A method and system for analyzing failure of submarine cable bend limiter

Abstract

The present invention relates to the technical field of submarine cable engineering equipment and discloses a method and system for analyzing the failure of submarine cable bend limiters. The method comprises: constructing a large-scale wave flume test system; conducting wave and current tests in the large-scale wave flume test system to obtain three-dimensional terrain evolution data of scour pits formed at a single pile foundation model, as well as the dynamic strain response and displacement of the submarine cable bend limiter model; constructing a hydrodynamic-sediment transport-submarine cable motion coupling numerical model based on the three-dimensional terrain evolution data, dynamic strain response, and displacement; and determining a quantitative relationship between the expansion of the scour range and the failure threshold of the submarine cable bend limiter based on the hydrodynamic-sediment transport-submarine cable motion coupling numerical model and different hydrodynamic conditions. This solution can quantitatively analyze the changing patterns of tensile stress and bending response of submarine cables and bend limiters, providing a reference for the optimized design and protection of offshore wind power pile-based submarine cable bend limiters.

Description

Technical Field

[0001] The present invention belongs to the technical field of submarine cable engineering equipment, and in particular relates to a method and system for analyzing failure of a submarine cable bend limiter. Background Art

[0002] In marine environments, submarine cable systems are prone to partial overhang due to current scouring and wave loads, resulting in dynamic bending stresses on bend limiters. Traditional failure analysis, often based on static mechanical models or single-physics field simulations, ignores the spatiotemporal coupling between scour pit expansion and the dynamic response of the submarine cable. This inability to accurately characterize the progressive impact of accumulated bending curvature on fatigue damage to protective structures under actual operating conditions poses a risk of sudden breakage in submarine cable systems.

[0003] Traditional technologies rely on static mechanical models and single-physics field simulations, failing to fully consider the effects of dynamic loads and multi-physics field coupling. Physical experiments often employ small-scale models, resulting in distorted scour patterns and failing to reflect the erosion patterns of the riprap protective layer caused by three-dimensional eddy currents around the actual pile foundations, as well as the motion characteristics of the submarine cable. Numerical simulations often decouple hydrodynamic scour, sediment transport, and structural response, lacking a synergistic mechanism for hydrodynamic, sediment, and submarine cable deformation. Failure threshold determination relies on empirical safety factors, and a quantitative correlation model between dynamic curvature accumulation and fatigue damage has not been established.

[0004] Therefore, it is urgent to develop an analysis method and system for the failure of submarine cable bend limiters, which can quantitatively analyze the tensile stress and bending response changes of submarine cables and bend limiters, and provide a reference for the optimal design and protection of offshore wind power pile foundation submarine cable bend limiters. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a method and system for analyzing the failure of submarine cable bend limiters, which can quantitatively analyze the tensile stress and bending response changes of submarine cables and bend limiters, and provide a reference for the optimized design and protection of offshore wind power pile foundation submarine cable bend limiters.

[0006] The present invention provides a method for analyzing failure of a submarine cable bend limiter, the method comprising the following steps:

[0007] S1. Construct a large-scale wave tank experimental system, which includes a single pile foundation model, a sandy seabed simulation layer, and a riprap protective layer;

[0008] S2. Conduct wave and current tests in a large-scale wave flume test system to obtain three-dimensional topographic evolution data of scour pits formed at the single pile foundation model, as well as the dynamic strain response and displacement of the submarine cable bend limiter model;

[0009] S3. Construct a coupled numerical model of hydrodynamics, sediment transport, and submarine cable motion based on 3D terrain evolution data, dynamic strain responses, and displacements.

[0010] S4. Based on the hydrodynamic-sediment transport-submarine cable motion coupled numerical model and different hydrodynamic conditions, the quantitative relationship between the scour range expansion and the failure threshold of the submarine cable bend limiter is determined.

