Trash holding net stress analysis test method and trash holding net stress calculation method

Abstract

The invention relates to the technical field of trash holding net stress analysis, and discloses a trash holding net stress analysis test method and a trash holding net stress calculation method.The stress analysis test method comprises the steps that various test power conditions of stress flowing water environments where trash holding nets are located are set; the method comprises the following steps: selecting various trash holding net sheets with different materials, net wire diameters and mesh sizes as different types of test net sheets; different types of test meshes are arranged in a fixed frame, and a plurality of tension and pressure sensors are arranged at preset positions to measure stress values of the test meshes under different test power conditions; based on the type of the test mesh and different test power conditions, obtaining a corresponding theoretical calculation value by using a preset stress calculation formula; and comparing the measured stress value with a theoretical calculation value obtained by calculation to obtain a test analysis result. According to the invention, stress analysis is carried out on different types of trash holding nets under the action of water flow, wave and wave flow, and a scientific basis is provided for design and test simulation of the trash holding nets.

Description

Technical Field

[0001] The invention relates to the technical field of force analysis of a trash net, and in particular to a trash net force analysis test method and a trash net force calculation method. Background Art

[0002] The pollution-blocking net at the water intake is the main line of defense for water intake safety and the basic guarantee for the reliable operation of downstream equipment. The function of the pollution-blocking net is to filter the water source and provide conditions for the normal operation of downstream equipment. With the continuous changes in the marine environment at home and abroad, the use of pollution-blocking nets has become more and more common. Pollution-blocking nets are usually arranged in the open channel of water intake. Different types of pollution-blocking nets are used according to different use requirements. There are three main functions of pollution-blocking nets. One is to intercept larger floating objects on the water; the second is to intercept smaller aquatic organisms, such as jellyfish, fish and shrimp; the third is special pollution-blocking nets, such as oil booms. However, during the outbreak period of marine organisms or severe sea conditions, such as storm surge conditions, the pollution-blocking net is prone to damage or structural fracture due to the pressure, resulting in a large number of marine organisms pouring into the open channel or pump room without obstruction. The force of the pollution-blocking net under the action of hydrodynamics is an important scientific research issue for cold source safety.

[0003] However, there are few studies on the hydrodynamics of trash nets under the action of water flow, waves and wave-current. Most of the drag coefficient tests on fishing nets are carried out by placing them in the middle of the water tank. The structure of the net itself affects the flow field. The flow velocity in the middle of the net is not consistent with the flow velocity in front of the net, and the relationship between force and flow velocity cannot be accurately calculated. Summary of the invention

[0004] In view of this, the present invention provides a force analysis test method for a trash net and a force calculation method for a trash net, which can solve the problem that the prior art cannot accurately obtain the relationship between the force and flow velocity of the trash net mesh. It can provide a force analysis calculation method for different types of trash nets under the action of water flow, waves, and wave currents, and provide a scientific basis for the design and test simulation of the trash net.

[0005] In a first aspect, the present invention provides a method for testing the force analysis of a trash net, the method comprising:

[0006] Set up various test dynamic conditions for the stressed water environment where the trash screen is located;

[0007] Select a variety of trash screen meshes with different materials, wire diameters, and mesh sizes as different types of test meshes;

[0008] Different types of test meshes are arranged in a fixed frame, and a plurality of tension and pressure sensors are arranged at preset positions to measure the force values ​​of the test meshes under different test dynamic conditions;

[0009] Based on the type of test mesh and different test dynamic conditions, the corresponding theoretical calculation value is obtained using the preset force calculation formula;

[0010] The test analysis results are obtained by comparing the force values ​​measured on the test mesh during the test with the theoretical calculated values ​​based on the preset force calculation formula.

[0011] The embodiment of the present invention can simulate different water flow velocities, changes in water flow direction, etc. that the trash net may encounter in an actual working environment by setting a variety of test dynamic conditions, and select test meshes of various materials, mesh diameters and mesh sizes to comprehensively evaluate the performance of different types of trash nets. Through comprehensive testing, data support can be provided for selecting the most suitable trash net for different application scenarios. The test analysis results can directly provide a reference for the design and optimization of the trash net; the measured force value is compared with the theoretical calculated value based on a preset force calculation formula, and the accuracy of the theoretical calculation can be verified through such comparative analysis; accurate understanding of the force conditions of the trash net can ensure that it can stably perform its trash interception function in actual applications, avoid damage to the trash net due to excessive force, and thus prevent the intercepted pollutants from leaking and causing harm to the downstream environment and facilities.

