Atomization simulation method for large depression angle drop flow flood discharge energy dissipater

Abstract

The invention discloses an atomization simulation method for a large-depression-angle drop flow flood discharge energy dissipater, and the method comprises the following steps: 1, carrying out a special test in a large-depression-angle drop flow flood discharge energy dissipation physical model, and measuring the water entry position, the water entry thickness and the water entry width of a drop flow tongue of the model, and the air entrainment concentrations of a plurality of positions on a water entry section; 2, parameters in an existing nappe mathematical model are adjusted according to the special test data in the step 1, so that the water entry position, the water entry thickness and the water entry width of the drop nappe in the adjusted nappe mathematical model are consistent with the special test measurement results in the step 1; and 3, simulating the random splashing process of the drop water tongue according to the adjusted water tongue mathematical model in the step 2 and the air entrainment concentration measured in the step 1, and calculating the atomization rainfall intensity and the atomization influence range caused by the drop water tongue. According to the atomization simulation method, the technical problem that the atomization intensity and the influence range cannot be accurately predicted in the prior art is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of high - dam flood - discharging atomization in water conservancy and hydropower engineering, and particularly relates to an atomization simulation method for a large - dip - angle dropping - flow flood - discharging energy - dissipater. Background Technique

[0002] With the construction of high - dam water conservancy projects with high water heads, large discharge capacities, and narrow river valleys, the atomization problem associated with flood discharge has become increasingly prominent. Currently, high dams usually adopt large - dip - angle flip - flow flood discharge, and the adopted dip angle is generally not less than 15°. A large amount of water mist generated during the flip - flow flood discharge of high dams will form a super - heavy rainstorm with an intensity far exceeding natural rainfall in the flood - discharging energy - dissipation area, and will spread downstream and to the side slopes on both banks under the action of the water - tongue wind. The high - concentration water mist will invade the natural slopes, endanger the stability of the slopes, induce landslides, and also cause water to enter the power - station powerhouse and affect the operation of mechanical and electrical equipment projects. It may also obscure the line of sight and even block traffic. Therefore, attention should be paid to the protection against flood - discharging atomization, especially the protection of the side slopes on both banks in the flood - discharging energy - dissipation area, the layout avoidance and protection of the powerhouse and mechanical and electrical equipment, etc.

[0003] Currently, model tests and numerical simulations are effective means for studying atomization problems. There are obvious scale - effect problems in large - scale atomization models. The conversion of the model rainfall intensity to the prototype rainfall intensity does not follow the gravity similarity criterion, and it is difficult to determine the rainfall - intensity similarity law. The atomization mathematical model simulates the air - borne movement of the water tongue and the random splashing process of water droplets according to parameters such as the shape of the water - discharging structure, flood - discharge combination, complex terrain, natural wind speed, and wind direction, and calculates the rainfall intensity and influence range of flood - discharging atomization. This atomization mathematical model has been widely applied in practice and is a semi - theoretical and semi - empirical mathematical model. The fully - aerated water - tongue model is generally adopted in the mathematical models of the existing technology. This model assumes that the water and air are fully mixed when the water tongue impacts the tail water. However, the characteristics of the large - dip - angle dropping - flow energy - dissipater are that the air - borne process of the water tongue is short and the aeration is insufficient, resulting in the fact that the assumption of full aeration does not conform to the actual situation. Using the fully - aerated model for numerical simulation usually leads to a larger simulation result and cannot accurately predict the atomization intensity and influence range. For the atomization prediction of the large - dip - angle dropping - flow energy - dissipater, when simply using a mathematical model to calculate the water tongue, there are inaccuracies in the calculation of water - tongue aeration, resulting in a large error in the result, while simply relying on physical model tests has a scale - effect problem and the accuracy is not high. Summary of the Invention

[0004] Aiming at the existing technical problems, the invention aims to provide an atomization simulation method for a large - dip - angle dropping - flow flood - discharging energy - dissipater, which can solve the technical problems that the physical model in the existing technology has a scale - effect problem and the mathematical model using the fully - aerated water - tongue model cannot accurately predict the atomization intensity and influence range.

[0005] In order to achieve the above object, the technical solution adopted by the invention is:

[0006] An atomization simulation method for a large-angle plunge flow flood discharge energy dissipator, comprising the following steps:

[0007] Step 1: Conduct a special test in a physical model of a large-angle plunge flow flood discharge energy dissipator to measure the water entry position, water entry thickness, water entry width of the model plunge flow water tongue, and the air entrainment concentration at multiple positions on the water entry cross-section;

[0008] Step 2: Adjust the parameters in the existing water tongue mathematical model using the special test data in Step 1, so that the water entry position, water entry thickness, and water entry width of the plunge flow water tongue in the adjusted water tongue mathematical model are consistent with the measurement results of the special test in Step 1;

[0009] Step 3: Simulate the random splashing process of the plunge flow water tongue according to the adjusted water tongue mathematical model in Step 2 and the measured air entrainment concentration in Step 1, and calculate the atomization rainfall intensity and atomization influence range caused by the plunge flow water tongue.

