Power plant water intake entrainment biomass loss estimation method considering different biological characteristics

Abstract

The invention relates to a power plant water taking entrainment biomass loss estimation method considering different biological characteristics. The method comprises the steps that a large-range two-dimensional water taking hydrodynamic model considering a sea area environment and water taking engineering design is established; verifying a hydrodynamic model result and analyzing a flow field; establishing a dynamic model considering the entrainment biological characteristics and the exercise ability; the water taking entrainment organism putting model is coupled with the entrainment organism dynamic model of the water taking hydrodynamic model; and estimating the water intake entrainment biomass loss. Aiming at the limitation of estimation of the water intake volume-load biomass loss of the power plant at present, the invention provides a method for estimating the water intake volume-load biomass loss of the power plant, which considers different biological characteristics, flow-following movement characteristics, water power environment of the power plant, water intake engineering design and the like, and comprehensively considers multiple factors; the estimation result of the water intake volume load biomass loss is more objective, and a scientific basis is provided for designing a water intake project, reducing the blocking risk, evaluating the water intake volume load biomass loss of the proposed power plant, evaluating the volume load biomass of the operated power plant and improving the water intake safety and the ecological friendliness.

Description

Technical Field

[0001] The present invention relates to a method for estimating biomass loss in a water intake volume of a power plant taking into account different biological characteristics. The method is an important method for estimating biological damage and ecological loss caused by the operation of hydraulic engineering projects, and is an evaluation method suitable for the operation safety and eco-friendliness of cooling water intake projects in power plants. Background Art

[0002] At present, my country's nuclear power plants are all located in coastal areas, using direct current cooling, with seawater near the plant site as the cooling water source. When a nuclear power plant is in operation, a large amount of cooling water needs to be drawn from the surrounding water bodies into the power plant to cool 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 prone to block the water intake filter, making it impossible for cooling water to flow into the cooling system normally, and important equipment cannot be cooled in time, which in turn affects the safe operation of the unit; smaller organisms are prone to directly enter the cooling system through the water intake pump room. Affected by mechanical loads, the survival rate is 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 the organisms.

[0003] Water intake usually refers to the process of passively carrying and transporting small aquatic organisms that enter the cooling water system along with the water intake. The carried organisms are injured or killed under the action of high pressure, high temperature and biocides. The monitoring results of biological losses in power plant water intake operation show that the carried organisms include zooplankton, fish eggs, larvae, juvenile fish, shrimp and young fish, which are usually small in size. The total amount of carried organisms is much larger than the amount of entrained organisms, accounting for the majority of the biological losses caused by water intake.

[0004] The current estimation method does not take into account the characteristics of the organisms themselves (such as the life history stage, shape characteristics, and organism density), the characteristics of the flow movement entering the nuclear power plant water intake system due to the influence of water intake confluence, the tidal characteristics of the water intake sea area, and the design characteristics of the water intake project. It is far from meeting the country's requirements for nuclear power safety and ecological operation. It is urgent to comprehensively consider multiple factors and propose a precise and objective scientific estimation method for the loss of biomass in the water intake impact area. Summary of the invention

[0005] In order to overcome the problems of the prior art, the present invention proposes a method for estimating the loss of biomass carried by water intake rolls of power plants that takes into account the characteristics of different organisms. The method comprehensively considers the characteristics of the carried organisms (life history stage, shape characteristics, organism density, movement ability, and characteristics of movement with the flow), the marine environment (topography, coastline, tidal field, etc.), the water intake design of the power plant (water intake volume, structural characteristics of the water intake project, etc.), and other factors, providing a scientific basis for scientifically designing water intake projects, reducing the risk of cold source blockage, and quantitatively evaluating the loss of biomass carried by water intake rolls of proposed power plants, post-evaluation of the biomass carried by water intake rolls of operating power plants, and improving the safety and eco-friendliness of nuclear power water intake.

[0006] The object of the present invention is achieved by: a method for estimating the biomass loss of a water intake volume of a power plant taking into account the characteristics of different organisms, 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 water intake marine topography, tidal conditions, shoreline characteristics, and the design size, water intake flow, 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 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:

[0008]

[0009] 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;

[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 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;

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

[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 term of momentum in the ξ and η directions; ρ0 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 change of water density ρ0;

[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] Where: s is the biological motion displacement; u p is the biological movement speed; u water is the water flow velocity;

[0030] 2) This type of rolled organisms has no ability to move, and their movement speed is consistent with the water flow velocity. The density of the organism is greater or less than the density of the water body. Due to the density difference, the force on the organism in the water body changes, making it follow the water flow with a certain hysteresis. The shape of the organism is relatively regular and approximately spherical. Considering the spherical shape, its motion control equation is:

[0031]

[0032] Where: p is the density of organisms;

[0033] 3) This type of organism has no movement ability, the movement speed is consistent with the water flow velocity, the organism density is similar to the water density, the organism shape is irregular, and the movement control equation is:

[0034]

[0035] 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;

[0036] 4) This type of rolled organisms has no ability to move, the movement speed is consistent with the water flow, the density of the organisms is different from that of the water body, the shape of the organisms is irregular, and the movement control equation is:

[0037]

[0038] (2) Dynamic model of a coiled organism with certain movement ability:

[0039] The rolling organisms with movement ability are generalized as small fish. The movement of small fish is generalized into three modes in the model:

[0040] 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;

[0041] Mode 2: If the water flow velocity at the location of the small fish is between the small fish's sensing velocity and the limit velocity, that is, the small fish's sensing velocity ≤ water flow velocity < the small fish's limit velocity, the small fish will show a tendency to flow, that is, countercurrent movement, and tend to move in the preferred 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 small fish's sensing ability range. In this range, if there is a small fish's preferred velocity area, the small fish's movement direction points to the nearest preferred velocity area;

[0042] 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 ≤ the water flow velocity, the small fish will be washed away by the water flow and move with the flow. 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 a coiled organism with certain movement ability, the control equation of the coiled organism movement is:

[0044]

[0045] Where: V f is the speed of the biological load. In mode 3, V f =u water ;

[0046] Step 4: A water intake and biomass delivery model that couples the water intake hydrodynamic model with the biomass dynamic model:

[0047] 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;

[0048] 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;

[0049] 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:

[0050]

[0051] Where: J iis the loading rate of the i-th type of organisms; N ini The biomass of type i organisms entering the water intake pump house; It is the i-th type of biomass released at the upstream section of water intake.

[0052] 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:

[0053]

[0054] 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.

[0055] The advantages and beneficial effects of the present invention are as follows: in view of the limitations that the current estimation of biomass loss in nuclear power water intake rolls cannot reflect the hydrodynamic environment of each power plant, the design of water intake projects, the characteristics of different biological loads (shape, organism density), movement characteristics and different mortality rates after entering the water intake system, the present invention proposes a method for estimating biomass loss in power plant water intake rolls that takes into account different biological characteristics and characteristics of downstream movement, and comprehensively considers multiple factors such as the characteristics of the biological loads (life history stage, shape characteristics, organism density, movement ability, downstream movement characteristics), the marine environment (topography, coastline, tidal field, etc.), and the water intake design of the power plant (water intake volume, structural characteristics of the water intake project, etc.), so that the estimation result of the biomass loss in the water intake roll is more objective, and provides a scientific basis for scientifically designing water intake projects, reducing the risk of cold source blockage, and quantitatively evaluating the biomass loss in the water intake rolls of proposed power plants, post-evaluating the biomass of the water intake rolls of operating power plants, and improving the safety and eco-friendliness of nuclear power water intake. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0058] Figure 2 Schematic diagram of three motion modes of a rolled organism in a dynamic model of a rolled organism with certain motion ability according to the method of an embodiment of the present invention;

[0059] Figure 3 It is a logical schematic diagram of the movement rules of the entrained organism in the dynamic model of the entrained organism with certain movement ability according to the method of the embodiment of the present invention;

[0060] Figure 4 It is a schematic diagram of the physical model arrangement for verifying the hydrodynamic model simulation results of the method described in the embodiment of the present invention. DETAILED DESCRIPTION

[0061] Example:

[0062] This embodiment is a method for estimating the biomass loss of a power plant water intake volume taking into account different biological characteristics. This embodiment can be applied to different environmental flows (i.e., tidal conditions) and different water intake engineering structures, and is classified and evaluated according to the characteristics and movement capabilities of the organisms on the volume. This application example uses a generalized example to specifically explain the method.

[0063] 1. Generalization of open channel structure types:

[0064] At present, all nuclear power plants in my country are located in coastal areas and adopt a direct current circulation cooling method. The seawater near the plant site is used as the cooling water source for the unit operation. That is, when the nuclear power unit is in operation, the power plant water intake system directly draws ambient seawater into the circulating cooling water system to cool the nuclear power unit and the condenser unit of the conventional island. The seawater is then directly discharged back into the water area after heat exchange. At present, the main water intake methods for power plants include open channel water intake, open channel culvert combined water intake, and culvert water intake. Among them, since the culvert water intake is located at the bottom of the water, the construction, operation, and maintenance are more difficult and the cost is higher. The operation and maintenance of open channel water intake are less difficult, the technology is more mature, and the application is wider. For example, more than 90% of nuclear power plants in my country use open channels for water intake.