[0011] Furthermore, in S1, the construction of a large-scale wave tank experimental system also includes:

[0012] The monopile foundation model is fixed vertically to the sandy seabed simulation layer;

[0013] The riprap protective layer includes uniform riprap working condition and uneven riprap working condition;

[0014] Divide the single pile foundation model into multiple sector-shaped protection areas, and fill the first target sector-shaped protection area with rubble to form a riprap protection layer under uniform riprap conditions;

[0015] Multiple sector-shaped protection areas are divided around the single pile foundation model, and boulders are dumped in the second target sector-shaped protection area to form a riprap protection layer under uneven riprap conditions.

[0016] Furthermore, in S2, obtaining the three-dimensional terrain evolution data of the scour pit formed at the single pile foundation model includes:

[0017] S21. Arrange an ultrasonic depth sensor array along multiple radial axes of the monopile foundation model, and evenly set a number of measuring points on each radial axis;

[0018] S22. Generate a three-dimensional dynamic terrain model of the scour pit based on real-time monitoring data of the ultrasonic depth sensor array.

[0019] Furthermore, in S2, obtaining the dynamic strain response and displacement of the submarine cable bending limiter model includes:

[0020] S23, arranging fiber Bragg grating sensors evenly along the circumferential and axial directions on the surface of the submarine cable bend limiter model to form a cross monitoring network;

[0021] S24. Based on the strain data of the fiber Bragg grating sensor, the displacement data and curvature change of the submarine cable bending limiter model are obtained through modal analysis.

[0022] Furthermore, in S3, the construction of the hydrodynamic model in the coupled numerical model of hydrodynamics, sediment transport and submarine cable motion includes:

[0023] S31a, close the RANS equations using the k-ε turbulence model with second-order terms;

[0024] The k-ε turbulence model expression is as follows:

[0025] ;

[0026] ;

[0027] in, is a second-order term, k represents turbulent energy, ε represents the rate of turbulent dissipation, u represents flow velocity, C μ represents the dimensionless coefficient, l represents the turbulence length scale;

[0028] S31b, calculate bed shear stress;

[0029] The calculation formula is as follows:

[0030] ;

[0031] Where τ represents the bed shear stress, τ t represents the wall pull, and n represents the unit normal vector perpendicular to the surface.

[0032] Furthermore, in S3, in the hydrodynamic-sediment transport-submarine cable motion coupled numerical model, the construction of the sediment transport model includes:

[0033] S32a, using bed shear stress and hydrodynamic model to solve the bed load transfer process;

[0034] S32b, based on the convection-diffusion equation, the passive transport of suspended sediment is calculated to obtain the suspended sediment concentration distribution in three-dimensional space;

[0035] S32c, mapping the suspended sediment concentration distribution in three-dimensional space to a two-dimensional bed surface grid using the finite area method;

[0036] S32d. The beach profile changes are solved based on the Exner equation and the suspended sediment concentration distribution mapped to a two-dimensional bed grid.

[0037] Furthermore, in S3, the construction of the wave-current-submarine cable model in the coupled numerical model of hydrodynamics-sediment transport-submarine cable motion includes:

[0038] S33a, establish a hybrid Eulerian-Lagrangian grid;

[0039] S33b, based on the RANS-VOF flow solver, the Reynolds-averaged Navier-Stokes equations and the free surface simulation method are used to perform fluid dynamics modeling and obtain the mechanical parameters;

[0040] S33c, based on the hybrid Euler-Lagrangian grid and mechanical parameters, the elastic rod theory is used to model the motion of the submarine cable, and the finite element method is used to solve the motion response of the submarine cable under the action of waves and currents;

[0041] S33d. Based on the motion response of the submarine cable under the action of waves and currents, the diffusion immersed boundary method is used to calculate the fluid motion caused by the submarine cable;

[0042] S33e, the extended k-ε turbulence model is used to correct the fluid motion caused by the submarine cable to obtain the final turbulence field.

