empirical formula, and the minimum submerged depth is only related to the average flow velocity of water intake, the height of the water intake and its geometric shape. Through the analysis of water intake characteristics, it is found that there are obvious differences in the influence on the upper water body in different water intake sea areas and different mushroom head designs, that is, the situation of the minimum submerged depth of the mushroom head is complex, and it is unreasonable to only consider three parameters such as the water intake flow velocity in the current design. Moreover, the current design specifications and methods lack comprehensive consideration of factors such as large water intake flow of nuclear power, complex tidal conditions in the environmental water area, and the influence of marine organisms, and it is difficult to meet the higher requirements of nuclear power water intake safety and ecological operation. In order to clarify the influence range of the deep water intake structure of nuclear power on the environmental water body, it is urgent to propose a method for estimating the water intake boundary layer that comprehensively considers the operation characteristics of nuclear power water intake and the characteristics of deep water intake inflow, so as to quantify the influence of the operation of the deep water intake structure on the environmental water body, identify the key prevention and control areas of cold source safety, and select a deep water intake structure with less influence on the environmental water body as much as possible to ensure the safety and ecological friendliness of nuclear power water intake and provide technical support. Summary of the Invention

[0004] To overcome the problems of the existing technology, the present invention proposes a method for estimating the intake boundary layer and its characteristic values of a mushroom-shaped water intake structure in a power plant. The proposed method introduces the concept of the intake boundary layer, comprehensively considering the structural characteristics, inflow characteristics, water intake volume, environmental flow, etc. of the mushroom-shaped water intake structure, to clarify the impact of the mushroom-shaped water intake structure on the environmental water body, propose key design parameters for the mushroom-shaped water intake structure suitable for nuclear power water intake, and provide a scientific basis for determining the key scope of nuclear power cold source prevention and control, etc. The proposed method is applicable to both single and multiple mushroom-shaped water intakes.

[0005] The object of the present invention is achieved as follows: A method for estimating the intake boundary layer and its characteristic values of a mushroom-shaped water intake structure in a power plant, the steps of the method are as follows:

[0006] Step 1, establish a three-dimensional flow field model of the water intake sea area including the mushroom-shaped water intake structure: Establish a three-dimensional flow field model of the water intake sea area including the mushroom-shaped water intake structure, obtain the terrain of the water intake sea area, environmental water flow conditions, shoreline characteristics, as well as the design dimensions, water intake flow rate, water intake velocity, water intake depth, etc. of the mushroom-shaped water intake structure, establish a 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, and simulate the flow field changes including the mushroom-shaped water intake structure and the water intake affected sea area; The control equations for flow field calculation are as follows:

[0007]

[0008] Where: u is the time-averaged velocity, t is the time, p is the pressure, ρ is the water body 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 Prandtl number of turbulent kinetic energy, ε is the turbulent dissipation rate, α ε is the Prandtl number of turbulent dissipation rate, G k is the generation term of turbulent kinetic energy caused by the average velocity gradient, C 1ε and C 2ε are constant coefficients;

[0009] Step 2, verify the flow field model based on the physical model experiment results: Construct a normal-scale physical model of the mushroom-shaped water intake structure in an indoor experimental flume, measure the flow velocity and flow direction of each characteristic section or characteristic point, compare and verify with the simulation results of the mathematical model. If the calculated values are in good agreement with the measured values, it means that the constructed mathematical model can reflect the basic characteristics of the water intake flow field changes, and the estimation of the intake boundary layer can be carried out based on this;

[0010] Step 3, Analysis of the water intake inflow characteristics and flow field of the mushroom-shaped water intake structure: According to the simulation results of the verified flow field model, analyze the inflow characteristics of the mushroom-shaped water intake structure and the impact characteristics of water intake on the environmental water body, and provide a basis for setting the particle injection control conditions in Step 4;

[0011] Step 4, Boundary layer analysis of the mushroom-shaped water intake structure based on discrete particle tracking: Based on the flow field simulation results, perform discrete particle tracking calculations. The control equation for particle motion is:

[0012]

[0013] where: m is the mass of the particle, v is the particle's motion velocity, F is the resultant force acting on the particle in the flow field; x is the displacement of the particle; during the tracking calculation, the particle is simplified as a moving mass point, that is, the mass of the particle and the resulting force in the flow field are not considered, i.e., m = 0; during the tracking calculation, is used to simulate the particle motion, then the motion trajectory of any particle can be expressed as:

[0014]

[0015] 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, is the displacement of the particle within Δt time;

[0016] Calculation process:

[0017] Particle injection: Uniformly and instantaneously inject particles at one time at the characteristic cross-section;

[0018] Set the particle injection control conditions based on the inflow characteristics of the mushroom-shaped water intake structure and the flow field analysis results, including the initial injection position, injection width, and injection water depth of the particles: Initial injection position setting of particles: Based on the flow field analysis results, ensure that the environmental incoming flow at this position is not affected by the water intake structure, that is, at the initial injection moment, the particles can be evenly distributed; Injection width setting: Based on the analysis results of the water intake inflow characteristics of the deep water intake structure, ensure that the cross-section width is wide enough, that is, the injected particles can completely cover the influence range of the water intake structure in the horizontal width direction; Injection depth: Inject particles at different water depths, and the interval of injection water depths should be as small as possible to clarify the tracking trajectories of the particles in the horizontal and vertical directions;

[0019] Determination of the boundary layer of the mushroom - type water intake structure: In the direction perpendicular to the ambient flow, by analyzing the tracer trajectories of particles, the maximum envelope range composed of tracer particles that can enter the water intake head is the water intake boundary layer of the mushroom - type water intake structure. Among them: In the direction perpendicular to the ambient flow, the maximum width of the tracer particles entering the interior of the mushroom - type water intake structure is the maximum width of water intake influence; In the direction perpendicular to the ambient flow, by statistically analyzing the depth of injection, the maximum thickness of the tracer particles that can enter the interior of the mushroom - type water intake structure is the maximum thickness of water intake influence. Among them, for particles with an initial position at the upper edge of the mushroom - type water intake structure, the corresponding thickness is the influence thickness above the upper edge of the mushroom - type water intake structure, denoted as S up , for particles with an initial position at the lower edge of the mushroom - type water intake structure, the corresponding thickness is the influence thickness below the lower edge of the water intake structure, denoted as S down ; The height of the intake window of the water intake structure is denoted as D; The vertical influence thickness S total of the deep - layer water intake structure is: S total = S up + D + S down ;

[0020] The water intake boundary layer characterizes the maximum range in which the deep - layer water intake structure affects the ambient water body in the direction perpendicular to the water flow. The range of the water intake boundary layer is drawn based on the maximum envelope range of the initial positions of all tracer particles that enter the water intake structure in the direction perpendicular to the ambient flow in step 4. Its engineering significance is that organisms within this envelope range are vulnerable to being affected by water intake and entering the water intake system, thus affecting water intake safety.

