Floating structure anchoring system design analysis method suitable for shallow water condition

Abstract

The invention provides a floating structure anchoring system design analysis method suitable for a shallow water condition, and particularly belongs to the technical field of floating equipment mooring. The method comprises the steps that firstly, the platform deformation energy requirement is calculated according to a platform structure type, and the residual deformation energy of an anchoring line configuration scheme is calculated based on the deformation energy principle; preferably selecting an anchoring scheme with the maximum residual deformation energy; then, based on a numerical method of a viscous flow theory, an overlapping grid method is coupled with a mooring cable dynamic simulation method, the floating structure motion response and the anchoring safety coefficient of the optimal scheme are checked, the layout scheme of the mooring system is determined through the scheme design and safety checking process, the whole design process is scientific and meticulous in logic, and the design efficiency is high. The method is high in performability and has practical engineering application guiding significance.

Description

Technical Field

[0001] The invention belongs to the technical field of floating equipment mooring, and in particular relates to a design and analysis method for a floating structure mooring system suitable for shallow water conditions. Background Art

[0002] The mooring technology of offshore engineering floating equipment is mainly based on mooring positioning and dynamic positioning. Mooring positioning is a traditional passive platform positioning method (such as catenary type, etc.), which is usually used in medium and deep waters. With the continuous development and innovation of offshore platform research and construction technology, the challenges faced by mooring systems are becoming increasingly high. Especially in shallow water environments, mooring positioning methods are difficult to rely on their own gravity to ensure the movement safety of the platform. New mooring system design solutions are extremely important.

[0003] In response to the problem of mooring system design, the existing technology has proposed a variety of solutions from the perspectives of mooring system scheme design and mooring system design methods. First, a shallow water mooring system design scheme including anchor chains, counterweights, buoyancy blocks and anchor foundations is proposed to meet the requirements of mooring restoring force and anchor chain tension; second, the influence of the second-order steady wave moment of pitch on the mooring system is considered, and the peak value of the second-order steady wave moment transfer function in the frequency domain, the maximum pitch motion angle and other parameters are analyzed, and the mooring system parameters that meet the target motion requirements are obtained through genetic algorithm optimization.

[0004] Since anchoring in shallow water is more susceptible to the impact of waves and currents, the marine environment for anchoring in shallow water is more complicated. The above solutions in the prior art cannot truly fit the actual shallow water marine environment, so that the final solution cannot meet the safety and reliability of shallow water anchoring. Summary of the invention

[0005] In view of the technical problem of low reliability of mooring system design schemes under shallow water conditions in the prior art, the present invention provides a design and analysis method for a mooring system of a floating structure under shallow water conditions, provides design ideas from the perspectives of structural type and design process, and forms a set of design and analysis methods for a mooring system under shallow water conditions, thereby solving the technical problems existing in the mooring system schemes under shallow water conditions in the prior art.

[0006] In a first aspect of the present invention, the present invention provides a design and analysis method for a floating structure mooring system suitable for shallow water conditions, characterized in that it comprises: Step S1, obtaining the environmental load value of the floating equipment according to the structure type of the floating equipment, the service sea area location and the hydrogeological conditions; Step S2, calculating the horizontal tension at the static equilibrium position according to the environmental load value of the floating equipment, and the hydrodynamic parameters of the platform calculated based on the frequency domain wave radiation / diffraction theory under the potential flow theory framework; Step S3, calculating the functional relationship between the mooring stiffness and the deformation energy requirement of the floating platform according to the platform hydrodynamic parameters and the stiffness range of the shallow water mooring system; Step S4, determining a plurality of different anchor chain parameters, calculating the functional relationship between horizontal tension and horizontal displacement according to the selected anchor chain parameters, and obtaining the stiffness and residual deformation energy of the mooring system at the static equilibrium position based on the functional relationship between horizontal tension and horizontal displacement and the horizontal tension at the static equilibrium position; Step S5, obtaining the deformation energy requirement of the platform according to the stiffness of the mooring system at the static equilibrium position and the functional relationship between the mooring stiffness and the deformation energy requirement of the floating platform, calculating the safety factor according to the platform energy requirement and the residual deformation energy, and selecting the mooring system whose safety factor meets the preset conditions as the system design scheme.

[0007] Furthermore, step S1 further includes: the environmental load value of the floating equipment includes wind load and flow load, wherein the calculation formula of the wind load is: ,in C w , C s , C h , A , V w They are wind force coefficient, platform shape coefficient, platform height coefficient, vertical projection area of ​​the platform windward surface and wind speed; flow load ,in C ss , C d , A c , A f , V c They are the flow coefficient, drag coefficient, the total projected area of ​​cylindrical components under the waterline, the total projected area of ​​flat plate components under the waterline and the flow velocity.