[0043] The present invention also provides a submarine cable bend limiter failure analysis system for executing the above-mentioned submarine cable bend limiter failure analysis method. The system includes the following modules:

[0044] Large-scale wave tank test system, which includes a single pile foundation model, a sandy seabed simulation layer, and a riprap protection layer;

[0045] The data acquisition module is connected to the large-scale wave flume test system and is used to conduct wave and current tests in the large-scale wave flume test system to obtain three-dimensional terrain evolution data of the scour pit formed at the single pile foundation model and the dynamic strain response and displacement of the submarine cable bending limiter model;

[0046] The model building module is connected to the data acquisition module and is used to build a coupled numerical model of hydrodynamics, sediment transport and submarine cable motion based on three-dimensional terrain evolution data, dynamic strain response and displacement;

[0047] The analysis module is connected to the model building module and is used to determine the quantitative relationship between the expansion of the scour range and the failure threshold of the submarine cable bending limiter based on the hydrodynamic-sediment transport-submarine cable movement coupled numerical model and different hydrodynamic conditions.

[0048] The embodiments of the present invention have the following technical effects:

[0049] This paper is based on a large-scale wave flume experimental system, combining ultrasonic depth sensor arrays with fiber Bragg grating sensing technology to fully capture the spatiotemporal coupling characteristics of the three-dimensional scour morphological evolution of the pile foundation and the dynamic strain of the bending limiter. The hydrodynamic-sediment transport coupling framework is constructed through the k-ε turbulence model and the Exner equation. The elastic rod theory is used to establish the submarine cable flexible body dynamics model. With the help of a hybrid Euler-Lagrangian grid, high-precision calculations of multi-physical field interactions are achieved. This coupling model innovatively introduces the diffusion immersed boundary method, which effectively characterizes the reaction of the submarine cable movement to the local flow field. The curvature accumulation characteristics of the bend limiter are extracted through modal analysis, and a correlation model between the scour pit expansion rate and the structural curvature growth is established; the differentiated experimental design of sector-shaped partitioned riprap protection reveals the regulation law of the spatial heterogeneity of the protective layer on the scour process. Combined with the dynamic failure threshold judgment method, it breaks through the limitations of the traditional empirical coefficient method and realizes dynamic early warning of the entire process from scour initiation to structural failure, thereby quantitatively analyzing the tensile stress and bending response variation laws of the submarine cable and the bend limiter, providing a reference for the optimal design and protection of the bend limiter of the offshore wind power pile foundation submarine cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0051] Figure 1 This is a flow chart of a method for analyzing failure of a submarine cable bend limiter provided by an embodiment of the present invention;

[0052] Figure 2 Schematic diagram of the arrangement of a single pile foundation model in a large-scale wave tank experimental system provided by an embodiment of the present invention;

[0053] Figure 3 This is a schematic diagram of the arrangement of a riprap protective layer provided by an embodiment of the present invention;

[0054] Figure 4 Schematic diagram of the scour pattern around a single pile foundation model during the rising and falling waves at different pile spacings provided by an embodiment of the present invention;

[0055] Figure 5 This is a flow chart for solving a wave-current-submarine cable coupling model provided by an embodiment of the present invention;

[0056] Figure 6 The diagram is a structural diagram of a submarine cable bend limiter failure analysis system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0057] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

[0058] The embodiment of the present invention provides a method for analyzing failure of a submarine cable bend limiter. Figure 1 This is a flow chart of a method for analyzing failure of a submarine cable bend limiter provided by an embodiment of the present invention. Figure 1 , the method comprises the following steps:

[0059] S1. Construct a large-scale wave tank experimental system, which includes a single pile foundation model, a sandy seabed simulation layer, and a riprap protective layer.

[0060] The large-scale wave tank used in this embodiment is 456m long, 5m wide, and 12m deep. It has a transparent glass observation area on one side and a concrete floor. It is equipped with a push-plate wave maker and a circulating water system. The wave maker is an absorption-type wave maker with a motor servo-driven push-plate. It can generate various regular and irregular waves, with an effective wave generation period of 2-10s and a maximum wave generation capacity of 3.5m. The maximum flow rate of the circulating water system is 15m 3 / s, and all control systems are computer-controlled. Connecting pipes are installed at both ends of the flume to maintain a constant water level on both sides of the model during the experiment. A concrete wave-absorbing device is also installed on one side of the flume to address wave reflections.