[0021] The calculation formula for the envelope area of the water intake boundary layer is:

[0022]

[0023] In the formula: A is the envelope area of the water intake boundary layer in the direction perpendicular to the ambient flow; H is the ambient water depth; h is the depth of particle injection; B' is the envelope width in the horizontal direction corresponding to the depth of particle injection.

[0024] Step 5: Identification of key factors affecting the water intake boundary layer of the mushroom - type water intake structure:

[0025] Repeat steps 1 to 4, calculate the characteristic values of the water intake boundary layer of the mushroom - type water intake structure under different sea areas, different water intake conditions, and different mushroom design conditions, and accumulate data for identifying the key factors affecting the characteristic values of the water intake boundary layer;

[0026] Conduct pairwise correlation analysis between the characteristic values of each water intake boundary layer and each environmental factor and water intake structure design factor. The analysis formula is as follows:

[0027]

[0028] Among them, r is the correlation coefficient, and its range is [-1, 1]. If |r| = 1, it is a perfect correlation; if r = 0, there is no linear correlation; if -1 ≤ r < 0, it is a negative correlation; if 0 < r ≤ 1, it is a positive correlation; if 0 ≤ |r| ≤ 0.3, it is a weak correlation; if 0.3 < |r| ≤ 0.5, it is a low correlation; if 0.5 < |r| ≤ 0.8, it is a significant correlation; if 0.8 < |r| ≤ 1, it is a high correlation.

[0029] n is the number of cases for analysis; i is the i-th case, and x i is the value of the independent variable in the i-th case. is the average value of the independent variables of n cases; y i is the value of the dependent variable in the i-th case. is the average value of the dependent variables of n cases.

[0030] The method for identifying key factors is as follows: Take the independent variables corresponding to 0.5 < |r| < 1 as key factors.

[0031] Step 6: Construction of a rapid estimation formula for the characteristic values and key design parameters of the water intake boundary layer of the mushroom-shaped water intake structure:

[0032] Extract the key factors identified in Step 5. According to the basic correlation relationships among various physical quantities, use the simplest possible physical quantities and operation relationships to describe the changes of the independent variable and the dependent variable. Combine the results of numerical simulation and physical model tests, consider the manifestation of the key factors affecting the water intake boundary layer in the formula, and based on the principle of dimensional harmony, use multiple regression analysis to construct a regression relationship to construct the characteristic values of the water intake boundary layer of the mushroom-shaped water intake structure, that is, the key design parameters S up 、S down and if multiple mushroom heads are used in series for water intake, the minimum center spacing B min between adjacent mushroom head designs.

[0033] The advantages and beneficial effects of the present invention are as follows: When the mushroom - shaped deep - water intake structure is used for water intake, the intake boundary layer of the water body in the intake environment is estimated, and the influence characteristics of the mushroom - shaped deep - water intake structure on the environmental water body are determined, taking into account multiple factors such as the characteristics of deep - water intake inflow, the design characteristics of the intake structure, and the changes in the environmental flow field. The existing design specifications are more empirical, only proposing empirical estimation methods for design parameters such as the minimum submergence depth of the intake structure, without estimating the intake boundary layer, and ignoring the design of different intake structures, the characteristics of intake inflow, and the environmental flow field, etc. This is obviously unreasonable. The present invention combines the inflow characteristics of the mushroom - shaped intake structure, comprehensively considers the influence range of water intake, and proposes an estimation method for the intake boundary layer and rapid estimation formulas for multiple key characteristic parameters, providing a basis for clarifying the influence range of the operation of the mushroom - shaped deep - water intake structure on the environmental water body, designing the mushroom - shaped intake structure more scientifically and efficiently, and improving the safety of nuclear power water intake. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention will be further described below in conjunction with the drawings and embodiments.

[0035] Figure 1 is a schematic structural diagram of the mushroom - shaped water intake structure based on the method of the embodiment of the present invention;

[0036] Figure 2 is a schematic diagram of the water - intake mushroom head structure, the mushroom - head water - intake boundary layer and its characteristic values of the mushroom - shaped water intake structure based on the method of the embodiment of the present invention, and is Figure 1 an enlarged view of the circled part in

[0037] Figure 3 a flowchart of the method of the embodiment of the present invention;

[0038] Figure 4 a fitting curve of the minimum submergence depth of the mushroom - head design (i.e., the influence thickness above the upper edge of a single mushroom head caused by water - intake confluence) of the application example of the method of the embodiment of the present invention;

[0039] Figure 5 a fitting curve of the influence thickness below the lower edge of a single mushroom head caused by water - intake confluence of the method of the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] Embodiment:

[0041] This embodiment is an estimation method for the water - intake boundary layer and its characteristic values of the mushroom - shaped water - intake structure of a power plant. There are various types of deep - water intake structures, including: mushroom - shaped, pier - shaped, flared - mouth - shaped, etc. The method of this embodiment is based on the mushroom - shaped water - intake structure. The structure of the described mushroom - shaped water - intake structure is as Figure 1 、2 As shown in the figure, it includes: a water intake main pipe 1 lying horizontally buried in the riverbed or seabed, at least one riser pipe 2 arranged along the water intake main pipe, the upper end of the riser pipe protruding from the riverbed or seabed, and a water intake mushroom head 3 arranged at the top of the riser pipe. The water intake mushroom head is an erected cylindrical shape, and the diameter of the cylindrical shape is larger than that of the riser pipe. The lower edge of the water intake mushroom head is a flared opening 301 smoothly connected to the riser pipe, the upper edge is a top cover 302, and the middle part is a grid inlet window 303 surrounding a circle. Water enters the water intake mushroom head from the surrounding grid and then enters the riser pipe, as Figure 2 shown by the direction of arrow G in the figure.

[0042] The steps of the method are as follows, and the process is as Figure 3 shown in the figure:

[0043] Step 1, establish a three-dimensional flow field model of the water intake sea area including the mushroom head type water intake structure: The flow field model can establish a full three-dimensional flow field model or a layered three-dimensional flow field model, and a two-dimensional flow field model cannot be used. The following takes the full three-dimensional flow field model as an example: simulate the hydraulic changes of the surrounding environmental flow and the water intake situation of the water intake structure.

[0044] Establish a three-dimensional flow field model of the water intake sea area including the mushroom head type water intake structure, obtain the terrain, tidal current conditions, shoreline characteristics of the water intake sea area, as well as the design dimensions, layout methods, water intake flow rate, average designed water intake velocity, and water intake depth of the mushroom head type water intake structure of the power plant, establish a mathematical model of the flow field in the water intake sea area, determine the simulation range, 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 in the sea area including the nuclear power water intake structure and the water intake affected sea area.