[0065] The survey of water intake open channels of nuclear power plants in my country shows that the length of water intake open channels of nuclear power plants in my country is less than 2 km, and the width is between 100m and 200m. According to the structural types and characteristics of typical water intake open channels of power plants, they are generalized into three types: straight dike type, straight dike + 90° arc diversion dike type, and straight dike + 180° arc diversion dike. The straight dike type is arranged perpendicular to the coastline. During high and low tides, the difference between the flow inside and outside the open channel is small. Since the straight dike type water intake open channel does not have a diversion dike (i.e., a breakwater), the water flow inside the open channel is greatly affected by the waves in the open sea, and the flow stability is poor. For the water intake open channel with an additional 90° or 180° arc diversion dike, its diversion dike can act as a breakwater to reduce the impact of offshore waves on the water body inside the open channel. That is, setting a breakwater at the entrance of the open channel can change the direction of the open channel entrance and prevent offshore waves from directly transmitting into the open channel and affecting the stability of the water flow in the open channel. However, due to the existence of the arc diversion dike, curved flow and non-uniform lateral flow usually occur inside the open channel, and the flow near the open channel mouth is quite different during high and low tides.

[0066] 2. Generalization of environmental flow and water intake operation conditions:

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

[0068] The characteristic parameters of power plant water intake open channel operation mainly include water depth, water flow rate, water flow rate, etc., which are related to the installed capacity of the power plant, the terrain conditions of the water intake water area, the type of water intake, etc. According to the survey, the average water depth of my country's nuclear power plant water intake open channel operation is 5-10m, the average water flow rate is 0.15-0.3m / s, and multiple units (about 5-6 units) at one site share one water intake open channel. At present, the cooling water flow rate of each unit in a million-kilowatt nuclear power plant is about 50-65m 3 / s, therefore, based on the water intake flow rate of a single unit of 50m 3 / s, for example, 6 units share one open channel for water intake, and the total flow rate of the open channel water intake is 300m 3 / s, the open channel water depth is 5m and the width is 200m, corresponding to an average flow rate of 0.3m / s.

[0069] 2) Generalization of tidal currents (sea environment currents):

[0070] For power plants located in coastal areas, the water areas they draw water from are greatly affected by tidal currents. According to research, tidal currents in the water areas of my country's coastal power plants generally show the characteristics of reciprocating coastal flows, with an average ebb and flow velocity of about 0.3m / s.

[0071] 3) Classification and generalization of the organisms contained in the volume:

[0072] Carried organisms can be divided into the following categories according to their movement ability: those without movement ability, mainly referring to fish eggs, plankton, fry, fish juveniles, shrimp larvae, etc.

[0073] Possessing certain motor abilities, it mainly refers to small fish or young fish of large fish.

[0074] Non-motile organisms can be divided into two types according to their body density: those with a density similar to that of water and can be suspended in the 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; according to their body shape, they can be divided into those with regular shape and can be generalized as a sphere; and those with irregular shape that cannot be directly generalized as a sphere.

[0075] For small fish with certain motor abilities or young large fish, they have a strong tendency to flow. According to their behavioral responses to changes in water flow velocity, the corresponding water flow velocity can be divided into induced flow velocity, preferred flow velocity, and limit flow velocity, etc.

[0076] When the water flow velocity of the environment where the fish is located is lower than the flow velocity sensed by the fish, the fish is insensitive to the change of water flow, swims in an uncertain direction, and exhibits a state of random movement.

[0077] When the flow velocity of the ambient water flow where the fish is located is between the induced flow velocity and the limit flow velocity, the fish has a strong tendency to flow, which manifests as countercurrent movement, and its tendency to flow is even stronger in some flow velocity ranges (i.e., preferred flow velocity).

[0078] When the flow rate of the surrounding water where the fish is located is greater than the fish's limiting flow rate, the fish will be washed away by the water flow. The fish needs to move at a speed greater than the flow rate of the surrounding water in order to turn in the water, but this is difficult to achieve. Therefore, it behaves as if it moves with the flow.

[0079] In summary, this embodiment makes the following assumptions about the organisms carried:

[0080] (I) Incapable of movement of the carried organisms:

[0081] (1) Organisms with a density similar to that of water and with regular shapes, such as fish eggs suspended in water.

[0082] (2) Organisms with a density greater than or less than the water density and with regular shapes. Organisms with a density greater than the water density are generally spherical, with diameters ranging from 1 mm to more than ten mm. They are spherical benthic organisms that live on the bottom of the water body, such as sea cucumbers, or organisms with a density less than the water density and with regular shapes, such as spherical algae floating in the water, such as brown cysts, etc.

