Method and system for predicting stress of submarine cable under impact of high-pressure water gun

Abstract

The invention discloses a submarine cable stress prediction method and system under the impact of a high-pressure water gun, and relates to the field of submarine cable operation and maintenance. At present, cable impact stress in high-pressure water gun construction cannot be quantitatively evaluated, and the method comprises the steps that finite element simulation software is utilized to establish a three-dimensional fluid-solid coupling finite element model of a submarine cable under impact of different high-pressure water gun flow speeds, and the model is utilized to solve and extract stress data of the submarine cable; processing a simulation result by using a nonlinear fitting method, and establishing a unary nonlinear fitting formula of different high-pressure water gun flow velocity impacts and submarine cable stress; obtaining a submarine cable stress prediction result according to a fitting formula and the current high-pressure water gun flow velocity; according to the technical scheme, the impact influence of the high-pressure water gun on the submarine cable can be quickly predicted to guide construction safety flow velocity control and prevent cable damage.

Description

Technical Field

[0001] The present invention relates to the field of operation and maintenance of submarine cables, and particularly to a method and system for predicting the stress of submarine cables under the impact of high-pressure water jets. Background Art

[0002] With the in-depth promotion of China's marine economic strategy and the large-scale development of offshore clean energy, submarine cables have become the core infrastructure for cross-sea power transmission and communication, undertaking the energy and information transmission tasks between islands and the mainland, and between offshore platforms and onshore power grids. Once a submarine cable fails due to external force impact, not only the repair cost is high, but also major social and economic losses such as regional power supply interruption and communication paralysis will occur.

[0003] Buried pipelines such as submarine natural gas pipelines often show local exposure or suspension under the influence of ocean current scouring and geological activities, and need to be regularly dug and re-buried for maintenance. To reduce construction risks, the industry generally uses non-contact trenchers, which form trenches by jetting high-speed water flow through high-pressure water jets to erode the seabed.

[0004] There is a spatial overlap between the operation area of the high-pressure water jet and the laying area of the submarine cable, and the high-speed water flow generates a dynamic fluid impact load on the adjacent cable body, which may cause structural damages such as cable insulation layer rupture, armor deformation, and even conductor fracture.

[0005] Since there is no mature method to establish a quantitative relationship between the flow velocity of the high-pressure water jet and the cable stress, the operation and maintenance personnel cannot predict the stress safety threshold of the cable at a specific flow velocity; in addition, the submarine environment is complex, and the in-situ test cost is extremely high and it is difficult to extract accurate stress data.

[0006] Therefore, there is an urgent need to develop a high-precision and low-cost modeling method for the stress-flow velocity relationship of submarine cables, provide a theoretical basis for setting the construction safety distance and flow velocity control of high-pressure water jets, and prevent cable impact damage accidents. Summary of the Invention

[0007] The technical problem to be solved and the technical task proposed by the present invention are to improve and refine the existing technical solutions, provide a method and system for predicting the stress of submarine cables under the impact of high-pressure water jets, and accurately and low-cost analyze the stress change of submarine cables under the impact of high-pressure water jets. For this purpose, the present invention adopts the following technical solutions.

[0008] A method for predicting the stress of a submarine cable under the impact of a high-pressure water jet based on a fluid-structure interaction model, comprising the following steps: 1) Establish a three-dimensional fluid-structure interaction finite element model of the submarine cable at different high-pressure water jet flow velocities, specifically including: 1.1) Construct a cable geometric model according to the layered structure of the submarine cable and the nozzle diameter d of the high-pressure water gun, where the cable length is not less than 3d, and set the material parameters of each structural layer; 1.2) Establish an outer flow domain model consistent with the cable length, and set the impact outlet of the high-pressure water gun directly above it; 1.3) Use the non-uniform grid division method to divide the hexahedral grid for the outer flow domain, gradually densifying from the edge of the outer flow domain to the periphery of the cable; use the sweeping mode to divide the grid for each layer of the cable; 1.4) Apply fully constrained boundary conditions to both ends of the cable, and set the binding contact between each structural layer; 1.5) Set the flow velocity range of the high-pressure water gun to 0 to the maximum flow velocity N, sample at intervals, and control the flow velocity change through a step function; 1.6) Solve the stress distribution of the cable at different flow velocities, and extract the maximum stress data samples of each layer; 2) Establish a fitting formula for stress and flow velocity through the nonlinear fitting method, including: 2.1) With the flow velocity as the independent variable and the stress as the dependent variable, select a polynomial, exponential or power function model to perform univariate nonlinear fitting on the sample data; 2.2) Through The coefficient of determination selects the optimal fitting method, and uses an independent data set to verify the accuracy of the fitting formula; 3) Obtain the stress prediction result of the submarine cable according to the verified fitting formula and the current flow velocity of the high-pressure water gun.