[0012] In an optional embodiment, the method further includes: calibrating each tension and compression sensor before the test to establish a relationship between the total force and the voltage, and measuring the force value of the fixed frame.

[0013] The embodiment of the present invention calibrates the tension and compression sensors before the test, and can accurately establish the relationship between the total force and the voltage. Because the output voltage signal of the sensor and the force it is subjected to are not a simple fixed correspondence, they will be affected by the characteristics of the sensor itself (such as sensitivity, linearity, etc.). Through calibration, the accurate functional relationship between the output voltage of each sensor and the actual force can be determined. For a sensor with a slight deviation in linearity, calibration can obtain its actual linear fitting equation, so that in subsequent tests, the corresponding force size can be calculated more accurately based on the measured voltage signal, reducing measurement errors.

[0014] In an optional embodiment, synchronous measurement values ​​of the multiple tension and pressure sensors are obtained and their resultant force value is calculated, and the resultant force value minus the force value of the fixing frame is used as the force value of the test mesh under the corresponding test dynamic conditions.

[0015] The embodiment of the present invention calculates the resultant force value by obtaining the synchronous measurement values ​​of multiple tension and pressure sensors, which can fully take into account the force conditions at different positions of the test mesh, thereby more accurately reflecting the force exerted on the entire mesh. This method of obtaining the force value of the mesh has a certain degree of versatility. For different types of pollution control net tests (such as changing the mesh size, the range of test dynamic conditions, etc.), as long as the synchronous measurement values ​​are obtained in the same way and the resultant force and the force of the fixed frame are processed, accurate mesh force values ​​can be obtained.

[0016] In an optional embodiment, the test dynamic conditions include: water flows with different flow rates, waves with different incident wave heights and wave periods, and wave flows formed by a combination of water flows and waves under different working conditions.

[0017] These various test power conditions of the embodiments of the present invention provide rich data support for the design of the trash net. During the design, reasonable parameters such as mesh material, mesh wire diameter, mesh size and fixing method can be determined according to the stress conditions and performance of the trash net under different power conditions. Understanding the performance of the trash net under various complex power conditions is helpful to formulate reasonable safety standards and maintenance plans.

[0018] In an optional implementation, the first force calculation formula is:

[0019] Where S is the area of ​​the trash net; θ is the mesh coefficient, which represents the ratio of the net rope projection area to the mesh area; ρ is the density of water; C D is the water flow resistance coefficient of the net rope; v is the average flow velocity in front of the net;

[0020] The second force calculation formula is:

[0021]

[0022] Where D is the diameter of the trash net rope; C D is the water flow resistance coefficient of the net rope; ρ is the density of water; v max is the maximum flow velocity before the net; C M is the inertia coefficient.

[0023] In an optional embodiment, the test analysis results include:

[0024] For the net rope Reynolds number close to or greater than 10 3 For the trash net with a small resistance coefficient, the drag coefficient is in the area with small changes, and the trash net mesh is simulated by the Tiannai rule; for the finer trash net, the net rope Reynolds number is less than 103, and its drag coefficient increases with the decrease of Reynolds number. Using the Tiannai rule to simulate the trash net will cause a large error.

[0025] Under the action of waves or wave currents, the maximum force on different types of trash nets is controlled by the velocity force. The theoretical force value calculated using the second force calculation formula is 1.0 to 1.1 times the test measured force value, and the velocity force value is much larger than the inertia force value.

[0026] In a second aspect, the present invention provides a method for calculating the force of a trash net, comprising: based on any of the trash net force analysis test methods described in the first aspect, the test analysis results obtained include:

[0027] Obtain the type of target trash-blocking net and the force-bearing water environment in which it is located;

[0028] If the target trash net is subjected to force under the action of a constant water flow, the corresponding force value is calculated based on the average flow velocity in front of the net using the first force calculation formula, wherein the water flow resistance coefficient is determined based on the Reynolds number of the net rope of the trash net;

[0029] If the target trash net is subjected to force due to waves or wave currents, the corresponding force value is calculated based on the maximum flow velocity in front of the net using the first force calculation formula, wherein the water flow resistance coefficient is determined based on the Reynolds number of the net rope.

