Estimation Method for Loss of Entrained Organisms in Power Plant Water Intake Considering Different Biological Characteristics

Abstract

The present invention relates to a method for estimating the loss of entrained organisms in power plant water intake considering different biological characteristics, including: establishing a large-scale two-dimensional water intake hydrodynamic model considering the sea area environment and water intake project design; verifying the results of the hydrodynamic model and analyzing the flow field; establishing a dynamic model considering the characteristics and movement ability of entrained organisms; establishing an entrained organism release model for the dynamic model of entrained organisms coupled with the water intake hydrodynamic model; estimating the loss of entrained organisms in water intake. In view of the limitations of the current estimation of the loss of entrained organisms in power plant water intake, the present invention proposes a method for estimating the loss of entrained organisms in power plant water intake considering different biological characteristics, the characteristics of movement with the flow, the hydrodynamic environment of the power plant, the design of the water intake project, etc. By comprehensively considering multiple factors, the estimation result of the loss of entrained organisms is more objective, providing a scientific basis for designing water intake projects, reducing the risk of blockage, evaluating the loss of entrained organisms in the water intake of proposed power plants, and post-evaluating the entrained organisms in operating power plants, improving the water intake safety and ecological friendliness.

Description

Technical Field

[0001] The present invention relates to a method for estimating the loss of entrained biomass in a power plant's water intake considering different biological characteristics. It is an important method for estimating the biological damage and ecological reduction caused by the operation of hydraulic engineering, and is an evaluation method applicable to the operation safety and ecological friendliness of a power plant's cooling water intake project. Background Art

[0002] Currently, nuclear power plants in China are evenly distributed along the coast and adopt the once-through cooling method, using seawater near the plant site as the cooling water source. When a nuclear power plant operates, a large amount of cooling water needs to be pumped from the surrounding environmental water body into the plant for cooling the nuclear reactor and important equipment. The cooling water carries a large number of organisms into the water intake system. Among them, larger organisms are likely to block the water intake filter screen, preventing the normal inflow of cooling water into the cooling system and making it impossible for important equipment to be cooled in time, thus affecting the safe operation of the unit; smaller entrained organisms are likely to directly enter the interior of the cooling system through the intake pump house. Affected by mechanical entrainment and other factors, their survival rate is relatively low, resulting in the death of organisms. Therefore, the entry of organisms into the nuclear power water intake system not only threatens the safe operation of nuclear power but also causes direct damage to organisms.

[0003] Water intake entrainment usually refers to the process of passive carrying and transmission of small aquatic organisms that enter the cooling water system along with the water intake. Entrained organisms are damaged or killed under the action of high pressure, high temperature, and biocides. The monitoring results of the biological loss caused by the operation of the power plant's water intake show that entrained organisms include zooplankton, fish eggs, larvae, juveniles, larvae of shrimps, and young fish, etc. They are usually small in size. The total amount of entrained organisms is much larger than the amount of blocked organisms and accounts for the main part of the biological loss caused by water intake.

[0004] Current estimation methods do not consider the biological characteristics of organisms themselves (such as the life history stage, shape characteristics, and organism density of organisms), the characteristics of the flow movement of organisms entering the nuclear power plant's water intake system affected by the water intake confluence, the tidal characteristics of the water intake sea area, the design characteristics of the water intake project, etc. They can no longer meet the national requirements for the safe and ecological operation of nuclear power. There is an urgent need to comprehensively consider multiple factors and propose a scientific estimation method for accurately and objectively estimating the loss of entrained biomass in the water intake impact area. Summary of the Invention

[0005] To overcome the problems of the existing technology, the present invention proposes a method for estimating the loss of entrained biomass in power plant water intake considering different biological characteristics. The method comprehensively considers various factors such as the characteristics of entrained organisms (life history stage, shape characteristics, organism density, motility, characteristics of movement with the flow), marine environment (topography, shoreline, tidal current field, etc.), and power plant water intake design (water intake volume, characteristics of the water intake project structure, etc.), providing a scientific basis for the scientific design of water intake projects, reducing the risk of cold source blockage, quantitatively evaluating the loss of entrained biomass in the water intake of proposed power plants, and post-evaluating the entrained biomass of operating power plants, so as to improve the safety and ecological friendliness of nuclear power water intake.

[0006] The object of the present invention is achieved as follows: A method for estimating the loss of entrained biomass in power plant water intake considering different biological characteristics, and the steps of the method are as follows:

[0007] Step 1, establish a large-scale two-dimensional water intake hydrodynamic model considering the marine environment and water intake project design: Obtain the topography of the water intake sea area, flood and ebb tidal current conditions, shoreline characteristics, as well as the design dimensions, water intake flow rate, water intake velocity, water intake depth, etc. of the power plant water intake project, establish a water intake hydrodynamic model, divide the calculation grid, determine the boundary conditions and initial conditions of the flow field simulation, and select appropriate calculation parameters to simulate the sea area flow field including the nuclear power water intake project and the sea area affected by water intake; The hydrodynamic model is based on the shallow water equations in the form of depth integration. The model adopts the Boussinesq-based and vertical hydrostatic pressure assumptions and uses curvilinear coordinates, and uses the σ vertical coordinate system vertically:

[0008]

[0009] Where: σ is the vertical coordinate in the curvilinear coordinate system; d is the water depth value below the reference plane; H is the total water depth; z is the vertical coordinate in the physical space; ζ is the free water surface elevation;

[0010] The model control equations include the continuity equation, momentum equation and density state equation, and the equations are closed through turbulence theory. The specific control equations are as follows:

[0011] Depth-averaged continuity equation:

[0012]

[0013] Where: t is time; ξ and η are the horizontal coordinates in the curvilinear coordinate system; G ξξ 、G ηη Are the conversion coefficients for converting the curvilinear coordinate system to the Cartesian coordinate system; U and V are the depth-averaged flow velocities in the ξ and η directions respectively; Q represents the source-sink term;

[0014] The momentum equations of the model in the horizontal directions ξ and η:

[0015]

[0016]

[0017] Where: f is the Coriolis parameter, f = 2Ωsinφ, Ω is the angular velocity of the earth's rotation, φ is the latitude; F ξ and F η are the turbulent momentum fluxes in the ξ and η directions, reflecting the Reynolds stress; P ξ and P η is the water pressure gradient in the ξ and η directions; M ξ and M η is the source and sink of momentum in the ξ and η directions; ρ 0 is the water density;

[0018] Since it is based on the shallow water equation, the model is based on hydrostatic pressure and the two-dimensional model does not consider the water density ρ 0 change;

[0019]

[0020] Bed bottom resistance In quadratic form:

[0021]

[0022] Among them: Xie Cai coefficient C 2D According to Xie Cai's formula Calculation, n is the roughness coefficient; P is the water pressure gradient; g is the gravitational acceleration;