[0009] This technical solution uses a three-dimensional fluid-structure interaction finite element model to simulate the dynamic interaction process between high-pressure water flow and the multi-layer structure of the cable, overcoming the defect of traditional static models that ignore the dynamic load of fluid impact. The material parameters are set according to the actual layered structure of the cable to ensure the authenticity of the mechanical response of the material. Both ends of the cable are fully constrained to simulate the actual laying state; the layers are bound in contact to avoid non-physical relative sliding. The step function is used to control the flow velocity to efficiently simulate the impact transient process. The outer domain uses hexahedral meshes + local refinement to balance the calculation accuracy and speed; the cable layered structure uses swept meshes to improve the meshing efficiency of complex geometries. Three types of models, polynomial / exponential / power function, are tried synchronously to avoid the limitations of a single model; independent data sets are used for verification to prevent overfitting and enhance the engineering generalization ability. Samples are generated based on the fluid-structure interaction simulation data, which not only retains the physical laws but also extracts a simple stress-flow velocity quantitative formula through fitting, facilitating rapid on-site look-up prediction. This technical solution can replace the costly and extremely risky in-situ seabed tests, and only need to input the flow velocity to output the stress value; the parameters can be adjusted flexibly (such as changing the cable material, water gun diameter) to adapt to different engineering scenarios. The prediction results can quantitatively evaluate the flow velocity threshold for safe operation of the high-pressure water gun to avoid cable damage (such as insulation layer rupture, armor deformation); provide a theoretical basis for the construction path planning of the trencher and reduce the operation and maintenance risks. This technical solution solves the three major pain points of "insufficient accuracy, difficult experiments, and lack of quantitative tools" in submarine cable stress prediction through high-fidelity simulation, intelligent sampling strategy and rigorous mathematical verification, and has both academic innovation and engineering implementation value, providing key technical support for the safe operation and maintenance of submarine energy infrastructure.

[0010] As a preferred technical means: in step 1.1), the layered structure of the submarine cable includes a conductor, a conductor shielding layer, an insulating layer, an insulating shielding layer, an armor layer and an outer sheath. When constructing the cable geometric model, the conductor is simplified to a cylinder, the conductor shielding layer, the insulating layer and the insulating shielding layer are combined into one layer, the armor layer is simplified to a torus, and the density, elastic modulus and Poisson's ratio of each layer are consistent with the actual parameters.

[0011] Combining the conductor shielding layer, the insulating layer and the insulating shielding layer into one layer reduces the number of meshes and shortens the simulation time. Conductor → cylinder, armor → torus, retaining the core mechanical characteristics and avoiding mesh distortion caused by unnecessary details (such as the helix structure of conductor strands, the gaps between armor wires), improving the swept mesh generation speed, and enhancing the convergence stability. The density, elastic modulus and Poisson's ratio match the measured values, ensuring the authenticity of the material parameters and reducing the stress prediction error; the mechanical responses of different layers are independent, retaining the constitutive differences of the conductor (metal), the combined layer (polymer), and the armor (composite material) to accurately capture the interlayer stress transfer path. It provides a high-cost-performance input basis for fluid-structure interaction simulation.

[0012] As a preferred technical means: in step 1.2), the outer domain is set as an open surface around.