[0010] The water entry position refers to the position where the central axis of the water jet contacts the downstream water surface. Usually, taking the starting point of the water jet (the end of the drop sill) as the reference point, it is expressed by the projection distance of the central axis of the water jet. The water entry thickness refers to the thickness of the water jet in the direction of water jet flow at the water entry section, and the water entry width refers to the width of the water jet expanding laterally at the water entry section. The results of the special tests provide data support for constructing an accurate mathematical model of the large depression angle drop flow water jet. By using the special test data of the existing physical model to conduct a feedback analysis on the existing water jet mathematical model, the water entry position, water entry thickness, and water entry width of the drop flow water jet in the adjusted water jet mathematical model are made consistent with the results of the special tests, thereby solving the problem of large errors in the current mathematical model during the calculation of water jet aeration. According to the adjusted water jet mathematical model and the measured aeration concentration, the random splashing process of the drop flow water jet is simulated, and the atomization rainfall intensity and atomization influence range caused by the drop flow water jet are calculated, thereby solving the problems of scale effect in the current physical model tests and the difficulty in determining the similarity ratio between the model rainfall intensity and the prototype rainfall intensity. Among them, the design and operation of the model tests can refer to the specification "Code for Conventional Hydraulic Model Tests in Hydropower and Water Conservancy Projects" (DL / T 5244-2010). The existing water jet mathematical model and the mathematical model of random water drop splashing can refer to the research on the theory of spillway flood discharge atomization and its mathematical model [D] (Tianjin University, Zhang Hua, 2003), the differential equation of motion of aerated water jet and its numerical solution [J] (Water Resources and Hydropower Engineering, Zhang Hua, Lian Jijian, 2004, (05): 46-48), the mathematical model of random water drop splashing of flip flow water jet [J] (Journal of Hydraulic Engineering, Zhang Hua, Lian Jijian, Li Huiping, 2003, (08): 21-25), and the research on the improvement of the mathematical model of flip flow flood discharge atomization and the analysis of influencing factors [D] (Tianjin University, Liu Fang, 2004). According to the calculated atomization rainfall intensity and the atomization protection zones specified in the specification "Technical Guide for Spillway Flood Discharge Atomization Protection in Hydropower Projects" (NB / T 11188-2023), different levels of atomization influence ranges can be divided.

[0011] Preferably, when conducting the special test in step 1, the following steps are specifically adopted:

[0012] Step 101: Open the gate at the starting point of the spillway, and let the water flow fall from the drop sill into the downstream water surface in the downstream pool, forming a model drop flow water jet. Observe the shape of the model drop flow water jet, control the valve of the water supply pipeline of the upstream water tank, and keep the water level of the upstream water tank at the test condition water level; keep the opening of the gate at the starting point of the spillway, and adjust the drainage volume of the drainage outlet of the downstream pool to keep the water level of the downstream pool surface stable.

[0013] Step 102: After forming a model drop flow water jet with a stable flow velocity, set multiple aeration concentration sensors at the water entry section of the water jet, record the incoming flow of the model drop flow water jet, measure the water entry position, water entry thickness, and water entry width of the model drop flow water jet, and record the aeration concentration measurement data.

[0014] Preferably, in step 102, the aeration concentration sensor is adjusted to ensure that the reading of the aeration concentration sensor in still water is zero; a plurality of adjusted aeration concentration sensors are evenly distributed at the water inlet section of the model nappe flow, and a grid layout method is adopted to cover the entire range of the water inlet section of the nappe. By setting a plurality of aeration concentration sensors, the variation law of the aeration concentration at the water inlet section is comprehensively evaluated.

[0015] Preferably, in step 2, the existing nappe mathematical model establishes a dynamic equation by using a micro control volume of a three-dimensional aerated nappe: Among them, x i represents the spatial coordinate (m) of the nappe microelement body, i = 1, 2, 3 represent the components along the x, y, and z directions, c f is the air resistance coefficient of the nappe microelement body, ρ a and ρ w are the densities of air and water (m 3 / s) respectively, v represents the velocity vector (m / s) of the nappe microelement body, v i represents the velocity component (m / s) of the nappe microelement body; v f represents the velocity vector (m / s) of the natural wind; v fi represents the velocity component (m / s) of the natural wind; is the average water content concentration of the nappe cross-section, g i represents the component of the gravitational acceleration (m / s 2 ), h is the thickness (m) of the nappe after diffusion; the longitudinal diffusion equation of the nappe: The transverse diffusion equation of the nappe: Among them, h and b are the thickness and width (m) of the nappe after diffusion respectively, k h and k b are the correction coefficients for the thickness and width diffusion of the nappe respectively, S is the curve coordinate of the nappe microelement body, ω is the diffusion angle along the path of the nappe (rad), and h0 and b0 are the thickness and width (m) of the nappe at the drop. When the nappe enters the water, the thickness of the nappe after diffusion is the water inlet thickness of the nappe at this time, and the width of the nappe after diffusion is the water inlet width of the nappe.

