Wind-fish fusion structure design method based on jacket foundation

Abstract

The invention provides a wind-fish fusion structure design method based on a jacket foundation, and the method comprises the following steps: S1, calculating the deformation of a net cage and the tension of a mooring rope through the hydrodynamic analysis of the net cage, designing a structure scheme and a mooring arrangement scheme of the net cage, and determining a preferable scheme of the deformation of the net cage and the tension of the mooring rope; s2, carrying out foundation bearing capacity analysis on the jacket after the net cage is additionally arranged on the optimal scheme; and S3, carrying out foundation fatigue analysis on the jacket after the net cage is additionally arranged on the optimal scheme. According to the scheme, net cage structure optimization, net cage mooring scheme optimization and the bearing capacity and fatigue checking process of the jacket foundation fusion aquaculture net cage structure are covered, and a feasible path is provided for fusion development of offshore wind power and marine ranching. Meanwhile, the design efficiency, safety and economical efficiency of the wind-fish fusion structure are improved, and the method can be conveniently applied to actual engineering projects.

Description

Technical Field

[0001] This invention relates to the field of marine engineering design methods, and in particular to a design method for a wind-fishery integrated structure based on a jacket foundation. Background Technology

[0002] As offshore wind power development gradually expands into mid- and far-sea areas, jacket foundations, currently the mainstay of wind turbine foundations under construction in my country's deep-sea region, offer advantages in integrating offshore wind power and marine ranching. By utilizing the lower members of the jacket foundation as mooring anchors, aquaculture cages can be arranged within the sea area inside the jacket foundation, eliminating the need for additional sea area usage. This reduces anchoring costs for aquaculture facilities, improves their resistance to wind and waves, and provides a convenient, efficient, and safe structural integration of offshore wind power and marine ranching. Furthermore, after the offshore wind turbines are operational, the turbine foundations can act as artificial reefs, attracting fish and creating a favorable habitat for marine life, thus promoting the restoration and protection of the marine ecosystem. Therefore, the structural design method of integrating jacket foundations with aquaculture cages is of great significance for promoting the integrated development of offshore wind power and marine ranching in my country.

[0003] Currently, there is no systematic design methodology for the integration of offshore wind turbine jacket foundations and aquaculture cages, resulting in low design efficiency. Furthermore, the hydrodynamic mechanisms of this integration remain unclear, and strength, modal, and fatigue analyses are still needed. In addition, existing calculations for integrated wind-fishery structures often treat the netting as a rigid body, failing to accurately simulate its deformation, posing safety hazards, and significantly overestimating its mooring force, thus increasing construction costs. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a design method for a wind-fishing integrated structure based on a jacket foundation, which can be applied to the scheme of adding aquaculture cages on wind turbines that are not yet in operation or have already been put into operation, thereby improving the design efficiency, safety and economy of the wind-fishing integrated structure.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A design method for a wind-fed integrated structure based on a jacket foundation, comprising the following steps: S1. Calculate the deformation of the net cage and the tension of the mooring ropes through hydrodynamic analysis, design the structural scheme and mooring arrangement scheme of the net cage, and confirm the optimal scheme for net cage deformation and mooring rope tension. S2. Conduct a bearing capacity analysis of the foundation of the guide frame after adding the cage in the preferred scheme; S3. At the same time, fatigue analysis of the guide frame foundation after the installation of the cage is carried out on the preferred scheme.

[0006] The beneficial effects of this invention are as follows: This invention proposes a systematic solution for the integrated structural design of jacket foundations and aquaculture cages. This solution encompasses the optimal selection of cage structures, the optimization of cage mooring schemes, and the load-bearing capacity and fatigue verification process for jacket foundation-integrated aquaculture cage structures, providing a feasible path for the integrated development of offshore wind power and marine ranching. Simultaneously, it improves the design efficiency, safety, and economy of wind-fishery integrated structures, and the method can be easily applied to practical engineering projects. Attached Figure Description

[0007] Figure 1 This is a schematic diagram of the wind-fishery fusion structure based on the jacket foundation of the present invention; Figure 2 This is a flowchart of the numerical simulation method for the design of a wind-fed integrated structure based on a jacket foundation, as described in this invention. Figure 3 This is a flowchart of the hydrodynamic analysis of the cage in this invention; Figure 4 This is a simplified model of the aquaculture cage structure based on the guide frame of the present invention; Figure 5 This is a schematic diagram of the deformation of the mesh garment of the present invention; Figure 6 Flowchart for analyzing the bearing capacity of the guide frame foundation after adding the cage in this invention; Figure 7 Flowchart of fatigue analysis of the guide frame foundation after adding the wire mesh cage to this invention; Figure 8 This is a schematic diagram of random wave force loading on the foundation structure of the jacket structure of the present invention; Figure 9 This is a schematic diagram of the random wave force loading on the cage structure of the present invention; Figure 10 This is a schematic diagram of random wind load loading according to the present invention.