[0013] The open surface of the outer basin conforms to the law of free diffusion of fluid, and can accurately simulate the fluid dynamics behavior in the real marine environment, solving the key defects of the traditional closed basin model; the traditional closed basin model has the following problems: the reflection of pressure waves at the boundary leads to false pressure accumulation, the outlet pressure needs to be set manually, which leads to subjective interference with the flow field, and the dissipation of fluid kinetic energy to the far field is ignored. The open surface model used in this technical solution has the following advantages: the pressure wave escapes freely, which conforms to the characteristics of infinite water area, which is conducive to reducing the impact pressure peak error; it automatically satisfies the mass conservation to achieve dynamic balance inlet / outlet flow, and the velocity distribution is more in line with the actual jet diffusion law; it simulates the energy attenuation process after water flow impact, so as to accurately capture the time attenuation characteristics of cable force. At the same time, it is also conducive to improving the calculation efficiency. The open boundary allows the fluid to enter and exit freely, avoiding the iterative solution of the pressure Poisson equation, which is conducive to reducing the number of calculation iterations; eliminating the numerical oscillation caused by pressure reflection in the closed model, which is conducive to increasing the time step, thereby shortening the total calculation time; using the simplest boundary conditions to solve the common problems of complex fluid impact simulation, and setting a new benchmark for fluid-solid coupling accuracy.

[0014] As a preferred technical means: in step 1.5), the interval between adjacent sample points shall not exceed 0.2N.

[0015] Avoid losing critical data in nonlinear areas.

[0016] As a preferred technical means: the number of samples M of the high-pressure water gun flow rate is an integer not less than 5, and the flow rate range is divided into a low-pressure area and a high-pressure area, wherein the interval between sample points in the high-pressure area is smaller than that in the low-pressure area.

[0017] The cable stress changes in the high-pressure area (close to the maximum flow velocity N) are usually more dramatic. Reducing the sample point interval (such as 0.2N interval in the low-pressure area and 0.1N interval in the high-pressure area) can increase the data density in the high-flow velocity section and more accurately capture nonlinear characteristics, which meets the engineering optimization requirements of fluid-solid coupling simulation.

[0018] As a preferred technical means: In step 2.2), calculate the Coefficient of determination and mean square error, select The model with a mean square error greater than 0.9 and the smallest mean square error is taken as the optimal fitting formula; the sample data is equally divided into a training set and a validation set, and the validation set is used to test the error of the fitting formula. If the error is within the allowable range, the fitting formula is used for subsequent submarine cable stress prediction; otherwise, the optimal fitting formula is re-screened.

[0019] Another technical solution of the present invention is a submarine cable stress prediction system, the submarine cable stress prediction system comprising: 1. A three-dimensional fluid-structure interaction finite element modeling module for establishing a simulation model of a submarine cable under different water jet velocities of a high-pressure water gun. The three-dimensional fluid-structure interaction finite element modeling module includes: A geometric modeling unit for constructing a cable geometric model according to the layered structure of the submarine cable and the diameter d of the high-pressure water gun nozzle, with the cable length not less than 3d, and setting the material parameters of each structural layer; An outer domain modeling unit for establishing an outer domain model with the same length as the cable and setting a high-pressure water gun impact outlet directly above it; A mesh generation unit for performing hexahedral mesh generation on the outer domain using a non-uniform mesh generation method, gradually densifying from the outer domain edge towards the cable periphery, and performing swept-mode mesh generation on each layer of the cable; A boundary condition setting unit for applying fully constrained boundary conditions to both ends of the cable and setting the binding contact between each structural layer; A flow velocity control unit for setting the high-pressure water gun flow velocity within the range of 0 to the maximum flow velocity N, sampling at intervals not exceeding 0.2N, and controlling the flow velocity change through a step function; A solution and data extraction unit for solving the stress distribution of the cable under different flow velocities and extracting the maximum stress data samples of each layer; 2. A non-linear fitting modeling module for establishing a quantitative relationship formula between stress and flow velocity, specifically including: A fitting model unit for fitting the sample data using polynomial, exponential, and power function models with flow velocity as the independent variable and stress as the dependent variable; A model screening unit for selecting the optimal fitting method through the coefficient of determination and verifying the accuracy of the fitting formula using an independent data set; 3. A stress prediction module for outputting the corresponding submarine cable stress prediction result according to the verified fitting formula and the input high-pressure water gun flow velocity value.

[0020] This technical solution ensures the prediction error through material fidelity, dynamic verification, and anti-interference algorithms. It transforms the complex fluid-structure interaction theory into a system of "input flow velocity → output stress", providing an efficient and reliable tool support for the operation and maintenance of submarine cables.

[0021] As a preferred technical means: In the geometric modeling unit, the layered structure of the submarine cable includes a conductor, a conductor shielding layer, an insulating layer, an insulating shielding layer, an armor layer, and an outer sheath. When constructing the cable geometric model, the conductor is simplified as a cylinder, the conductor shielding layer, insulating layer, and insulating shielding layer are combined into one layer, the armor layer is simplified as a torus, and the density, elastic modulus, and Poisson's ratio of each layer are consistent with the actual parameters.