[0016] Specifically, in step 2, the flow velocity coefficient, air resistance coefficient c f , the correction coefficient k h for the thickness diffusion of the nappe, and the correction coefficient k b for the width diffusion of the nappe in the nappe mathematical model are adjusted. Among them, the flow velocity of the nappe at the drop is calculated through the flow velocity coefficient.

[0017] Preferably, in step 3, according to the adjusted mathematical model of the water tongue, determine the entry position, entry thickness, entry width, entry speed, entry angle of the falling water tongue, as well as the spatial coordinates and splash volume of each atomization source; each atomization source randomly generates the initial velocity, emission angle, deflection angle, and diameter parameters of the splashed water droplets according to the probability density function describing the randomness of the splashed water droplets. The number of splashed water droplets corresponds to the splash volume. By statistically analyzing the landing positions of all splashed water droplets and calculating the atomized rainfall intensity on the plane, determine the spatial influence range of the atomization effect.

[0018] Preferably, in step 3, the equation for the splash volume q is where κ is an empirical coefficient; dl is the line differential (m) of the outer edge of the entry section of the falling water tongue, v z is the projection (m / s) of the water tongue entry velocity on the z-axis, h1 is the entry thickness of the water tongue, and C is the water content concentration of this line differential. Divide the edge of the entry section into several line differentials as the atomization sources for flood discharge atomization; calculate the water content concentration of each atomization source through the aeration concentration of the entry section measured in step 1, and substitute the water content concentration into the equation for the splash volume q to calculate the splash volume of each atomization source.

[0019] Specifically, in the physical model of large depression angle falling flow flood discharge energy dissipation adopted in step 1, the depression angle range is 15° - 30°. The stilling basin structure is set according to the detailed drawing of the water discharge building body type and follows the gravity similarity criterion. The downstream water surface elevation is calculated and determined according to the design flow rate and the relationship between the downstream water level and the flow rate. The adopted depression angle range is 15° - 30°. This angle range can achieve a better effect of reducing atomization. Key control the elevation at the end of the stilling basin, the depression angle of the stilling basin, and the outlet width. The specific design and operation of the model test can refer to the specification "Code for Conventional Hydraulic Model Tests in Hydropower and Water Conservancy Projects" (DL / T 5244 - 2010).

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. The atomization simulation method for large depression angle falling flow flood discharge energy dissipation works of the present invention combines two research methods of model test and numerical simulation. It applies a special physical model test to study the entry position parameters of the falling water tongue and the aeration concentration of the entry section, constructs a mathematical model of the falling water tongue through feedback analysis, and then calculates the atomized rainfall intensity and atomization influence range caused by the falling water tongue using the flood discharge atomization mathematical model.

[0022] 2. The atomization simulation method for large depression angle falling flow flood discharge energy dissipation works of the present invention effectively solves the problem of large errors in the calculation of water tongue aeration in the existing mathematical model and the problems of scale effect and difficulty in determining the similarity ratio between the model rainfall intensity and the prototype rainfall intensity faced in the physical model test by integrating the advantages of the two research methods of model test and numerical simulation, and realizes high-precision simulation of the falling flow flood discharge atomization process. Brief Description of the Drawings

[0023] Figure 1 is a flowchart of the atomization simulation method for the large depression angle drop flow flood discharge energy dissipator of the present invention;

[0024] Figure 2 is Figure 1 a schematic diagram of the model structure adopted during the model test in

[0025] In the figure

[0026] 1 - spillway; 2 - drop sill; 3 - model drop flow water tongue; 4 - aeration concentration sensor; 5 - computer; 6 - downstream water surface; 7 - downstream pool; 8 - drainage outlet; 9 - projection distance of the water tongue center axis; 10 - water tongue entry thickness; 11 - water tongue center axis. Detailed Embodiment

[0027] The present invention will be described in detail below with reference to the drawings and in conjunction with embodiments. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. For the convenience of description, words such as "upper", "lower", "left", and "right" hereinafter only indicate the same directions as the upper, lower, left, and right directions of the drawings themselves, and do not limit the structure.