[0008] Label Explanation: 1. Main legs of the jacket support; 2. Fan working platform; 3. Aquaculture cage; 4. Steel wire rope; 5. Fan pile legs. Detailed Implementation

[0009] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0010] Glossary: ​​Rayleigh damping is a classic simplified model for simulating viscous damping of materials in structural dynamics; Matlab software, Matrix Lab software.

[0011] Please refer to Figures 1 to 10A design method for a wind-fed integrated fishing structure based on a jacket foundation includes the following steps: S1, calculating the deformation of the cage and the tension of the mooring ropes through hydrodynamic analysis, designing the structural scheme and mooring arrangement scheme of the cage, and confirming the preferred scheme for cage deformation and mooring rope tension; S2, conducting a bearing capacity analysis of the jacket foundation after adding the cage to the preferred scheme; S3, simultaneously conducting a fatigue analysis of the jacket foundation after adding the cage to the preferred scheme. As can be seen from the above description, the beneficial effects of this invention are as follows: A design method for a wind-fishery integrated structure based on a jacket foundation encompasses the optimization of cage structure selection, cage mooring scheme optimization, and the load-bearing capacity and fatigue verification process for a cage structure integrated with a jacket foundation, providing a feasible path for the integrated development of offshore wind power and marine ranching. Simultaneously, it improves the design efficiency, safety, and economy of wind-fishery integrated structures, and this method can be easily applied to practical engineering projects. Furthermore, the hydrodynamic analysis and calculation of the cage includes the following steps: S11, establishing a simplified finite element model of the cage structure integrated with the guide frame; S12, selecting the drag force coefficient, inertial force coefficient, and velocity attenuation coefficient; S13, determining the netting grouping scheme; S14, conducting hydrodynamic response analysis under extreme wave and current loads. As described above, the hydrodynamic analysis and calculation of the cage is carried out through a four-step orderly process: first, a model is built and key coefficients are selected; then, the netting scheme is determined; and finally, response analysis under extreme working conditions is carried out to obtain the optimal scheme with small cage deformation and mooring rope tension, fewer mooring points, and larger aquaculture space.

[0012] Furthermore, the analysis of the bearing capacity of the jacket foundation after the addition of the cages includes the following steps: S21, extracting the maximum mooring rope tension at the cage mooring point based on the marine organism attachment situation of the cages; S22, establishing a jacket foundation model in SACS software and creating cage mooring points on the model; S23, adding the corresponding mooring rope tension at each cage mooring point, and adding wind turbine load, wave current load, self-weight load, and pile-soil action; S24, conducting structural static analysis. As described above, the load-bearing capacity analysis of the jacket foundation after the addition of the cages was based on the actual marine environment. By extracting key loads, establishing a professional model, and superimposing multiple loads, the static structural analysis was finally completed, ensuring the safety of the scheme.

[0013] Furthermore, the fatigue analysis of the jacket foundation after the addition of the cage includes the following steps: S31, establishing an overall finite element model of the jacket foundation integrated with the aquaculture cage structure in ABAQUS software; S32, conducting overall model modal analysis on the overall finite element model of the jacket foundation integrated with the aquaculture cage structure; S33, calculating random wave force; S34, applying the random wave force, gravity, and buoyancy calculated in step S33 to the simplified finite element model of the jacket foundation integrated with the aquaculture cage structure established in the cage hydrodynamic analysis step, and calculating the dynamic response of the cage structure under random wave action; S35, establishing a finite element model of the jacket foundation and calculating the dynamic response of the jacket foundation under random wind and waves after considering the cage load; S36, screening fatigue analysis nodes and calculating the hot spot stress of the nodes; S37, performing rainflow counting on the hot spot stress in Matlab software to obtain the stress amplitude and cycle number, and calculating the fatigue damage and fatigue life of the analysis nodes during the 25-year operation period of the wind turbine based on the SN curve and Miner's linear fatigue cumulative damage criterion.

[0014] As described above, the fatigue analysis of the jacket foundation after the installation of the cage involves modeling, modal analysis, load calculation, dynamic response analysis, node selection and stress treatment. Finally, combined with professional standards, fatigue damage and life estimation are completed, forming a complete and scientific analysis process covering model construction to life assessment, which further ensures the safety of the solution.

[0015] Furthermore, step S11 includes establishing a numerical model of the jacket foundation and wire rope using beam elements based on ABAQUS software, establishing a numerical model of the netting and wire rope using truss elements, simplifying the jacket foundation into a line model of four main legs and pile legs, and fixing the boundary between the jacket foundation and the wire rope.