[0045] The flow field calculation control equations are as follows:

[0046]

[0047] Where: u is the time-averaged velocity, m / s; t is the time, s; p is the pressure, pa; ρ is the water body density, kg / m 3 ; μ eff is the turbulent effective viscosity, pa·s; k is the turbulent kinetic energy, m 2 / s 2 ; I is the second-order unit tensor, α k is the Prandtl number of turbulent kinetic energy, ε is the turbulent dissipation rate, m 2 / s 3 ; α ε is the Prandtl number of turbulent dissipation rate, G k is the turbulent kinetic energy generation term caused by the average velocity gradient, C 1ε = 1.42, C 2ε = 1.68.

[0048] Step 2: Verify the flow field model based on the results of physical model experiments: Construct a normal-scale physical model of the mushroom-head water intake structure in an indoor experimental flume, measure the flow velocity and direction at each characteristic cross-section or characteristic point, compare and verify with the simulation results of the mathematical model. The calculated values are in good agreement with the measured values, indicating that the constructed mathematical model can reflect the basic characteristics of the water intake flow field changes, and the estimation of the water intake boundary layer can be carried out accordingly.

[0049] The physical model established in the laboratory shall conform to the following principles: It shall meet the requirements of flow field similarity. There shall be sufficient transition areas at the inlet and outlet sections of the model to ensure the similarity of inlet and outlet flows. The model design shall mainly be based on gravity similarity, taking into account requirements such as resistance similarity and water body buoyancy similarity. To ensure the similarity between the model flow pattern and the prototype, it is necessary to ensure that the Reynolds number of the model water flow is greater than the critical Reynolds number, and ensure that the model water body enters the self-similar region. Usually, a large-scale normal physical model with a scale of 1:100 is adopted, mainly to simulate the environmental flow and the water intake inflow process of the mushroom head.

[0050] Step 3: Analyze the water intake inflow characteristics and flow field of the mushroom-head water intake structure: According to the simulation results of the verified flow field model, carry out the analysis of the water intake inflow characteristics of the mushroom-head water intake structure and the influence characteristics of water intake on the environmental water body, etc., and provide a basis for setting the particle injection control conditions in Step 4.

[0051] The mushroom head belongs to near-bottom water intake, and has little influence on the water intake confluence of the upper layer of water. The environmental flow is affected by the combined influence of the mushroom head structure obstruction and water intake confluence in the middle and lower layers and near the bottom of the water body, and the environmental flow shows characteristics such as deflection and aggregation to varying degrees. Among them, the flow field change in the water area at the same layer as the water intake window of the mushroom head is more obvious.

[0052] The velocity distribution around the periphery of the water intake window of a single mushroom head is complex. Under different water depths and different average water intake velocities, the basic characteristics of the velocity distribution at the water intake window are as follows: The oncoming flow on the upstream side of the water intake window can directly enter the interior of the mushroom head. There is also water intake on both sides; the water intake on the backflow side is more complex. When the average water intake velocity is greater than the environmental velocity, there is an obvious water intake phenomenon on the backflow side; when the average water intake velocity is close to the environmental velocity, there is a slight water intake phenomenon on the backflow side; when the average water intake velocity is less than the environmental velocity, there is basically no water intake on the backflow side.

[0053] When multiple mushroom heads are connected in series for water intake, the water intake situation of each mushroom head is similar to that of a single mushroom head, and the change of environmental water depth has little influence on the water intake distribution, that is, under different environmental water depth conditions, the influence ranges of water intake of each mushroom head in the water depth direction and horizontal direction have little difference. The water intake characteristics of multiple mushroom heads are as follows: The oncoming flow on the upstream side of the water intake window can directly enter the interior of the mushroom head; there is also water intake on both sides; the water intake on the backflow side is more complex. The flow field of multiple mushroom heads shows a certain symmetry around the central mushroom head.

[0054] Step 4, Boundary layer analysis of the mushroom-shaped water intake structure based on discrete particle tracking: Based on the results of the flow field simulation, discrete particle tracking calculations are carried out. The control equation for particle motion is as follows:

[0055]

[0056] Where: m is the mass of the particle, kg; v is the particle's motion velocity, m / s; F is the resultant force acting on the particle in the flow field, including the drag force of the water flow, the gravity and buoyancy forces acting on the particle, etc., and x is the displacement of the particle, N. When performing the tracking calculation, the particle is simplified as a moving mass point, that is, the mass of the particle and the forces acting on it in the flow field caused by this are not considered, that is, m = 0. When performing the tracking calculation, is used to simulate the particle motion, then the motion trajectory of any particle can be expressed as:

[0057]

[0058] Where: x(t) is the position of the particle at time t, m; x(t + Δt) is the position of the particle at time t + Δt, m; is the displacement of the particle within Δt time, m.

[0059] Calculation process:

[0060] Particle release: Uniformly release all particles instantaneously at the characteristic cross-section.

[0061] Based on the inflow characteristics of the mushroom-shaped water intake structure and the results of the flow field analysis, particle release control conditions are set, including the initial release position, release width, and release water depth of the particles. Setting of the initial particle release position: Based on the results of the flow field analysis, ensure that the ambient incoming flow (i.e., the ambient flow field) at this position (cross-section) is not affected by the water intake structure. That is, at the initial release moment, the particles can be evenly distributed; Setting of the release width: Based on the analysis results of the inflow characteristics of the deep water intake structure, ensure that the cross-section width is wide enough. That is, the released particles can completely cover the influence range of the water intake structure in the horizontal width direction; Release depth: Release particles at different water depths, and the interval of the release water depth should be as small as possible, such as 0.1 m, to clarify the tracking trajectories of the particles in the horizontal (i.e., width) and vertical (i.e., water depth) directions.

[0062] Determination of the boundary layer of the mushroom - head water intake structure: In the direction perpendicular to the ambient flow, by analyzing the tracer trajectories of particles, the maximum envelope range composed of the tracer particles that can enter the water intake head is the water intake boundary layer of the mushroom - head water intake structure in this design case. Among them: In the direction perpendicular to the ambient flow, the maximum width of the tracer particles entering the inside of the mushroom - head water intake structure is the maximum width of the water intake influence; In the direction perpendicular to the ambient flow, by statistically analyzing the depth direction of particle injection, the maximum thickness of the tracer particles that can enter the inside of the mushroom - head water intake structure is the maximum thickness of the water intake influence. Among them, for the particles with the initial position above the upper edge of the mushroom - head water intake structure (i.e., above the intake window), the corresponding thickness is the influence thickness above the upper edge of the mushroom - head water intake structure, denoted as S up ; For the particles with the initial position below the lower edge of the mushroom - head water intake structure (i.e., below the intake window), the corresponding thickness is the influence thickness below the lower edge of the water intake structure, denoted as S down ; The height of the intake window of the water intake structure is denoted as D; The vertical influence thickness S total of the deep - layer water intake structure is: S total = S up + D + S down .

[0063] The water intake boundary layer characterizes the maximum range of the deep - layer water intake structure affecting the ambient water body in the direction perpendicular to the water flow. The range of the water intake boundary layer is drawn based on the maximum envelope range of the initial positions of all tracer particles entering the water intake structure in the direction perpendicular to the ambient flow in step 4. Its engineering significance is that the organisms within this envelope range are easily affected by the water intake and enter the water intake system, thus affecting the water intake safety.