[0028] As Figure 1 shown, a method for simulating atomization of a large depression angle drop flow flood discharge energy dissipator in this embodiment includes the following steps:

[0029] Step 1: Conduct a special test in the physical model of the large depression angle drop flow flood discharge energy dissipator, and measure the entry position, entry thickness, entry width of the model drop flow water tongue, and the aeration concentration at multiple positions on the entry cross-section;

[0030] Step 101: Adopt the model structure as Figure 2 shown, open the gate at the starting point of the spillway 1, the water flow falls from the drop sill 2 into the downstream water surface 6 in the downstream pool, forming the model drop flow water tongue 3, observe the shape of the model drop flow water tongue 3, control the valve of the water supply pipeline of the upstream water tank, and keep the water level of the upstream water tank at the test condition water level; keep the opening of the gate at the starting point of the spillway 1, and adjust the drainage volume of the drainage outlet 8 of the downstream pool 7 so that the water level of the downstream pool surface remains stable;

[0031] Step 102: After the model nappe flow 3 with a stable flow rate is formed, fifteen aeration concentration sensors 4 are arranged at the water entry section of the nappe flow to record the incoming flow rate of the model nappe flow 3, measure the water entry position, water entry thickness, and water entry width of the model nappe flow 3, and record the aeration concentration measurement data. When measuring the aeration concentration, first adjust the aeration concentration sensor 4 to ensure that the reading of the aeration concentration sensor 4 in still water is zero. Then, evenly distribute the fifteen adjusted aeration concentration sensors 4 at the water entry section of the model nappe flow 3 in a grid layout manner to cover the entire range of the water entry section of the nappe flow, record the aeration concentration measurement data, and transmit it to the computer 5. As Figure 2 shown, the water entry position refers to the position where the central axis 11 of the nappe flow contacts the downstream water surface, with the starting point of the nappe flow (the end of the drop weir) as the reference point, represented by the projection distance 9 of the central axis of the nappe flow. The water entry thickness 10 is the thickness of the nappe flow in the direction of the nappe flow at the water entry section;

[0032] Step 2: Use the special test data in Step 1 to perform feedback analysis and adjustment on the parameters in the existing nappe flow mathematical model, so that the water entry position, water entry thickness, and water entry width of the nappe flow in the adjusted nappe flow mathematical model are consistent with the measurement results of the special test in Step 1;

[0033] Step 3: According to the adjusted nappe flow mathematical model in Step 2 and the measured aeration concentration in Step 1, simulate the random splashing process of the nappe flow, and calculate the atomization rainfall intensity and atomization influence range caused by the nappe flow.

[0034] When conducting the special test in the physical model in Step 1, the design and operation of the model test refer to the specification "Code for Conventional Hydraulic Model Tests in Hydropower and Water Conservancy Projects" (DL / T 5244-2010). The specific model structure is as described in the following table:

[0035]

[0036] The test data measured during the special test are as shown in the following table:

[0037] Projection distance of the center axis of the water jet / m Thickness at water entry / m Width at water entry / m 25.6 12 29.6

[0038] The aeration concentration data measured by the aeration concentration sensors at the water entry section during the special test are as shown in the following table. The point (0,0) represents the water entry point of the central axis of the nappe flow. x represents the axis in the direction of the nappe flow, and the positive direction is the lateral extension direction to the right when the observer faces downstream. y represents the horizontal transverse axis perpendicular to the x-axis, and the positive direction is the lateral extension direction to the right when the observer faces downstream:

[0039]

[0040]

[0041] In Step 2, the existing water jet mathematical model refers to the research on the theory of spillway atomization of hydropower stations and its mathematical model [D] (Zhang Hua, Tianjin University, 2003) and the differential equation of the motion of aerated water jets and its numerical solution [J] (Water Resources and Hydropower Engineering, Zhang Hua, Lian Jijian, 2004, (05): 46-48). A dynamic equation is established using the micro-control volume of the three-dimensional aerated water jet: where, x i represents the spatial coordinate (m) of the water jet micro-element body, i = 1, 2, 3 represent the components along the x, y, and z directions, c f is the air resistance coefficient of the water jet micro-element body, ρ a and ρ w are the densities of air and water (m 3 / s) respectively, v represents the velocity vector (m / s) of the water jet micro-element body, v i represents the velocity component (m / s) of the water jet micro-element body; v f represents the velocity vector (m / s) of the natural wind; v fi represents the velocity component (m / s) of the natural wind; is the average water content concentration of the water jet cross-section, g i represents the component of the gravitational acceleration (m / s 2 ), h is the thickness (m) of the water jet after diffusion; the longitudinal diffusion equation of the water jet: The lateral diffusion equation of the water jet: where, h and b are the thickness and width (m) of the water jet after diffusion respectively, k h and k b are the diffusion correction coefficients of the water jet thickness and width respectively, S is the curve coordinate of the water jet micro-element body, ω is the diffusion angle along the path (rad) of the water jet, h0 and b0 are the thickness and width (m) of the water jet at the drop. The width of the water jet at the drop is equal to the width of the drop, both are b0, and h0 can be calculated through the flow rate, upstream water level, drop elevation, velocity coefficient, and b0. The initial conditions in this water jet mathematical model are

[0042]

[0043] In the formula: x0, y0, z0 represent the position coordinates (m) of the drop in space; v0 is the initial velocity (m / s) of the water jet at the drop, which can be calculated through the upstream water level, drop elevation, and velocity coefficient; β is the depression angle (rad) of the drop; is the plane deflection angle (rad) of the drop.