[0030] In an optional implementation, the first force calculation formula is:

[0031]

[0032] Where S is the area of ​​the trash net; θ is the mesh coefficient, which represents the ratio of the net rope projection area to the mesh area; ρ is the density of water; C D is the water flow resistance coefficient of the net rope; under the action of constant water flow, v is the average flow velocity in front of the net; under the action of waves or wave currents, v is the maximum flow velocity in front of the net.

[0033] In an optional embodiment, when the Reynolds number of the net rope is close to or greater than 10 3 The trash screen is less than 10 5 When , the water flow resistance coefficient is 1.2.

[0034] The method for calculating the force of the trash net in the embodiment of the present invention can relatively easily complete the force calculation of the trash net under different water flow conditions, while ensuring that the calculation results have a reasonable basis, which helps engineering personnel to accurately grasp the force conditions of the trash net so as to provide a scientific basis for subsequent design, maintenance and other related work and test simulation. When applied to nuclear power plants, it can provide nuclear power design units with the renovation of existing power plants and the design of new power plants, and provide data support for the monitoring and early warning systems of nuclear power plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 is a schematic diagram of a flow chart of a force analysis test of a trash-blocking net according to an embodiment of the present invention;

[0037] Figure 2 is a schematic diagram of a test arrangement according to an embodiment of the present invention;

[0038] Figure 3 is a diagram showing the distribution of water flow velocity along the depth direction according to an embodiment of the present invention;

[0039] Figure 4 It is the horizontal flow velocity and vertical flow velocity process under the action of waves according to an embodiment of the present invention (H=0.112m, T=1.5s);

[0040] Figure 5 It is the horizontal flow velocity process under the action of waves and wave currents according to an embodiment of the present invention (H=0.112m, T=1.5s);

[0041] Figure 6 is a schematic diagram of a test trash-blocking net according to an embodiment of the present invention;

[0042] Figure 7 is a schematic diagram of a test arrangement of a trash screen according to an embodiment of the present invention;

[0043] Figure 8 is a schematic diagram of sensor calibration test results according to an embodiment of the present invention;

[0044] Fig. 9 The results of the force test of different types of trash screens under the action of water flow according to the embodiment of the present invention;

[0045] Fig.10 The results of force tests on different types of trash-blocking nets under the action of waves according to the embodiments of the present invention;

[0046] Fig.11 The results of the stress test on different types of trash screens under the action of water flow and waves in working condition 2 of the embodiment of the present invention;

[0047] Fig.12 The results of the stress test of different types of trash screens under the action of water flow and waves in working condition 4 of the embodiment of the present invention;

[0048] Fig.13This is the stress process of the test mesh 3 under the action of waves and wave currents (H=0.112m, T=1.5s). DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0050] The analysis of international nuclear water withdrawal incidents by the World Association of Nuclear Operators shows that no matter which reactor type and water withdrawal scheme is used, water withdrawal safety incidents continue to occur. Therefore, the issue of marine biological control in the cooling system of nuclear power plants in my country has received increasing attention. On the one hand, such incidents not only cause huge economic losses to nuclear power plants and threaten the safety and stability of cooling sources, but on the other hand, if nuclear water withdrawal causes a large number of biological entrainment and aggregation, it will also cause losses to marine life and affect the environmental friendliness of nuclear power projects.

[0051] At present, there are few studies on the hydrodynamics of the trash net under the action of water flow, waves and wave flow. For the resistance coefficient test of the fishing net mesh, most of them are placed in the middle of the water tank. Its own structure affects the flow field. The flow velocity in the middle of the mesh is not consistent with the flow velocity in front of the net, and the relationship between force and flow velocity cannot be accurately calculated. To this end, the present invention provides a force analysis and calculation method for different types of trash nets under the action of water flow, waves and wave flow, providing a scientific basis for the design and experimental simulation of the trash net. It provides nuclear power design units with the reconstruction of existing power plants and the design of new power plants, and provides data support for the monitoring and early warning system of nuclear power plants.

[0052] Figure 1 FIG. 1 is a flow chart of a method for calculating the force of a trash net according to an embodiment of the present invention. Figure 1 As shown, the process includes the following steps:

[0053] Step S101, setting test dynamic conditions of the stressed water environment where various trash-blocking nets are located.