[0022] As a preferred technical means: in the flow rate control unit, the number of samples M of the high-pressure water gun flow rate is an integer not less than 5, and the flow rate range is divided into a low-pressure area and a high-pressure area, where the sample point interval in the high-pressure area is smaller than that in the low-pressure area.

[0023] As a preferred technical means: the model screening unit calculates the coefficient of determination and mean square error of each fitting model, and selects the model with a coefficient of determination greater than 0.9 and the smallest mean square error as the optimal fitting formula; the sample data is equally divided into a training set and a validation set, and the validation set is used to test the error of the fitting formula. If the error is within the allowable range, the fitting formula is used for subsequent submarine cable stress prediction; otherwise, the optimal fitting formula is re-screened.

[0024] Beneficial effects: 1. The present invention makes full use of the characteristics of various simulation analysis methods and can accurately obtain the deformations of each layer of the submarine cable under different high-pressure water gun flow rates.

[0025] 2. The present invention overcomes the disadvantages of difficult physical experiments, high cost, low efficiency, and difficult data extraction.

[0026] 3. The present invention proposes a non-linear fitting method to obtain the relationship between the stress of the submarine cable body and the high-pressure water gun flow rate, which is convenient for calculation, accurate in data, and convenient for engineering practice. Description of the drawings

[0027] Figure 1 is the flowchart for establishing the relationship between the stress of the submarine cable body and the high-pressure water gun flow rate of the present invention.

[0028] Figure 2 is the internal structure of the submarine cable.

[0029] Figure 3 is Figure 2 the enlarged view of part A of

[0030] Figure 4 is the schematic diagram of the submarine cable structure.

[0031] Figure 5 is the effect diagram of the external domain grid division of the submarine cable.

[0032] Figure 6 is the grid division diagram of the submarine cable model.

[0033] Figure 7 is the stress diagram of the submarine cable.

[0034] Figure 8 is the fitting diagram of the relationship between the stress of the submarine cable and the high-pressure water gun flow rate. Specific implementation manners

[0035] The technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings of the specification.

[0036] Embodiment 1: The method for predicting the stress of a submarine cable under the impact of a high-pressure water gun based on a fluid-structure interaction model includes establishing the relationship between the stress of the submarine cable body and the flow velocity of the high-pressure water gun and predicting the stress of the submarine cable under the impact of the high-pressure water gun based on the established relationship between the stress of the submarine cable body and the flow velocity of the high-pressure water gun. The specific process of establishing the relationship between the stress of the submarine cable body and the flow velocity of the high-pressure water gun is as Figure 1 shown, and includes the following steps: S1: Establish a three-dimensional fluid-structure interaction finite element model of the submarine cable under different flow velocities of the high-pressure water gun, specifically including: S1.1: According to the layered structure of the submarine cable and the diameter d of the high-pressure water gun nozzle, construct a cable geometric model, where the cable length is not less than 3d, and set the material parameters of each structural layer; S1.2: Establish an outer flow domain model with the same length as the cable, and set a high-pressure water gun impact outlet directly above it; S1.3: Adopt a non-uniform grid division method to perform hexahedral grid division on the outer flow domain, gradually densifying from the edge of the outer flow domain to the periphery of the cable; perform grid division on each layer of the cable using the sweep mode; S1.4: Apply fully constrained boundary conditions to both ends of the cable, and set the contact between each structural layer to be bonded; S1.5: Set the high-pressure water gun flow velocity range from 0 to the maximum flow velocity N, sample at intervals, and control the flow velocity change through a step function; S1.6: Solve the stress distribution of the cable under different flow velocities, and extract the maximum stress data samples of each layer; S2: Establish a fitting formula for stress and flow velocity through a non-linear fitting method, including: S2.1: Using the flow velocity as the independent variable and the stress as the dependent variable, select a polynomial, exponential or power function model to perform univariate non-linear fitting on the sample data; S2.2: Through the coefficient of determination, select the optimal fitting method, and verify the accuracy of the fitting formula using an independent data set.

[0037] When it is necessary to predict the stress of the submarine cable under the impact of the high-pressure water gun, the stress prediction result of the submarine cable is obtained according to the verified fitting formula and the current flow velocity of the high-pressure water gun.