[0023] Step 2: Verification of hydrodynamic model results and flow field analysis: Use measured data or physical model experimental data corresponding to the power plant to be evaluated to verify the hydrodynamic model simulation results to ensure that the calculation results of the hydrodynamic model are consistent with the measured results, that is, the calculation results of the hydrodynamic model can reflect the actual flow field conditions in the water intake sea area;

[0024] Step 3, establish a dynamic model of the entrained organisms taking into account the characteristics and movement ability of the organisms: the entrained organisms include plankton, fish eggs, larvae, juvenile fish, shrimp larvae and young fish with movement ability without movement ability. The dynamic model of the entrained organisms is established according to the density, shape characteristics and whether the entrained organisms have the ability to move actively:

[0025] (1) Dynamic model of a coiled organism without motion ability:

[0026] 1) This type of rolled organisms has no ability to move, and their movement speed is consistent with the flow velocity. The density of the organisms is similar to that of the water body, and their shapes are regular. In the hydrodynamic model, the regular shapes of the organisms are generalized as spheres, and their movement control equations are:

[0027]

[0028] u p = u water

[0029] In the formula: s is the displacement of biological movement; u p is the speed of biological movement; u water is the flow velocity of the water current;

[0030] 2) This type of entrained organism has no motility, its movement speed is consistent with the flow velocity of the water current, the density of the organism is greater than or less than the density of the water body. Due to the change in the force on the organism in the water body caused by the density difference, its following of the water current shows a certain hysteresis. The shape of the organism is relatively regular, approximately spherical. Considering it as a sphere, its motion control equation is:

[0031]

[0032] In the formula: ρ p is the density of the organism;

[0033] 3) This type of entrained organism has no motility, its movement speed is consistent with the flow velocity of the water current, the density of the organism is approximately the same as the density of the water body, and the shape of the organism is irregular. Its motion control equation is:

[0034]

[0035] In the formula: f d is the drag coefficient of the organism; γ is the shape coefficient of the organism, V p is the volume of the organism; S p is the surface area of the organism;

[0036] 4) This type of entrained organism has no motility, its movement speed is consistent with the water current, there is a difference between the density of the organism and the density of the water body, and the shape of the organism is irregular. Its motion control equation is:

[0037]

[0038] (2) Dynamic model of entrained organisms with certain motility:

[0039] The entrained organisms with motility are generalized as small fish. In the model, the movement of small fish is generalized into three modes:

[0040] Mode 1: If the flow velocity of the water current at the location where the small fish is located is less than the induction flow velocity of the small fish, that is, the flow velocity of the water current < the induction flow velocity of the small fish, the small fish shows random movement;

[0041] Mode 2: If the water flow velocity at the location of small fish is between the sensing velocity and the limit velocity of small fish, that is, the sensing velocity of small fish ≤ water flow velocity < the limit velocity of small fish, small fish show rheotaxis, that is, countercurrent movement, and tend to move within the preferred velocity range; the countercurrent movement of small fish is manifested as: moving in the opposite direction of the environmental water flow, and its countercurrent movement range is a certain angular sector range, and the radius of the sector is the sensing ability range of small fish. Within this range, if there is a preferred velocity area for small fish, the movement direction of small fish points to the nearest preferred velocity area;

[0042] Mode 3: If the water flow velocity at the location of small fish is greater than the limit velocity of small fish, that is, the limit velocity of small fish ≤ water flow velocity, small fish are washed away by the water flow, showing a movement with the flow, and its relative movement velocity to the water flow is 0, that is, the absolute movement velocity is the water flow velocity;

[0043] Dynamic model of entrained organisms with certain movement ability, and the movement control equation of entrained organisms is:

[0044]

[0045] In the formula: V f is the movement velocity of entrained organisms. In Mode 3, V f = u water ;

[0046] Step 4, the intake entrained organism release model coupling the intake hydrodynamic model and the entrained organism dynamic model:

[0047] Coupling of the intake hydrodynamic model and the entrained organism dynamic model: The calculation result of the intake hydrodynamic model is used as the input condition of the entrained organism dynamic model. The location of the entrained organism in the intake sea area is obtained through the calculation of the hydrodynamic model. The entrained organism dynamic model then selects the corresponding model for calculation according to the organism density, shape characteristics and its active movement ability, and obtains the change of the organism's location over time;

[0048] Construction of the organism release model: Set an entrained organism release section upstream of the intake structure, release a large number of entrained organisms, and according to the calculation result of the coupling model, obtain the location change of the organisms under the influence of the intake water flow and the final number of organisms entering the intake pump house under different intake sea area environmental flow conditions;

[0049] The situation of entering the intake pump house is characterized by the entrainment rate of organisms. The entrainment rate of organisms refers to the percentage of the number of organism individuals entering the intake pump house affected by the intake confluence in the total number of released organisms. Its calculation formula is as follows:

[0050]

[0051] In the formula: J iis the biological entrainment rate of the i-th category; N ini is the biomass of the i-th category of organisms entering the water intake pump house; is the biomass of the i-th category of entrained organisms released at the upstream section of the water intake.

[0052] Step 5, Estimation of the loss of entrained organisms in water intake: The calculation formula for the loss of entrained organisms is as follows:

[0053]

[0054] In the formula: W is the loss of entrained organisms; W i is the loss of the i-th category of entrained organism resources; S i is the mortality rate of the i-th category of organisms after entering the water intake system.

[0055] The advantages and beneficial effects of the present invention are as follows: Aiming at the limitations that the current estimation of the loss of entrained organisms in nuclear power water intake cannot reflect the hydrodynamic environment of each power plant, the design of the water intake project, the characteristics of different entrained organisms (shape, organism density), movement characteristics, and different mortality rates after entering the water intake system, the present invention proposes an estimation method for the loss of entrained organisms in power plant water intake considering different biological characteristics and flow movement characteristics. It comprehensively considers various factors such as the characteristics of entrained organisms (life history stage, shape characteristics, organism density, movement ability, flow movement characteristics), marine environment (terrain, shoreline, tidal current field, etc.), and power plant water intake design (water intake volume, structural characteristics of the water intake project, etc.), making the estimation result of the loss of entrained organisms in water intake more objective. It provides a scientific basis for the scientific design of the water intake project, reducing the risk of cold source blockage, quantitatively evaluating the loss of entrained organisms in the water intake of proposed power plants, and post-evaluating the entrained organisms in operating power plants, improving the safety and ecological friendliness of nuclear power water intake. Description of the Drawings

[0056] The present invention will be further described below in conjunction with the drawings and embodiments.