[0064] The calculation formula for the envelope area of the water intake boundary layer is:

[0065]

[0066] In the formula: A is the envelope area of the water intake boundary layer in the direction perpendicular to the ambient flow, m 2 ; H is the ambient water depth, m; h is the particle injection depth, m; B’ is the envelope width in the horizontal direction corresponding to the particle injection depth, m, as Figure 2 shown. The smaller the envelope area of the water intake boundary layer, the relatively smaller the impact of the water intake on the ambient water body.

[0067] Step 5: Identification of the key factors affecting the water intake boundary layer (maximum width and thickness in the water depth direction) of the mushroom - head water intake structure.

[0068] Repeat steps 1 to 4 to calculate the characteristic values of the intake boundary layer of the mushroom-shaped intake structure under different sea areas, different water intake conditions, and different mushroom head design conditions (i.e., the maximum width, maximum thickness, the influence thickness above the upper edge of the intake structure, and the influence thickness below the lower edge, etc.), and accumulate a certain amount of data to identify the key factors affecting the characteristic values of the intake boundary layer.

[0069] The factors affecting the mushroom head intake boundary layer are complex, such as the mushroom head structure (diameter, height of the inlet window), water intake operation (designed average intake flow velocity), and environmental flow (environmental flow velocity, environmental water depth), etc.

[0070] Perform pairwise correlation analysis on each characteristic value of the intake boundary layer (referred to as the dependent variable) and each environmental factor and design factor (such as environmental water depth, mushroom head intake flow velocity, mushroom head diameter, etc.) (referred to as the independent variable). The analysis formula is as follows:

[0071]

[0072] Among them, r is the correlation coefficient, and its range is [-1, 1]. If |r| = 1, it is a perfect correlation; if r = 0, there is no linear correlation; if -1 ≤ r < 0, it is a negative correlation; if 0 < r ≤ 1, it is a positive correlation; if 0 ≤ |r| ≤ 0.3, it is a weak correlation; if 0.3 < |r| ≤ 0.5, it is a low correlation; if 0.5 < |r| ≤ 0.8, it is a significant correlation; if 0.8 < |r| ≤ 1, it is a high correlation.

[0073] n is the number of cases for analysis, i is the i-th case, that is, the n cases obtained by repeating steps 1 to 4; x i is the value of the independent variable (characteristic value of the intake boundary layer, such as the influence thickness above the upper edge of the mushroom head, the influence thickness below the lower edge of the mushroom head, etc.) in the i-th case, is the average value of the independent variables of n cases; y i is the value of the dependent variable in the i-th case, is the average value of the dependent variables of n cases.

[0074] The method for identifying the key factors is: take the independent variable corresponding to 0.5 < |r| < 1 as the key factor.

[0075] The correlation analysis results of the mushroom head show that: water depth, designed mushroom head intake flow velocity have a significant positive correlation with the influence thickness; mushroom head diameter, environmental flow velocity, and height of the mushroom head inlet window have a significant negative correlation with the influence thickness.

[0076] Step 6: Construction of a rapid estimation formula for the characteristic values of the intake boundary layer of the mushroom-shaped intake structure and key design parameters (estimation of design characteristic values, Figure 2 The dotted line in indicates the envelope range of the mushroom head intake boundary layer and the schematic diagram of its characteristic values):

[0077] The key influencing factors identified in Step 5 are: water depth, designed flow velocity of the mushroom head water intake, mushroom head diameter, ambient flow velocity, and height of the intake window of the mushroom head. The influence of the mushroom head water intake in the water depth direction may include: the influence thickness S above the upper edge of the intake window due to water intake; the influence thickness S below the lower edge of the intake window due to water intake; the overall influence thickness S in the water depth direction, etc. Among them, the influence thickness above the upper edge of the intake window due to the mushroom head water intake, that is, the minimum submergence depth, is one of the key parameters in the design of the mushroom head. up ; the influence thickness S below the lower edge of the intake window due to water intake down ; the overall influence thickness S in the water depth direction due to water intake total and so on. Among them, the influence thickness above the upper edge of the intake window due to the mushroom head water intake, that is, the minimum submergence depth, is one of the key parameters in the design of the mushroom head.

[0078] In this embodiment, during the fitting process of the influence thickness formula of the mushroom head, based on the basic correlation between physical quantities, the simplest physical quantities and operation relationships are used to describe the changes of independent variables and dependent variables. Combining the results of numerical simulation and physical model tests, considering the manifestation of key factors affecting the intake boundary layer in the formula, physical quantities such as water intake depth, the ratio of water intake flow velocity to ambient flow velocity, and the equivalent hydraulic diameter of the intake area of the mushroom head water intake are taken into account. Based on the principle of dimensional harmony, a regression relationship is constructed using multiple regression analysis, and the fitting formula is as follows:

[0079]

[0080] Where: S up is the designed minimum submergence depth, that is, the influence thickness above the upper edge of a single mushroom head caused by water intake confluence, m (as shown in Figure 2 ); V is the designed flow velocity of the mushroom head water intake, m / s; U is the ambient average flow velocity, m / s; d is the mushroom head diameter, m; D is the height of the intake window of the mushroom head; a and b are fitting constants, a = 0.29, b = 0.60; the fitting curve is as shown in Figure 4 .

[0081]

[0082] Where: S down is the influence thickness below the lower edge of a single mushroom head caused by water intake confluence, m (as shown in Figure 2 ); a' and b' are fitting constants, a' = 0.80, b' = 1.28. The fitting curve is as shown in Figure 5 .

[0083] The maximum thickness S of the influence of the mushroom head in the water depth direction total = S up + D + S down . It represents the thickness of the water layer from which biological or debris sources that need to be mainly controlled in the vertical direction due to the mushroom head water intake, that is, its control range can be considered based on the maximum depth of the influence of the mushroom head in the water depth direction.

[0084] Currently, when designing the mushroom head, the GORDON formula is mainly used to calculate the minimum submergence depth of the water intake according to the "Code for Design of Intakes of Hydropower Stations" (DL / T 5398-2007) and the "Code for Design of Intakes of Water Resources and Hydropower Projects" (SL 285-2003). The engineering significance of the minimum submergence depth: The intake of pressure water diversion projects (such as tunnels) requires a certain submergence depth to avoid the entry of entrained air vortices into the water intake project, causing harmful engineering safety problems such as cavitation. When the depth of the water intake structure from the water surface is greater than the minimum submergence depth, such harmful engineering problems are not likely to occur.

[0085] S up Comparison of the estimation formula with the estimation results of the traditional GORDON formula: S up The estimated results are generally greater than the estimated results of the GORDON formula (the estimated results of the minimum submergence depth). That is, in the case of the mushroom head water intake method, the GORDON formula cannot give an adequate safety submergence depth. It is more appropriate to use this estimation formula for estimating and analyzing the requirements of the minimum submergence depth of the mushroom head and the safety prevention of the water cooling source.