[0016] As described above, the numerical models of the wire mesh and wire rope are established by combining beam and truss elements in ABAQUS software. The foundation of the jacket is simplified into a line model of four main legs and pile legs. The boundaries between the jacket foundation and the wire rope are fixed and constrained, which greatly improves the accuracy of the numerical model and lays the foundation for subsequent steps.

[0017] Furthermore, step S13 includes simplifying the mesh model by using a mesh grouping method, merging several real meshes into a single virtual computational mesh.

[0018] As can be seen from the above description, simplifying the mesh model by using the mesh grouping method can improve the convenience and efficiency of calculation.

[0019] Furthermore, step S21 includes the need to be aware that when extracting the maximum mooring rope tension at the net cage mooring point, the attachment of marine organisms to the net cage will change the density of the net, and the drag coefficient and velocity attenuation coefficient of the net cage need to be re-determined based on empirical formulas or experiments.

[0020] As can be seen from the above description, adjusting various parameters according to the actual conditions of the ocean improves the accuracy of the calculations.

[0021] Furthermore, step S24 includes checking the member strength UC value and node punching shear UC value in the result file of the static analysis of the structure. If the UC value is less than 1, it means that the foundation of the guide frame still meets the structural stress control standard after the addition of the cage, and the structure will not be damaged.

[0022] As can be seen from the above description, by analyzing the results obtained from the previous steps and then measuring them according to specific parameters, it can be finally determined whether the results meet the standards.

[0023] Furthermore, step S32 includes the overall model modal analysis, which calculates the model's natural frequency, which should be located between the wind turbine rotation frequency and the blade passage frequency, taking into account a 10% safety margin.

[0024] As can be seen from the above description, considering a 10% safety margin can prevent the natural frequency of the wind turbine integrated machine structure from being coupled with the rotation frequency of the wind turbine and the passing frequency of the blades, and at the same time reserve a buffer space for the parameter deviations that may occur in the structure during long-term operation, so as to avoid structural damage caused by resonance.

[0025] Furthermore, step S33 includes applying the wind load on the wind turbine blades to the mass point at the center of the wind turbine hub in the form of a concentrated force, and dividing the tower structure into several layers by applying the wind load on the tower structure in each layer into a concentrated force applied to the midpoint of that layer.

[0026] As can be seen from the above description, the wind load loading method of this wind turbine adopts a simplified approach, loading the wind load of the wind turbine blades as a concentrated force onto the center mass point of the hub. At the same time, the tower is divided into layers, and the random wind load of each layer is simplified into a concentrated force loaded at the midpoint of the layer. This simplifies the calculation process and can specifically transfer the wind load effect of different parts. Embodiment 1 of the present invention is as follows: Please refer to Figure 1 One type of wind-fishing integrated structure based on a jacket foundation involves installing an integral aquaculture cage inside the jacket foundation. The top of the cage is located at a certain height above sea level to prevent fish from escaping. The sides of the cage are moored to the main legs of the jacket foundation by netting ropes, and the bottom of the cage is moored to the steel wire ropes connecting the wind turbine pile legs by netting ropes, forming a huge aquaculture space and realizing the deep integration of offshore wind power and marine ranching.

[0027] Please refer to Figure 2 In this embodiment, a design method for a wind-fishery integrated structure based on a jacket foundation involves calculating the deformation of the net cage and the tension of the mooring ropes through hydrodynamic analysis, designing the structural scheme and mooring arrangement of the net cage, and comprehensively optimizing the optimal net cage scheme that combines low deformation and mooring rope tension, fewer mooring points, and large aquaculture space, thus achieving both economy and safety. The design of the scheme involves initially assuming values ​​for parameters such as netting density, the number of mooring points, and the location of mooring points within the framework of the integral net cage. These parameters are then continuously optimized using hydrodynamic analysis of the net cage using the controlled variable method. For each net cage structural scheme, the mooring tension at each point of the net cage can be calculated. This mooring tension needs to be less than the breaking force of the netting rope itself to ensure that the rope does not break, and it also needs to ensure that the stress generated by the mooring component after applying this mooring tension is less than its yield strength, i.e., no structural damage will occur. The volume loss of the net cage can be calculated through its deformation; the smaller the volume loss, the safer the fish cultured within the net cage. Therefore, the volume loss and mooring rope tension data of various cage structure schemes were calculated and compared. The scheme with the smallest volume loss, low mooring rope tension, and meeting design requirements was selected as the optimal scheme. Mooring force and cage deformation data were calculated using finite element software, while cage volume loss was calculated manually using the formula proposed in this invention based on cage deformation data. Subsequently, the bearing capacity analysis of the jacket foundation after adding the cage was conducted on the optimal scheme. Strength analysis, deformation analysis, and pile foundation bearing capacity analysis were performed on the jacket foundation after adding the cage system under extreme conditions to ensure that the integrated structure meets the control standards for structural stress, deformation, and bearing capacity. Simultaneously, modal analysis of the jacket foundation after adding the cage was conducted on the optimal scheme to calculate the natural frequency of the jacket foundation integrated with the aquaculture cage structure. This structure includes the wind turbine, tower, transition section, jacket, cage, wire rope, and foundation. The natural frequency of the structure was ensured to avoid the wind turbine rotation frequency and blade passing frequency range, and a certain safety margin was considered. Damping and stiffness coefficients were calculated using the first two natural frequencies. Transient dynamic analysis of the jacket foundation after the addition of the net cages was conducted to determine the dynamic response of the jacket foundation integrated with the aquaculture net cage structure. Stress-time history curves of key nodes were obtained and rainflow counts were performed. The stress amplitude and cycle number after rainflow counting were substituted into the SN curve to conduct fatigue analysis of the jacket foundation after the addition of the net cages. Fatigue damage and fatigue life of key nodes were calculated according to Miner's linear fatigue cumulative damage criterion. The jacket foundation integrated with the aquaculture net cage structure, verified through strength and fatigue checks, was determined as the final wind-fishery integrated design scheme, providing strong support for the long-term stable operation of the wind-fishery integrated structure over a 25-year operating period.