[0044] The initial conditions for the operation of the water jet mathematical model are the upstream water level, downstream water level, flow rate, drop elevation, position coordinates of the drop in space, width b0 of the drop, depression angle β of the drop, and plane deflection angle of the drop The velocity coefficient, the air resistance coefficient of the water jet, the correction coefficient for the thickness diffusion of the water jet, and the correction coefficient for the width diffusion of the water jet. Based on the entry position, entry thickness, and entry width from the special test results, the velocity coefficient, air resistance coefficient c f 、the correction coefficient k for the thickness diffusion of the water jet h 、and the correction coefficient k for the width diffusion of the water jet b are subjected to feedback analysis to adjust the water jet mathematical model so that it is consistent with the special test results in terms of the entry position, entry thickness, and entry width.

[0045] Specific data Projection distance of the center axis of the water jet / m Thickness at water entry / m Width at water entry / m Test value 25.6 12 29.6 Calculated value before feedback analysis 23.19 7.21 22.96 Calculated value after feedback analysis 25.66 12.05 29.52

[0046]

[0047] In the above table, the calculation formula for the velocity coefficient is In the formula, s is the flow path from the start of the overflow dam surface curve to the bucket section; H is the elevation difference from the upstream water level to the end of the drop; Δ is the absolute roughness of the dam surface, taking Δ = 0.001 m; q is the unit discharge of the drop section, and the calculated velocity coefficient through the empirical formula is 0.617. The formula is from the literature: Calculation of the Velocity Coefficient of the Overflow Dam Surface [J]. Journal of Hydraulic Engineering, Xia Yuchang, 1980, (04): 62-67.

[0048] The air resistance coefficient can be obtained by looking up the relationship diagram between the Froude number Fr0 at the outlet section and the air resistance coefficient c f . It is calculated that Fr0 = 7.163. Looking up the diagram, c f is taken as 2.3. The diagram is from the literature: Trajectory and Shooting Distance of the Aerated Water Jet in the Air [J], Journal of Tianjin University, Liu Xuanlie, Liu Jun, Yao Zhongda, etc., 1989, (02): 23-30.

[0049] The calculation formula for the average water content concentration of the water jet cross-section is Fr0 is the Froude number at the drop outlet section, v is the velocity of the water jet in the air, and h0 is the thickness of the water jet at the drop outlet section. The formula is from the literature: Experimental Study on the Aeration Diffusion of the Three-Dimensional Water Jet in the Air [J], Journal of Hydraulic Engineering, Liu Xuanlie, Liu Jun, 1989, (11): 10-17.

[0050] The calculation formula for the initial conditions of the differential equation of the water jet movement is

[0051] Among them, x0 and y0 represent the plane coordinates of the drop position, taking 0, 0 here; H n represents the elevation of the drop; H down represents the downstream water level; v0 represents the velocity of the water jet at the drop, calculated using the velocity coefficient H uprepresents the upstream water level; β j represents the depression angle of the drop weir; represents the planar rotation angle of the drop weir, which is taken as 0 here.

[0052] Then at the initial moment, the initial conditions of the differential equation of the water jet movement are

[0053] The boundary condition is x3 = 0

[0054] When running to the boundary condition, the mathematical model of the water jet stops calculating, and the time at this moment is t end , and the state of the water jet is

[0055] The coordinates of the center of the water jet at the initial moment are (0, 0, 11.04); the coordinates of the center of the water jet at the termination moment are (25.66, 0, 0). The throw distance is 25.66 m, which is the water entry position of the water jet.

[0056] Through the calculation of the mathematical model, the water entry position (25.66, 0, 0) of the center line of the water jet, the water entry thickness of the water jet is 12.05 m, the water entry width is 29.52 m, the water entry speed is 37.38 m / s, and the water entry angle is 31.24°