[0086] Engineering significance: When designing a mushroom head type water intake structure, it can be considered that the submergence depth under the most unfavorable working conditions of the mushroom head (that is, the distance from the top cover of the mushroom head to the water surface) needs to be greater than S up , to ensure that no harmful engineering problems such as suction vortices occur during the operation of the mushroom head water intake. When designing the safety protection range of the mushroom head water intake, a depth of at least S total needs to be considered, that is, more than 50% of marine organisms or foreign objects may enter the water intake system from this depth, and key prevention is required, and comprehensive prevention is also considered in combination with biological characteristics.

[0087] When multiple mushroom head type water intake structures take water in series, the designed minimum center distance B between adjacent mushroom heads min Estimation:

[0088] The influence width of the mushroom head water intake in the horizontal direction is an important basis for determining the distance between mushroom heads. When designing the distance between water intake mushroom heads, the entrainment superposition effect caused by multiple mushroom head water intakes should be avoided as much as possible.

[0089] The average incoming water flow in the water body in the space environment corresponding to adjacent mushroom heads (the water body within the center distance between adjacent mushroom heads and within the influence thickness of the mushroom head water intake) should be not less than the water intake of a single mushroom head. That is, it is required that the adjacent mushroom head center distance B (the distance between the center axes of the mushroom heads, as shown in Figure 1 ) is not less than B min (the width of the boundary layer of the mushroom head water intake, as shown in Figure 2 ) with the requirement that B > B min .

[0090] The influence of mushroom head water intake on the same layer of the inflow window is significant, and there is also a certain influence above the upper edge and below the lower edge of the mushroom head. Refer to the maximum thickness S of the influence of the mushroom head in the water depth direction. total Based on the estimation formula of min the following estimation formula of B is proposed:

[0091]

[0092] Where: B min is the minimum designed center spacing between adjacent mushroom heads, in m; Q is the water intake of a single mushroom head, in m 3 / s.

[0093] During the design of the water intake structure, in order to avoid the entrainment superposition effect caused by the water intake of multiple mushroom heads, the minimum designed center spacing of the mushroom heads needs to be greater than the maximum width of the influence of the mushroom head water intake in the horizontal direction.

[0094] During the design of deep water intake, the influence of this water intake method on the environmental water body can be judged based on the estimation results of the mushroom head water intake boundary layer and its characteristic values, and a design with less impact on the environmental water body should be adopted as much as possible (the estimation result of step 4, and the envelope area of the water intake boundary layer should be as small as possible).

[0095] During the design of deep water intake, the safety of the structure and the safety prevention of the cooling water source for water intake need to be specifically considered, and the characteristic values of the water intake boundary layer are estimated. Based on the estimation results of the mushroom head water intake boundary layer, that is, S up 、S down 、S total and the envelope area of the water intake boundary layer and other indicators to judge the depth range that needs to be key protected and the impact on the environmental water body of this water intake method, and a design with a relatively concentrated protection range (that is, S up 、S down 、S total is relatively small) and less impact on the environmental water body (that is, A) should be adopted as much as possible. When arranging the depth of the mushroom head in the water depth direction of the water body, the submerged water depth of the upper edge of the mushroom head inflow window needs to be greater than S up to ensure that no harmful suction vortices are generated during water intake operation and reduce the impact of cavitation on the water intake structure; when using multiple mushroom heads in series for water intake, the design needs to consider the spacing between each mushroom head, and the center spacing between adjacent mushroom heads is not less than B min to reduce the entrainment superposition effect caused by the water intake of multiple mushroom heads.

[0096] Application example:

[0097] The estimation method described in this embodiment is applicable to the estimation of the water intake boundary layer of different terrains, tides, and single and multiple mushroom head type water intake structures. For the convenience of explanation, the following uses the specific data of the application example to illustrate. Considering the same terrain, tide conditions and the same water intake volume, etc., only the changes in the design size and number of mushroom heads are considered.

[0098] Environmental flow in the water intake sea area:

[0099] Tidal current condition: Alongshore reciprocating current, the environmental flow velocity in the sea area is 0.3 m / s; Shoreline: Straight shoreline.

[0100] Flow direction: Unidirectional flow. Since the mushroom-shaped water intake structure is axisymmetric along the center, the flow fields caused by the reciprocating current are symmetric whether it is flood tide or ebb tide. Therefore, the reciprocating current can be simplified as a unidirectional incoming flow for consideration.

[0101] Topography (water depth): The water depth in the sea area of nuclear power plants adopting deep water intake is usually relatively deep. In the example, the water depths of 8 m, 10 m, and 15 m are considered.

[0102] Water intake depth of the mushroom head: Corresponding to the topography, they are 8 m, 10 m, and 15 m respectively.

[0103] Number of mushroom heads: They are single, three, and five respectively.

[0104] Water intake of a single mushroom head: 10 m 3 / s; The water intake of each mushroom head in multiple mushroom heads is also 10 m 3 / s.

[0105] Average flow velocity of water intake of a single mushroom head: They are 0.2 m / s, 0.3 m / s, and 0.5 m / s respectively, that is, the water intake of a single mushroom head remains unchanged, and the corresponding mushroom head diameters are: 6.37 m, 4.25 m, and 2.55 m.

[0106] Structural parameters of a single mushroom head: Inflow window ( Figure 2 D) height is 2.5 m, the height from the lower edge of the mushroom head to the seabed ( Figure 2 h1) is 2.5 m, and the height of the water intake riser above the seabed ( Figure 2 h2) is 1 m, and the diameter of the water intake riser ( Figure 2 d1) is 2 m.

[0107] In this application example, by repeating Steps 1 to 4, 12 different boundary layers of mushroom head water intake were calculated, and data were accumulated, providing a basis for carrying out Step 5. The 12 different cases are designed as shown in Table 1:

[0108] Table 1 Statistical table of different case settings

[0109]

[0110] Among them, the first case is used to illustrate Steps 1 to 4:

[0111] The first case:

[0112] Environmental flow in the water intake sea area:

[0113] Tidal current condition: Alongshore reciprocating current, the environmental flow velocity in the sea area is 0.3 m / s; Shoreline: Straight shoreline.

[0114] Flow direction: Unidirectional flow. Since the mushroom-shaped water intake structure is axisymmetric about the center, the flow fields caused by the reciprocating current during flood tide or ebb tide are symmetric. Therefore, the reciprocating current can be simplified as a unidirectional incoming flow for consideration.

[0115] Topography (water depth): 8 m.

[0116] Water intake depth of the mushroom head: Corresponding to the topography, it is 8 m.

[0117] Number of mushroom heads: Single.

[0118] Water intake of a single mushroom head: 10 m 3 / s.