[0028] Please refer to Figure 3 In this embodiment, the hydrodynamic analysis of the cage includes: Step S11: Establish a simplified finite element model of the integrated aquaculture cage structure based on the jacket foundation. Using ABAQUS software, beam elements are used to establish numerical models of the jacket foundation and wire ropes, and truss elements are used to establish numerical models of the netting and netting ropes. This establishes a simplified finite element model of the integrated aquaculture cage structure based on the jacket foundation. Figure 4 As shown, to improve computational efficiency, the jacket foundation is simplified into a line model of four main legs and pile legs, and the jacket foundation and the wire rope boundary are fixedly constrained. The accuracy of this method in calculating the deformation and stress of the mesh is verified in paper [1].

[0029] [1]Zhu R, Xiu Y, Tu Z, et al. Numerical simulation of hydrodynamic characteristics of offshore wind power jacket base with net cage structure[J]. Ships and Offshore Structures, 2025: 1-15. Step S12: Select the drag force coefficient, inertia force coefficient, and velocity attenuation coefficient. The input current load should consider its variation along water depth. The formula for calculating the current load per unit length at depth z below sea level can be expressed as:

[0030] In the formula: f (z) represents the ocean current load acting on a structural unit of unit length; For the density of seawater, take 1024 kg / m³. 3 ; This is the drag coefficient; D The diameter of the net rope; U C (z) represents the ocean current velocity, which varies with water depth and is calculated according to the DNVGL-ST-0437 specification, specifically as follows:

[0031]

[0032] In the formula: z This is the vertical distance from the sea surface; U tide0 This refers to the surface current velocity of the sea. U wind0 The velocity of the wind-induced current at the sea surface; d For water depth; d 0 represents the reference depth of the wind-induced flow's influence. d 0 = 50m;k Let be a coefficient; considering the worst-case scenario, we can take 0.03. V m (10m) represents the 10-minute average wind speed at 10m above the average sea surface.

[0033] Waves under extreme conditions can be simulated using Stokes' fifth-order wave model, and wave forces on the jacket foundation and cage can be calculated using the Morrison equation:

[0034] In the formula: F The wave force acting on a unit length of structure; The drag force acting on a unit length of structure; The inertial force acting on a unit length of structure; For the density of seawater, take 1024 kg / m³. 3 ; This is the drag coefficient; D The diameter of the net rope; U The relative velocity between the water particle perpendicular to the axis of the structural unit and the structural unit; The relative acceleration between the water particle and the structural unit, which is perpendicular to the axis of the structural unit. This is the inertial force coefficient.

[0035] The flow velocity of water decreases after passing through the upstream netting of the gabion structure, which will reduce the hydrodynamic force on the downstream netting. To improve the accuracy of numerical simulation, an appropriate velocity attenuation coefficient needs to be set when calculating wave and current loads.

[0036] The drag force coefficient and inertia force coefficient can be selected according to engineering specifications, such as harbor hydrology specifications, API specifications, DNV specifications, etc., or they can be selected according to appropriate empirical formulas. The velocity attenuation coefficient is mainly selected according to empirical formulas. To improve the accuracy of numerical simulation calculation results, model tests can also be carried out to calculate the two key design parameters, the drag force coefficient and the velocity attenuation coefficient, based on measured data.

