Dynamic distribution design method for float-type single-point load of inner turret

Abstract

The invention relates to the technical field of single-point load dynamic distribution, in particular to an inner turret float type single-point load dynamic distribution design method. The method comprises the following steps: S1, establishing a wet surface model according to an FPSO hull molded line in an SESAM software HydroD module, establishing a quality model according to FPSO loading information, and performing hydrodynamic analysis based on the wet surface model and the quality model to obtain an FPSO overall motion response operator RAO; and S2, a mooring model is established in Orcaflex software according to the wind current force coefficient, mooring cable parameters, mooring arrangement and key control working conditions of the FPSO, meanwhile, a motion response operator RAO is imported, and full-coupling mooring time domain analysis is carried out to obtain dynamic data. According to the design, the detachable characteristic of an inner turret buoy and a ship body is fully considered, a plurality of coupling structural bodies are subjected to systematic stress analysis, acting force on a mooring connecting piece is decomposed along a force transmission path, a dynamic balance equation is established, and two pieces of software SESAM and Orcaflex are used for conducting hydrodynamic analysis and mooring time domain analysis respectively.

Description

Technical Field

[0001] The invention relates to the technical field of single-point load dynamic distribution, in particular to a design method for internal turret buoy type single-point load dynamic distribution. Background Art

[0002] FPSO is a major facility for the development of offshore oil and gas fields, especially in sea areas far from the shore and lacking surrounding pipeline networks. As of 2019, there are more than 200 FPSOs serving in oil fields in various sea areas around the world. In order to reduce the external loads encountered and improve the movement performance of the facilities, FPSOs in sea areas with harsh environmental conditions generally use single-point mooring, and nearly 50% of FPSOs use single-point mooring. The single-point mooring system is one of the key equipment in the field of marine engineering. Its basic principle is to fasten the FPSO to the sea through a mooring point that can rotate 360°, so that the FPSO has a weather vane effect. The internal turret buoy single point is widely used as an economical and practical form of FPSO development.

[0003] The buoy-type single point is detachable and can be detached when environmental conditions exceed the design requirements, and can be reconnected again in good weather. This feature determines the particularity of the connection between the single-point mooring device and the FPSO and the complexity of the load path transmission. As a traditional floating development device, such as a ship-shaped FPSO, the specification provides a calculation method based on the maximum bending moment and shear force in the ship. The bending moment and shear force envelope values ​​of each section can be obtained through specifications and calculations for structural design and verification; for another example, for semi-submersible platforms, the relevant specifications also provide extreme value calculation conditions under design wave conditions, making structural verification and design simple and feasible, but there are no specifications and guidelines for the relevant design of detachable single points, and a design method is urgently needed to solve this problem.

[0004] The FPSO with internal turret buoy mooring is fixed in the deep sea by a single-point device. The mooring load is changing all the time. The force transmitted to the buoy turret, bearing, caliper and hull through the mooring connector is also changing constantly. The maximum force at each position occurs at different times. Finding the extreme design load at each position and the design load at other corresponding positions at the corresponding time has become the primary task of the buoy single-point design. In the past, due to the limitation of computing resources, a simplified method was adopted to perform simple processing of each load. The designed structural form is often conservative, and it is impossible to find other design parameters corresponding to the most dangerous design conditions.

[0005] In summary, a design method for dynamic distribution of single-point loads on an inner turret pontoon is provided. Summary of the invention

[0006] The purpose of the present invention is to provide a design method for dynamic load distribution of an inner turret pontoon single point, so as to solve the problems raised in the above background technology that there are no specifications and guidelines for the relevant design of a detachable single point and the traditional design structure is conservative.

[0007] To achieve the above object, the present invention provides a method for designing a single-point load dynamic distribution of an inner turret buoy, comprising the following steps:

[0008] S1. In the HydroD module of SESAM software, a wet surface model is established according to the FPSO hull lines, a mass model is established according to the FPSO loading information, and a hydrodynamic analysis is performed based on the wet surface model and the mass model to obtain the FPSO overall motion response operator RAO;

[0009] S2. In the Orcaflex software, a mooring model is established according to the wind flow coefficient, mooring cable parameters, mooring arrangement and key control conditions of the FPSO. At the same time, the motion response operator RAO is imported to perform a fully coupled mooring time domain analysis to obtain dynamic data;

[0010] S3. In accordance with the overall coordinate system of the Orcaflex software, the mooring force on the FPSO single-point mooring connection at each moment is decomposed in-plane and out-of-plane based on dynamic data to obtain the in-plane component, the component perpendicular to the plane and the point of action;