[0119] Average intake flow velocity of a single mushroom head: 0.2 m / s, that is, the diameter of the mushroom head is 6.37 m.

[0120] Structural parameters of a single mushroom head: Inlet window ( Figure 2 in D) height 2.5 m, height of the lower edge of the mushroom head from the seabed ( Figure 2 in h1) is 2.5 m, where the height of the water intake riser from the seabed ( Figure 2 in h2) is 1 m, that is, considering bottom sand prevention, etc., a siltation depth of 1 m is set, and the diameter of the water intake riser ( Figure 2 in d1) is 2 m.

[0121] Considering the minimum submergence depth of 0.22 m (calculated according to the empirical formula in the existing specification), that is, the upper edge of the inlet window of the mushroom head needs to be ≥0.22 m from the water surface. In this design, the upper edge of the inlet window of the mushroom head is 3 m from the water surface, meeting the requirements. The estimation process of the water intake boundary layer is as follows:

[0122] Step 1, establish a three-dimensional flow field model of the water intake sea area including the mushroom-shaped water intake structure (taking the full three-dimensional flow field model as an example): Simulate the flow field changes including the mushroom head and the surrounding environmental flow and the water intake situation of the water intake structure.

[0123] Establish a mathematical model of the flow field in the water intake sea area. The calculation area is 600×200 m, and the calculation grid is divided. The grid size in the near area of the mushroom head is about 0.2 m.

[0124] Determine the boundary conditions and initial conditions for the flow field simulation: For the ambient inflow, the velocity inlet boundary condition is adopted; for the ambient outflow, the pressure outlet boundary condition is adopted; for the seabed and the shore wall, the no-slip boundary condition is adopted; for the water surface, the free-slip boundary condition is adopted; for the inflow at the trumpet-shaped water intake, the velocity inlet boundary condition is adopted; Initial condition: The initial flow velocity is taken as the flow velocity of the upstream incoming flow, and the flow field simulation is carried out.

[0125] Step 2, verify the flow field model based on the physical model test results:

[0126] Construct a normal-scale physical model of the mushroom-shaped water intake structure in the indoor experimental flume. The scale is determined according to the experimental purpose and the specific conditions of the laboratory. Here, the scale is 1:15.

[0127] The basic principles for the physical model design are as follows:

[0128] 1) The similarity requirements of the flow field need to be ensured;

[0129] 2) Sufficient transition regions are required at the inlet and outlet sections of the model to ensure the similarity requirements of the inflow and outflow;

[0130] 3) The test is carried out based on the steady flow under the generalized representative water depth, flow velocity, and flow direction conditions.

[0131] Based on the above analysis and combined with the requirements of relevant codes and specifications, the test model for this project needs to adopt a large-scale normal flume test model. The model design criteria and basic requirements are as follows:

[0132] The model design should mainly be based on gravity similarity, taking into account the requirements of resistance similarity, water body buoyancy similarity, etc. Among them:

[0133] Gravity similarity criterion;

[0134] Buoyancy similarity.

[0135] According to the above model similarity criteria, the model scale relationship is as follows:

[0136] Discharge scale: Q r =L r 5 / 2 ;

[0137] Velocity scale:

[0138] Meanwhile, to ensure the similarity between the model flow pattern and the prototype, it is necessary to ensure that the Reynolds number of the model water flow is greater than the critical Reynolds number to ensure that the model water body enters the self-similarity region.

[0139] The flow velocity and direction at the characteristic points of the water intake structure are measured by an electromagnetic current meter and compared with the results of the flow field simulation. The comparison results between the numerical simulation and the flow field of the flume experiment show that the calculated values are in good agreement with the measured values, that is, the constructed mathematical model can reflect the basic characteristics of the change of the water intake flow field, and the estimation of the water intake boundary layer can be carried out accordingly.

[0140] Step 3: Analysis of the water intake inflow characteristics and flow field of the mushroom head type water intake structure:

[0141] The simulation results show that:

[0142] In the same layer of water area of the intake window of the water intake head, the influence of water intake is obvious. There is a certain tendency of streamline deflection and aggregation in the near-surface water body. Due to the influence of the mushroom head blocking the flow, there is a region with relatively slow flow velocity in the near-bottom water body. Within the range of the water intake inflow window, the inflow mainly comes from the oncoming flow direction and the peripheries on both sides of the mushroom head, and there is a certain outflow phenomenon on the backflow surface; the water intake inflow enters the riser in a rotational flow pattern; in the water layer near the bottom edge of the mushroom head window, due to the influence of the water intake confluence and the projection effect of the bottom edge structure of the mushroom head, a small area of relatively low flow velocity region first appears on the oncoming flow surface, and then the flow velocity increases rapidly. In a local area on the backflow surface, a small area of low flow velocity region also appears due to the blockage of the water intake structure. The water flow that cannot enter the water intake riser forms an upward vertical outflow on the backflow surface under the action of the flow deflection at the lower edge of the mushroom head; the phenomenon of the water body below the lower edge of the mushroom head window being sucked into the water intake head is not obvious, and there is a certain backflow behind the riser.

[0143] Step 4: Boundary layer analysis of the mushroom head type water intake structure based on discrete particle tracing:

[0144] Carry out tracer calculation:

[0145] Particle injection: Uniformly and instantaneously inject at one time at the characteristic cross-section.

[0146] Injection control conditions: Injection initial position setting: Based on the results of the flow field analysis, an injection cross-section is set 300 m upstream of the water intake. At the initial injection moment, the particles can be evenly distributed to meet the requirement that the ambient oncoming flow at the injection cross-section is not affected by the water intake structure; Injection width setting: Based on the analysis results of the water intake inflow characteristics of the mushroom head, when the injection width is 100 m, the injected particles can completely cover the influence range of the water intake structure in the horizontal width direction; Injection depth h: Inject particles at different water depths, and the interval of the injection water depth is as small as possible, such as 0.1 m, to obtain the tracer trajectories of the particles in the horizontal (i.e., width) and vertical (i.e., water depth) directions.

[0147] According to the particle tracer trajectories, count the particles that can enter the water intake system to obtain the horizontal influence range of the mushroom head water intake, as shown in Table 2.

[0148] Table 2 Statistics of the water intake influence of the mushroom head type deep water intake structure in Case 1

[0149] Injection depth h (m) Horizontal influence width B’ (m) 0～2 0 3 4.5 4 7.5 5 8.8 6 8.7 7 0

[0150] Determination of the water intake boundary layer of the mushroom head: In the direction perpendicular to the ambient incoming flow, by analyzing the tracer trajectories of the particles, the maximum envelope range composed of the tracer particles that can enter the water intake structure is the water intake boundary layer in this design case. Among them, in the direction perpendicular to the ambient incoming flow, the maximum width of the tracer particles entering the interior of the water intake structure is the maximum width of the water intake influence; in the direction perpendicular to the ambient incoming flow, by statistically analyzing the depth of release, the maximum thickness of the tracer particles that can enter the interior of the water intake structure is the maximum thickness of the water intake influence. Among them, when the initial position of the particle is above the upper edge of the water intake structure (i.e., above the inflow window), the corresponding thickness is the influence thickness above the upper edge of the water intake structure, denoted as S up , when the initial position of the particle is below the lower edge of the water intake structure (i.e., below the inflow window), the corresponding thickness is the influence thickness below the lower edge of the water intake structure, denoted as S down ; the height of the inflow window is denoted as D; the vertical influence thickness of the deep water intake structure is: S total = S up + D + S down .