[0083] (3) Organisms with an irregular shape and a density similar to that of water, i.e., young organisms suspended in water, such as fry, young fish, and shrimp.

[0084] In addition, the density of organisms varies with the water body, and there are irregularly shaped coiled organisms, such as hydra.

[0085] (ii) Organisms with certain mobility:

[0086] The moving organisms that affect the water intake of nuclear power plants are mainly small fish or juveniles of large fish, with a length of several millimeters to tens of millimeters. This embodiment generalizes such moving organisms that affect the water intake of nuclear power plants as small fish. The induced flow velocity of these small fish in the motion model is selected as 0.10m / s, the preferred flow velocity range is 0.20-0.50m / s, and the limit flow velocity is 0.60m / s.

[0087] When swimming, fish sense the direction through the water flow. The flow velocity when the fish begins to show a trend reaction is the induced flow velocity; the preferred flow velocity is an important indicator of fish gathering. Within the range of flow velocities that they can overcome, fish often like to gather in a flow velocity area that is most suitable for them and move upstream. This flow velocity range is the preferred flow velocity; the limiting flow velocity refers to the maximum water flow velocity that fish can overcome. When this flow velocity is exceeded, they stop moving upstream or start to move with the flow.

[0088] The specific steps of the method described in this embodiment are as follows: Figure 1 As shown:

[0089] 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, 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 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 Boussinesq and vertical hydrostatic pressure assumptions and uses curvilinear coordinates, and the σ vertical coordinate system is used vertically:

[0090]

[0091] Wherein: σ is the vertical coordinate in the curvilinear coordinate system; d is the water depth below the reference plane (the reference plane can be the free water surface or any horizontal plane, which can be set as needed); 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, momentum equation and 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 is the conversion coefficient from the curvilinear coordinate system to the rectangular coordinate system; U and V are the average flow velocities in the directions of ξ and η, respectively; Q represents the source and sink items, such as the water intake and discharge of power plants.

[0096] The momentum equations of the model in the horizontal direction ξ and η are:

[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, 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 are the source and sink terms of momentum in the ξ and η directions; ρ0 is the water density.

[0099] 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.

[0100]

[0101]

[0102] Bed bottom resistance In quadratic form:

[0103]

[0104] Among them: Xie Cai coefficient C 2D According to Xie Cai's formula Calculation, n is the roughness coefficient, which can be calibrated according to measured data or determined based on experience; P is the water pressure gradient; g is the acceleration of gravity.

[0105] 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 or the physical model experimental measurement results, 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 based on the control equation and discrete method. The physical model is a scale model of the real site built in the laboratory and follows the experimental specifications (such as gravity similarity and buoyancy similarity required by the experiment). It can reflect the flow field of the real site to a certain extent. The field measured data is the result of actual measurement at the real site. Both the physical model and the field measurement can reflect the changes in the actual flow field. Therefore, this step mainly uses the results of the physical model experiment or the results of the field measurement to compare the simulation results of the mathematical model, and then adjusts the parameter settings of the mathematical model so that the simulation results of the mathematical model are as consistent as possible with the changes in the actual flow field.

[0107] 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:

[0108] (1) Dynamic model of a coiled organism without motion ability:

[0109] 1) In this embodiment, a type of rolling organisms that have no movement ability, whose movement speed is consistent with the flow speed of water, whose biological density is similar to that of the water body, and whose regular shape is called "type ① rolling organisms". Type ① rolling organisms can be generalized as spheres in the hydrodynamic model, and the forces on each phase are the same. The motion control equation of type ① rolling organisms is:

[0110]

[0111] u p =u water

[0112] Where: s is the biological motion displacement; u p is the biological movement speed; u water is the water flow velocity; this equation is applicable to simulating regular-shaped and non-motile entrained organisms such as fish eggs that are suspended in the water body after absorbing water and swelling.

[0113] 2) In this embodiment, a type of organism that has no movement ability, whose movement speed is consistent with the water flow speed, and whose biological density is greater or less than the water body density, i.e., a type of organism that has a certain difference in density with the water body, is called "Type ② organisms". Due to the change in the force applied to the organism in the water body caused by the density difference, the Type ② organisms show a certain hysteresis in following the water flow. The shape of the Type ② organisms is relatively regular, approximately spherical. Considering the spherical shape, its motion control equation is:

[0114]

[0115] Where: p is the density of organisms.