[0061] Figure 2 Schematic diagram of the arrangement of a single pile foundation model in a large-scale wave tank experimental system provided by an embodiment of the present invention. Figure 3 This is a schematic diagram of the arrangement of a riprap protective layer provided by an embodiment of the present invention, see Figure 2 and Figure 3 , building a large-scale wave tank experimental system also includes:

[0062] The monopile foundation model is fixed vertically to the sandy seabed simulation layer;

[0063] The riprap protective layer includes uniform riprap working condition and uneven riprap working condition;

[0064] Divide the single pile foundation model into multiple sector-shaped protection areas, and fill the first target sector-shaped protection area with rubble to form a riprap protection layer under uniform riprap conditions;

[0065] Multiple sector-shaped protection areas are divided around the single pile foundation model, and boulders are dumped in the second target sector-shaped protection area to form a riprap protection layer under uneven riprap conditions.

[0066] A 4m thick, 100m long sand layer was set at the bottom of the flume as the scour sand bed. The experimental sand was non-cohesive, uniform sand. The geometric characteristics of the riprap and bend limiter were determined based on the results of the field investigation. A 50cm diameter, highly transparent acrylic cylinder was placed in the center of the sand bed as a single pile. Its bottom was reinforced with concrete to prevent shaking during the experiment. The wave measurement system used a large-scale dynamic capacitive wave height measurement system with a range of 5m. Seven wave height meters were installed on the upstream sidewall of the flume to record wave parameters. Figure 2 (a) and Figure 2 (b) The flow measurement system uses a single-point ultrasonic Doppler velocimeter (ADV) and an ultrasonic Doppler profiler (ADCP), which are installed on the side of the pile and about 10 m upstream from the pile, and 0.25 m from the bottom sand bed.

[0067] According to the actual on-site engineering project, the scale of the model is selected to be 1:13 to eliminate the influence of the scale effect. The model values ​​and prototype values ​​of the main experimental parameters are shown in Table 1. At the same time, different wave heights are selected to expand the experimental conditions:

[0068] Table 1 Model experimental parameters

[0069]

[0070] First, experiments were conducted without riprap protection measures. Doppler flowmeters were used to monitor the flow field around the single pile, ultrasonic depth sensors were used to monitor the real-time scouring around the single pile, and underwater laser scanners were used to monitor large-scale terrain changes. The temporal and spatial evolution characteristics of the terrain around the pile foundation were obtained. The terrain around the pile foundation was then restored to an unscoured state. Riprap protection was deployed in key scouring areas. Wave and flow experiments were then conducted again to monitor the temporal and spatial evolution of the terrain around the single pile foundation model and identify key locations for riprap protection. Figure 3 , the protection area is divided into different fan-shaped sub-areas, and rock filling is carried out in different fan-shaped areas to form different riprap plane layout plans, among which, Figure 3 (a) is the working condition of uniform stone throwing. Figure 3 (b) The uneven stone dumping condition is observed. By observing the local sediment scouring process of the pile foundation, the key locations of the scouring initiation and development process are explored, providing a reference for the formulation of the pile foundation stone dumping construction plan.

[0071] S2. Conduct wave and current tests in a large-scale wave flume test system to obtain three-dimensional terrain evolution data of scour pits formed at the single pile foundation model and the dynamic strain response and displacement of the submarine cable bend limiter model.

[0072] In some embodiments, S2 includes the following sub-steps:

[0073] S21. Arrange an ultrasonic depth measuring sensor array along multiple radial axes of the monopile foundation model, and evenly set a number of measuring points on each radial axis.

[0074] S22. Generate a three-dimensional dynamic terrain model of the scour pit based on real-time monitoring data of the ultrasonic depth sensor array.

[0075] In some embodiments, see Figure 2 (c) shows the radial position of the ultrasonic echo sounder. Four pressure sensors were placed circumferentially and axially along the monopile foundation model, for a total of 16 sensors, measuring the stresses on the monopile foundation model under different operating conditions. SeaTek ultrasonic echo sounders were used to monitor the scouring process at 40 measurement points in real time, with a maximum sampling frequency of 20 Hz. Ultrasonic echo sounders were distributed around the pile in eight radial directions, 1.5 m from the sand bed. The closest distance to the pile surface was 10 cm. SeaTek was used to measure topographic changes near the monopile in real time, and the data was processed to generate a three-dimensional topographic map. High-definition digital cameras, all connected via synchronization equipment and controlled by a computer, were placed inside the cylinder to record the shape and position of underwater riprap, the temporal and spatial evolution of the topography, and the motion of the submarine cable bend limiter in real time.