[0054] The test dynamic conditions set in the embodiment of the present invention include: water flows with different flow rates, waves that do not pass the incident wave height and wave period, and wave flows formed by the combination of water flows and waves under different working conditions.

[0055] In one embodiment, the experiment was conducted in a wave pool of a certain research institute, and the experimental arrangement was as follows: Figure 2As shown, the water tank is 60m long, 1.2m high and 0.8m wide. The water tank can generate waves and currents at the same time. The waves are generated by servo motors and related control systems, and the water flow is controlled by a frequency converter. The flow rate is measured by the ultrasonic point flow rate measuring instrument Vectrino (Little Dragon) produced by NORTEC. The measurement range is adjustable to ±4.0m / s (±1.0m / s in this test), and the measurement accuracy is ±0.5% of the measured value. The specific test power conditions are as follows:

[0056] (1) Water flow

[0057] The water depth of this test is 0.4m. The test considers 4 different water flow conditions, with flow velocity ranging from 0.1m / s to 0.5m / s. The test flow velocity and its distribution along the water depth under different working conditions are shown in Figure 3 By measuring the average flow velocity at water depths of 0.04m, 0.12m, 0.20m, 0.28m and 0.36m in sections, the average flow velocity of section 1 under flow condition 1 is 0.18m / s; the average flow velocity of section 2 under flow condition 2 is 0.28m / s; the average flow velocity of section 3 under flow condition 3 is 0.37m / s; and the average flow velocity of section 4 under flow condition 4 is 0.46m / s.

[0058] (2) Waves

[0059] The test targets a variety of incident wave height and wave period combinations. The test wave conditions are shown in Table 1. The wave height varies between 0.085m and 0.214m, and there are three wave periods, namely 1.2s, 1.5s and 1.8s.

[0060] Table 1 Test wave conditions

[0061]

[0062] Under the action of waves alone, the reciprocating flow velocity process caused by waves at a depth of 0.2m was measured using a small dragon (H = 0.112m, T = 1.5s. The horizontal and vertical flow velocity processes under wave conditions are shown in Figure 4 ), and the average value of the maximum flow velocity in front of the positive net of each wave was analyzed, see Table 2.

[0063] Table 2 Average value of maximum forward flow velocity in front of the net under wave action

[0064]

[0065] (3) Wave + Flow Combination

[0066] In the wave and current combination test, two current velocities are fixed, including two ( Figure 2The test was carried out under the conditions of water flow condition 2 and water flow condition 4), and the waves in Table 2 were superimposed. During the test, the wave and the current were in the same direction. Under the action of wave and current (water flow condition 2, wave H = 0.112m, T = 1.5s), the horizontal flow velocity process is shown in Figure 5 After superimposing the wave reciprocating flow, the average values ​​of the maximum forward flow velocity of a single wave at a water depth of 0.2 m are shown in Tables 3 and 4.

[0067] Table 3 Average value of maximum forward flow velocity after superimposing waves at constant water flow (flow rate condition 2)

[0068]

[0069] Table 4 Average value of maximum forward flow velocity after superimposing waves at constant water flow (flow rate condition 4)

[0070]

[0071]

[0072] Step S102, selecting a plurality of trash-blocking nets of different materials, wire diameters, and mesh sizes as different types of test nets.

[0073] In the embodiment of the present invention, the test trash screen mesh is selected from the commonly used mesh structure, including different materials, mesh diameters, and mesh sizes, a total of six types, see Figure 6 The material of the test mesh of the trash net is iron wire, the diameter of the net rope is 3.5mm, the mesh foot length is 36.1mm, it is a diamond net, the mesh angle is 33.6°, and the mesh coefficient is 0.866; the material of the test mesh is iron wire, the diameter of the net rope is 1.5mm, the mesh foot length is 25.0mm, it is a square net, the mesh coefficient is 0.712, and the mesh angle is 90°; the test mesh is woven with high-strength nylon three-strand twisted rope, the net rope diameter is 6.0mm, the mesh foot length is 40.0mm, it is a square net, and the mesh coefficient is 0.80 0, mesh angle 90°; Test mesh piece 4 is woven from three-strand twisted polyester rope, with a rope diameter of 3.0mm, a mesh foot length of 43.0mm, a square mesh, a mesh coefficient of 0.886, and a mesh angle of 90°; Test mesh piece 5 is made of steel wire, with a rope diameter of 0.2mm, a mesh foot length of 1.25mm, a square mesh, a mesh coefficient of 0.705, and a mesh angle of 90°; Test mesh piece 6 is made of nylon, with a rope diameter of 0.2mm, a special woven net, a mesh coefficient of 0.750, and a mesh angle of 90°

[0074] Step S103, different types of test meshes are arranged in a fixed frame, and a plurality of tension and pressure sensors are arranged at preset positions to measure the force values ​​of the test meshes under different test dynamic conditions.