[0116] This equation is suitable for simulating relatively regular shapes, density that is somewhat different from that of the water body, and no movement of the entrained organisms. Class ② entrained organisms include some spherical benthic organisms that inhabit the bottom of the water body, such as sea sweet potatoes and other organisms with a density greater than the density of the water body, and some organisms such as algae floating in the water body with a density less than the density of the water body. In actual application analysis, organisms with a density greater than that of the water body and organisms with a density less than that of the water body can be analyzed separately, such as entrained organisms ②a (organism density greater than that of the water body) and entrained organisms ②b (organism density less than that of the water body) in the application example of this embodiment.

[0117] 3) In this embodiment, a type of organisms that have no movement ability and whose movement speed is consistent with the water flow, but whose biological density is similar to that of the water body and whose biological shape is irregular, are called "③ type of organisms". The biological density of ③ type of organisms is similar to that of the water body, and they are irregularly shaped organisms, i.e., juvenile organisms suspended in the water body, such as fry, young fish, shrimp and other fry. The ③ type of organisms introduces the biological shape coefficient γ, and its motion control equation is:

[0118]

[0119] Where: f dis the resistance coefficient of the organism (usually 1, but can also be determined based on biological experiments or expert experience); γ is the shape coefficient of the organism (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 shape coefficient of the organism, the shape coefficient of a spherical organism is equal to 1, and the shape coefficient of other organisms is less than 1); V p is the volume of the organism; S p is the surface area of ​​an organism.

[0120] This equation is suitable for simulating fish larvae, juvenile fish, shrimp larvae and other organisms that are in the early life history stage, have relatively irregular shapes, density similar to that of water bodies, and are incapable of movement.

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

[0122] (2) Dynamic model of a coiled organism with certain movement ability:

[0123] Small-sized fish and other entrained organisms have certain movement capabilities and relative movement with the water flow. The density of organisms is usually greater than that of water, but they can adjust their state and position in the water through their own movement. Therefore, the influence of the density difference between organisms and water on the movement of organisms is not considered. Due to the complex shape of organisms, it is difficult to consider the shape coefficient. Therefore, the movement behavior of this type of entrained organisms is mainly defined based on the movement state of the organisms in the water flow. This type of entrained organisms is called "Class ④ entrained organisms".

[0124] Specifically, the shape and density of organisms with mobility are not taken into consideration because the migration of such organisms in water is not driven by the density difference between them and the water body or the change in force caused by their irregular shape, but by their own mobility and their response to water flow conditions, which leads to changes in their position in the water.

[0125] When the flow rate of the ambient water flow at the fish's location is less than the flow rate sensed by the fish, the fish will exhibit random movement; when the flow rate of the ambient water flow at the fish's location is greater than the flow rate sensed by the fish, the fish will be affected by the water flow and begin to move upstream at a certain angle (the fan-shaped area in the upstream direction: the fan-shaped angle and radius are determined based on the fish's visual ability, which can be obtained through experiments, expert experience or research literature). The fish will preferentially move upstream in a flow rate area that they consider to be more suitable. This flow rate area is the fish's preferred flow rate. If there is no preferred flow rate area, the fish will move randomly in the upstream direction; when the flow rate of the ambient water flow at the fish's location is greater than the limiting flow rate, the fish will move with the flow.

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

[0127] In summary, the movement of small fish-carrying organisms, mainly juvenile fish, can be divided into three modes: Figure 2 As shown:

[0128] Each movement mode is determined based on the comparison between the water flow velocity of the environment where the small fish is located and the induced flow velocity and the limit flow velocity:

[0129] Mode 1: Figure 2 On the left, if the water velocity at the location of the fry is less than the fry's sensed velocity, that is, the water velocity < the fry's sensed velocity, the fry will move randomly with uncertain directions. f is the movement speed of the fry, its size is a random value within the swimming ability range of the fry (i.e., within the range of 0 to the limit flow velocity of the fry), and the direction is randomly selected.

[0130] Mode 2: Figure 2 In the middle dotted box, if the water flow velocity at the location of the juvenile is between the juvenile's sensed flow velocity and the limit flow velocity, that is, the juvenile's sensed flow velocity ≤ water flow velocity < juvenile's limit flow velocity, the juvenile will show a strong tendency to flow, specifically, countercurrent movement, and will tend to move in the preferred flow velocity range. The countercurrent movement of the juvenile is manifested as: the countercurrent movement range is within a fan-shaped range at a certain angle in the opposite direction of the ambient water flow, and the radius of the fan-shaped range is its sensing ability range. If there is a preferred flow velocity area within its countercurrent movement range, then its movement direction points to the nearest preferred flow velocity area, which is mode 2①. Figure 2 The left side of the middle dotted box; if there is no preferred flow rate area, its movement direction is randomly in mode 2② within its movement range, Figure 2 On the right side of the middle dotted box.