[0076] S23, arranging fiber grating sensors circumferentially and evenly on the surface of the submarine cable bend limiter model to form a cross monitoring network.

[0077] S24. Based on the strain data of the fiber Bragg grating sensor, obtain the displacement data and curvature change of the submarine cable bend limiter model through modal analysis.

[0078] In some embodiments, fiber optic Bragg grating sensors are fixed to the surface of the submarine cable bend limiter model using epoxy resin glue, so that they are evenly arranged circumferentially and axially along the surface of the model, and the strain, displacement, vibration frequency and other data of the model are measured. The acquisition and processing of optical fiber signals uses the JEME-iFBG series multi-channel fiber optic Bragg grating demodulator, with a sampling frequency of up to 1000 Hz and a wavelength range of 1510 to 1590 nm. The collected strain data is processed using modal analysis to obtain displacement data. Under conditions of different riprap uniformity around the pile foundation, the swing amplitude and curvature changes of the submarine cable bending limit value are monitored throughout the scour development process, especially to explore the destructive instability threshold of the submarine cable outlet end as the scour pit expands.

[0079] S3. Construct a coupled numerical model of hydrodynamics, sediment transport, and submarine cable motion based on three-dimensional terrain evolution data, dynamic strain response, and displacement.

[0080] In some examples, calculations were performed using a coupled pile hydrodynamic and nonlinear sediment model based on the OpenFOAM platform. The model used a k-ε turbulence model with a second-order term to close the RANS equations, and the bed shear stress was estimated using the method proposed by Arzani et al. (2016). In this example, the PIMPLE algorithm was used to solve the governing equations. This method fully combines the characteristics of the PISO and SIMPLE algorithms, as follows:

[0081] 1) Construction of the hydrodynamic model includes:

[0082] S31a, close the RANS equations using the k-ε turbulence model with second-order terms;

[0083] The k-ε turbulence model expression is as follows:

[0084] ;

[0085] ;

[0086] The expressions of k and ε are as follows:

[0087] ;

[0088] ;

[0089] in, is a second-order term, k represents turbulent energy, ε represents the rate of turbulent dissipation, u represents flow velocity, T is the transposition operation, C μ represents a dimensionless coefficient, which can be taken as an empirical value of 0.09, l represents the turbulence length scale, and v t represents the turbulent kinematic viscosity coefficient, t represents time, represents the vector differential operator, ρ represents the fluid density, σ k The turbulent Prandtl number represents the turbulent kinetic energy equation, which is 1, σ ε The turbulent Prandtl number representing the dissipation rate equation is 1.3, C 1ε represents the turbulence generation coefficient, which is 1.44, C 2ε represents the turbulence dissipation coefficient, which is 1.92;

[0090] S31b, calculate bed shear stress;

[0091] The calculation formula is as follows:

[0092] ;

[0093] ;

[0094] Where τ represents the bed shear stress, τ t represents the wall traction, n represents the unit normal vector perpendicular to the surface, and σ represents the stress tensor;

[0095] The stress tensor σ is calculated as follows:

[0096] ;

[0097] Where p represents pressure, I represents the Kronecker function, and 2μS represents the viscous stress term determined by the bottom fluid motion.

[0098] 2) Construction of sediment transport model includes:

[0099] S32a, using bed shear stress and hydrodynamic model to solve the bed load transfer process;

[0100] S32b, based on the convection-diffusion equation, the passive transport of suspended sediment is calculated to obtain the suspended sediment concentration distribution in three-dimensional space;

[0101] S32c, mapping the suspended sediment concentration distribution in three-dimensional space to a two-dimensional bed surface grid using the finite area method;

[0102] S32d. The beach profile changes are solved based on the Exner equation and the suspended sediment concentration distribution mapped to a two-dimensional bed grid.