[0038] The following takes a 500 kV oil-filled submarine cable as the research object to describe the technical solution in detail.

[0039] 1. Taking a 500 kV oil-filled submarine cable as the research object, its internal structure is as Figure 2 、 Figure 3As shown in the figure, from the inside to the outside are the oil duct, copper conductor, conductor shielding layer, insulating layer, insulation shielding layer, copper braid, lead alloy sheath, strengthening layer, first lining layer, anti-corrosion layer, anti-moth layer, second lining layer, armor, and outer sheath.

[0040] The cable dimensions and the material parameters of each layer structure are shown in Table 1 and Table 2. The mechanical properties of the conductor shielding layer, insulating layer, and insulation shielding layer are similar, and the conductor shielding and insulation shielding are very thin, so the insulating layer is combined; the first copper braid, strengthening layer, and second copper braid are very thin, so they are combined into the lead alloy sheath; the material parameters of the first lining layer, anti-corrosion layer, anti-moth layer, and second lining layer are similar, and the first lining layer, anti-moth layer, and second lining layer are very thin, so the anti-corrosion layer is combined.

[0041] Table 1 Cable Dimension Parameters

[0042] Table 2 Submarine Cable Material Parameter Table

[0043] 2. Establish a three-dimensional fluid-structure interaction finite element model of the submarine cable under different high-pressure water gun flow rates, and use this model to simulate the stress distribution of the submarine cable under different high-pressure water gun flow rates.

[0044] When using finite element simulation software to establish a finite element model of the submarine cable, it is necessary to go through steps such as element and material model selection, geometric model establishment, mesh generation, and load application. The specific content is as follows: (1)Model setting The finite element analysis method can flexibly set the structure and material parameters of the submarine cable, as well as set various boundary conditions, etc., and can comprehensively simulate the working conditions of the submarine cable. For example Figure 4 is a schematic diagram of the overall submarine cable and high-pressure water gun impact. Set the diameter of the high-pressure water gun to 60 cm, and the selected modeling length of the submarine cable should not be less than 3 times the diameter of the high-pressure water gun. Finally, the length of the submarine cable is selected as 2.3 m; according to the actual situation of the high-pressure water gun impacting the submarine cable at present, select the impact position of the high-pressure water gun to be in the center of the submarine cable; according to the actual high-pressure water gun impact flow rate, set the flow rate to vary within the range of 0 - 10 m / s, and according to the environment of the ocean where the submarine cable is located, set the boundary distances on the left and right to be 1 m each.

[0045] (2)Finite element setting Select the fluid module and transient structure module in the finite element simulation software for stress analysis of each layer of materials of the submarine cable under the impact of the high-pressure water gun. Use the fluid module to analyze the water flow domain process of the high-pressure water gun impact, and use the transient structure module to calculate the structural changes and stress analysis of the submarine cable under impact.

[0046] After determining the element type and material parameters, a transient finite element model of the submarine cable can be established according to the structure and geometric model size of the submarine cable for mesh generation. The denser the mesh generation, the more accurate the calculation results, but the computational effort will increase geometrically. Since the submarine cable body and the surrounding water undergo drastic changes during the impact of the high-pressure water jet, the meshes in these areas are made denser. Using the method of manual mesh generation, the mesh size is set to 150 mm in the outer flow domain, and the meshes gradually become denser near the submarine cable. The hexahedron meshes are used, and the sweep method and surface mesh generation method are adopted for the submarine cable model to generate meshes for the submarine cable. As Figure 5 and Figure 6 shown, the mesh shape is regular, the density is moderate, and the distribution is uniform, meeting the requirements of calculation accuracy.

[0047] Analyzing the actual laying situation of the submarine cable, it is found that the length of the submarine cable is generally several kilometers to dozens of kilometers. When a section of the submarine cable is impacted by a high-pressure water jet, the two ends of the submarine cable can be approximately considered fixed. Fixed constraints are applied to the two ends of the submarine cable to fix the two ends of the submarine cable.

[0048] (3) Finite element model calculation and result analysis To accurately obtain the relationship between the stress of the submarine cable and the flow velocity of the high-pressure water jet, sufficient data samples are required. The flow velocity of the high-pressure water jet is set to 3 m / s, 5 m / s, 7 m / s, 9 m / s, and 10 m / s, the calculation time is set to 0.2 s, and the time step is 0.002 s. Finite element models are established and solved respectively, and finally the stress of the submarine cable is extracted from the results.