[0011] S4. According to the relative positions of the single-point mooring connector and the hydraulic caliper, the MCM upper ring, the MCM lower ring and the bearing, a dynamic mechanical equilibrium equation is established to obtain the relationship between the design loads R, V and H of the single-point turret, the buoy and the MCM and the shape of the buoy, the component in the plane, the component perpendicular to the plane and the point of action;

[0012] S5. Perform a bubble search algorithm to search and sort each R, V and H at each moment in the time domain analysis, obtain the maximum values ​​of R, V and H respectively, and record the value of the component in the plane, the component perpendicular to the plane and the point of action at the corresponding moment, and record other corresponding information until the search is completed;

[0013] S6. By using the equivalent simplification method, the relevant information R, V and H maximum values, the components in the plane corresponding to the maximum values, the components perpendicular to the plane and the points of action, the mooring forces on each mooring connection, the in-plane and out-of-plane angles are sorted out to obtain the mechanical equations of the complex coupled body. Multi-physics field coupling parameters and nonlinear coefficients are introduced into the mechanical equations to complete the single-point load design distribution.

[0014] As a further improvement of the technical solution, the wet surface model is established according to the FPSO hull lines, comprising the following steps:

[0015] S1.1. Import the FPSO hull line data into the SESAM HydroD module;

[0016] S1.2. Clean and correct the input profile data and set the mesh density to use a finer mesh in the wet surface area;

[0017] S1.3. Use the function of HydroD module to mesh the hull surface and generate the corresponding hydrodynamic analysis parameters, and use high-order boundary element method to optimize the generated hydrodynamic analysis parameters, paying special attention to the mesh density of key areas such as bow, stern and bilge;

[0018] S1.4. Define boundary conditions and set the location of free surfaces depending on the intended analysis type.

[0019] As a further improvement of the technical solution, the quality model is established according to the FPSO loading information, comprising the following steps:

[0020] S1.5. Collect quality information data of each part of FPSO;

[0021] S1.6. Input mass information data, specifying the mass of each part and its position in the hull coordinate system;

[0022] S1.7. Define the global coordinate system and the mass distribution of the FPSO. The mass distribution includes the mass of the hull structure, the weight of the liquid compartments, the mass of the equipment and other loads. For each compartment, input the type, density, volume and loading status of the liquid;

[0023] S1.8. Calculate the total center of gravity position and calculate the moment of inertia and product of inertia to create a mass model.

[0024] As a further improvement of the technical solution, the introduction of the motion response operator RAO to perform a fully coupled mooring time domain analysis includes the following steps:

[0025] S2.1. Define the time step and duration of the analysis and set the time window for the analysis;

[0026] S2.2, import the motion response operator RAO into the mooring analysis software Orcaflex, start the fully coupled mooring time domain analysis, generate the motion response function of six degrees of freedom, and consider the combined effects of waves, wind and water flow, introduce the excitation coefficient to optimize the motion response function;

[0027] S2.3. Record the tension, position and shape of the mooring lines over time.

[0028] As a further improvement of the technical solution, the motion response function is:

[0029]

[0030] Considering the combined effects of waves and currents, the motion response function is optimized as follows:

[0031]

[0032] Among them, AO i1 (g) represents the optimized motion response function; AO i (g) represents the motion response function; X i (g) represents the response amplitude of the system in the i-th degree of freedom; i represents the number of the degree of freedom; represents the linear response function; J(g) represents the excitation coefficient; g represents the frequency; U wave (g) represents the amplitude of wave excitation; U wind (g) represents the amplitude of wind excitation; U current (g) represents the amplitude of water flow excitation.

[0033] As a further improvement of the technical solution, the in-plane and out-of-plane decomposition of the mooring force on the FPSO single-point mooring connection at each moment based on the dynamic data includes the following steps:

[0034] S3.1. Extract the mooring force acting on the FPSO single-point mooring connection at each moment from the time domain analysis results;

[0035] S3.2. The platform where the single-point mooring connection is located is the XY plane;

[0036] S3.3, decompose the mooring force into a component Fxy in the plane and a component Fz perpendicular to the plane;

[0037] S3.4. Determine the position b of the point of action of the mooring force and project the point of action into and out of the plane.

[0038] As a further improvement of the technical solution, the dynamic mechanical equilibrium equation is established as follows: according to the characteristics of the inner turret buoy-type single-point structure, the force acting on the mooring connector is transmitted and mechanically simplified along the force transmission path of the buoy turret, the bearing, the cone and the hull MCM.