[0057] Figure 1 is the flow chart of the method described in the embodiment of the present invention;

[0058] Figure 2 is a schematic diagram of three movement modes of the entrained organisms in the dynamic model of entrained organisms with certain movement ability described in the embodiment of the present invention;

[0059] Figure 3 is a schematic diagram of the movement rule logic of the entrained organisms in the dynamic model of entrained organisms with certain movement ability described in the embodiment of the present invention;

[0060] Figure 4 is a schematic diagram of the physical model layout for verifying the simulation results of the hydrodynamic model described in the embodiment of the present invention. Detailed Embodiments

[0061] Example:

[0062] This example is a method for estimating the loss of entrained organisms in the water intake of a power plant considering different biological characteristics. This example can be applied to different environmental flows (i.e., tidal conditions) and different water intake project structures, and classified and evaluated according to the characteristics and movement abilities of entrained organisms. This application example specifically explains the method with a generalized example.

[0063] I. Generalization of the structural type of the water intake open channel:

[0064] At present, all nuclear power plants in China are located in coastal areas and adopt the once-through cooling method, using the seawater near the plant site as the cooling water source during the operation of the unit. That is, when the nuclear power unit is operating, the water intake system of the power plant directly extracts environmental seawater into the circulating cooling water system to cool the nuclear power unit, the condenser unit of the conventional island, etc. After heat exchange, the seawater is directly discharged back into the water area. At present, the main water intake methods of power plants are open channel water intake, combined open channel and culvert water intake, and culvert water intake. Among them, because culvert water intake is located at the bottom of the water, the construction, operation, maintenance, etc. are more difficult and the cost is higher, while the open channel water intake has less difficulty in operation, maintenance, etc., and the technology is relatively mature and widely used. For example, more than 90% of nuclear power plants in China use open channel water intake.

[0065] The investigation of the water intake open channels of nuclear power plants in China shows that: the length of the water intake open channels of nuclear power plants in China is within 2 km, and the width is between 100 m and 200 m; according to the typical structural type and characteristics of the water intake open channels of power plants, they are generalized into three types: straight dike type, straight dike + 90° arc-shaped guide dike type, and straight dike + 180° arc-shaped guide dike. The straight dike type is arranged perpendicular to the shoreline. During flood and ebb tides, the flow difference inside and outside the open channel is small. Since there is no guide dike (i.e., breakwater) in the straight dike type water intake open channel, the water flow inside the open channel is greatly affected by the offshore waves, and the flow stability is poor. For the water intake open channels with 90° or 180° arc-shaped guide dikes added, the guide dikes can act as breakwaters, reducing the influence of offshore waves on the water body inside the open channel. That is, by setting a breakwater at the entrance of the open channel, the direction of the open channel entrance can be changed to avoid the direct transmission of offshore waves into the open channel, affecting the water flow stability inside the open channel. However, due to the existence of the arc-shaped guide dike, there are usually bend flows and non-uniform lateral flows inside the open channel, and during flood and ebb tides, the flow difference near the open channel entrance is large.

[0066] II. Generalization of environmental flow and water intake operation conditions:

[0067] 1) Generalization of the operation conditions of open channel water intake:

[0068] The main operating characteristic parameters of the open channel water intake for power plants mainly include the water intake depth, water intake velocity, water intake flow rate, etc., which are related to the installed capacity of the power plant, the topographic conditions of the water intake area, the type of water intake, etc. According to the investigation, the average water depth during the operation of the open channel water intake for nuclear power plants in China is 5 - 10 m, and the average water intake velocity is 0.15 - 0.3 m / s. It is mainly the case that one water intake open channel is shared by multiple (about 5 - 6) units at one site. Currently, the cooling water flow rate of each unit of a million - kilowatt - class nuclear power plant is about 50 - 65 m 3 / s. Therefore, taking the water intake flow rate of a single unit as 50 m 3 / s and six units sharing one water intake open channel as an example, the total water intake flow rate of the open channel is 300 m 3 / s. The water depth of the open channel is taken as 5 m and the width is taken as 200 m, corresponding to an average water intake velocity of 0.3 m / s for the open channel.

[0069] 2) Generalization of tidal current (marine environmental flow):

[0070] For power plants located in coastal areas, the water intake area of the sea is greatly affected by tidal currents. According to the investigation, the tidal currents in the water intake areas of coastal sites in China generally show the characteristics of along - shore reciprocating currents, and the average flood and ebb current velocities are about 0.3 m / s.

[0071] 3) Classification and generalization of entrained organisms:

[0072] Entrained organisms can be classified according to their motility as follows: Those without motility mainly refer to fish eggs, plankton, larvae, juveniles, and larvae of shrimps, etc.

[0073] Those with certain motility mainly refer to small fish or juveniles of large fish.

[0074] Non - motile organisms can be further classified according to their organism density as those with a density similar to that of water and can be suspended in water; those with a density different from that of water and mainly float on the water surface or sink to the bottom of the water body; and according to their organism shape as those with regular shapes that can be generalized as spherical; those with irregular shapes that cannot be directly generalized as spherical.

[0075] For small fish or juveniles of large fish with certain motility, they have a strong tendency towards the water flow. According to their behavioral responses to changes in water flow velocity, the corresponding water flow velocities can be divided into induction velocity, preferred velocity, limit velocity, etc.

[0076] When the environmental water flow velocity at the location where the fish is located is less than the fish's induction velocity, at this time, the fish is not sensitive to the change in water flow, swims in an uncertain direction, and shows a random movement state.

[0077] When the environmental water flow velocity at the location where the fish is located is between the induction velocity and the limit velocity, the fish has a strong tendency to flow, showing a counter - current movement, and its tendency to flow is stronger in some velocity intervals (i.e., the preferred velocity).

[0078] When the environmental water flow velocity at the location where the fish is located is greater than the limit velocity of the fish, the fish will be washed away by the water flow. The fish needs to have a movement speed greater than the environmental water flow velocity to turn in the water, but it is difficult for it to reach this speed. Therefore, it shows a state of moving with the flow.

[0079] In summary, the following assumptions are made for the entrained organisms in this embodiment:

[0080] (I) Entrained organisms without motility:

[0081] (1) Entrained organisms with an organism density approximately equal to the water density and regular shapes, i.e., entrained organisms such as fish eggs suspended in water.

[0082] (2) Entrained organisms with an organism density greater than or less than the water density and regular shapes. The entrained organisms are generalized as spherical shapes with diameters ranging from 1 mm to more than a dozen millimeters. Spherical benthic organisms such as Acaudina molpadioides that inhabit the bottom layer of the water with a density greater than the water density, or entrained organisms with a density less than the water density and regular shapes, such as spherical algae floating in the water, such as Phaeocystis globosa, etc.

[0083] (3) Entrained organisms with an organism density approximately equal to the water density and irregular shapes, i.e., biological larvae suspended in water, such as entrained organisms like larval fish, juvenile fish, and larval shrimp.

[0084] In addition, entrained organisms with an irregular shape and a difference in organism density from the water, such as entrained organisms like Hydra.

[0085] (II) Entrained organisms with certain motility:

[0086] The entrained organisms with motility that affect nuclear power water intake are mainly small-sized fish or the juveniles of large-sized fish, with lengths ranging from a few millimeters to dozens of millimeters. In this embodiment, such entrained organisms with motility that affect nuclear power water intake are generalized as small-sized fish. The induced flow velocity of these small-sized fish in the motion model is selected as 0.10 m / s, the preferred flow velocity range is 0.20 - 0.50 m / s, and the limit velocity is 0.60 m / s.