[0049] The stress results of the submarine cable obtained by finite element solution are as Figure 6 shown. The deformation is the largest at the position where the submarine cable is impacted by the high-pressure water jet, and the deformation of the remaining positions decreases from the inside out, which is in line with the actual situation.

[0050] Extract the stress results of each layer of the submarine cable from the solution results of the fluid-structure interaction finite element model, and draw a three-dimensional stress nephogram, as Figure 7 shown. It can be seen from the figure that when the impact flow velocity of the high-pressure water jet on the submarine cable is 5 m / s, the maximum deformation of the submarine cable is 0.524 mm. The deformation of the submarine cable increases with the increase of the impact flow velocity of the high-pressure water jet, and shows a non-linear trend.

[0051] 3. Nonlinear fitting method By analyzing the experimental data, the above data belong to single-variable non-linear data, and a univariate non-linear fitting model needs to be constructed. The following steps are taken for analysis: The first step: Establish a univariate non-linear fitting formula for the impact flow velocity of the high-pressure water jet and the stress of the submarine cable. Polynomial fitting, exponential fitting method, and power function fitting method are respectively selected for data fitting, and at the same time, the fitting degrees of different methods are compared. By comparing Coefficient of determination The closer it is to 1, the better the fitting degree. Select Among the fitting methods with a value greater than 0.9, select the fitting method with the highest fitting degree as the fitting method between the stress of the submarine cable body and the flow velocity of the high-pressure water gun, and select the most appropriate model parameters; let the impact flow velocity of the high-pressure water gun be m, and the stress on the submarine cable be n. It can be analyzed from Table 3 that the equation obtained by the power series fitting method has the best fitting coefficient for m and n and a smaller SSE. Its optimal equation is shown in Equation (1). Similarly, the equations for polynomial fitting and exponential fitting methods are shown in Equations (2) and (3). The fitting coefficient is the best and the SSE is smaller. Its optimal equation is shown in Equation (1). Similarly, the equations for polynomial fitting and exponential fitting methods are shown in Equations (2) and (3).

[0052] (1) (2) (3) Table 3 Statistical data of each model in the regression calculation of the flow velocity of the high-pressure water gun and the stress of the submarine cable

[0053] Step 2: Conduct verification to judge reliability and desirability.

[0054] Use two groups of new data to verify the fitting characteristics and accuracy of the constructed unary nonlinear fitting formula. As Figure 8 shown in the fitting diagram of the relationship between the stress of the submarine cable and the flow velocity of the high-pressure water gun. By observing the image, the calculation error of the proposed formula method is within the allowable range, the calculation speed is fast, and it has strong engineering practical value, but there is still room for improvement in the number and accuracy of the fitting data.

[0055] Example 2: The submarine cable stress prediction system includes: 1. A three-dimensional fluid-structure interaction finite element modeling module for establishing a simulation model of the submarine cable under different high-pressure water gun flow velocities; the three-dimensional fluid-structure interaction finite element modeling module includes: A geometric modeling unit for constructing a cable geometric model according to the layered structure of the submarine cable and the diameter d of the high-pressure water gun nozzle. The cable length is not less than 3d, and the material parameters of each structural layer are set; the conductor is simplified as a cylinder, the conductor shielding layer, the insulating layer, and the insulating shielding layer are combined into one layer, and the armor layer is simplified as an annular body. The density, elastic modulus, and Poisson's ratio of each layer are consistent with the actual parameters.

[0056] An outer domain modeling unit for establishing an outer domain model with the same length as the cable and setting a high-pressure water gun impact outlet directly above it.

[0057] The mesh division unit uses a non-uniform mesh division method to perform hexahedral mesh division on the outer domain, gradually densifying from the edge of the outer domain towards the cable and performing swept-mode mesh division on each layer of the cable.

[0058] The boundary condition setting unit applies fully constrained boundary conditions to both ends of the cable and sets the binding contact between each structural layer.

[0059] The flow velocity control unit sets the flow velocity of the high-pressure water gun in the range from 0 to the maximum flow velocity N, samples at intervals not exceeding 0.2N, and controls the change in flow velocity through a step function; the number of samples M of the flow velocity of the high-pressure water gun is an integer not less than 5, and the flow velocity range is divided into a low-pressure area and a high-pressure area, where the sample point interval in the high-pressure area is smaller than that in the low-pressure area.