[0037] Step S13: Determine the netting grouping scheme. Due to the massive size of the aquaculture cages, performing hydrodynamic calculations on a single mesh size in the finite element numerical model would require extremely high computational costs. Therefore, a netting grouping method is adopted to simplify the netting model, merging several real meshes into a single virtual computational mesh, thereby improving computational efficiency. The mesh grouping method is based on the principles of mechanical and geometric similarity and satisfies the following conditions: ①If the projected area along the flow direction is the same for both the virtual mesh after grouping and the real mesh before grouping, then we have:

[0038] ②If the weight of the virtual mesh after grouping is the same as the weight of the real mesh before grouping, then:

[0039] ③If the stiffness of the virtual mesh after grouping is the same as that of the real mesh before grouping, then:

[0040] In the formula: D 1, D 2 represents the mesh diameter before and after grouping; NT 1. N T2 represents the number of horizontal meshes in the netting before and after grouping, respectively; NN 1. NN 2 represents the number of vertical meshes in the net before and after grouping, respectively; n is the number of meshes in the grouping, that is, the number of real meshes before grouping contained in one virtual mesh after grouping; , These represent the mesh density before and after clustering; E 1, E 2 represents the elastic modulus of the network before and after grouping.

[0041] Please refer to Figure 4 Based on the model framework established in step S11, simplified models of the aquaculture cage structure with different netting grouping schemes were established. After netting grouping, the deformation of the cage and the tension of the mooring rope under wave and current loads were analyzed. The grouping scheme with netting deformation and mooring rope tension data that are closer to the actual netting before grouping and with high computational efficiency was selected as the subsequent research scheme.

[0042] Step S14: Conduct hydrodynamic response analysis under extreme wave and current loads. Perform hydrodynamic response analysis on a simplified model of the jacket foundation integrated aquaculture cage structure with netting. First, conduct a sensitivity analysis of the jacket foundation integrated cage structure to the wave inrush angle. Considering the most unfavorable situation, set the wave and current to be incident in the same direction, and set different wave inrush angles for calculation. Find the wave inrush angle with the largest volume loss and mooring rope tension after deformation of the jacket foundation integrated cage structure for subsequent calculations. Then, establish a series of numerical model schemes for the jacket foundation integrated aquaculture cage structure, calculate the maximum cage volume loss and mooring rope tension under different netting density, cage mooring point layout, and cage layout depth schemes. Considering both safety and economy, select the cage design scheme with the smallest cage volume loss, smallest mooring rope tension, least netting material, fewest cage mooring points, and largest cage layout depth as the final jacket foundation integrated aquaculture cage structure design scheme, and conduct subsequent verification.

[0043] The volume loss of an integral wire mesh cage can be calculated using the following method: Please refer to Figure 5 The single mesh is divided into segments along the depth. The volume enclosed by the area between adjacent meshes before and after deformation is taken as a calculation unit. The volume loss of each segment is accumulated to obtain the volume loss of the single mesh.

[0044] The volumetric loss within a computing unit can be expressed as:

[0045]

[0046] The total volume loss of the cage can be expressed as:

[0047] In the formula, V pi It is the volume loss of a single computing unit; U i It is the displacement of the central node within a single computational unit. U iaverage It is the average value of the displacement; L It is the length of the net cage; H i It is the height between adjacent mesh elements within a computing unit; n It is the number of central nodes within a single computing unit; m It is the number of computational units, which is equal to the number of mesh elements in the Z direction minus 1; C vr This is the total volume loss of the net cage. V p0 It is the volume of the cage before deformation.

[0048] It is important to note that the mesh length involved in calculating net density must be less than the body length and width of the farmed fish to prevent fish from escaping. The drag coefficient and current velocity attenuation coefficient of the net differ under different net density conditions and must be determined based on empirical formulas or experiments. Since the wave and current effects on the net cages gradually decrease with increasing water depth, the overall arrangement of net cage mooring points can be denser at the top and sparser at the bottom, minimizing the number of mooring points in deep waters. A certain distance must be maintained between the bottom elevation of the net cages and the mud surface to prevent seabed debris from being washed up and damaged by ocean currents.

[0049] Please refer to Figure 6In this embodiment, the hydrodynamic analysis of the net cage includes: Step S21, extracting the maximum mooring rope tension at the mooring point of the net cage based on the attachment of marine organisms. Based on the attachment of marine organisms, the maximum mooring rope tension at each mooring point under extreme wave and current loads is extracted as a point load by viewing the support reactions in the x, y, and z directions of the structure at the mooring point in the calculation result file of the finite element software. That is, the forces in the x, y, and z directions at the connection points of all net ropes and the main leg or pile leg of the jacket at the moment of maximum mooring rope tension are extracted. It should be noted that the attachment of marine organisms will change the density of the netting; therefore, the drag force coefficient and velocity attenuation coefficient of the net cage need to be re-determined based on empirical formulas or experiments. The drag force coefficient and inertia force coefficient of the jacket foundation and wire ropes can be directly selected as fixed values ​​according to the specifications.

[0050] Step S22: Establish a basic model of the jacket structure in the SACS software, and create mooring points for the cages on the model.