[0039] As a further improvement of the technical solution, the relationship between the design loads R, V and H of the single-point turret, the buoy and the MCM and the buoy shape, the component in the plane, the component perpendicular to the plane and the point of action is obtained, including the following steps:

[0040] S4.1. For each moment, calculate R, V and H to determine the point of action of the mooring force;

[0041] S4.2. Calculate the in-plane angle and out-of-plane angle;

[0042] S4.3. Record R, V, H and the position, magnitude, in-plane and out-of-plane angles of the mooring force at each moment.

[0043] As a further improvement of the technical solution, the bubble search algorithm is sorted as follows: through the bubble search algorithm, the maximum values ​​of R, V and H acting on the single-point coupling body are obtained, and the design load of the required coupling body is obtained through the load dynamic distribution method in the fully coupled time-domain mooring analysis.

[0044] As a further improvement of the technical solution, the mechanical equation of the complex coupling body is specifically:

[0045] R = α.[Fxy(h1+h2)-b*Fz];

[0046] V=β·[Fxy(h1+h2)-b*Fz]+Fz;

[0047] H=γ·[Fxy(h1+h2)-b*Fz]-Fxy;

[0048] The multi-physics field coupling parameters and nonlinear coefficients are introduced into the mechanical equations as follows:

[0049] R′=α·[Fxy(h1+h2)-b*Fz]+k non ·Fxy 2 +μ·Ffl;

[0050] V′=β·[Fxy(h1+h2)-b*Fz]+Fz+k non ·Fz 2 +μ·Ffl;

[0051] H′=γ·[Fxy(h1+h2)-b*Fz]-Fxy+k non ·Fxy 2 +μ·Ffl;

[0052] Wherein, h1 is the distance from the upper bearing to the lower bearing, h2 is the distance from the lower bearing to the center of the mooring connector, H is the horizontal force exerted on the buoy by the hull, V is the vertical force exerted on the buoy by the hydraulic caliper, R is the force exerted on the buoy by the lower ring of the hull MCM, R′ is the force exerted on the buoy by the lower ring of the hull MCM after the introduction of multi-physics coupling parameters and nonlinear coefficients, V′ is the vertical force exerted on the buoy by the hydraulic caliper after the introduction of multi-physics coupling parameters and nonlinear coefficients, H′ is the horizontal force exerted on the buoy by the hull after the introduction of multi-physics coupling parameters and nonlinear coefficients, α, β, γ are related to the specific single point shape and friction coefficient, Fxy is the mooring force component in the plane, b is the size of the action point position in the plane, Fz is the mooring force component perpendicular to the plane, k non is the nonlinear coefficient, μ is the coefficient related to fluid dynamics, and Ffl is the fluid load.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] 1. In the dynamic distribution design method of the internal turret buoy single-point load, the detachable characteristics of the internal turret buoy and the hull are fully considered, and a systematic force analysis is carried out on multiple coupled structures. The force on the mooring connector is decomposed along the force transmission path and a dynamic equilibrium equation is established. The hydrodynamic analysis and mooring time domain analysis are carried out using SESAM and Orcaflex software respectively, and the force conditions of the buoy-type single point in the deep sea are simulated to realize real-time force analysis of multiple coupled bodies. The extreme design loads of each coupled body are screened by reading the result database using the bubble search sorting algorithm. At the same time, the corresponding other design loads under the extreme design load are considered, and a numerical analysis model of the internal turret single-point force is constructed, which can accurately predict the structural load, realize technological innovation, and has extremely high engineering value.

[0055] 2. In the design method of the internal turret buoy single-point load dynamic distribution, the maximum design load of the single-point turret, buoy and MCM is determined through detailed mechanical analysis and bubble search algorithm. This method helps to identify the weak links in the system, allowing engineers to strengthen or improve these parts during the design stage, and ultimately achieve the optimal design of the entire system. In addition, the introduction of multi-physics field coupling parameters and nonlinear coefficient mechanical equations makes the design closer to the actual working conditions, further improving the overall performance of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 is a flow chart of the overall method of the present invention;

[0057] Figure 2 Provide the overall process of load dynamic distribution design method;

[0058] Figure 3It is a single-point coupling structure of the inner turret;

[0059] Figure 4 It is the force and equilibrium equation of each part of the single-point coupling body of the inner turret. DETAILED DESCRIPTION

[0060] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0061] Example: See Figure 1 As shown, this embodiment provides a method for designing a dynamic distribution of a single-point load of an inner turret buoy type, comprising the following steps:

[0062] S1. In the HydroD module of SESAM software, a wet surface model is established according to the FPSO hull lines, and a mass model is established according to the FPSO loading information (such as Figure 2 Step S7.1), perform a hydrodynamic analysis based on the wet surface model and the mass model (such as Figure 2 S7.2) to obtain the FPSO overall motion response operator RAO (such as Figure 2 S7.3);

[0063] In this embodiment, a wet surface model is established according to the FPSO hull lines, including the following steps:

[0064] S1.1. Import the FPSO hull line data into the SESAM HydroD module. The hull line data includes the transverse section, longitudinal section and waterline of the hull.