[0103] Figure 4 This is a schematic diagram of the scouring pattern around the pile of a single pile foundation model during the wave rising and falling process under different pile spacings provided by an embodiment of the present invention. Figure 4 , where (a)~(d) are the wave rising process, and (e)~(h) are the wave falling process.

[0104] 3) Construction of the wave-current-submarine cable model includes:

[0105] S33a, establish a hybrid Eulerian-Lagrangian grid;

[0106] S33b, based on the RANS-VOF flow solver, the Reynolds-averaged Navier-Stokes equations and the free surface simulation method are used to perform fluid dynamics modeling and obtain the mechanical parameters;

[0107] S33c, based on the hybrid Euler-Lagrangian grid and mechanical parameters, the elastic rod theory is used to model the motion of the submarine cable, and the finite element method is used to solve the motion response of the submarine cable under the action of waves and currents;

[0108] S33d. Based on the motion response of the submarine cable under the action of waves and currents, the diffusion immersed boundary method is used to calculate the fluid motion caused by the submarine cable;

[0109] S33e, the extended k-ε turbulence model is used to correct the fluid motion caused by the submarine cable to obtain the final turbulence field.

[0110] Figure 5 This is a flow chart of solving a wave-current-submarine cable coupling model provided by an embodiment of the present invention. An interface module is developed in the model to realize information exchange between wave-current-submarine cable model components. The model solving process is as follows: Figure 5 As shown in Figure 2. At each time step, the cable motion is first solved using the velocity output from the wave-flow hydrodynamic model. The velocity and acceleration at the center of the fluid grid cell are interpolated to the structural grid points. After solving for the cable motion, the hydrodynamic force at each structural grid point is evenly distributed to the surrounding fluid cells using the following formula:

[0111] ;

[0112] Where X represents the position vector within the fluid grid, F hd Indicates the dynamic water pressure, represents the Lagrangian structured grid, represents the Dirac function;

[0113] In the fluid momentum equation of the RANS-VOF solver, the smoothed cable force is used as the source term, and the fluid momentum equation is as follows:

[0114] ;

[0115] Where U represents the velocity vector, represents the effective dynamic viscosity, , represents the molecular dynamic viscosity, represents the turbulent eddy viscosity, represents the pseudo-dynamic pressure, , g represents the acceleration due to gravity;

[0116] The standard steps of the RANS-VOF flow solver (i.e., VOF and PISO algorithms) are then followed. Similarly, the turbulence generation term induced by the cable at each structure grid point is smoothly distributed to the surrounding fluid cells using the following formula:

[0117]

[0118] Among them, Pv(X) represents the turbulent pressure at point X, and Pv(r) represents the turbulent pressure at point r.

[0119] The smoothed turbulence is added to the transport equations for solving the k-ε turbulence model. The new flow velocity is then used to solve for the cable motion in the next time step.

[0120] S4. Based on the hydrodynamic-sediment transport-submarine cable motion coupled numerical model and different hydrodynamic conditions, the quantitative relationship between the scour range expansion and the failure threshold of the submarine cable bend limiter is determined.

[0121] The failure threshold of the cable bend limiter can be determined based on its material properties. This threshold represents the threshold at which the cable bend limiter is damaged. Finally, the wave-current-cable coupling module was incorporated into the pile foundation hydrodynamic and nonlinear sediment coupling model to develop a coupled numerical model of hydrodynamics, sediment transport, and cable motion. This model was then validated to investigate the cable's motion response during the spatiotemporal evolution of the scour pit under varying hydrodynamic conditions. The results also quantitatively analyzed the variations in the tensile stress and bending response of the cable and bend limiter.