[0087] Fish perceive direction through water flow when swimming. The flow velocity at which the fish begins to show a flow-following response is the induced flow velocity; the preferred flow velocity is an important indicator for fish aggregation. Within the flow velocity range that the fish can overcome, they often like to gather and swim upstream in a certain flow velocity region that is most suitable for them. This flow velocity range is the preferred flow velocity; the limit velocity refers to the maximum water flow velocity that the fish can overcome. When exceeding this flow velocity, it stops swimming upstream or begins to move with the flow.

[0088] The specific steps of the method in this embodiment are as follows, and the process is as Figure 1 shown:

[0089] Step 1: Establish a large-scale two-dimensional water intake hydrodynamic model considering the sea area environment and the design of the water intake project: Obtain the topography of the water intake sea area, the ebb and flood tide conditions, the shoreline characteristics, as well as the design dimensions, water intake flow rate, water intake velocity, water intake depth, etc. of the power plant water intake project. Establish a water intake hydrodynamic model, divide the computational grid, determine the boundary conditions and initial conditions for the flow field simulation, and select appropriate computational parameters to simulate the flow field of the sea area including the nuclear power water intake project and the sea area affected by the water intake. The hydrodynamic model is based on the shallow water equations in the form of depth integration. The model adopts the Boussinesq assumption and the vertical hydrostatic pressure assumption and uses curvilinear coordinates, and the σ vertical coordinate system is used vertically:

[0090]

[0091] where: σ is the vertical coordinate in the curvilinear coordinate system; d is the water depth value below the reference plane (the reference plane can be the free water surface, can be any horizontal plane, and can be set according to needs); H is the total water depth; z is the vertical coordinate in physical space; ζ is the free water surface elevation.

[0092] The model control equations include the continuity equation, the momentum equation, and the density state equation, and the equations are closed through turbulence theory. The specific control equations are as follows:

[0093] Depth-averaged continuity equation:

[0094]

[0095] where: t is time; ξ and η are the horizontal coordinates in the curvilinear coordinate system; G ξξ 、G ηη are the transformation coefficients for converting the curvilinear coordinate system to the Cartesian coordinate system; U and V are the depth-averaged velocities in the ξ and η directions respectively; Q represents the source-sink term, such as the intake and discharge of the power plant.

[0096] Momentum equations of the model in the horizontal directions ξ and η:

[0097]

[0098] where: f is the Coriolis parameter, f = 2Ωsinφ, Ω is the angular velocity of the earth's rotation, φ is the latitude; F ξ and F η are the turbulent momentum fluxes in the ξ and η directions respectively, reflecting the Reynolds stress; P ξ and P η are the water pressure gradients in the ξ and η directions; M ξ and M η are the source-sink terms of momentum in the ξ and η directions; ρ 0 is the water body density.

[0099] Since it is based on the shallow water equations, the model is based on hydrostatic pressure and the two-dimensional model does not consider the variation of water density ρ. 0 Change.

[0100]

[0101]

[0102] Bed resistance Adopts a quadratic form:

[0103]

[0104] Where: Chezy coefficient C 2D Calculated according to the Chezy formula n is the roughness coefficient, which can be calibrated based on measured data or taken according to experience; P is the water pressure gradient; g is the acceleration due to gravity.

[0105] Step 2, Verification of the hydrodynamic model results and flow field analysis: The simulation results of the hydrodynamic model are verified using measured data or the physical model experiment data corresponding to the power plant to be evaluated, so as to ensure that the calculation results of the hydrodynamic model are consistent with the measured results or the measurement results of the physical model experiment, that is, the calculation results of the hydrodynamic model can reflect the actual flow field conditions in the water intake area.

[0106] The hydrodynamic model is a mathematical model established based on control equations and discretization methods. The physical model is a scale model of the real field built in the laboratory and following experimental specifications (such as the criteria of gravity similarity, buoyancy similarity, etc. according to experimental needs), which can reflect the flow field of the real field to a certain extent. The on-site measured data are the results of actual measurements in the real field. Both the physical model and the on-site measurements can reflect the changes in the actual flow field. Therefore, in this step, the results of the physical model experiment or the on-site measured results are mainly used to compare with the simulation results of the mathematical model, and then the parameter settings of the mathematical model are adjusted to make the simulation results of the mathematical model as consistent as possible with the changes in the actual flow field.

[0107] Step 3, Establish a dynamic model of entrained organisms considering biological characteristics and motility: Entrained organisms include plankton, fish eggs, larvae, juveniles, shrimp larvae without motility and juveniles with motility. A dynamic model of entrained organisms is established according to the organism density, shape characteristics and whether they have active motility of entrained organisms:

[0108] (1) Dynamic model of entrained organisms without motility:

[0109] 1) In this embodiment, a type of entrained organism that has no motility, a movement speed consistent with the water flow velocity, a biological density approximate to that of the water body, and a regular shape is called "type ① entrained organism". Type ① entrained organisms can be generalized as spheres in the hydrodynamic model, and the forces on each phase are isotropic. The motion control equation for type ① entrained organisms is:

[0110]

[0111] u p =u water

[0112] In the formula: s is the displacement of the organism's movement; u p is the movement speed of the organism; u water is the water flow velocity; this equation is applicable to simulating entrained organisms with regular shapes such as fish eggs suspended in the water body after absorbing water and swelling and having no motility.

[0113] 2) In this embodiment, a type of entrained organism that has no motility, a movement speed consistent with the water flow velocity, and a biological density greater than or less than that of the water body, that is, a type of entrained organism with a certain difference from the water body density is called "type ② entrained organism". Due to the change in the force on the organism in the water body caused by the density difference, the follow-up of type ② entrained organisms to the water flow shows a certain hysteresis. The shape of the organism of type ② entrained organisms is relatively regular, approximately spherical. Considering it as a sphere, its motion control equation is:

[0114]

[0115] In the formula: ρ p is the biological density.

[0116] This equation is applicable to simulating entrained organisms with relatively regular shapes, a certain difference in density from the water body, and no motility. Type ② entrained organisms include some spherical benthic organisms inhabiting the bottom of the water body, such as sea cucumbers with a density greater than that of the water body, and some floating algae in the water body with a density less than that of the water body. In actual application analysis, organisms with a biological density greater than and less than that of the water body can be analyzed separately, such as entrained organism ②a (biological density greater than that of the water body) and entrained organism ②b (biological density less than that of the water body) in the application example of this embodiment.