[0051] Step S23: Add the corresponding mooring rope tension at each cage mooring point, and add wind turbine load, wave current load, self-weight load, and pile-soil action. In the seainp file, in addition to wind turbine load, wave current load, and self-weight load, add the mooring rope tension load extracted in step S21 at the corresponding locations of the cage mooring points established in step S22. The pile-soil action is simulated in the psiinp file using the form of soil springs. A certain degree of scour, corrosion, and marine organism attachment of the jacket foundation is considered during the calculation.

[0052] Step S24: Conduct static analysis in SACS software. Check the member strength UC value and node punching shear UC value in the results file. If the UC value is less than 1, it indicates that the jacket foundation still meets the structural stress control standard after the addition of the gabion, and the structure will not be damaged. Simultaneously, check in the results file whether the maximum settlement of the foundation structure is controlled within 100mm, whether the flange face inclination angle of the jacket foundation is controlled below 0.5°, and whether the pile foundation mud surface rotation angle is controlled below 0.25°, ensuring that the jacket foundation after the addition of the gabion meets the structural deformation control standards of DNVGL-ST-0126-2018 and FD003-2007 specifications. Furthermore, it is necessary to conduct a pile bearing capacity analysis of the jacket after the addition of the gabion according to NB / T 10105-2018 specification to verify the axial compressive bearing capacity and tensile bearing capacity of the single pile of the jacket foundation.

[0053] Please refer to Figure 7In this embodiment, the fatigue analysis of the jacket foundation after the addition of the cage includes: Step S31, establishing an overall finite element model of the jacket foundation integrated with the aquaculture cage structure in ABAQUS software. This structure includes a fan, tower, transition section, jacket, cage, wire rope and foundation. The self-weight of the fan is loaded onto the flange face of the transition section in the form of a concentrated force. Solid soil elements or soil springs can be used to simulate the pile-soil action. It is recommended to use soil springs to simulate the pile-soil action, use beam elements to simulate the pile foundation, jacket foundation and wire rope, and use shell elements to improve calculation efficiency.

[0054] Step S32: Conduct modal analysis of the overall model of the integrated aquaculture cage structure based on the jacket foundation and calculate the natural frequency of the model. According to the DNVGL-ST-0126-2018 specification, and in accordance with the rigid-flexible structure design, the natural frequency of the integrated wind-fishery machine structure should be located between the wind turbine rotation frequency (1P) and the blade passing frequency (3P), and a 10% safety margin is considered to verify the natural frequency of the model.

[0055] Step S33: Calculate random wave forces. Since the majority of the cage structure is below the water surface, it is heavily affected by wave loads but largely unaffected by wind loads. Therefore, the main impact of adding cages is on the fatigue of the jacket foundation. Based on the actual sea conditions for fatigue calculation, the random wave forces acting on the jacket foundation and cage system structure are first calculated using a random wave spectrum model in Matlab software. Considering a certain degree of marine organism attachment to the cages, the drag force coefficient and velocity attenuation coefficient of the cages are determined based on empirical formulas or experiments. The drag force coefficient and inertia coefficient of the jacket foundation and wire ropes can be directly selected as fixed values ​​according to specifications. Then, the random wind loads acting on the wind turbine and tower are calculated using a random wind spectrum model in Matlab software.

[0056] Please refer to Figure 8 and Figure 9 Random wave forces are applied as point loads to the jacket foundation and the gabion structure. The underwater portion of the jacket is divided into several layers, and the random wave forces on each member in each layer are simplified as concentrated forces applied to the midpoint of the member. The underwater portion of the gabion structure is also divided into several layers, with each individual mesh line as the calculation unit. The water particle velocities and accelerations at different depths in each layer of the gabion are simplified to the water particle velocities and accelerations at the midpoint of that layer. The random wave forces on the mesh lines in each layer are then calculated using the Morison equation and applied to the intersections between the mesh lines. Since the four steel wire ropes are modeled using beam elements and are located at the same depth, line loads can be directly applied to their structure.

[0057] Please refer to Figure 10The wind load on the wind turbine blades is applied as a concentrated force to the mass point at the center of the wind turbine hub. Similarly, the wind load on the tower is applied by dividing the tower structure into several layers. The random wind load on the tower structure in each layer is simplified as a concentrated force applied to the midpoint of that layer.

[0058] Step S34: Apply the random wave forces, gravity, and buoyancy calculated in step S33 to the simplified model established in the hydrodynamic analysis step of the net cage, and calculate the dynamic response of the net cage structure under random wave action. Since the overall model of the aquaculture net cage structure integrated with the jacket foundation is a rigid-flexible coupled structure, the structural calculation has strong nonlinearity. To facilitate calculation convergence and improve calculation efficiency, a step-by-step calculation method is adopted to add random wave forces. Apply the random wave forces, gravity, and buoyancy calculated in step three to the simplified model established in the hydrodynamic analysis step of the net cage, calculate the dynamic response of the net cage structure under random wave action, and extract the tension-time history data of the net ropes at each net cage mooring point. It should be noted that since the net ropes are only under tension and not compression, to further simulate the real situation, when the tension data of the net ropes extracted in this step contains pressure, the data needs to be processed to change the value corresponding to pressure to 0, retaining only the tension.