[0060] The solution and data extraction unit solves the stress distribution of the cable at different flow velocities and extracts the maximum stress data samples of each layer.

[0061] Second, the non-linear fitting modeling module is used to establish a quantitative relationship formula between stress and flow velocity, specifically including: The fitting model unit fits the sample data with polynomial, exponential, and power function models, taking the flow velocity as the independent variable and the stress as the dependent variable.

[0062] The model screening unit, through selects the optimal fitting method by the coefficient of determination and verifies the accuracy of the fitting formula using an independent data set; calculates the coefficient of determination and mean square error of each fitting model, and selects the model with a coefficient of determination greater than 0.9 and the smallest mean square error as the optimal fitting formula; divides the sample data into a training set and a validation set equally, and uses the validation set to test the error of the fitting formula. If the error is within the allowable range, the fitting formula is used for subsequent submarine cable stress prediction; otherwise, the optimal fitting formula is re-screened.

[0063] Third, the stress prediction module is used to output the corresponding submarine cable stress prediction result according to the verified fitting formula and the input high-pressure water gun flow velocity value.

[0064] Through the technical characteristics of precise modeling, intelligent fitting, and rapid prediction, this system constructs a complete submarine cable stress prediction solution. It transforms complex physical processes into computable digital models, combining engineering practicality and technological advancement, providing efficient and reliable tool support for submarine cable operation and maintenance.

[0065] It can be understood that the detailed function implementation of the above modules can be referred to the introduction in the foregoing method embodiments, and no other elaboration is made here.

[0066] The method and system for predicting the stress of submarine cables under the impact of high-pressure water guns shown above are specific embodiments of the present invention, which have already reflected the substantial features and progress of the present invention. According to actual usage requirements, equivalent modifications can be made under the inspiration of the present invention, and all are within the scope of protection of this solution.

Claims

1. A method for predicting the stress of a submarine cable under the impact of a high-pressure water gun based on a fluid-structure interaction model, characterized in that It includes the following steps: 1) Establish a three-dimensional fluid-structure interaction finite element model of the submarine cable under different high-pressure water gun flow rates, specifically including: 1.1) According to the layered structure of the submarine cable and the diameter d of the high-pressure water gun nozzle, construct a cable geometric model, where the cable length is not less than 3d, and set the material parameters of each structural layer; 1.2) Establish an outer domain model with the same length as the cable, and set a high-pressure water gun impact outlet directly above it; 1.3) Use the non-uniform grid division method to divide the outer domain into hexahedral grids, which are gradually refined from the outer domain edge to the cable periphery; use the sweep mode to divide the grids of each layer of the cable; 1.4) Apply fully constrained boundary conditions to both ends of the cable, and set the binding contact between each structural layer; 1.5) Set the high-pressure water gun flow rate range from 0 to the maximum flow rate N, sample at intervals, and control the flow rate change through a step function; 1.6) Solve the stress distribution of the cable under different flow rates, and extract the maximum stress data samples of each layer; 2) Establish a fitting formula for stress and flow rate through non-linear fitting method, including: 2.1) Taking the flow rate as the independent variable and the stress as the dependent variable, select polynomial, exponential or power function models to perform univariate non-linear fitting on the sample data; 2.2) By selecting the optimal fitting method through the coefficient of determination and verifying the accuracy of the fitting formula using an independent dataset; 3) According to the verified fitting formula and the current high-pressure water gun flow rate, obtain the stress prediction result of the submarine cable.

2. The method for predicting the stress of a submarine cable under the impact of a high-pressure water gun based on a fluid-structure interaction model according to claim 1, wherein: In step 1.1), the layered structure of the submarine cable includes a conductor, a conductor shielding layer, an insulating layer, an insulating shielding layer, an armor layer and an outer sheath. When constructing the cable geometric model, the conductor is simplified as a cylinder, the conductor shielding layer, the insulating layer and the insulating shielding layer are combined into one layer, the armor layer is simplified as a torus, and the density, elastic modulus and Poisson's ratio of each layer are consistent with the actual parameters.

3. The method for predicting the stress of a submarine cable under the impact of a high-pressure water gun based on a fluid-structure interaction model according to claim 1, wherein: In step 1.2), the periphery of the outer domain is set as an open surface.