[0075] Since the trash screen mesh is mostly made of flexible materials, in order to measure the force on the trash screen, the embodiment of the present invention fixes the mesh in a metal frame. The plane size of the metal frame is 0.79×0.4m. The four corners of the metal frame are fixed on the base through tension and pressure sensors, as shown in the figure. Figure 7 The embodiment of the present invention calculates the resultant force value by obtaining the synchronous measurement values ​​of multiple tension and pressure sensors, which can fully take into account the force conditions at different positions of the test mesh, thereby more accurately reflecting the force exerted on the entire mesh. This method of obtaining the force value of the mesh has a certain versatility. For different types of pollution control net tests (such as changing the mesh size, the range of test dynamic conditions, etc.), as long as the synchronous measurement values ​​are obtained in the same way and the resultant force and the force of the fixed frame are processed, the accurate force value of the mesh can be obtained.

[0076] Before the test of the embodiment of the present invention, each tension and compression sensor is calibrated to establish the relationship between the total force and the voltage. The sensor calibration test results are shown in Figure 8 . Calibration of the tension and compression sensors before the test can accurately establish the relationship between the total force and the voltage. Because the output voltage signal of the sensor and the force it is subjected to are not a simple fixed correspondence, they will be affected by the characteristics of the sensor itself (such as sensitivity, linearity, etc.). Through calibration, the accurate functional relationship between the output voltage of each sensor and the actual force can be determined. For a sensor with a slight deviation in linearity, calibration can obtain its actual linear fitting equation, so that in subsequent tests, the corresponding force size can be calculated more accurately based on the measured voltage signal, reducing measurement errors.

[0077] Step S104, based on the type of the test mesh and different test dynamic conditions, a preset force calculation formula is used to obtain a corresponding theoretical calculation value.

[0078] Specifically, the trash net is usually in a fluid environment such as water flow or waves, and its force situation is relatively complex. In this case, Morrison's formula can be used to consider the effects of inertia force and velocity force on the trash net respectively.

[0079] When the trash screen mesh is subjected to a constant flow, only the velocity force on the trash screen is considered. Therefore, under the action of a constant flow perpendicular to the axis of the cylinder, the resistance of the cylinder per unit length is:

[0080]

[0081] F is the force on the cylinder, C D is the water flow resistance coefficient of the net rope, D is the cylinder diameter, ρ is the water density, and v is the average flow velocity in front of the net.

[0082] The mesh of the trash net is generally square or diamond-shaped. The uniform diameter of the net rope is D, the length of the mesh foot is l, and the mesh angle is ф. The mesh coefficient θ is defined as the ratio of the projected area of ​​the net rope to the area of ​​the net sheet, then:

[0083]

[0084] For a fixed trash net, under the condition of being restricted on both sides, when the flow rate through the cross section is fixed, the actual flow velocity through the net will increase due to the obstruction of the trash net mesh, and its flow velocity increase coefficient k is:

[0085]

[0086] When the net nodes of the trash net are small, their influence on the mesh force can be ignored; the calculated local deformation of the mesh is small, and its influence on the overall force can also be ignored. The net ropes in the mesh can be considered as rough cylinders, and their force can be calculated according to formula (1). When the water flow direction is perpendicular to the trash net mesh, its force is the superposition of the force of the net ropes in the mesh. The formula for calculating the force of the trash net mesh under the action of water flow is:

[0087]

[0088] F is the force on the trash screen with an area of ​​S, D = Sθ, ρ is the density of water, v is the average flow velocity in front of the screen, C D is the water flow resistance coefficient of the net rope.

[0089] The water flow resistance coefficient C of the net rope in formula (4) D Related to Reynolds. The C of each test trash net rope in the embodiment of the present invention D The values ​​are shown in Table 6. Formula (4) is used to calculate the forces on different trash screens under the action of water flow in this test, and the relationship between the forces and the flow velocity is obtained as follows: Fig. 9 The calculation results are compared with the test results, and the two are in good agreement.