[0117] 3) In this embodiment, a type of entrained organism that has no motility, a movement speed consistent with the water flow, but a biological density approximate to that of the water body and an irregular organism shape is called "type ③ entrained organism". The biological density of type ③ entrained organisms is approximate to that of the water body, and they are entrained organisms with irregular shapes, that is, biological larvae suspended in the water body, such as larval fish, juvenile fish, larval shrimp, etc. Type ③ entrained organisms introduce a biological shape coefficient γ, and its motion control equation is:

[0118]

[0119] In the formula: f d is the biological resistance coefficient (usually taken as 1, and can also be determined according to biological experiments or expert experience); γ is the biological shape coefficient (the ratio of the surface area of a sphere with the same volume as the organism to the surface area of the organism is the biological shape coefficient, the shape coefficient of a spherical organism is equal to 1, and the shape coefficients of other organisms are less than 1); V p is the volume of the organism; S p is the surface area of the organism.

[0120] This equation is applicable to simulating entrained organisms such as larvae, juveniles, and shrimp larvae in the early life history stage of organisms, which have relatively irregular shapes, densities similar to that of water, and no motility.

[0121] If there is a certain difference between the density of the organism and that of water, the above motion control equation adds a velocity change term caused by the buoyancy effect of water on the organism due to the density difference, that is, a velocity change term caused by the buoyancy effect is added to the control equation The control equation is

[0122] (2) Dynamic model of entrained organisms with certain motility:

[0123] Entrained organisms such as small-sized fish have a certain motility and a certain relative motion with the water flow. The density of the organism is usually greater than that of water, but they can adjust their states and positions in the water through their own movements. Therefore, the influence of the density difference between the organism and water on the organism's movement is not considered; due to the complex shape of the organism, it is difficult to consider it through the shape coefficient. Therefore, the movement behavior of this type of entrained organism is mainly defined based on the movement state of the organism in the water flow. This type of entrained organism is called "Type ④ entrained organism".

[0124] Specifically, the reasons for not considering the shape and density of organisms with motility are as follows: The migration movement of this type of organism in water is not driven by the density difference between it and water or the force change caused by irregular shape, but by its own motility and its response relationship to water flow conditions, etc., which leads to the change of its position in water.

[0125] When the environmental water flow velocity at the location where the fish is located is less than the fish's induction velocity, the fish exhibits random movement; when the environmental water flow velocity at the location where the fish is located is greater than the fish's induction velocity, the fish is affected by the water flow induction and begins to move upstream at a certain angle (the fan-shaped area in the upstream direction: the fan angle and radius are determined according to the fish's visual ability and can be obtained through experiments, expert experience, or research literature). The fish preferentially moves upstream within a certain water flow velocity area that it considers more suitable. This water flow velocity area is the fish's preferred velocity. If there is no preferred velocity area, the fish will move randomly within the upstream direction; when the environmental water flow velocity at the location where the fish is located is greater than the limit velocity, the fish moves with the flow.

[0126] The induction velocity, preferred velocity, limit velocity, swimming ability of small fish, and the perception area (i.e., the fan-shaped area) in the upstream direction can all be obtained through fish swimming behavior experiments, historical data, expert experience, or on-site monitoring results.

[0127] In summary, the movement of small fish, mainly fry, as entrained organisms is divided into three modes, as Figure 2 shown:

[0128] Each movement mode is judged based on the comparison of the water flow velocity at the environmental position where the small fish is located with the induction velocity and limit velocity:

[0129] Mode 1: Figure 2 On the left side, if the water flow velocity at the location where the fry is located is less than the fry's induction velocity, that is, the water flow velocity < fry's induction velocity, the fry exhibits random movement with an indefinite direction. In Mode 1, V f is the movement speed of the fry, and its magnitude is a random value within the fry's swimming ability range (i.e., within the range of 0 to the fry's limit velocity), and the direction is randomly selected.

[0130] Mode 2: Figure 2 In the middle dashed box, if the water flow velocity at the location where the fry is located is between the fry's induction velocity and limit velocity, that is, fry's induction velocity ≤ water flow velocity < fry's limit velocity, the fry exhibits strong flow-tropism, specifically manifested as moving upstream, and is more inclined to move within the preferred velocity range. The upstream movement of the fry is manifested as: within a fan-shaped range at a certain angle in the opposite direction of the environmental water flow direction is its upstream movement range, and the radius of the fan-shaped range is its induction ability range. If there is a preferred velocity area within its upstream movement range, then its movement direction points to the nearest preferred velocity area as Mode 2①, Figure 2 on the left side within the middle dashed box; if there is no preferred velocity area, then its movement direction is random within its movement range as Mode 2②, Figure 2 on the right side within the middle dashed box.

[0131] The angle and range of the induction ability, that is, the angle and radius of the fan, can be obtained through expert experience or biological experiments.

[0132] Mode 3: Figure 2 On the right side, if the water flow velocity at the position where the juvenile fish is located is greater than the critical velocity of the juvenile fish, that is, the critical velocity of the juvenile fish ≤ water flow velocity, the juvenile fish is washed away by the water flow, showing a movement with the flow. Its movement speed is the water flow speed, and its movement control equation is:

[0133]

[0134] In the formula: V f is the movement speed of the entrained organism. In Mode 3, V f = u water r ;

[0135] The movement rule logic diagram of the entrained organism with certain movement ability is as Figure 3 shown.

[0136] Step 4, the entrained organism release model for coupling the water intake hydrodynamic model and the entrained organism dynamic model:

[0137] Coupling of the water intake hydrodynamic model and the entrained organism dynamic model: The output results of the water intake hydrodynamic model (such as hydraulic information such as environmental water flow velocity) are used as the input conditions of the entrained organism dynamic model. The flow field conditions (water depth, flow velocity, etc.) at the position where the entrained organism is located in the water intake sea area are calculated through the hydrodynamic model (that is, input the position coordinates of the entrained organism in the water intake sea area, and obtain the hydraulic information at this position through interpolation of the hydrodynamic model, providing a basis for judging the movement state and the law of movement with the flow of the entrained organism). The entrained organism dynamic model selects the corresponding model for calculation according to the organism density, shape characteristics, movement ability and the environmental flow velocity at the position, and obtains the change of the organism's position with time.

[0138] Construction of the organism release model: Set a release section upstream of the water intake open channel (the distance from the water intake structure and the distance from the shore are such that it is not affected by the water intake structure and the movement trajectory of the organism can envelope the water intake entrance), release a large number of entrained organisms (the number of entrained organisms released can be determined according to the results of the marine organism survey, or a larger biomass can be set according to the power plant's needs). According to the calculation results of the entrained organism dynamic model, obtain the position change of the organism under the influence of the water intake water flow and the final situation of entering the water intake pump house under different environmental flow conditions in the water intake sea area.

[0139] The situation of entering the water intake pump house is characterized by the organism entrainment rate. The organism entrainment rate is the percentage of the number of organism individuals entering the water intake pump house affected by the water intake confluence in the total amount of organisms released. Its calculation formula is as follows:

[0140]

[0141] In the formula: Ji is the entrainment rate of the i-th type of organism; N ini is the biomass of the i-th type of organism entering the water intake pump house; N 0i is the biomass of the i-th type of entrained organism released at the upstream section of the water intake.