[0057] In step 3, according to the adjusted mathematical model of the water jet, determine the water entry position, water entry thickness, water entry width, water entry speed, water entry angle of the falling water jet, as well as the spatial coordinates and splashing amounts of each atomization source. Each atomization source randomly generates the initial velocity, emission angle, offset angle and diameter parameters of the splashing water droplets according to the probability density function describing the randomness of the splashing water droplets. The number of splashing water droplets corresponds to the splashing amount. By statistically analyzing the landing positions of all splashing water droplets and calculating the atomization rainfall intensity of the plane, determine the spatial influence range of the atomization effect. The mathematical model of random splashing of water droplets refers to the mathematical model of random splashing of water droplets of the ski-jump jet [J] (Journal of Hydraulic Engineering, Zhang Hua, Lian Jijian, Li Huiping, 2003, (08): 21 - 25) and the research on the improvement of the mathematical model of ski-jump flood discharge atomization and analysis of influencing factors [D] (Tianjin University, Liu Fang, 2004). This mathematical model has been applied in the Mardang Hydropower Station and the Baihetan Hydropower Station. For details, see the research on the mathematical model of flood discharge atomization of the Mardang Hydropower Station [J] (Water Resources and Hydropower Engineering, Qi Chunfeng, Lian Jijian, Liu Fang, etc., 2017, 48(12): 106 - 110 + 194) and the calculation and analysis of flood discharge atomization of large-scale hydropower stations [J] (Journal of Hydroelectric Energy, Liu Zhiping, Liu Haitao, Sun Shuangke, 2014, 33(02): 111 - 115).

[0058] Based on the water jet entry position, entry width, and thickness, the outer contour of the water jet entry cross-section can be obtained, that is, the position information of the water jet entry line. The outer side and the two side entry lines of the water jet are equally spaced and divided, and it is discretized into several micro-spray line source segments with a width of dl. The coordinates of the center points of each micro-spray line source segment can be obtained using the position information of the water jet entry line. According to the aeration concentration of the test results and the coordinates of the center points of the micro-spray line source segments, the aeration concentration of each micro-spray line source segment is obtained by grid interpolation, and the water content concentration of each micro-spray line source segment is calculated through the aeration concentration. Substitute the water content concentration into the calculation formula to obtain the effective spray volume of each micro-spray line source segment. The number of spray droplets of each micro-spray line source segment is where the equation for the spray volume q is where κ is an empirical coefficient; dl is the line differential (m) of the outer edge of the entry cross-section of the falling water jet, v z is the projection of the water jet entry velocity on the z-axis (m / s), h1 is the entry thickness of the water jet, and C is the water content concentration of this line differential; the edge of the entry cross-section is divided into several line differentials as the atomization sources of flood discharge atomization. The aeration concentration of each atomization source is calculated by interpolation through the aeration concentration of the entry cross-section measured in step 1, and the water content concentration is calculated by subtracting this aeration concentration from 1. Substitute the water content concentration into the equation of the spray volume q to calculate the spray volume of each atomization source. The calculation equation for the number of spray droplets is: In the formula, q is the spray volume, is the mode of the particle size of the spray droplets, taking 0.005 m.

[0059] The following table shows the position information and spray volume of each micro-spray line source segment, where x represents the axis of the water jet flow direction, and the positive direction points to the downstream direction of the water jet flow. y represents the horizontal transverse axis perpendicular to the x-axis, and the positive direction is the transverse extension direction pointing to the right when the observer faces downstream. The point (0, 0) represents the entry point of the central axis of the water jet.

[0060]

[0061] Construct a probability density function to describe the randomness of the spray droplets. The initial velocity v0, diameter d, exit angle β, and deflection angle of the four random variables of the spray droplets are all independent of each other. v0 and d follow a gamma distribution, and β and follow a normal distribution. Their probability density functions are respectively:

[0062]

[0063] In the formula, Take 4 m / s, is the mode of the initial velocity of the water droplets; a d Take 2, is the mode value of the particle size of the splashing water droplets, taking 0.005 m; μ β is the mode value of the water droplet exit angle, σ β takes π / 32; takes the deflection angle of the falling water tongue mathematical model on the water inlet plane, takes π / 9; and μ β can be calculated by the following formula:

[0064]

[0065] μ β = 44 + 0.32v j - 0.07α

[0066] In the above formula, v j is the water inlet velocity (m / s) of the falling water tongue mathematical model; α is the water inlet angle (°) of the falling water tongue mathematical model.

[0067] According to the probability density function describing the randomness of the splashing water droplets, a splashing water droplet with an initial velocity of v0, a diameter of d, an exit angle of β, and a deflection angle of is randomly sampled. The splashing water droplet moves in the environment of the water tongue wind and the natural wind, and the water droplet is simultaneously affected by the combined action of gravity, air resistance, and buoyancy. The motion differential equation of the water droplet is

[0068]

[0069] In the above formula: x, y, and z represent the displacement amounts of the water droplet in three directions in space; v x , v y , v z represent the velocities of the water droplet in three directions in space; c f is the air resistance coefficient of the water droplet; d is the diameter of the water droplet; ρ a is the local air density; ρ w is the density of water; g is the acceleration due to gravity; v f x , v f y , v f z represent the components of the environmental wind speed in three directions in space; v is the water droplet velocity vector; v f is the environmental wind speed vector.