[0065] S1.2. Clean and correct the input line data to ensure that there are no cross lines, overlapping surfaces or other geometric defects, and set the mesh density to use a finer mesh in the wet surface area (i.e. the part immersed in water);

[0066] S1.3. Use the function of HydroD module to mesh the hull surface and generate corresponding hydrodynamic analysis parameters (hydrodynamic analysis parameters include FPSO overall motion response operator RAO), and use high-order boundary element method to optimize the generated hydrodynamic analysis parameters, paying special attention to the mesh density of key areas such as bow, stern and bilge, where the hydrodynamic effects are more complex;

[0067] Among them, by using high-order polynomials to approximate the distribution of physical quantities on the boundary, HOBEM can simulate actual physical phenomena more accurately, especially for those complex problems that require high-precision analysis, such as the movement of ships in waves and the hydrodynamic response of marine structures.

[0068] S1.4. Depending on the type of analysis intended (e.g., hydrostatic pressure, wave effects, etc.), define boundary conditions and set the location of the free surface to simulate different drafts.

[0069] Furthermore, a quality model is established according to the FPSO loading information, including the following steps:

[0070] S1.5. Collect quality information data of each part of FPSO, including the hull itself, cargo, equipment and fuel;

[0071] S1.6. Input mass information data, specifying the mass of each part and its position in the hull coordinate system;

[0072] S1.7. Define the global coordinate system and the mass distribution of the FPSO. The mass distribution includes the mass of the hull structure, the weight of the liquid compartments, the mass of the equipment and other loads. For each compartment, input the type, density, volume and loading status of the liquid;

[0073] S1.8. Calculate the total center of gravity position and calculate the moment of inertia and product of inertia to create a mass model.

[0074] S2. In the Orcaflex software, a mooring model is established based on the wind flow coefficient, mooring cable parameters, mooring arrangement and key control conditions of the FPSO (e.g. Figure 2 Step S7.5), and at the same time, the motion response operator RAO is imported to perform a fully coupled mooring time domain analysis to obtain dynamic data; (such as Figure 2 Step S7.4)

[0075] The dynamic data include the time history data of the FPSO's six degrees of freedom motion (i.e. roll, pitch, yaw, heave, surge and sway) and the tension of its mooring lines;

[0076] In this embodiment, the motion response operator RAO is imported to perform a fully coupled mooring time domain analysis, including the following steps:

[0077] S2.1. Define the time step and duration of the analysis and set the time window of the analysis to ensure that all sea state changes of interest are covered;

[0078] S2.2, import the motion response operator RAO into the mooring analysis software Orcaflex, start the fully coupled mooring time domain analysis, generate the motion response function of six degrees of freedom, including drift, sway, heave, roll, pitch, yaw, etc., and consider the combined effects of waves, wind and current, introduce the excitation coefficient to optimize the motion response function;

[0079] Among them, the mooring time domain analysis records the magnitude of the mooring force on each mooring connection at each moment, the in-plane and out-of-plane angles of the mooring force, the number of the analysis condition, and the hull loading information for subsequent search;

[0080] Furthermore, the motion response function is:

[0081]

[0082] Waves and currents are two common natural phenomena in the marine environment. They act together on offshore structures and produce complex motion responses. If the simultaneous influence of these two forces is not considered, the simulation results may deviate from the actual situation. Therefore, comprehensive consideration of the two can improve the accuracy and reliability of the simulation; the combined action of waves and currents will cause the structure to bear greater stress and strain than a single factor. By considering the combined action of these two forces, the safety and stability of the structure can be more comprehensively evaluated to ensure that the structure can remain intact under extreme conditions; the optimized motion response function can more accurately reflect the dynamic behavior of FPSO in the actual marine environment, especially when multiple environmental loads such as waves, currents and wind act together; by introducing the excitation coefficient to describe the coupling effect between multiple excitation sources, the various complex environmental conditions that FPSO may encounter in real sea areas can be better simulated; considering the combined action of waves and currents, the motion response function is optimized as follows:

[0083]

[0084] Among them, AO i1 (g) represents the optimized motion response function; AO i (g) represents the motion response function; X i (g) represents the response amplitude of the system in the i-th degree of freedom; i represents the number of the degree of freedom, including drift, sway, heave, roll, pitch, and yaw; represents the linear response function; J(g) represents the excitation coefficient, which is used to describe the coupling effect between multiple excitation sources. It quantifies the interaction strength of multiple excitation sources at different frequencies; g represents the frequency; U wave (g) represents the amplitude of wave excitation; U wind (g) represents the amplitude of wind excitation; U current(g) represents the amplitude of water flow excitation;

[0085] S2.3. Record the tension, position and shape of the mooring lines over time.

[0086] S3. In accordance with the overall coordinate system of the Orcaflex software, the mooring force on the FPSO single-point mooring connection at each moment is decomposed in-plane and out-of-plane based on dynamic data to obtain Fxy (component in the plane), Fz (component perpendicular to the plane) and the action point b;

[0087] In this embodiment, the mooring force on the FPSO single-point mooring connection at each moment is decomposed into in-plane and out-of-plane based on dynamic data, including the following steps:

[0088] S3.1. Extract the mooring forces acting on the FPSO single-point mooring connection at each moment from the time domain analysis results. These mooring forces are three-dimensional vectors.

[0089] S3.2. The platform where the single-point mooring connection is located is the XY plane;

[0090] S3.3, decompose the mooring force into a component Fxy in the plane and a component Fz perpendicular to the plane;

[0091] S3.4. Determine the position b of the point of action of the mooring force and project the point of action into and out of the plane.

[0092] S4. According to the geometric shapes and relative positions of the single point mooring connection and the hydraulic caliper, MCM upper ring, MCM lower ring and bearing (such as Figure 2 Step S7.6), establish the dynamic mechanical equilibrium equation (such as Figure 2 Step S7.7) obtains the relationship between the design loads R (radial), V (vertical) and H (horizontal) of the single-point turret, buoy and MCM and the buoy shape, Fxy, Fz and b;

[0093] In this embodiment, the dynamic mechanical equilibrium equation is established as follows: according to the characteristics of the inner turret buoy-type single-point structure, the force acting on the mooring connection is transmitted and mechanically simplified along the force transmission path of the buoy turret, the bearing, the cone and the hull MCM;

[0094] Among them, according to the characteristics of the single-point structure of the inner turret buoy, the force acting on the mooring connection is transmitted and mechanically simplified along the MCM force transmission path of the buoy turret, bearing, cone and hull, which can simplify the three-dimensional complex problem into a two-dimensional equivalent problem; MCM is the connection structure between the hull and the single-point buoy, and the structural form of the inner turret single-point coupling body is as follows Figure 3 shown.

[0095] Furthermore, the relationship between the design loads R (radial), V (vertical) and H (horizontal) of the single-point turret, buoy and MCM and the buoy shape, Fxy, Fz and b is obtained, including the following steps:

[0096] S4.1. For each moment, calculate R (radial), V (vertical) and H (horizontal) to determine the position of the point of action of the mooring force;

[0097] S4.2. Calculate the in-plane angle and out-of-plane angle;

[0098] S4.3. Record the R (radial), V (vertical), H (horizontal) and mooring force positions, magnitudes, in-plane and out-of-plane angles at each moment.

[0099] Furthermore, in the mooring time domain analysis, the magnitude of the mooring force on each mooring connector at each moment, the in-plane and out-of-plane angles of the mooring force are recorded. The in-plane angle is the angle between the mooring chain and the vertical direction, and the out-of-platform angle is the angle between the mooring chain and the horizontal direction. The overall coordinate system is generally based on the platform where the single-point mooring connector is located as the XY plane, the bow of the FPSO is the positive direction of the X-axis, the port side is the positive direction of the Y-axis, the center is the centroid of the connector, and the positive direction of the Z-axis is determined by the right-hand rule. The mooring force on the single-point mooring connector of the FPSO at each moment is decomposed in the plane and out of the plane to obtain Fxy, Fz and the point of action b, where Fxy is the resultant force of all mooring connectors in the horizontal direction, Fz is the resultant force of all mooring connectors in the vertical direction, and b is the distance of the resultant force of all mooring connectors relative to the central axis.