[0090] Table 6 Calculation speed force coefficients of each mesh

[0091]

[0092] Under the action of waves and wave currents, considering the effect of inertia force and velocity force on the trash screen, the force per unit length of the cylinder is calculated using Morrison formula (5):

[0093]

[0094] Where D is the diameter of the trash net rope; C D is the water flow resistance coefficient of the net rope; ρ is the density of water; v max is the maximum flow velocity before the net; C M is the inertia coefficient.

[0095] The stress test results of different types of trash nets under wave action are as follows: Fig.10 As shown in the figure, since the rope of the trash net is thinner, usually D / L (diameter / length of the thinner rope of the trash net) is smaller, and the trash net is mostly located in shallow water areas, generally h / L (water depth / (trash net rope / length) is smaller, and the inertial force is usually smaller than the velocity resistance, and there is a phase difference between the two. Therefore, for the wave action of the trash net, its maximum force is controlled by the velocity force. The velocity distribution under the action of waves and wave currents is related to the depth, and after the waves are superimposed, the velocity of the bottom water flow will increase, but it is generally more uniform along the cross section; because the wave surface is constantly changing under the action of waves, the present invention takes the maximum velocity in front of the net at the middle depth (0.5h) measured in the test for calculation.

[0096] Under the action of waves and wave currents, the stress on the trash screen mesh is calculated using formula method (5) and the maximum measured flow velocity. The stress test results of different types of trash screens under the action of water flow and waves in working condition 2 are shown in Figure 2. Fig.11 As shown in Figure 4, the stress test results of different types of trash screens under the action of water flow and waves in working condition 4 are as follows: Fig.12 As shown, the force process of the test mesh 3 widely used in practical applications under the action of waves and wave currents (H = 0.112m, T = 1.5s) is provided. Fig.13 . The results show that the calculation results of formula (5) are generally larger than the test results, especially for flexible nylon nets and meshes with thinner ropes. This is mainly because: under the conditions of waves and wave currents, the flow on the trash net mesh is a periodic reciprocating flow, and the water flow at the maximum flow velocity in front of the net lasts for a short time. At the same time, the horizontal flow velocity of the waves varies greatly along the water depth direction. Therefore, the result calculated according to the maximum flow velocity in front of the net is too large. The test results show that the calculation result is about 1.0 to 1.1 times larger than the test result. In engineering applications, from a safety perspective, under the action of waves or wave currents, the maximum flow velocity in front of the net can be used to calculate the maximum force on the trash net. At the same time, because the value of the velocity force is much larger than the value of the inertia force, that is, the inertia force is much smaller than the value of the velocity force, the influence of the inertia force on the calculation result of the velocity force is almost negligible. Therefore, for the calculation under the action of waves or wave currents, formula (4) can also be used.

[0097] Step S5, comparing the force value measured during the test of the test mesh with the theoretical calculated value calculated based on a preset force calculation formula to obtain a test analysis result.

[0098] The physical model test of the trash net is an important method to obtain the design parameters of the trash net and optimize the design. When conducting the force model test of the trash net, it is inevitable to reduce the overall size of the trash net. However, if the mesh of the trash net is also simulated completely according to the geometric scale, the originally fine mesh wire cannot be simulated, and the mesh is also airtight, resulting in distortion of the hydrodynamic simulation. Some scholars such as Tanai in Japan have proposed some fishing net simulation methods, which can be used for reference in the simulation of trash nets. According to the relationship between the resistance coefficient of the cylindrical net rope and the Reynolds number, as well as the analysis of the force test results of different types of trash nets in the embodiments of the present invention, the simulation of the trash net mesh needs to comply with the following requirements: For the net rope Reynolds number close to or greater than 10 3 The drag coefficient of the trash net is in the area with small changes (C D =1.2), the trash net mesh can be simulated by the field law; for a relatively fine trash net, the net rope Reynolds number is less than 10 3 The resistance coefficient increases as the Reynolds number decreases. At this time, using the Tanner law to simulate the trash net will cause a large error. Under this test condition, we can analyze the specific situation and optimize the trash net simulation method while ensuring similar hydrodynamic conditions.