[0059] Step S35: Establish a finite element model of the jacket foundation and calculate the dynamic response of the jacket foundation under random wind and wave action, considering the load of the net cage. Considering a certain degree of scouring, corrosion, and marine organism attachment, a finite element structural model of the jacket foundation is established. This structure includes the wind turbine, tower, transition section, jacket, net cage, wire rope, and foundation. The gravity of the wind turbine is loaded as a concentrated force at the center mass point of the wind turbine hub. Due to the large weight of the jacket wind turbine, the inertial force is significant, and damping has a crucial impact. Therefore, when calculating the dynamic response of the jacket foundation integrated with the aquaculture net cage structure, Rayleigh damping needs to be added to the jacket wind turbine. Rayleigh damping simplifies the damping matrix to a linear combination of the mass matrix and stiffness matrix:

[0060] In the formula: and These are the mass damping coefficient and the stiffness damping coefficient, respectively, which are related to the damping ratio and the natural frequency.

[0061] In the formula: The damping ratio is determined according to the GB 50011-2010 standard. w i Let be the natural frequency of the i-th mode shape of the structure. Select two reference frequencies and The damping coefficient and stiffness coefficient can then be obtained using the following formula:

[0062]

[0063] Therefore, the damping coefficient and stiffness coefficient of the aquaculture cage structure can be calculated by using the first two natural frequencies of the jacket foundation integrated with the aquaculture cage structure calculated in step S32.

[0064] Apply time-history loads of net cage mooring rope tension at the mooring points of the main legs and pile legs of the jacket, and apply the random wave force, gravity, and buoyancy of the jacket calculated in step S33 to the jacket foundation. Perform transient dynamic analysis on the jacket foundation model and calculate the dynamic response of the jacket foundation under random wave action and random wind load after considering the net cage load.

[0065] Step S36: Screen fatigue analysis nodes and calculate node hot spot stresses. At this point, we obtain the nominal stress of the nodes, so we first screen nodes prone to fatigue failure. We focus on the Mises stress at the intersections of the jacket structure members, extracting the stress-time history curves of nodes with high stress, and using the four-point rainflow counting method in Matlab to count the rainflows, obtaining the stress amplitude and cycle number. We further screen one or more nodes with large stress amplitudes as the final fatigue analysis nodes. For the determined fatigue analysis nodes, we extract the axial force and bending moment at the node over a certain time period. According to the DNVRP C203 Fatigue Design of Offshore Steel Structures standard, we calculate the corresponding stress concentration factor. By multiplying the stress caused by the axial force and the stress caused by the bending moment by their respective stress concentration factors and then superimposing them, we can obtain the hot spot stress of the analysis node over a certain time period.

[0066] Step S37: In Matlab, the four-point rainflow counting method is used to count the rainflow of hot spot stress, obtain the stress amplitude and cycle number of hot spot stress, substitute it into the SN curve in the engineering specification, and then calculate the fatigue damage and fatigue life of the key node during the 25-year operation period of the wind turbine according to the Miner linear fatigue cumulative damage criterion.

[0067] The calculation method for fatigue damage can be expressed by the following formula:

[0068] In the formula: D The total structural fatigue damage over a certain period of time; The fatigue life safety factor; n iTo calculate the number of cycles of stress amplitude within a time period; N i This represents the number of cycles required to reach the stress amplitude required for structural failure, calculated based on the SN curve.

[0069] To ensure that the structure does not experience fatigue failure, the total fatigue damage D of the wind turbine structure during its 25-year operating period must be less than 1.

[0070] The formula for calculating the fatigue life of a node is: Fatigue life of a node = 25 / D.

[0071] If the total fatigue damage of the key nodes of the jacket foundation calculated after adding the cage is less than 1, it means that the cage design scheme is feasible after fatigue verification.

[0072] In summary, this invention provides a systematic solution for the design of integrated wind-fishery structures based on jacket foundations, encompassing cage structure optimization, mooring scheme optimization, and structural load-bearing capacity and fatigue verification processes. This provides a feasible path for the integrated development of offshore wind power and marine ranching. The invention considers cage flexibility in hydrodynamic calculations, resolving the deviations in stress and deformation calculations caused by traditional rigid body equivalent design, thus improving the accuracy of results. Furthermore, it innovatively proposes a method for calculating the volume loss of integrated cages combined with jacket wind turbine foundations, providing crucial support for cage structure design. In addition, the numerical simulation method for integrated wind-fishery structures based on jacket foundations in this invention features a clear design process and high computational efficiency, making it easy to apply to practical engineering projects.