[0100] S5. Perform a bubble search algorithm to search and sort each R, V and H at each moment in the time domain analysis, and obtain the maximum values ​​of R, V and H respectively. At the same time, record the Fxy, Fz and b values ​​at the corresponding moment, and record other corresponding information, including the working conditions at the corresponding moment, the in-plane angle and out-plane angle of the mooring leg, etc., until the search is completed (such as Figure 2 Step S7.8);

[0101] In this embodiment, the bubble search algorithm sorting is specifically performed as follows: by using the bubble search algorithm, the maximum values ​​of R, V and H acting on the single-point coupling body are obtained, and the design load of the required coupling body is obtained by the load dynamic distribution method in the full-coupled time-domain mooring analysis;

[0102] Among them, the bubble search algorithm is a relatively simple sorting algorithm in the field of computer science. It repeatedly visits the element column to be sorted, compares two adjacent elements in turn, and swaps them if the order (such as from large to small, the first letter from Z to A) is wrong. The work of visiting elements is repeated until there are no adjacent elements that need to be swapped; through the bubble search algorithm, the maximum values ​​of R, V and H acting on a single-point coupling body can be obtained, and the design load of the required coupling body can be obtained through the load dynamic distribution method in the fully coupled time-domain mooring analysis.

[0103] S6. By using the equivalent simplification method, the maximum values ​​of relevant information R, V and H are sorted out, and the Fxy, Fz, b, mooring forces on each mooring connection under the working conditions corresponding to the maximum values, the in-plane and out-of-plane angles, the mechanical equations of the complex coupling body are obtained, and the multi-physics field coupling parameters and nonlinear coefficients are introduced into the mechanical equations to complete the single-point load design distribution (such as Figure 2 Step S7.9), wherein the forces and balance equations of each part of the inner turret single-point coupling body are as follows: Figure 4 As shown;

[0104] In this embodiment, according to the stress characteristics of the buoy structure, an equivalent simplification method is used to obtain the mechanical equation of the complex coupling body. Through the equivalent simplification method, the originally very complex multi-physics field coupling problem can be simplified into a set of relatively simple equations, which helps to reduce the calculation cost and improve the calculation speed, making the problem easier to solve; the equivalent simplification method can help identify the key variables and relationships in the system, through which more uncertain factors can be considered in the design process, thereby making the design more robust; the mechanical equation of the complex coupling body is specifically:

[0105] R = α.[Fxy(h1+h2)-b*Fz];

[0106] V=β·[Fxy(h1+h2)-b*Fz]+Fz;

[0107] H=γ·[Fxy(h1+h2)-b*Fz]-Fxy;

[0108] In actual engineering problems, physical phenomena often do not exist in isolation, but are mutually influential and coupled. The introduction of multi-physics coupling parameters is to simulate this interaction more accurately, thereby improving the model's ability to describe actual problems. Many physical processes show obvious nonlinear characteristics under large deformation or high stress conditions. The introduction of nonlinear coefficients is intended to capture these nonlinear effects in order to more realistically reflect the actual behavior of the system. The introduction of multi-physics coupling parameters and nonlinear coefficients enables the model to more accurately predict the dynamic response of the system, especially when nonlinear or coupling effects are significant. By introducing multi-physics coupling parameters and nonlinear coefficients, the model can be better adapted to a wider range of working conditions and environmental changes, including behavior under extreme conditions. The introduction of multi-physics coupling parameters and nonlinear coefficients in the mechanical equations is:

[0109] R′=α·[Fxy(h1+h2)-b*Fz]+k non ·Fxy 2 +μ·Ffl;

[0110] V′=β·[Fxy(h1+h2)-b*Fz]+Fz+k non ·Fz 2 +μ·Ffl;

[0111] H′=γ·[Fxy(h1+h2)-b*Fz]-Fxy+k non ·Fxy 2 +μ·Ffl;

[0112] Among them, h1 is the distance from the upper bearing to the lower bearing, h2 is the distance from the lower bearing to the center of the mooring connector, H is the horizontal force exerted on the buoy by the hull, V is the vertical force exerted on the buoy by the hydraulic caliper, R is the force exerted on the buoy by the lower ring of the hull MCM, R′ is the force exerted on the buoy by the lower ring of the hull MCM after the introduction of multi-physics field coupling parameters and nonlinear coefficients, V′ is the vertical force exerted on the buoy by the hydraulic caliper after the introduction of multi-physics field coupling parameters and nonlinear coefficients, H′ is the horizontal force exerted on the buoy by the hull after the introduction of multi-physics field coupling parameters and nonlinear coefficients, α, β, γ are related to the specific single point shape and friction coefficient, Fxy is the mooring force component in the plane, that is, the magnitude of the mooring force on the xy plane, b is the magnitude of the action point position in the plane, that is, the distance of the mooring force action point relative to a reference point, Fz is the mooring force component perpendicular to the plane, that is, the magnitude of the mooring force in the z direction, k non is the nonlinear coefficient, which is used to describe the nonlinear effect. When the mooring force is large, the nonlinear effect becomes significant and the nonlinear term needs to be considered. μ is a coefficient related to fluid dynamics, which is used to describe the influence of fluid load on the system. Ffl is the fluid load, that is, the additional load caused by waves, wind, water current, etc.