[0151] Among them, S up is an important design parameter, that is, the minimum submergence depth of the water intake structure. The engineering significance of the minimum submergence depth: The water inlet of a pressure water diversion project (such as a tunnel) requires a certain submergence depth to avoid the entry of entrained air vortices into the interior of the water intake structure, causing harmful engineering safety problems such as cavitation. When the depth of the water intake structure from the water surface is greater than the minimum submergence depth, such harmful engineering problems are not likely to occur.

[0152] In this example, S up = 0.1m; D = 2.5m; S down = 1.2m; S total = S up + D + S down = 3.8m.

[0153] The envelope area of the water intake boundary layer is: 26.75m 2 , and the diagram of the water intake boundary layer is as shown in Figure 2 ( Figure 2 the dotted line in it is the envelope interface line of the water intake boundary layer).

[0154] Referring to the above process, change the structural design of the mushroom head, the water intake flow rate, or the water intake environment, etc. According to the cases listed in Table 1, repeat Steps 1 to 4 to accumulate data. Obtain the characteristic values of the mushroom head water intake boundary layer in 12 cases. The results are shown in Table 3 as follows:

[0155] Table 3 Statistical Table of Characteristic Values of the Mushroom Head Water Intake Boundary Layer

[0156]

[0157]

[0158] *Note: 1 / 3 means the 1st mushroom head among 3 mushroom heads.

[0159] Step 5: Identification of key factors affecting the intake boundary layer of the mushroom head type water intake structure:

[0160] The factors affecting the intake boundary layer of the mushroom head are complex, such as the mushroom head structure (diameter, height of the inflow window), intake operation (designed average intake velocity), and ambient flow (ambient velocity, ambient water depth), etc. The characteristics of the intake boundary layer of a single mushroom head (different designed intake velocities, ambient water depths, etc.) and multiple (three, five) mushroom heads were comprehensively analyzed. By performing a correlation analysis of the influencing thickness of the mushroom head intake with factors such as ambient water depth, mushroom head intake velocity, and mushroom head diameter, the results show that: the influencing thickness of the water body at the upper and lower edges of the mushroom head has a certain relationship with the mushroom head size, intake velocity, and water depth, etc., that is, the water depth and the designed mushroom head intake velocity are positively correlated with the influencing thickness; the mushroom head diameter is negatively correlated with the influencing thickness. The identified key influencing factors are: designed mushroom head intake velocity, intake ambient water depth, ambient average velocity, mushroom head diameter, and height of the mushroom head inflow window.

[0161] Step 6: Construction of rapid estimation formulas for the characteristic values of the intake boundary layer and key design parameters of the mushroom head type water intake structure:

[0162] The key design parameters of the mushroom head type water intake structure include: S up 、S down and if multiple mushroom heads are used for series intake, the minimum designed center distance B min between adjacent mushroom heads, where S up 、S down are the characteristic values of the mushroom head intake boundary layer.

[0163] Extract the key factors identified in Step 5: designed mushroom head intake velocity, intake ambient water depth, ambient average velocity, mushroom head diameter, and height of the mushroom head inflow window. According to the basic correlation relationships between various physical quantities, use the simplest possible physical quantities and operation relationships to describe the changes of independent variables and dependent variables. Combine the results of numerical simulation and physical model tests, consider the manifestation of key factors affecting the intake boundary layer in the formula, and based on the principle of dimensional harmony, use multiple regression analysis to construct a regression relationship and construct a rapid estimation formula:

[0164]

[0165] Where: S up is the designed minimum submergence depth, that is, the influencing thickness above the upper edge of a single mushroom head caused by the intake confluence, m (such asFigure 2 as shown; V is the designed flow velocity of the mushroom head for water intake, m / s; U is the average environmental flow velocity, m / s; d is the diameter of the mushroom head, m; D is the height of the inflow window of the mushroom head; a and b are fitting constants, a = 0.29, b = 0.60; the fitting curve is as Figure 4 shown.

[0166]

[0167] Where: S down is the influence thickness below the lower edge of a single mushroom head caused by water intake confluence, m (as Figure 2 shown); a' and b' are fitting constants, a' = 0.80, b' = 1.28. The fitting curve is as Figure 5 shown.

[0168] The maximum thickness S affected by the mushroom head in the water depth direction total = S up + D + S down . It represents the thickness of the water layer from which organisms or debris that need to be mainly prevented and controlled during mushroom head water intake in the vertical direction, that is, its prevention and control range can be considered based on the maximum depth affected by the mushroom head in the water depth direction.

[0169] When multiple mushroom head type water intake structures take water in series, the designed minimum center distance B between adjacent mushroom heads min is estimated as:

[0170] The influence width of mushroom head water intake in the horizontal direction is an important basis for determining the distance between mushroom heads. When designing the distance between water intake mushroom heads, the entrainment superposition effect caused by multiple mushroom head water intakes should be avoided as much as possible.

[0171] The average inflow of water in the water body within the space environment corresponding to adjacent mushroom heads (the water body within the center distance between adjacent mushroom heads and within the influence thickness of mushroom head water intake) should be not less than the water intake of a single mushroom head. That is, it is satisfied that the center distance B between adjacent mushroom heads (the distance between the center axes of the mushroom heads, as Figure 1 shown) is not less than B min (the width of the water intake boundary layer of the mushroom head, as Figure 2 shown).

[0172] Mushroom head water intake has a significant influence on the same layer of the inflow window, and also has a certain influence above the upper edge and below the lower edge of the mushroom head. Referring to the estimation formula for the maximum thickness S affected by the mushroom head in the water depth direction total , the estimation formula for B min is proposed as follows:

[0173]

[0174] Where: B min is the designed minimum center distance between adjacent mushroom heads, m; Q is the water intake of a single mushroom head, m3 / s.