[0070] The initial value conditions of the motion differential equation of the water droplet are

[0071]

[0072] In the above formula: x0 and y0 represent the position coordinates (m) of the atomization source; v0 is the initial velocity (m / s) of the water droplets; β is the emission angle (°) of the water droplets; is the deflection angle (°) of the water droplets. According to the randomly sampled v0, d, β, Substitute into the above formula, and use the fourth-order Runge-Kutta method to solve the above formula to calculate the movement trajectory and ground landing point of the splashing water droplets. Repeat the above process for this micro-splashing line source segment until the landing points of all the splashing water droplets in this micro-splashing line source segment are all calculated, and then calculate the next micro-splashing line source segment. Discretize the grid of the atomization calculation area. When all the micro-splashing line source segments are calculated, the landing points and volumes of all the splashing water droplets can be obtained. For each tiny grid in the atomization calculation area, according to the calculated water droplet landing points, add up the volumes of all the water droplets falling into this grid, and the rainfall intensity of this grid can be obtained. After all the grids are calculated, the rainfall intensity of the overall area can be obtained.

[0073] According to the calculated atomization rainfall intensity of the overall area and the atomization protection zoning specified in the Code for Atomization Protection Technology of Spillway Discharges in Hydropower Projects (NB / T 11188-2023), the atomization rainfall intensity caused by spillway discharges is divided into the following four regions:

[0074] 1. Water tongue breakup and splash zone: rainfall intensity ≥ 50 mm / h. When the atomization rainfall reaches this standard, it will cause greater disasters to the hillside and buildings, and may cause landslides and damage to buildings. Therefore, it is necessary to protect the mountain bodies on both sides within this range and avoid building buildings within this range;

[0075] 2. Dense fog and heavy rain zone: 10 mm / h ≤ rainfall intensity < 50 mm / h. This level of fog and rain will cause harm to the power station hub. Buildings should be protected. If the highway is within this range, vehicle traffic should be prohibited;

[0076] 3. Light fog and rainfall zone: 2 mm / h ≤ rainfall intensity < 10 mm / h. The harm to the project within this range is relatively small and generally will not cause disasters;

[0077] 4. Light fog and water vapor dispersion zone: rainfall intensity ≤ 2 mm / h. The atomization within this range has no impact on the project.

[0078] According to the calculated atomization rainfall intensity, the atomization influence range is divided as described in the following table:

[0079]

[0080] Among them, the position of the end of the drop weir is at the station number 100 meters downstream of the dam axis. The longitudinal range of the water jet breakup and splash zone is from 134 meters to 447 meters, indicating that this area starts from the station number 134 meters downstream of the dam axis and extends to the station number 447 meters. The maximum climbing elevations on the left bank and the right bank are 1644 meters and 1650 meters respectively, indicating that the maximum climbing elevation in this area on the left bank is 1644 meters and on the right bank is 1650 meters.

[0081] The longitudinal range of the thick fog and heavy rain area is from 130 meters to 484 meters, indicating that this area starts from the station number 130 meters downstream of the dam axis and extends to the station number 484 meters. The maximum climbing elevations on the left bank and the right bank are 1652 meters and 1659 meters respectively, indicating that the maximum climbing elevation in this area on the left bank is 1652 meters and on the right bank is 1659 meters.

[0082] The longitudinal range of the light fog and rainfall area is from 128 meters to 523 meters, indicating that this area starts from the station number 128 meters downstream of the dam axis and extends to the station number 523 meters. The maximum climbing elevations on the left bank and the right bank are 1661 meters and 1671 meters respectively, indicating that the maximum climbing elevation in this area on the left bank is 1661 meters and on the right bank is 1671 meters.

[0083] The content clarified in the above embodiments should be understood that these embodiments are only used to illustrate the invention more clearly and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modification of this embodiment by those skilled in the art all fall within the scope defined by the appended claims of the present invention.

Claims

1. An atomization simulation method for a large depression angle overfall flood discharge and energy dissipation project, characterized in that: It includes the following steps: Step 1: Conduct a special test in the physical model of large-depression-angle plunge flow flood discharge and energy dissipation, measure the water entry position, water entry thickness, water entry width of the model plunge water jet, and the air entrainment concentration at multiple positions on the water entry cross-section; Step 2: Adjust the parameters in the existing water jet mathematical model using the special test data in Step 1, so that the water entry position, water entry thickness, and water entry width of the plunge water jet in the adjusted water jet mathematical model are consistent with the measurement results of the special test in Step 1; Step 3: Simulate the random splashing process of the plunge water jet according to the adjusted water jet mathematical model in Step 2 and the measured air entrainment concentration in Step 1, and calculate the atomization rainfall intensity and atomization influence range caused by the plunge water jet.