[0113] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and the above embodiments and descriptions are only preferred examples of the present invention, and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A design method for dynamic distribution of single-point loads of an inner turret buoy type, characterized by: The following steps are involved: S1. In the HydroD module of SESAM software, a wet surface model is established according to the FPSO hull lines, a mass model is established according to the FPSO loading information, and a hydrodynamic analysis is performed based on the wet surface model and the mass model to obtain the FPSO overall motion response operator RAO; S2. In the Orcaflex software, a mooring model is established according to the wind flow coefficient, mooring cable parameters, mooring arrangement and key control conditions of the FPSO. At the same time, the motion response operator RAO is imported to perform a fully coupled mooring time domain analysis to obtain dynamic data; S3. In accordance with the overall coordinate system of the Orcaflex software, the mooring force on the FPSO single-point mooring connection at each moment is decomposed in-plane and out-of-plane based on dynamic data to obtain the in-plane component, the component perpendicular to the plane and the point of action; S4. According to the relative positions of the single-point mooring connector and the hydraulic caliper, the MCM upper ring, the MCM lower ring and the bearing, a dynamic mechanical equilibrium equation is established to obtain the relationship between the design loads R, V and H of the single-point turret, the buoy and the MCM and the shape of the buoy, the component in the plane, the component perpendicular to the plane and the point of action; S5. Perform a bubble search algorithm to search and sort each R, V and H at each moment in the time domain analysis to obtain the maximum values ​​of R, V and H, and record the values ​​of the components in the plane, the components perpendicular to the plane and the points of action at the corresponding moment, and record other corresponding information until the search is completed; S6. By using the equivalent simplification method, the relevant information R, V and H maximum values, the components in the plane corresponding to the maximum values, the components perpendicular to the plane and the points of action, the mooring forces on each mooring connection, the in-plane and out-of-plane angles are sorted out to obtain the mechanical equations of the complex coupled body. Multi-physics field coupling parameters and nonlinear coefficients are introduced into the mechanical equations to complete the single-point load design distribution.

2. The inner turret buoy type single point load dynamic distribution design method according to claim 1 is characterized by: In S1, a wet surface model is established according to the FPSO hull lines, comprising the following steps: S1.

1. Import the FPSO hull line data into the SESAM HydroD module; S1.

2. Clean and correct the input profile data and set the mesh density to use a finer mesh in the wet surface area; S1.

3. Use the function of HydroD module to mesh the hull surface and generate the corresponding hydrodynamic analysis parameters, and use high-order boundary element method to optimize the generated hydrodynamic analysis parameters, paying special attention to the mesh density of key areas such as bow, stern and bilge; S1.

4. Define boundary conditions and set the location of free surfaces depending on the intended analysis type.

3. The inner turret buoy type single point load dynamic distribution design method according to claim 2 is characterized by: In S1, a quality model is established according to the FPSO loading information, including the following steps: S1.

5. Collect quality information data of each part of FPSO; S1.

6. Input mass information data, specifying the mass of each part and its position in the hull coordinate system; S1.

7. Define the global coordinate system and the mass distribution of the FPSO. The mass distribution includes the mass of the hull structure, the weight of the liquid compartments, the mass of the equipment and other loads. For each compartment, input the type, density, volume and loading status of the liquid; S1.

8. Calculate the total center of gravity position and calculate the moment of inertia and product of inertia to create a mass model.

4. The inner turret buoy type single point load dynamic distribution design method according to claim 4 is characterized by: In S2, the motion response operator RAO is imported to perform a fully coupled mooring time domain analysis, including the following steps: S2.

1. Define the time step and duration of the analysis and set the time window for the analysis; S2.2, import the motion response operator RAO into the mooring analysis software Orcaflex, start the fully coupled mooring time domain analysis, generate the motion response function of six degrees of freedom, and consider the combined effects of waves, wind and water flow, introduce the excitation coefficient to optimize the motion response function; S2.