[0175] Finally, it should be noted that the above is only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred arrangement, those of ordinary skill in the art should understand that the technical solution of the present invention (such as the structural type of the mushroom head, the application of various formulas, the sequence of steps, etc.) can be modified or equivalently replaced without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. Method for estimating intake boundary layer and its characteristic values of mushroom-shaped water intake structure in power plant, characterized in that, The steps of the method are as follows: Step 1, establish a three-dimensional flow field model of the water intake sea area including the mushroom head type water intake structure: Establish a three-dimensional flow field model of the water intake sea area including the mushroom head type water intake structure, obtain the terrain of the water intake sea area, environmental water flow conditions, shoreline characteristics, as well as the design dimensions, water intake flow rate, water intake velocity, and water intake depth of the mushroom head type water intake structure, establish a 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, and simulate the flow field changes including the mushroom head type water intake structure and the water intake affected sea area; The control equations for the flow field calculation are as follows: where: u is the time-averaged velocity, t is the time, p is the water pressure, ρ is the 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 Prandtl number of turbulent kinetic energy, ε is the turbulent dissipation rate, α ε is the Prandtl number of turbulent dissipation rate, G k is the generation term of turbulent kinetic energy caused by the mean velocity gradient, C 1ε and C 2ε are constant coefficients; Step 2, verify the flow field model based on the physical model experiment results: Construct a normal scale physical model of the mushroom head type water intake structure in an indoor experimental flume, measure the flow velocity and flow direction of each characteristic section or characteristic point, compare and verify with the simulation results of the mathematical model. If the calculated values and the measured values are in good agreement, it means that the constructed mathematical model can reflect the basic characteristics of the water intake flow field changes, and the estimation of the water intake boundary layer can be carried out accordingly; Step 3, analyze the water intake inflow characteristics and flow field of the mushroom head type water intake structure: According to the simulation results of the verified flow field model, carry out the analysis of the water intake inflow characteristics of the mushroom head type water intake structure and the influence characteristics of the water intake on the environmental water body, and provide a basis for setting the particle injection control conditions in Step 4; Step 4, boundary layer analysis of the mushroom head type water intake structure based on discrete particle tracking: Based on the flow field simulation results, perform discrete particle tracking calculations. The control equation for particle movement is: Where: m is the mass of the particle, v is the velocity of the particle, F is the resultant force acting on the particle in the flow field; x is the displacement of the particle; during tracer calculation, the particle is simplified as a moving mass point, that is, the mass of the particle and the force acting on it in the flow field caused thereby are not considered, that is, m = 0; during tracer calculation, is used to simulate the particle motion, then the motion trajectory of any particle is expressed as: where: x(t) is the position of the particle at time t, and x(t+Δt) is the position of the particle at time t+Δt, the displacement of the particle within the time period; Calculation process: Particle injection: Uniformly and instantaneously inject at one time at the characteristic section; Set the particle injection control conditions based on the water intake inflow characteristics and flow field analysis results of the mushroom head type water intake structure, including the initial injection position, injection width, and injection depth of the particles: Setting of the initial injection position: Based on the flow field analysis results, ensure that the environmental incoming flow at this section is not affected by the water intake structure, that is, at the initial injection moment, the particles can be evenly distributed; Setting of the injection width: Based on the analysis results of the water intake inflow characteristics of the deep water intake structure, ensure that the section width is wide enough, that is, the injected particles can completely cover the influence range of the water intake structure in the horizontal width direction; Injection depth: Inject particles at different water depths, and the interval of the injection water depth is as small as possible to clarify the tracer trajectories of the particles in the horizontal and vertical directions; Determination of the boundary layer of the mushroom-shaped water intake structure: In the direction perpendicular to the ambient flow direction, by analyzing the tracer trajectories of particles, the maximum envelope range composed of the tracer particles that can enter the water intake head is the water intake boundary layer of the mushroom-shaped water intake structure. Among them, in the direction perpendicular to the ambient flow direction, the maximum width of the tracer particles that enter the interior of the mushroom-shaped water intake structure is the maximum width of the water intake influence; in the direction perpendicular to the ambient flow direction, by statistically analyzing the depth direction of the injection, the maximum thickness of the tracer particles that can enter the interior of the mushroom-shaped water intake structure is the maximum thickness of the water intake influence. Among them, for the particles with the initial position at the upper edge of the mushroom-shaped water intake structure, the corresponding thickness is the influence thickness above the upper edge of the mushroom-shaped water intake structure, denoted as S up , for the particles with the initial position at the lower edge of the mushroom-shaped water intake structure, the corresponding thickness is the influence 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 denoted as D; the vertical influence thickness S total of the deep water intake structure is: S total = S up + D + S down ; The water intake boundary layer represents the maximum range of the influence of the deep water intake structure on the environmental water body in the direction perpendicular to the water flow. The range of the water intake boundary layer is drawn based on the maximum envelope range of the initial positions of all tracer particles entering the water intake structure in the direction perpendicular to the environmental incoming flow in Step 4. Its engineering significance is that the organisms within this envelope range are vulnerable to being affected by the water intake and entering the water intake system, thereby affecting the water intake safety; The calculation formula for the envelope area of the water intake boundary layer is: In the formula: A is the envelope area of the water intake boundary layer in the direction perpendicular to the environmental incoming flow; H is the environmental water depth; h is the particle injection depth; B' is the envelope width in the horizontal direction corresponding to the particle injection depth; Step 5: Identify the key factors affecting the water intake boundary layer of the mushroom head type water intake structure Repeat steps 1 to 4 to calculate the characteristic values of the intake boundary layer of the mushroom-shaped intake structure under different sea areas, different water intake conditions, and different mushroom head design conditions, and accumulate data to identify the key factors affecting the characteristic values of the intake boundary layer; Conduct a pairwise correlation analysis of each characteristic value of the intake boundary layer with each environmental factor and intake structure design factor. The analysis formula is as follows: Among them, r is the correlation coefficient, and its range is [-1, 1]. If |r| = 1, it is a perfect correlation; if r = 0, there is no linear correlation; if -1 ≤ r < 0, it is a negative correlation; if 0 < r ≤ 1, it is a positive correlation; if 0 ≤ |r| ≤ 0.3, it is a weak correlation; if 0.3 < |r| ≤ 0.5, it is a low correlation; if 0.5 < |r| ≤ 0.8, it is a significant correlation; if 0.8 < |r| ≤ 1, it is a high correlation; n is the number of cases for analysis, i is the i-th case, and x i is the value of the independent variable in the i-th case, and is the average value of the independent variables of n cases; y i is the value of the dependent variable in the i-th case, and is the average value of the dependent variables of n cases; The method for identifying key factors is: take the corresponding independent variables with 0.5 < |r| < 1 as key factors; Step 6: Construction of a rapid estimation formula for the characteristic values of the intake boundary layer and key design parameters of the mushroom-shaped intake structure: Extract the key factors identified in Step 5. Based on the basic correlation relationships between various physical quantities, use the most concise physical quantities and operational relationships to describe the changes of independent variables and dependent variables. Combine the results of numerical simulation and physical model tests, consider the manifestation of key factors affecting the water intake boundary layer in the formula, and construct a regression relationship using multiple regression analysis based on the principle of dimensional harmony. Construct the characteristic values of the water intake boundary layer of the mushroom-shaped water intake structure, that is, the key design parameter S of the mushroom head up 、S down and if multiple mushroom heads are used in series for water intake, the minimum center spacing B between adjacent mushroom head designs min for rapid estimation formula.

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