[0142] Step 5, Estimation of the loss of entrained organism biomass: Based on the hydrodynamic change law in the water intake sea area and the calculation results of the entrained organism dynamic model, analyze and obtain the biomass of different types of entrained organisms affected by the water intake confluence and entering the water intake system (i.e., entering the water intake pump house) under the corresponding water intake sea area environment flow and water intake project structure, and then calculate the loss of entrained organism biomass according to the mortality rate of different types of entrained organisms after entering the water intake system.

[0143] The calculation formula for the loss of entrained organisms is as follows:

[0144]

[0145] In the formula: W is the loss of entrained organisms; W i is the loss of the i-th type of entrained organism resources (i = fish eggs, plankton, larvae / shrimps, juvenile fish, etc., mainly classified according to the shape, density, motility, etc. of the aforementioned organisms); S i is the mortality rate of the i-th type of organism after entering the water intake system. The mortality rate of entrained organisms can be obtained based on the monitoring data or operation experience of the power plant, or can also be obtained based on the research results of predecessors.

[0146] Application example:

[0147] The water intake open channel in this application example is of the straight dyke + 90° arc-shaped guide dyke type. The length of the straight dyke section is 800 m, 400 m on land and 400 m in the sea area, the width is 200 m, the water intake depth is 5 m, and the water intake flow velocity is 0.3 m / s. The tidal current in the environmental sea area is an alongshore reciprocating current, and the flood and ebb tidal current velocities are both 0.3 m / s. The water depth in the environmental sea area is the same as the water intake depth of the open channel.

[0148] Step 1, Establish a large-scale two-dimensional water intake hydrodynamic model considering the sea area environment and water intake project design.

[0149] The calculation area includes the water intake project (i.e., the water intake open channel of the straight dyke + 90° arc-shaped guide dyke) and the external sea area. The shoreline is 12000 m in the alongshore direction and 2000 m in the offshore direction. The mesh is divided into unstructured meshes for the arc-shaped guide dyke part of the open channel and structured meshes for the rest. Local refinement is carried out at the arc-shaped guide dyke of the open channel and the side walls of the open channel. The number of meshes is about 22 million.

[0150] Boundary conditions: The shore boundary is a fixed wall; when simulating the flood tide, the incoming flow at the positive X-axis boundary is taken as the environmental positive incoming flow, that is, the positive incoming flow. When simulating the ebb tide, the incoming flow at the negative X-axis boundary is taken as the environmental negative incoming flow, that is, the negative incoming flow; the upstream boundary of the environmental flow is a velocity inlet, and the downstream boundary of the environmental flow is a pressure outlet; the seabed roughness height is 0.03 m, the roughness coefficient is 0.5, and the intake of the pump house is a velocity inlet.

[0151] Initial conditions: Start with the static flow condition.

[0152] Step 2, Verification of the hydrodynamic model results and flow field analysis: Use the measured data or the corresponding physical model experimental data to verify the simulation results of the hydrodynamic model to ensure that the calculated hydrodynamic process is basically consistent with the measured process. In this example, the physical model experimental data is used to verify the hydrodynamic simulation results.

[0153] Establish a physical model for verifying the hydrodynamic model in the laboratory, as Figure 4 shown. Considering the principles of model design and model similarity conditions, and taking into account the model test site conditions and factors such as water supply and power supply, the physical model range is finally selected as 30 m × 20 m, with a length scale ratio of 1:100 to the mathematical model, a velocity scale ratio of 1:10, and a flow rate scale ratio of 1:100,000. Due to the limited test site, the downstream direction (i.e., the length) cannot be fully replicated according to the scale. Finally, the digital model area corresponding to the physical model is the area of 3 km × 2 km around the simulated intake channel. The intake channel is located Figure 4 at the lower part in the middle, with a straight dike + 90° arc-shaped guide dike type in the channel.

[0154] The inlet and outlet of the physical model are connected to the underground reservoir through multiple pumps and pipes to achieve a closed-loop circulation. Each pump is connected to the computer system to accurately distribute the flow rate. Flow straightening devices (as Figure 4 shown) are laid before the upstream inlet pump and after the downstream outlet pump to eliminate the excess energy of the pump and achieve the purpose of uniform inflow and outflow. The boundary flow rates of the upstream and downstream of the physical model are obtained according to the digital model results. For the outlet at the rear boundary of the intake channel, in order to ensure the uniformity of the outflow, an overflow weir is used for outflow, and one pump is installed to control the outflow flow rate. Water level detectors are arranged in the flow field to monitor the water level change in real time to ensure the normal progress of the experiment. The channel model in the experiment is assembled in multiple sections and can be disassembled. Figure 4 The layout of the channel is shown when the environmental positive incoming flow occurs. For the case of environmental negative incoming flow, the inlet and outlet of the environmental flow remain unchanged, and only the arc-shaped guide dike of the channel needs to be reversed against the water flow to meet the requirements.

[0155] Model verification includes: flow pattern verification and velocity verification:

[0156] Flow pattern verification: To verify the accuracy and suitability of the mathematical model, a comparative verification of the flow field was carried out in combination with the research results of the physical model test of the flow field in the water intake open channel. The results show that the numerically calculated flow field well reflects the water flow patterns inside and outside the water intake open channel in the physical model: under the pick-up flow action on the upstream incoming flow at the straight dike of the open channel, the water flow converges, and part of the water flow enters the water intake open channel under the water intake entrainment action. There is a water flow split at the head of the arc-shaped guide dike. Due to the lower water flow velocity inside the dike head and the higher water flow velocity outside, a small part of the water flow inside the dike head flows countercurrently to the outside. Under the guiding action of the arc-shaped guide dike, the main flow in the open channel is concentrated on the right side inside the open channel, and the left side is the recirculation area.

[0157] Flow velocity verification: When the environmental flow is the forward incoming flow and the reverse incoming flow respectively, for two characteristic cross-sections inside the water intake open channel of the 90° arc-shaped guide dike, the flow velocities obtained from the numerical simulation calculation are compared and verified with the flow velocities measured in the physical model test.

[0158] The flow field and flow velocity distribution obtained from the numerical simulation calculation are in good agreement with the test measurement, and can well reflect the distribution of the water intake flow field. The subsequent steps can be carried out.

[0159] Step 3: Establish a dynamic model of entrained organisms considering biological characteristics and motility:

[0160] Entrained organisms include plankton without motility, fish eggs, larvae, juveniles, shrimp larvae, etc. and juveniles with certain motility. According to the organism density, shape characteristics and whether they have active motility of the entrained organisms, a dynamic model of entrained organisms is established by classification.