4. The method for predicting the stress of a submarine cable under the impact of a high-pressure water gun based on a fluid-structure interaction model according to claim 1, characterized in that: In step 1.5), the interval between adjacent sample points does not exceed 0.2N.

5. The method for predicting the stress of submarine cables under the impact of high-pressure water guns based on the fluid-structure interaction model according to claim 4, wherein: The number of samples M of the high-pressure water gun flow rate is an integer not less than 5, and the flow rate range is divided into a low-pressure area and a high-pressure area, where the sample point interval in the high-pressure area is smaller than that in the low-pressure area.

6. The method for predicting the stress of a submarine cable under the impact of a high-pressure water gun based on a fluid-structure interaction model according to claim 1, characterized in that: In step 2.2), calculate the coefficient of determination and mean square error of each fitting model, and select the model with a coefficient of determination greater than 0.9 and the smallest mean square error as the optimal fitting formula; divide the sample data into a training set and a validation set equally, and use the validation set to test the error of the fitting formula. If the error is within the allowable range, use this fitting formula for subsequent submarine cable stress prediction; Otherwise, re-screen the optimal fitting formula.

7. A submarine cable stress prediction system using the submarine cable stress prediction method based on a fluid-structure interaction model according to claim 1, characterized in that It includes: I. A three-dimensional fluid-structure interaction finite element modeling module for establishing a simulation model of the submarine cable under different high-pressure water gun flow rates; The three-dimensional fluid-structure interaction finite element modeling module includes: A geometric modeling unit for constructing a cable geometric model according to the layered structure of the submarine cable and the diameter d of the high-pressure water gun nozzle, with the cable length not less than 3d, and setting the material parameters of each structural layer; An outer domain modeling unit for establishing an outer domain model with the same length as the cable and setting a high-pressure water gun impact outlet directly above it; A grid division unit for using the non-uniform grid division method to divide the outer domain into hexahedral grids, gradually refining from the outer domain edge to the cable periphery, and dividing the grids of each layer of the cable in a sweep mode; A boundary condition setting unit for applying fully constrained boundary conditions to both ends of the cable and setting the binding contact between each structural layer; A flow rate control unit for setting the high-pressure water gun flow rate in the range from 0 to the maximum flow rate N, sampling at intervals, and controlling the flow rate change through a step function; A solution and data extraction unit, which solves the stress distribution of the cable at different flow rates and extracts the maximum stress data samples of each layer; 2. A non-linear fitting modeling module, which is used to establish a quantitative relationship formula between stress and flow rate, specifically including: A fitting model unit, which takes the flow rate as the independent variable and the stress as the dependent variable, and fits the sample data with polynomial, exponential and power function models; Model screening unit, through select the optimal fitting method by the coefficient of determination and verify the accuracy of the fitting formula using an independent dataset; 3. A stress prediction module, which is used to output the corresponding submarine cable stress prediction result according to the verified fitting formula and the input high-pressure water gun flow rate value.

8. The submarine cable stress prediction system according to claim 7, characterized in that: In the geometric modeling unit, the layered structure of the submarine cable includes a conductor, a conductor shielding layer, an insulating layer, an insulating shielding layer, an armor layer and an outer sheath. When constructing the cable geometric model, the conductor is simplified into a cylinder, the conductor shielding layer, the insulating layer and the insulating shielding layer are combined into one layer, and the armor layer is simplified into an annular body. The density, elastic modulus and Poisson's ratio of each layer are consistent with the actual parameters.

9. The undersea cable stress prediction system according to claim 7, wherein: In the flow rate control unit, the number of samples M of the high-pressure water gun flow rate is an integer not less than 5, and the flow rate range is divided into a low-pressure area and a high-pressure area, where the sample point interval in the high-pressure area is smaller than that in the low-pressure area.

10. The submarine cable stress prediction system according to claim 7, wherein: The model screening unit calculates the coefficient of determination and mean square error of each fitting model, and selects the model with a coefficient of determination greater than 0.9 and the smallest mean square error as the optimal fitting formula; equally divide the sample data into a training set and a validation set, use the validation set to test the error of the fitting formula, and if the error is within the allowable range, use this fitting formula for subsequent submarine cable stress prediction; Otherwise, re-screen the optimal fitting formula.

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