3. Record the tension, position and shape of the mooring lines over time.

5. The inner turret buoy type single point load dynamic distribution design method according to claim 5 is characterized by: In S2.2, the motion response function is: Considering the combined effects of waves and currents, the motion response function is optimized as follows: Among them, AO i1 (g) represents the optimized motion response function; AO i (g) represents the motion response function; X i (g) represents the response amplitude of the system in the i-th degree of freedom; i represents the number of the degree of freedom; represents the linear response function; J(g) represents the excitation coefficient; g represents the frequency; U wave (g) represents the amplitude of wave excitation; U wind (g) represents the amplitude of wind excitation; U current (g) represents the amplitude of water flow excitation.

6. The inner turret buoy type single point load dynamic distribution design method according to claim 5 is characterized by: In S3, based on the dynamic data, the mooring force on the FPSO single-point mooring connection at each moment is decomposed into in-plane and out-of-plane, including the following steps: S3.

1. Extract the mooring force acting on the FPSO single-point mooring connection at each moment from the time domain analysis results; S3.

2. The platform where the single-point mooring connection is located is the XY plane; S3.3, decompose the mooring force into a component Fxy in the plane and a component Fz perpendicular to the plane; S3.

4. Determine the position b of the point of action of the mooring force and project the point of action into and out of the plane.

7. The inner turret buoy type single point load dynamic distribution design method according to claim 6 is characterized by: In S4, the dynamic mechanical equilibrium equation is established as follows: according to the characteristics of the inner turret buoy-type single-point structure, the force acting on the mooring connection is transmitted and mechanically simplified along the force transmission path of the buoy turret, the bearing, the cone and the hull MCM.

8. The inner turret buoy type single point load dynamic distribution design method according to claim 7 is characterized by: In S4, the relationship between the design loads R, V and H of the single-point turret, buoy and MCM and the buoy shape, the component in the plane, the component perpendicular to the plane and the point of action is obtained, which includes the following steps: S4.

1. For each moment, calculate R, V and H to determine the point of action of the mooring force; S4.

2. Calculate the in-plane angle and out-of-plane angle; S4.

3. Record R, V, H and the position, magnitude, in-plane and out-of-plane angles of the mooring force at each moment.

9. The inner turret buoy type single point load dynamic distribution design method according to claim 8 is characterized by: In S5, the bubble search algorithm sorting is specifically performed as follows: by using the bubble search algorithm, the maximum values ​​of R, V and H acting on the single-point coupling body are obtained, and in the full-coupled time-domain mooring analysis, the design load of the required coupling body is obtained by the load dynamic distribution method.

10. The inner turret buoy type single point load dynamic distribution design method according to claim 9, characterized in that: In S6, the mechanical equation of the complex coupling body is specifically: R = α.[Fxy(h1+h2)-b*Fz]; V=β·[Fxy(h1+h2)-b*Fz]+Fz; H=γ·[Fxy(h1+h2)-b*Fz]-Fxy; The multi-physics field coupling parameters and nonlinear coefficients are introduced into the mechanical equations as follows: R′=α·[Fxy(h1+h2)-b*Fz]+k non ·Fxy 2 +μ·Ffl; V′=β·[Fxy(h1+h2)-b*Fz]+Fz+k non ·Fz 2 +μ·Ffl; H′=γ·[Fxy(h1+h2)-b*Fz]-Fxy+k non ·Fxy 2 +μ·Ffl; Wherein, h1 is the distance from the upper bearing to the lower bearing, h2 is the distance from the lower bearing to the center of the mooring connector, H is the horizontal force exerted on the buoy by the hull, V is the vertical force exerted on the buoy by the hydraulic caliper, R is the force exerted on the buoy by the lower ring of the hull MCM, R′ is the force exerted on the buoy by the lower ring of the hull MCM after the introduction of multi-physics coupling parameters and nonlinear coefficients, V′ is the vertical force exerted on the buoy by the hydraulic caliper after the introduction of multi-physics coupling parameters and nonlinear coefficients, H′ is the horizontal force exerted on the buoy by the hull after the introduction of multi-physics coupling parameters and nonlinear coefficients, α, β, γ are related to the specific single point shape and friction coefficient, Fxy is the mooring force component in the plane, b is the size of the action point position in the plane, Fz is the mooring force component perpendicular to the plane, k non is the nonlinear coefficient, μ is the coefficient related to fluid dynamics, and Ffl is the fluid load.

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