[0161] Dynamic model of entrained organisms:

[0162] (1) Dynamic model of entrained organisms without motility:

[0163] 1) Specific setting parameters of type ① entrained organisms in this application example: organism density ρ p =ρ 0 =998.2 g / cm 3 ; generalized spherical organism diameter = 0.01 m.

[0164] 2) Specific setting parameters of type ②a entrained organisms in this application example: when the organism density is greater than the water body density: ρ p =998.4 g / cm 3 ,generalized spherical organism diameter = 0.01 m.

[0165] 3) Specific setting parameters of type ②b entrained organisms in this application example: when the organism density is less than the water body density: ρ p =998.0 g / cm 3 ,generalized spherical organism diameter = 0.01 m.

[0166] 4) In this application example, specific parameters are set for type ③ entrained organisms: biological density ρ p = ρ 0 = 998.2 g / cm 3 ; The generalized spherical diameter of the organism is 0.01 m, and the shape coefficient of the organism is 0.5.

[0167] The setting of the above parameters can be determined based on biological characteristics, on-site monitoring data, and expert experience.

[0168] (2) Dynamic model of entrained organisms with certain motility:

[0169] Fish with motility (type ④ entrained organisms): The fish affected by nuclear power water intake are usually small fish or the juveniles of large fish. In the motion model, the induced flow velocity of the fish is selected as 0.10 m / s, the preferred flow velocity range is 0.20 - 0.50 m / s, and the limit flow velocity is 0.60 m / s. Judgments are made based on the comparison between the flow velocity of the water where the fish is located and the induced flow velocity and limit flow velocity of the fish. This application example is for juveniles.

[0170] Mode 1: If the flow velocity of the water where the juvenile fish is located is less than the induced flow velocity of 0.1 m / s, that is, the flow velocity of the water < the induced flow velocity of the juvenile fish, the juvenile fish shows random movement with an indefinite direction. In mode 1, V f is the movement speed of the juvenile fish, and its magnitude is a random value within the swimming ability range of the juvenile fish, and the direction is randomly selected.

[0171] Mode 2: If the flow velocity of the water where the juvenile fish is located is between the induced flow velocity of 0.10 m / s and the limit flow velocity of 0.60 m / s of the juvenile fish, that is, the induced flow velocity of the juvenile fish ≤ the environmental flow velocity < the limit flow velocity of the juvenile fish, the juvenile fish shows countercurrent movement and moves within the fan-shaped range of the countercurrent towards the preferred flow velocity range (0.20 - 0.50 m / s), and its movement direction points to the nearest preferred flow velocity area; if there is no preferred flow velocity area within its countercurrent movement range, it moves randomly within the range.

[0172] The fan-shaped range of the countercurrent: The countercurrent movement is shown as the countercurrent movement range within a 60° fan-shaped range in the opposite direction of the environmental flow direction, and the radius of the fan is 10 m (the angle and radius are determined according to the fish vision research literature and expert experience).

[0173] Mode 3: If the flow velocity of the water where the juvenile fish is located is greater than the limit flow velocity of 0.60 m / s of the juvenile fish, that is, the limit flow velocity of the juvenile fish ≤ the environmental water flow velocity, the juvenile fish is washed away by the water and shows advective movement, and its movement speed is the water flow speed.

[0174] Step 4, the water intake entrained organism release model that couples the water intake hydrodynamic model and the entrained organism dynamic model:

[0175] Coupling of the water intake hydrodynamic model and the entrained organism dynamic model: The calculation results of the water intake hydrodynamic model (hydraulic information such as environmental water flow velocity) will be used as the input conditions for the entrained organism dynamic model. The entrained organisms move under the changing flow field. At each time step (the time steps of the hydrodynamic model and the entrained organism dynamic model need to be consistent), the hydraulic information is unidirectionally transmitted to the organism dynamic model, and the change of the organism's position over time is given according to the organism dynamic model.

[0176] Construction of the organism release model: Set an entrained organism release section upstream of the water intake open channel (the distance from the water intake structure and the offshore distance should be such that it is not affected by the water intake structure and the organism's trajectory can envelope the entrance of the water intake open channel). According to the entrained organism dynamic model, obtain the position changes of the organisms under the influence of the water intake flow and the final situation of entering the water intake pump house under different environmental flows (i.e., forward incoming flow and reverse incoming flow) in the water intake sea area.

[0177] Organism release position: The upstream release position of the organisms and the offshore distance should not be affected by the water intake structure. After multiple trial calculations, a location 2500 m upstream of the water intake open channel is selected, and the offshore distance is 600 m (the offshore distance needs to be determined according to the farthest offshore distance of the open channel embankment head, which is 600 m in this example; it can also be determined according to the actual distribution of organisms in the biological survey).

[0178] The situation of entering the water intake pump house is characterized by the organism entrainment rate.

[0179] Calculation of the organism entrainment rate: The percentage of the number of organism individuals entering the water intake pump house affected by the water intake confluence in the total number of released organisms. The calculation results are shown in Table 1 and Table 2:

[0180] Table 1 Statistical table of the entrainment rate of non-motile entrained organisms for forward / reverse incoming flow

[0181]

[0182] Table 2 Statistical table of the entrainment rate of motile entrained organisms for forward / reverse incoming flow

[0183]

[0184] Step 5, Estimation of the loss of the entrained organism biomass in water intake:

[0185] The operation monitoring results of an application example for a power plant show that: After the fish eggs (category ①) entering the cooling water system pass through the water intake pump house and enter the cooling water system, due to mechanical damage, temperature rise, and chlorination, the average mortality rate is about 100%; the average mortality rate of benthic organisms (category ②a) is about 33.3%; the average mortality rate of plankton (category ②b) is about 55%; the average mortality rate of juvenile shrimps (category ③) is about 40.7%; the average mortality rate of juvenile fish (category ④) is 43.9%.

[0186] In this application example, the loss amount of the coiled organisms is the sum of the loss amounts of various types of coiled organisms. Due to the lack of measured data, it is assumed that the input amount of each type of organism is 10 5 tails. Then:

[0187] W = (10 5 × 37.27% + 10 5 × 21.63%) × 100% + (10 5 × 6.49% + 10 5 × 4.83%) × 33.3% + (10 5 × 25.6% + 10 5 × 0%) × 55% + (10 5 × 37.27% + 10 5 × 21.69%) × 40.7% + (10 5 × 0% + 10 5 × 0.31%) × 43.9%

[0188] = 100882.4 tails.