[0099] The present invention conducts force tests on different types of trash-blocking nets under the action of water flow, waves and wave-current, studies the force calculation method, and obtains the following conclusions:

[0100] (1) Under the action of constant water flow, the forces on different types of trash nets can be calculated by superimposing the resistance of the net ropes, that is, formula (4). Under the condition of a certain flow rate, due to the action of the trash net, the speed of the trash net increases, and the speed increase coefficient is inversely proportional to the air permeability coefficient of the trash net; the resistance coefficient of the trash net mesh is related to the resistance coefficient of the net rope. When the Reynolds number of the net rope is close to or greater than 10 3 Trash net (less than 10 5 ), the drag coefficient can be taken as 1.2.

[0101] (2) Under the action of waves or wave currents, the maximum force on different types of trash nets is controlled by the velocity force. Studies have shown that the maximum force on the trash net calculated using formula (4) and the measured horizontal flow velocity is 1.0 to 1.1 times greater than the test value; in engineering applications, from a safety perspective, under the action of waves or wave currents, the maximum flow velocity in front of the net can be used to calculate the maximum force on the trash net.

[0102] (3) For the net rope Reynolds number close to or greater than 10 3 For a small trash net, the field rule can be used to simulate the trash net; for a relatively fine trash net, if the net rope Reynolds number is less than 10 3 , the simulation method of the pollution control net can be optimized according to the specific situation and the hydrodynamic similarity can be ensured.

[0103] The embodiment of the present invention can simulate different water flow velocities, changes in water flow direction, etc. that the trash net may encounter in an actual working environment by setting a variety of test dynamic conditions, and select test meshes of various materials, mesh diameters and mesh sizes to comprehensively evaluate the performance of different types of trash nets. Through comprehensive testing, data support can be provided for selecting the most suitable trash net for different application scenarios. The test analysis results can directly provide a reference for the design and optimization of the trash net; the measured force value is compared with the theoretical calculated value based on a preset force calculation formula, and the accuracy of the theoretical calculation can be verified through such comparative analysis; accurate understanding of the force conditions of the trash net can ensure that it can stably perform its trash interception function in actual applications, avoid damage to the trash net due to excessive force, and thus prevent the intercepted pollutants from leaking and causing harm to the downstream environment and facilities.

[0104] The embodiment of the present invention further provides a method for calculating the force of a trash net, based on the test analysis results obtained by the above-mentioned trash net force analysis test method, including:

[0105] Step 201, obtaining the type of the target trash-blocking net and the force-bearing water environment in which it is located;

[0106] Step 202, if the target trash-blocking net is subjected to force under the action of a constant water flow, the corresponding force value is calculated based on the average flow in front of the net using a first force calculation formula, wherein the water flow resistance coefficient is determined based on the Reynolds number of the net rope of the trash-blocking net;

[0107] Step 203, if the target trash net is subjected to force under the action of waves or wave currents, the corresponding force value is calculated based on the maximum flow velocity in front of the net using the first force calculation formula, wherein the water flow resistance coefficient is determined based on the Reynolds number of the net rope of the trash net.

[0108] Specifically, the first force formula is calculated as:

[0109]

[0110] Where S is the area of ​​the trash net; θ is the mesh coefficient, which represents the ratio of the net rope projection area to the mesh area; ρ is the density of water; C D is the water flow resistance coefficient of the net rope; v is the average flow velocity in front of the net under the action of constant water flow, and v is the maximum flow velocity in front of the net under the action of waves or wave currents. 3 The trash screen is less than 10 5 When , the drag coefficient is 1.2.

[0111] The area S, mesh coefficient θ, water density ρ, resistance coefficient CD, and average flow velocity v of the trash net can usually be obtained through measurement, empirical data, or known conditions in actual application scenarios. And for the key parameter of water flow resistance coefficient, its determination method (based on the net rope Reynolds number) and specific value conditions (the net rope Reynolds number is 1.2 when it is within a specific range) are also clarified. This relatively clear and explicit calculation method with a relatively conventional parameter acquisition method makes the force calculation method highly operational in actual application, and can easily complete the force calculation of the trash net under different water flow conditions. At the same time, it ensures that the calculation results have a reasonable basis, which helps engineering personnel to accurately grasp the force conditions of the trash net in order to provide a scientific basis for subsequent design, maintenance and other related work and test simulation. When applied to nuclear power plants, it can provide nuclear power design units with the transformation of existing power plants and the design of new power plants, and provide data support for the monitoring and early warning system of nuclear power plants.