[0131] The angle and range of the sensing capability, that is, the angle and radius of the sector, 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 location of the fry is greater than the fry's limiting velocity, that is, the fry's limiting velocity ≤ water flow velocity, the fry will be washed away by the water flow and move with the flow. Its movement speed is the water flow velocity, and its motion control equation is:

[0133]

[0134] Where: V f is the speed of the biological load. In mode 3, V f =u waterr ;

[0135] The logic diagram of the movement rules of organisms with certain movement ability is as follows Figure 3 shown.

[0136] Step 4: A water intake and biomass delivery model that couples the water intake hydrodynamic model with the biomass dynamic model:

[0137] Coupling of the water intake hydrodynamic model and the dynamic model of the entrained organisms: The output results of the water intake hydrodynamic model (such as hydraulic information such as the environmental water flow velocity) are used as the input conditions of the dynamic model of the entrained organisms. The flow field conditions (water depth, flow velocity, etc.) of the entrained organisms in the water intake sea area are calculated through the hydrodynamic model (that is, the position coordinates of the entrained organisms in the water intake sea area are input, and the hydraulic information of the position is obtained through interpolation of the hydrodynamic model, which provides a basis for determining the movement state of the entrained organisms and the law of their movement with the flow). The dynamic model of the entrained organisms selects the corresponding model for calculation based on the density, shape characteristics, movement ability and environmental flow velocity of the organisms, and obtains the changes in the position of the organisms over time.

[0138] Construction of biological release model: set up a release section upstream of the water intake open channel (the distance from the water intake structure and the distance from the shore shall not be affected by the water intake structure and the trajectory of biological movement can envelope the water intake entrance), release a large number of carried organisms (the number of carried organisms released can be determined according to the results of the marine biological survey, or a larger biomass can be set according to the needs of the power plant), and obtain the position changes of organisms under the influence of the water intake flow and their final entry into the water intake pump room under different water intake sea environmental flow conditions based on the calculation results of the carried organism dynamic model.

[0139] The situation of entering the water intake pump house is characterized by the biological loading rate. The biological loading rate is 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 organisms released. The calculation formula is as follows:

[0140]

[0141] Where: J i is the loading rate of the i-th type of organisms; N ini N is the biomass of the i-th type of organisms entering the water intake pump house; 0i It is the i-th type of biomass released at the upstream section of water intake.

[0142] Step 5, estimation of loss of biomass in the water intake roll: Based on the hydrodynamic variation law of the water intake sea area and the calculation results of the dynamic model of the carried organisms, the biomass of different types of carried organisms entering the water intake system (i.e. entering the water intake pump house) under the influence of water intake confluence under the corresponding water intake sea area environmental flow and water intake project structure is analyzed, and then the loss of biomass in the water intake roll is calculated based on the mortality rate of different types of carried organisms after entering the water intake system.

[0143] The formula for calculating the loss of biomass on board is as follows:

[0144]

[0145] Where: W is the loss of biomass; W i is the loss of the i-th type of biological resources (i = fish eggs, plankton, larvae / shrimp, juvenile fish, etc., mainly classified according to the shape, density, movement ability, etc. of the aforementioned organisms); S i is the mortality rate of the i-th type of organisms after entering the water intake system. The mortality rate of the carried organisms can be obtained based on the monitoring data or operating experience of the power plant, or based on previous research results.

[0146] Application examples:

[0147] The water intake open channel in this application example is a straight dike + 90° arc diversion dike type, with a straight dike section length of 800m, 400m on land and sea respectively, a width of 200m, a water intake depth of 5m, and a water intake flow rate of 0.3m / s. The tide in the environmental sea area is a reciprocating flow along the coast, with both the rising and falling tides at 0.3m / s, and the water depth in the environmental sea area is the same as the water depth of the open channel water intake.

[0148] Step 1: Establish a large-scale two-dimensional water intake hydrodynamic model that takes into account the marine environment and water intake project design.

[0149] The calculation area includes the water intake project (i.e., the water intake open channel of straight dike + 90° arc diversion dike) and the external sea area. The coastline is 12,000 m along the shore and 2,000 m offshore. The grid is divided into unstructured grids for the open channel arc diversion dike part and structured grids for the rest. Local encryption is performed on the open channel arc diversion dike and the side walls of the open channel, and the number of grids is about 22 million.

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

[0151] Initial conditions: static flow conditions are used for calculation.