2. The atomization simulation method for large depression angle overfall flood dissipation energy dissipator according to claim 1, characterized in that: When conducting the special test in Step 1, the following steps are specifically adopted: Step 101: Open the gate at the starting point of the spillway, and the water flow falls from the drop sill into the downstream water surface in the downstream pool, forming a model plunge water jet. Observe the shape of the model plunge water jet, control the valve of the water supply pipeline of the upstream water tank, and keep the water level of the upstream water tank at the test condition water level; keep the opening degree of the gate at the starting point of the spillway, and adjust the drainage volume of the drainage outlet of the downstream pool to keep the water level of the downstream pool surface stable; Step 102: After forming a model plunge water jet with a stable flow velocity, set multiple air entrainment concentration sensors at the water entry cross-section of the water jet, record the incoming flow rate of the model plunge water jet, measure the water entry position, water entry thickness, water entry width of the model plunge water jet, and record the air entrainment concentration measurement data.

3. The atomization simulation method for large-angle plunge flow flood discharge and energy dissipation works according to claim 2, characterized in that: In Step 102, adjust the air entrainment concentration sensors to ensure that the readings of the air entrainment concentration sensors in still water are zero; evenly distribute multiple adjusted air entrainment concentration sensors at the water entry cross-section of the model plunge water jet, using a grid layout method to cover the entire range of the water entry cross-section of the water jet.

4. The atomization simulation method for the large depression angle overfall flood discharge and energy dissipation structure according to claim 1, wherein: In Step 2, the existing water jet mathematical model establishes the dynamic equation by using the micro control volume of the three - element aerated water jet: Among them, x i represents the spatial coordinate (m) of the water jet micro - element body, i = 1, 2, 3 represent the components along the x, y, and z directions, c f is the air resistance coefficient of the water jet micro - element body, ρ a and ρ w are the densities of air and water (m 3 / s) respectively, v represents the velocity vector (m / s) of the water jet micro - element body, v i represents the velocity component (m / s) of the water jet micro - element body; v f represents the velocity vector (m / s) of the natural wind; v fi represents the velocity component (m / s) of the natural wind; is the average water - containing concentration of the water jet cross - section, g i represents the component of the gravitational acceleration (m / s 2 ), h is the thickness (m) of the water jet after diffusion; the longitudinal diffusion equation of the water jet: The transverse diffusion equation of the water jet: Among them, h and b are the thickness and width (m) of the water jet after diffusion respectively, k h and k b are the diffusion correction coefficients of the water jet thickness and width respectively, S is the curve coordinate of the water jet micro - element body, ω is the diffusion angle along the path (rad) of the water jet, h0 and b0 are the thickness and width (m) of the water jet at the drop - off.

5. The atomization simulation method for large depression angle plunge flow flood discharge and energy dissipation works according to claim 4, characterized in that: In Step 2, adjust the flow velocity coefficient, air resistance coefficient c f , water tongue thickness diffusion correction coefficient k h , water tongue width diffusion correction coefficient k b in the water tongue mathematical model.

6. The atomization simulation method for large depression angle plunging flow flood discharge and energy dissipation works according to claim 5, characterized in that: In Step 3, determine the water entry position, water entry thickness, water entry width, water entry velocity, water entry angle, and the spatial coordinates and splashing volume of each atomization source according to the adjusted water jet mathematical model; each atomization source randomly generates the initial velocity, emission angle, offset angle, and diameter parameters of the splashing water droplets according to the probability density function describing the randomness of the splashing water droplets. The number of splashing water droplets corresponds to the splashing volume. By statistically analyzing the landing positions of all splashing water droplets and calculating the atomization rainfall intensity on the plane, determine the spatial influence range of the atomization effect.

7. The atomization simulation method for large depression angle overfall flood dissipation energy dissipator according to claim 6, characterized in that: In Step 3, the equation for the splash volume q is where κ is an empirical coefficient; dl is the linear differential (m) of the outer edge of the inlet cross-section of the falling water jet, v z is the projection (m / s) of the water jet inlet velocity on the z-axis, h1 is the inlet thickness of the water jet, C is the water content concentration of this linear differential; the edge of the inlet cross-section is divided into several linear differentials as the atomization sources of flood discharge atomization; the water content concentration of each atomization source is calculated through the aeration concentration of the inlet cross-section measured in Step 1, and the water content concentration is substituted into the equation for the splash volume q to calculate the splash volume of each atomization source.

8. The atomization simulation method for the large depression angle plunge flow flood discharge and energy dissipation structure according to any one of claims 1 to 7, characterized in that: In the physical model of large-depression-angle plunge flow flood discharge and energy dissipation used in Step 1, the depression angle range is 15° - 30°. The drop sill structure is set according to the detailed drawing of the water discharge building body type and follows the gravity similarity criterion. The downstream water surface elevation is calculated and determined according to the design flow rate and the relationship between the downstream water level and the flow rate.

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