[0112] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A test method for analyzing the stress of a trash-blocking net, characterized in that: include: Set up various test dynamic conditions for the stressed water environment where the trash screen is located; Select a variety of trash screen meshes with different materials, wire diameters, and mesh sizes as different types of test meshes; Different types of test meshes are arranged in a fixed frame, and a plurality of tension and pressure sensors are arranged at preset positions to measure the force values ​​of the test meshes under different test dynamic conditions; Based on the type of test mesh and different test dynamic conditions, the corresponding theoretical calculation value is obtained using the preset force calculation formula; The test analysis results are obtained by comparing the force values ​​measured on the test mesh during the test with the theoretical calculated values ​​based on the preset force calculation formula.

2. The method according to claim 1, characterized in that Also includes: Before the test, each tension and compression sensor is calibrated to establish the relationship between the total force and the voltage, and the force value of the fixed frame is measured.

3. The method according to claim 2, characterized in that When conducting the test, the synchronous measurement values ​​of the multiple tension and pressure sensors are obtained and their resultant force value is calculated, and the resultant force value minus the force value of the fixing frame is used as the force value of the test mesh under the corresponding test dynamic conditions.

4. The method according to claim 1, characterized in that: The test dynamic conditions include: water flows with different flow rates, waves with different incident wave heights and wave periods, and wave flows formed by the combination of water flows and waves under different working conditions.

5. The method according to claim 4, characterized in that The corresponding theoretical calculation value is obtained by using a preset force calculation formula based on the type of test mesh and different test dynamic conditions, including: If the test mesh is subjected to force under the action of a constant water flow, the corresponding theoretical force value is calculated based on the first force calculation formula to obtain the corresponding theoretical value; If the test mesh is subjected to force under the action of waves or wave currents, the corresponding theoretical force value is calculated based on the second force calculation formula to obtain the corresponding theoretical value.

6. The method according to claim 5, characterized in that The first force calculation formula is: Where S is the area of ​​the trash net; θ is the mesh coefficient, which represents the ratio of the net rope projection area to the mesh area; ρ is the density of water; C D is the water flow resistance coefficient of the net rope; v is the average flow velocity in front of the net; The second force calculation formula is: Where D is the diameter of the trash net rope; C D is the water flow resistance coefficient of the net rope; ρ is the density of water; v max is the maximum flow velocity before the net; C M is the inertia coefficient.

7. The method according to claim 6, characterized in that The test analysis results include: For the net rope Reynolds number close to or greater than 10 3 The drag coefficient of the trash net is in the area with small changes, and the trash net mesh is simulated by the field law; while for the finer trash net, the net rope Reynolds number is less than 10 3 , its drag coefficient increases as the Reynolds number decreases, and using the Tanei rule to simulate the trash screen will cause a large error; Under the action of waves or wave currents, the maximum force on different types of trash nets is controlled by the velocity force. The theoretical force value calculated using the second force calculation formula is 1.0 to 1.1 times the test measured force value, and the velocity force value is much larger than the inertia force value.

8. A method for calculating the force of a trash net, based on the test analysis results obtained by the test method for analyzing the force of a trash net according to any one of claims 1 to 7, characterized in that: include: Obtain the type of target trash-blocking net and the force-bearing water environment in which it is located; If the target trash net is subjected to force under the action of a constant water flow, the corresponding force value is calculated based on the average flow velocity in front of the net using the first force calculation formula, wherein the water flow resistance coefficient is determined based on the Reynolds number of the net rope of the trash net; If the target trash net is subjected to force due to waves or wave currents, the corresponding force value is calculated based on the maximum flow velocity in front of the net using the first force calculation formula, wherein the water flow resistance coefficient is determined based on the Reynolds number of the net rope.

9. The method according to claim 8, characterized in that The first force formula is calculated as: Where S is the area of ​​the trash net; θ is the mesh coefficient, which represents the ratio of the net rope projection area to the mesh area; ρ is the density of water; C D is the water flow resistance coefficient of the net rope; under the action of constant water flow, v is the average flow velocity in front of the net; under the action of waves or wave currents, v is the maximum flow velocity in front of the net.

10. The method according to claim 9, characterized in that When the Reynolds number of the net rope is close to or greater than 10 3 The trash screen is less than 10 5 When , the resistance coefficient of the net rope is 1.2.

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