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

[0153] Physical models for verifying the hydrodynamic model are established in the laboratory, such as Figure 4 As shown. Taking into account the principles of model design and model similarity conditions, as well as the conditions of the model test site and factors such as water supply and power supply, the physical model range is finally selected to be 30m×20m, with a length scale of 1:100, a velocity scale of 1:10, and a flow scale of 1:100000. Due to the limited test site, the downstream direction (i.e., length) cannot be fully replicated according to the scale. The final digital model area corresponding to the physical model is a 3km×2km area around the simulated inlet open channel. The water intake open channel is located at Figure 4 The lower middle part is an open channel straight embankment + 90° arc diversion embankment type.

[0154] The inlet and outlet of the physical model are connected to the underground water tank through multiple pumps and pipes to achieve closed-loop circulation. Each pump is connected to the computer system to accurately distribute the flow. A flow equalization device (such as Figure 4 As shown in the figure, the excess energy of the water pump is eliminated to achieve uniform inflow and outflow. The upstream and downstream boundary flows of the physical model are obtained based on the numerical model results. At the boundary outlet of the water intake open channel, in order to ensure the uniformity of the outflow, an overflow weir is used for outflow, and a pump is installed to control the outflow flow. A water level detector is arranged in the flow field to monitor the water level changes in real time to ensure the normal progress of the test. The open channel model in the test is assembled in multiple sections and can be disassembled. Figure 4 The figure shows the layout of the open channel when the environment is flowing in the forward direction. For the environment flowing in the reverse direction, the inlet and outlet of the environment flow remain unchanged, and the need can be met by simply replacing the arc-shaped diversion dam of the open channel to face the back of the water flow.

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

[0156] Flow pattern verification: In order to verify the accuracy and suitability of the mathematical model, the flow field was compared and verified in combination with the results of the physical model test of the water intake open channel flow field. The results show that the numerical calculation flow field reflects the flow pattern of water inside and outside the water intake open channel in the physical model well: the upstream flow converges under the diversion effect of the upstream side of the open channel straight dike, and part of the water flows into the water intake open channel under the water intake suction effect, and there is a diversion at the head of the arc diversion dike. Due to the low flow velocity inside the dike head and the high flow velocity outside, a small part of the water inside the dike head flows back to the outside, and the water flow inside the open channel is concentrated on the right side of the open channel under the diversion effect of the arc diversion dike. The left side is the recirculation area.

[0157] Flow velocity verification: For the two characteristic sections inside the 90° arc diversion dike water intake open channel when the environmental flow is in the forward and reverse directions, the flow velocity calculated by numerical simulation is compared with the flow velocity measured by physical model test.

[0158] The flow field and velocity distribution obtained by numerical simulation are in good agreement with the experimental measurements and can well reflect the distribution of water intake flow field. Subsequent steps can be carried out.

[0159] Step 3: Establish a dynamic model of the onboard organism that takes into account biological characteristics and movement capabilities:

[0160] Carried organisms include plankton, fish eggs, larvae, fish fry, shrimp larvae and young fish with certain mobility. A dynamic model of carried organisms is established based on their density, shape characteristics and whether they have active mobility.

[0161] Roll-loaded biological dynamic model:

[0162] (I) Dynamic model of a coiled organism without motion ability:

[0163] 1) Specific setting parameters for type ① of the organisms in this application example: organism density ρ p =ρ0=998.2g / cm 3 ; Generalized spherical organism diameter = 0.01m.

[0164] 2) This application example sets specific parameters for Class ②a biota: When the biota density is greater than the water density: ρ p =998.4g / cm 3 , generalized spherical organism diameter = 0.01m.

[0165] 3) This application example sets specific parameters for Class ②b rolled organisms: When the organism density is less than the water density: ρ p =998.0g / cm 3 , generalized spherical organism diameter = 0.01m.

[0166] 4) This application example sets specific parameters for Class ③ of the carried organisms: Organism density ρ p =ρ0=998.2g / cm 3 ; Generalized biological spherical diameter = 0.01m, organism shape coefficient 0.5.

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

[0168] (II) Dynamic model of a coiled organism with certain movement ability:

[0169] Fish with the ability to move (Class ④ of the entrained organisms): The fish affected by nuclear power water intake are usually small fish or juveniles of large fish. The induced flow velocity of fish in the movement model is selected as 0.10m / s, the preferred flow velocity range is 0.20-0.50m / s, and the limit flow velocity is 0.60m / s. The judgment is made based on the comparison between the water flow velocity of the fish's environment and the induced flow velocity and the limit flow velocity of the fish. This application example is juvenile fish.

[0170] Mode 1: If the water velocity at the location of the fry is less than the sensing velocity of 0.1 m / s, that is, the water velocity < the sensing velocity of the fry, the fry will move randomly with uncertain directions. f is the movement speed of the fry, its size is a random value within the swimming ability range of the fry, and the direction is randomly selected.