[0122] This paper is based on a large-scale wave flume experimental system, combining ultrasonic depth sensor arrays with fiber Bragg grating sensing technology to fully capture the spatiotemporal coupling characteristics of the three-dimensional scour morphological evolution of the pile foundation and the dynamic strain of the bending limiter. The hydrodynamic-sediment transport coupling framework is constructed through the k-ε turbulence model and the Exner equation. The elastic rod theory is used to establish the submarine cable flexible body dynamics model. With the help of a hybrid Euler-Lagrangian grid, high-precision calculations of multi-physical field interactions are achieved. This coupling model innovatively introduces the diffusion immersed boundary method, which effectively characterizes the reaction of the submarine cable movement to the local flow field. The curvature accumulation characteristics of the bend limiter are extracted through modal analysis, and a correlation model between the scour pit expansion rate and the structural curvature growth is established; the differentiated experimental design of sector-shaped partitioned riprap protection reveals the regulation law of the spatial heterogeneity of the protective layer on the scour process. Combined with the dynamic failure threshold judgment method, it breaks through the limitations of the traditional empirical coefficient method and realizes dynamic early warning of the entire process from scour initiation to structural failure, thereby quantitatively analyzing the tensile stress and bending response variation laws of the submarine cable and the bend limiter, providing a reference for the optimal design and protection of the bend limiter of the offshore wind power pile foundation submarine cable.

[0123] The embodiment of the present invention further provides a submarine cable bend limiter failure analysis system, which is used to execute the above-mentioned submarine cable bend limiter failure analysis method. Figure 6 This is a schematic diagram of the structure of a submarine cable bending limiter failure analysis system provided by an embodiment of the present invention, see Figure 6 , the system includes the following modules:

[0124] Large-scale wave tank test system, which includes a single pile foundation model, a sandy seabed simulation layer, and a riprap protection layer;

[0125] The data acquisition module is connected to the large-scale wave flume test system and is used to conduct wave and current tests in the large-scale wave flume test system to obtain three-dimensional terrain evolution data of the scour pit formed at the single pile foundation model and the dynamic strain response and displacement of the submarine cable bending limiter model;

[0126] The model building module is connected to the data acquisition module and is used to build a coupled numerical model of hydrodynamics, sediment transport and submarine cable motion based on three-dimensional terrain evolution data, dynamic strain response and displacement;

[0127] The analysis module is connected to the model building module and is used to determine the quantitative relationship between the expansion of the scour range and the failure threshold of the submarine cable bending limiter based on the hydrodynamic-sediment transport-submarine cable movement coupled numerical model and different hydrodynamic conditions.

[0128] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A method for analyzing failure of a submarine cable bend limiter, characterized in that: The method comprises the following steps: S1. Construct a large-scale wave tank experimental system, which includes a single pile foundation model, a sandy seabed simulation layer, and a riprap protective layer; S2. Conducting a wave and current test in the large-scale wave flume test system to obtain three-dimensional topographic evolution data of a scour pit formed at the monopile foundation model and dynamic strain response and displacement of a submarine cable bend limiter model; S3. Constructing a coupled numerical model of hydrodynamics, sediment transport, and submarine cable motion based on the three-dimensional terrain evolution data, the dynamic strain response, and the displacement; S4. Determine the quantitative relationship between the expansion of the scour range and the failure threshold of the submarine cable bend limiter based on the hydrodynamic-sediment transport-submarine cable motion coupled numerical model and different hydrodynamic conditions.

2. The method for analyzing failure of a submarine cable bend limiter according to claim 1, characterized in that: In S1, constructing a large-scale wave tank experimental system also includes: The monopile foundation model is vertically fixed to the sandy seabed simulation layer; The riprap protective layer includes a uniform riprap working condition and an uneven riprap working condition; Dividing the single pile foundation model into a plurality of sector-shaped protection areas, and filling the first target sector-shaped protection area with rubble to form a riprap protection layer under a uniform riprap working condition; A plurality of sector-shaped protection areas are divided around the single pile foundation model, and rocks are dumped and filled in the second target sector-shaped protection area to form a riprap protection layer under uneven riprap working conditions.

3. The method for analyzing failure of a submarine cable bend limiter according to claim 2, characterized in that: In S2, obtaining the three-dimensional terrain evolution data of the scour pit formed at the single pile foundation model includes: S21, arranging an array of ultrasonic depth measuring sensors along multiple radial axes of the monopile foundation model, with a number of measuring points evenly arranged on each radial axis; S22: Generate a three-dimensional dynamic terrain model of the scour pit based on the real-time monitoring data of the ultrasonic depth sensor array.