[0189] Finally, it should be noted that the above is only used to illustrate the technical solution of the present invention and not to limit it. Although the present invention has been described in detail with reference to the preferred arrangement, those of ordinary skill in the art should understand that the technical solution of the present invention (such as the structural form of the diversion open channel, 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. A method for estimating biomass loss in a power plant water intake volume taking into account the characteristics of different organisms, characterized in that: The steps of the method are as follows: Step 1, establish a large-scale two-dimensional water intake hydrodynamic model considering the marine environment and water intake project design: obtain the water intake marine topography, tidal conditions, shoreline characteristics, and the design size, water intake flow, water intake velocity, and water depth of the power plant water intake project, establish a water intake hydrodynamic model, divide the calculation grid, determine the boundary conditions and initial conditions of the flow field simulation, and select appropriate calculation parameters to simulate the flow field of the sea area including the nuclear power water intake project and the water intake affected sea area; the hydrodynamic model is based on the shallow water equation in the form of water depth integral. The model adopts the assumption based on Boussinesq and vertical hydrostatic pressure and uses curvilinear coordinates, and the σ vertical coordinate system is used vertically: Where: σ is the vertical coordinate in the curvilinear coordinate system; d is the water depth below the reference plane; H is the total water depth; z is the vertical coordinate in physical space; ζ is the free water surface elevation; The model control equations include the continuity equation, momentum equation and density state equation, and the equations are closed through turbulence theory. The specific control equations are as follows: Depth-averaged continuity equation: Where: t is time; ξ and η are the horizontal coordinates in the curvilinear coordinate system; G ξξ , G ηη is the conversion coefficient from the curvilinear coordinate system to the rectangular coordinate system; U and V are the average water depth velocities in the ξ and η directions, respectively; Q represents the source and sink term; The momentum equations of the model in the horizontal directions ξ and η are: Where: f is the Coriolis parameter, f = 2Ωsinφ, Ω is the angular velocity of the earth's rotation, φ is the latitude; F ξ and F η are the turbulent momentum fluxes in the ξ and η directions, reflecting the Reynolds stress; P ξ and P η is the water pressure gradient in the ξ and η directions; M ξ and M η is the source and sink term of momentum in the ξ and η directions; ρ0 is the water density; Since it is based on the shallow water equation, the model is based on hydrostatic pressure, and the two-dimensional model does not consider the change of water density ρ0; Bed bottom resistance In quadratic form: Among them: Xie Cai coefficient C 2D According to Xie Cai's formula Calculation, n is the roughness coefficient; P is the water pressure gradient; g is the gravitational acceleration; Step 2: Verification of hydrodynamic model results and flow field analysis: Use measured data or physical model experimental data corresponding to the power plant to be evaluated to verify the hydrodynamic model simulation results to ensure that the calculation results of the hydrodynamic model are consistent with the measured results, that is, the calculation results of the hydrodynamic model can reflect the actual flow field conditions in the water intake sea area; Step 3, establish a dynamic model of the entrained organisms taking into account the characteristics and movement ability of the organisms: the entrained organisms include plankton, fish eggs, larvae, juvenile fish, shrimp larvae and young fish with movement ability without movement ability. The dynamic model of the entrained organisms is established according to the density, shape characteristics and whether the entrained organisms have the ability to move actively: (1) Dynamic model of a coiled organism without motion ability: 1) Class ① The organisms on the roll have no ability to move, and their movement speed is consistent with the water flow velocity. The density of the organisms is similar to that of the water body, and their shapes are regular. In the hydrodynamic model, the regular shapes of the organisms are generalized as spheres, and their movement control equations are: in p =in water Where: s is the biological motion displacement; u p is the biological movement speed; u water is the water flow velocity; 2) Class ② The organisms carried by the organisms have no ability to move. Their movement speed is consistent with the water flow velocity. The density of the organisms is greater or less than the density of the water body. Due to the density difference, the force on the organisms in the water body changes, which makes them show a certain hysteresis in following the water flow. The shape of the organisms is relatively regular and approximately spherical. Considering the spherical shape, their movement control equation is: Where: p is the density of organisms; 3) Class ③ The organisms carried on the roll have no movement ability, the movement speed is consistent with the water flow velocity, the density of the organism is similar to the density of the water body, the shape of the organism is irregular, and the movement control equation is: Where: f d is the drag coefficient of the organism; γ is the shape coefficient of the organism, V p is the volume of the organism; S p is the surface area of ​​the organism; if the density of the organism is different from that of the water body and the shape of the organism is irregular, the velocity change term caused by the buoyancy effect is added to the motion control equation The motion control equation is: (2) Dynamic model of a coiled organism with certain movement ability: The locomotive organisms are generalized as small fish, and the locomotion of small fish is generalized into three modes in the model. Mode 1: If the water flow velocity at the location of the small fish is less than the induced flow velocity of the small fish, that is, the water flow velocity < the induced flow velocity of the small fish, the small fish will show random movement; Mode 2: If the water flow velocity at the location of the small fish is between the small fish's induced flow velocity and the limit flow velocity, that is, the small fish's induced flow velocity ≤ water flow velocity < the small fish's limit flow velocity, the small fish will show a tendency to flow, that is, countercurrent movement, and tend to move in the preferred flow velocity range; the countercurrent movement of small fish is manifested as: moving in the opposite direction of the ambient water flow, and its countercurrent movement range is a certain angle fan range, and the fan radius is the fish's sensing ability range. In this range, if there is a small fish's preferred flow velocity area, the small fish's movement direction points to the nearest preferred flow velocity area; Mode 3: If the water flow velocity at the location of the small fish is greater than the limiting flow velocity of the small fish, that is, the limiting flow velocity of the small fish is ≤ the water flow velocity, the small fish will be washed away by the water flow and move with the flow. Its relative movement velocity is 0, that is, the absolute movement velocity is the water flow velocity. Dynamic model of a coiled organism with certain movement ability, the control equation of the coiled organism movement is: Where: V f is the speed of the biological load. In mode 3, V f =u water ; Step 4: A water intake and biomass delivery model that couples the water intake hydrodynamic model with the biomass dynamic model: Coupling of water intake hydrodynamic model and dynamic model of onboard organisms: The calculation results of the water intake hydrodynamic model are used as the input conditions of the dynamic model of onboard organisms. The location of onboard organisms in the water intake area is calculated by the hydrodynamic model. The dynamic model of onboard organisms then selects the corresponding model for calculation based on the density, shape characteristics and active movement ability of the organisms, and obtains the change of the location of the organisms over time; Construction of biological release model: Set up a biological release section upstream of the water intake structure, release a large number of biological rolls, and obtain the position changes of organisms under the influence of water intake flow and the number of organisms that eventually enter the water intake pump room under different water intake sea area environmental flow conditions according to the calculation results of the coupling model; The situation of entering the water intake pump house is characterized by the biological loading rate. The biological loading rate refers to the percentage of the number of biological individuals entering the water intake pump house affected by the water intake confluence to the total amount of biological input. The calculation formula is as follows: Where: J i is the loading rate of the i-th type of organisms; The biomass of type i organisms entering the water intake pump house; The i-th type of biomass released at the upstream section of water intake; Step 5: Estimation of loss of biomass in water collection rolls: The formula for calculating loss of biomass in water collection rolls is as follows: Where: W is the loss of biomass; W i is the loss of biological resources in the i-th category; S i is the mortality rate of the i-th type of organisms after entering the water intake system.

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