[0073] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A design method for a wind-fed integrated structure based on a jacket foundation, characterized in that: Includes the following steps, S1. Calculate the deformation of the net cage and the tension of the mooring ropes through hydrodynamic analysis, design the structural scheme and mooring arrangement scheme of the net cage, and confirm the optimal scheme for net cage deformation and mooring rope tension. S2. Conduct a bearing capacity analysis of the foundation of the guide frame after adding the cage in the preferred scheme; S3. At the same time, fatigue analysis of the guide frame foundation after the installation of the cage is carried out on the preferred scheme.

2. The design method for a wind-fed integrated structure based on a jacket foundation according to claim 1, characterized in that: The hydrodynamic analysis and calculation of the cage includes the following steps. S11. Establish a simplified finite element model of the integrated aquaculture cage structure based on the guide frame; S12. Select the drag force coefficient, inertia force coefficient, and velocity attenuation coefficient; S13. Determine the mesh clothing grouping scheme; S14. Conduct hydrodynamic response analysis under extreme wave and current loads.

3. The design method for a wind-fed integrated structure based on a jacket foundation according to claim 2, characterized in that: The analysis of the bearing capacity of the guide frame foundation after the installation of the cage includes the following steps. S21. Based on the attachment of marine organisms in the net cage, extract the maximum mooring rope tension at the net cage mooring point; S22. Establish a basic model of the jacket structure in SACS software, and create mooring points for the cages on the model; S23. Add the corresponding mooring rope tension at the mooring point of the cage, and add the wind turbine load, wave current load, self-weight load and pile-soil action. S24. Conduct structural static analysis.

4. The design method for a wind-fed integrated structure based on a jacket foundation according to claim 3, characterized in that: The fatigue analysis of the guide frame foundation after the installation of the wire mesh cage includes the following steps. S31. Establish an overall finite element model of the integrated aquaculture cage structure based on the guide frame in ABAQUS software; S32. Conduct overall model modal analysis on the overall finite element model of the integrated aquaculture cage structure based on the guide frame foundation; S33. Calculate random wave forces; S34. Apply the random wave force, gravity, and buoyancy calculated in step S33 to the simplified finite element model of the integrated aquaculture cage structure established in the hydrodynamic analysis step of the cage, and calculate the dynamic response of the cage structure under the action of random waves. S35. Establish a finite element model of the jacket foundation and calculate the dynamic response of the jacket foundation under random wind and wave action after considering the cage load. S36. Select fatigue analysis nodes and calculate node hotspot stress; S37. In Matlab software, rainflow counting is performed on hot spot stress to obtain stress amplitude and cycle number. Based on the SN curve and Miner linear fatigue cumulative damage criterion, the fatigue damage and fatigue life of the analyzed node during the 25-year operation period of the wind turbine are calculated.

5. The design method for a wind-fed integrated structure based on a jacket foundation according to claim 2, characterized in that: Step S11; This includes using ABAQUS software to create numerical models of the jacket foundation and wire rope using beam elements, and to create numerical models of the netting and wire rope using truss elements. The jacket foundation is simplified into a line model of four main legs and pile legs, and the boundaries between the jacket foundation and the wire rope are fixedly constrained.

6. The design method for a wind-fed integrated structure based on a jacket foundation according to claim 2, characterized in that: Step S13; This includes using a mesh grouping method to simplify the mesh model, merging several real meshes into a single virtual computational mesh.

7. The design method for a wind-fed integrated structure based on a jacket foundation according to claim 3, characterized in that: Step S21; When extracting the maximum mooring rope tension at the mooring point of the net cage, it is important to note that the attachment of marine organisms to the net cage will change the density of the net. The drag coefficient and velocity attenuation coefficient of the net cage need to be re-determined based on empirical formulas or experiments.

8. The design method for a wind-fed integrated structure based on a jacket foundation according to claim 3, characterized in that: Step S24; The results file of the static analysis of the structure includes checking the member strength UC value and the node punching shear UC value. If the UC value is less than 1, it means that the foundation of the jacket still meets the structural stress control standard after the addition of the cage, and the structure will not be damaged.

9. The design method for a wind-fed integrated structure based on a jacket foundation according to claim 4, characterized in that: Step S32; The modal analysis of the overall model should include calculating the model's natural frequency, which should be between the rotor rotation frequency and the blade passage frequency, with a 10% safety margin.

10. The design method for a wind-fed integrated structure based on a jacket foundation according to claim 4, characterized in that: Step S33; The wind load on the wind turbine blades is applied as a concentrated force to the mass point at the center of the wind turbine hub. The wind load on the tower is divided into several layers, and the random wind load on the tower structure in each layer is simplified as a concentrated force applied to the midpoint of that layer.

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