4. The method for analyzing failure of a submarine cable bend limiter according to claim 2, characterized in that: In S2, obtaining the dynamic strain response and displacement of the submarine cable bending limiter model includes: S23, evenly arranging fiber Bragg grating sensors along the circumferential and axial directions on the surface of the submarine cable bend limiter model to form a cross monitoring network; S24. Based on the strain data of the fiber Bragg grating sensor, obtain the displacement data and curvature change of the submarine cable bend limiter model through modal analysis.

5. The method for analyzing failure of a submarine cable bend limiter according to claim 1, characterized in that: In S3, in the hydrodynamic-sediment transport-submarine cable motion coupled numerical model, the construction of the hydrodynamic model includes: S31a, close the RANS equations using the k-ε turbulence model with second-order terms; The k-ε turbulence model expression is as follows: ； ； in, is a second-order term, k represents turbulent energy, ε represents the rate of turbulent dissipation, u represents flow velocity, C μ represents the dimensionless coefficient, l represents the turbulence length scale; S31b, calculate bed shear stress; The calculation formula is as follows: ； Where τ represents the bed shear stress, τ t represents the wall pull, and n represents the unit normal vector perpendicular to the surface.

6. A method for analyzing failure of a submarine cable bend limiter according to claim 5, characterized in that: In S3, in the hydrodynamic-sediment transport-submarine cable motion coupled numerical model, the construction of the sediment transport model includes: S32a, solving the bed load transfer process using the bed shear stress and the hydrodynamic model; S32b, based on the convection-diffusion equation, the passive transport of suspended sediment is calculated to obtain the suspended sediment concentration distribution in three-dimensional space; S32c, mapping the suspended sediment concentration distribution in three-dimensional space to a two-dimensional bed surface grid using the finite area method; S32d. The beach profile changes are solved based on the Exner equation and the suspended sediment concentration distribution mapped to a two-dimensional bed grid.

7. A method for analyzing failure of a submarine cable bend limiter according to claim 6, characterized in that: In S3, the construction of the wave-current-submarine cable model in the hydrodynamic-sediment transport-submarine cable motion coupled numerical model includes: S33a, establish a hybrid Eulerian-Lagrangian grid; S33b, based on the RANS-VOF flow solver, the Reynolds-averaged Navier-Stokes equations and the free surface simulation method are used to perform fluid dynamics modeling and obtain the mechanical parameters; S33c, based on the hybrid Euler-Lagrangian grid and the mechanical parameters, adopting elastic rod theory to model the motion of the submarine cable, and solving the motion response of the submarine cable under the action of waves and currents by using the finite element method; S33d. Based on the motion response of the submarine cable under the action of waves and currents, the diffusion immersed boundary method is used to calculate the fluid motion caused by the submarine cable; S33e, the extended k-ε turbulence model is used to correct the fluid motion caused by the submarine cable to obtain the final turbulence field.

8. A submarine cable bend limiter failure analysis system, used to execute the submarine cable bend limiter failure analysis method according to any one of claims 1 to 7, characterized in that: The system includes the following modules: A large-scale wave tank test system, comprising a single pile foundation model, a sandy seabed simulation layer, and a riprap protective layer; a data acquisition module connected to the large-scale wave flume test system, configured to conduct a wave and current test in the large-scale wave flume test system to obtain three-dimensional topographic evolution data of a scour pit formed at the monopile foundation model, and dynamic strain response and displacement of a submarine cable bending limiter model; a model construction module, connected to the data acquisition module, for constructing a hydrodynamic-sediment transport-submarine cable motion coupling numerical model based on the three-dimensional terrain evolution data, the dynamic strain response and the displacement; An analysis module is connected to the model building module and is used to determine the quantitative relationship between the expansion of the scour range and the failure threshold of the submarine cable bending limiter based on the hydrodynamic-sediment transport-submarine cable movement coupled numerical model and different hydrodynamic conditions.

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