[0171] Mode 2: If the water flow velocity at the location of the fry is between the fry's induced flow velocity of 0.10 m / s and the limit flow velocity of 0.60 m / s, that is, the fry's induced flow velocity ≤ ambient flow velocity < fry's limit flow velocity, the fry will exhibit countercurrent movement and move toward the preferred flow velocity range (0.20-0.50 m / s) within the fan-shaped range of the countercurrent, with the direction of movement pointing to the nearest preferred flow velocity area; if there is no preferred flow velocity area within its countercurrent movement range, it will move randomly within the range.

[0172] Sector range of countercurrent: The countercurrent movement is manifested as a sector range of 60° in the opposite direction of the environmental flow, and the sector radius is 10m (the angle and radius are determined based on fish vision research literature and expert experience).

[0173] Mode 3: If the water flow velocity at the location of the fry is greater than the fry's limit flow velocity of 0.60 m / s, that is, the fry's limit flow velocity ≤ the ambient water flow velocity, the fry will be washed away by the water flow and move with the flow, and its movement speed is the water flow velocity.

[0174] Step 4: A water intake and biomass delivery model that couples the water intake hydrodynamic model with the biomass dynamic model:

[0175] Coupling of the water intake hydrodynamic model and the dynamic model of the onboard organisms: The calculation results of the water intake hydrodynamic model (hydraulic information such as environmental water flow velocity) will be used as the input conditions of the dynamic model of the onboard organisms. The onboard organisms move under the changes of the flow field. At each time step (the time step of the hydrodynamic model must be consistent with the time step of the dynamic model of the onboard organisms), the hydraulic information is transmitted unidirectionally to the biological dynamic model, and the biological dynamic model gives the changes in the position of the organisms over time.

[0176] Construction of biological release model: a biological release section is set up upstream of the open water intake channel (the distance from the water intake structure and the distance from the shore are based on the principle that they are not affected by the water intake structure and the trajectory of the organisms can envelop the entrance of the open water intake channel). According to the dynamic model of the biological release section, the position changes of the organisms under the influence of the water intake flow and their final entry into the water intake pump house under different water intake sea area environmental flows (i.e. forward flow and reverse flow) are obtained.

[0177] Biological placement location: The upstream biological placement location and offshore distance should not be affected by water intake structures. After multiple calculations, the location 2500m upstream of the open water intake channel and 600m offshore were selected (the offshore distance needs to be determined based on the farthest distance from the open channel embankment to the shore, which is 600m in this example; it can also be determined based on the actual distribution of organisms in biological surveys).

[0178] The conditions entering the water intake pump house are characterized by the biological loading rate.

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

[0180] Table 1 Statistics of the carrying rate of non-motile organisms in forward / reverse flow

[0181]

[0182] Table 2 Statistics of the carrying rate of organisms with mobility in forward / reverse flow

[0183]

[0184] Step 5, estimate the biomass loss of the water volume:

[0185] Application example: The results of monitoring the operation of a power plant show that after the fish eggs (Class ①) enter the cooling water system through the water intake pump room, the average mortality rate is about 100% due to mechanical damage, temperature rise and chlorination; the average mortality rate of benthic organisms (Class ②a) is about 33.3%; the average mortality rate of plankton (Class ②b) is about 55%; the average mortality rate of shrimp larvae (Class ③) is about 40.7%; and the average mortality rate of young fish (Class ④) is 43.9%.

[0186] The loss of biomass in this application example is the sum of the loss of all types of biomass. Due to the lack of actual measurement data, it is assumed that the amount of each type of biomass released is 10 5 tail, then:

[0187] W=(10 5 ×37.27%+10 5 ×21.63%)×100%+(10 5 ×6.49%+105 ×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 tail.

[0189] Finally, it should be noted that the above is only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred arrangement scheme, a person skilled in the art should understand that the technical solution of the present invention (such as the structural form of the open channel for water diversion, the application of various formulas, the sequence of steps, etc.) can be modified or replaced by equivalents 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 different biological characteristics, 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, 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 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 direction 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) 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: 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) This type of rolled organisms has no ability to move, and their movement speed is consistent with the water flow velocity. The density of the organism is greater or less than the density of the water body. Due to the density difference, the force on the organism in the water body changes, making it follow the water flow with a certain hysteresis. The shape of the organism is relatively regular and approximately spherical. Considering the spherical shape, its motion control equation is: Where: p is the density of organisms; 3) This type of organism has no movement ability, the movement speed is consistent with the water flow velocity, the organism density is similar to the water density, the organism shape 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; 4) This type of rolled organisms has no ability to move, the movement speed is consistent with the water flow, the density of the organisms is different from that of the water body, the shape of the organisms is irregular, and the movement 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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