[0008] Furthermore, step S2 further comprises: The horizontal tension value at the static equilibrium position calculated according to the environmental load value of the floating equipment is: T 0 = F H = F w + F cs ; Calculate the platform hydrodynamic parameters, including the added mass, based on the frequency domain wave radiation / diffraction theory in the potential flow theory framework A , Radiation Damping B and wave excitation forceF。

[0009] Furthermore, step S3 further includes: Step S31, calculating the surge motion response amplitude of the platform according to the environmental load value of the floating equipment and the stiffness range of the shallow water mooring system; Step S32, calculating the energy spectrum of the surge motion according to the surge motion response value and the wave action conditions, and then obtaining the meaningful value of the surge motion response; Step S33, based on the deformation energy principle, the deformation energy requirements of the floating equipment under different mooring stiffnesses are calculated, and the functional relationship between the mooring stiffness and the deformation energy requirements of the floating platform is calculated.

[0010] Furthermore, step S3 further includes: Step S31, considering the system stiffness of shallow water mooring K Below 2000kN / m, according to the formula Calculate the surging motion response amplitude RAO of the platform with mooring stiffness ranging from 0 to 2000 kN / m surge ,Right now X The component in the surge direction is M For platform quality, X is the motion response of the platform; Step S32: Based on the surging motion response value and the incident wave spectrum S w ( w ) Calculate the energy spectrum of the oscillatory motion , get the 1 / 10 meaningful value corresponding to the longitudinal motion ,in ; Step S33, calculating the deformation energy requirement of the floating structure based on the deformation energy principle , the functional relationship between the mooring stiffness and the deformation energy demand of the floating platform under the action of irregular waves is calculated.

[0011] Furthermore, step S4 further comprises: Select multiple sets of anchor chain parameters, and calculate the functional relationship between horizontal tension and horizontal displacement according to the selected multiple sets of anchor chain parameters: , the mooring stiffness of the mooring system is obtained by calculating the horizontal tension at the static equilibrium position and residual deformation energy ,in, x 0. T 0 are the deformation and horizontal tension of the mooring system at the static equilibrium position, x m is the deformation of the mooring system at the extreme position.

[0012] Furthermore, step S5 further includes: According to the mooring stiffness parameters obtained in step S4 K And the functional relationship between the mooring stiffness and the deformation energy demand of the floating platform in step 2, the platform energy demand is calculated E P , calculate the safety factor based on the platform energy demand and residual deformation energy k = E M / E P ,in k= 1.4, if k > 1.4, the corresponding mooring scheme shall be taken as the alternative mooring system design scheme.

[0013] Furthermore, the method of the present invention further comprises: Step S6, based on the numerical solver of viscous flow theory, the overlapping grid method is applied to couple the dynamic simulation method of mooring cables to check the motion response of the floating structure and the safety factor of anchoring of the selected scheme. Based on computational fluid dynamics and concentrated mass method, the platform motion response and anchor chain force analysis are completed, the platform motion and anchor chain force under the action are quickly analyzed, and the optimal anchoring scheme is determined.

[0014] Furthermore, step S6 further includes: Step S61, using model building software to build a floating structure model and export the model file; importing the model file into the constructed calculation model, and performing grid division, assigning relevant physical parameters to the imported floating structure model, and designing relevant water depth and wave conditions according to the service sea area location and hydrogeological conditions in step S1, and verifying the accuracy and convergence of the model; Step S62, based on the verified numerical model and the water depth and wave conditions, the anchor chain forces are analyzed using the concentrated mass method for the number of anchor chains and the connection positions used in the target mooring structure design; Step S63, analyzing the maximum force of each anchor chain, finding the mooring structure and the number of anchors that meet the requirements of the mooring force safety factor, and obtaining the optimal mooring solution.

[0015] Furthermore, the physical parameters related to the imported floating structure model in step S61 specifically include: The floating platform and anchor chain are respectively assigned corresponding physical parameters and boundary conditions; the VOF method is used to express the gas and liquid phases: , ,in For the i The volume fraction of the fluid, is the gas density, is the liquid density, is the gas viscosity, is the dynamic viscosity of the liquid.

[0016] Further, in step S62, analyzing the anchor chain stress by using the concentrated mass method includes: The concentrated mass method divides the anchor chain into multiple nodes with mass, and the nodes are connected by massless springs. i Tension in the segment ,in is the elastic modulus, is the anchor chain diameter, , and For Node i +1 and node i The global position vector of Direction by Node i Point to Node i +1, is the anchor chain strain value; internal damping force ,in is the internal damping coefficient, is the strain rate; the interaction between the mooring cable and the seabed ,in, The anchor chain is stretched to its full length. is the anchor chain diameter, is the seabed stiffness coefficient, is the seabed damping coefficient, is the seafloor elevation, is the node coordinate, for Find the differential, for z Unit vector of direction; lateral drag force ,in, is the water density, , is the node speed, is the anchor chain diameter, is the lateral drag coefficient; tangential drag ,in is the tangential resistance coefficient; after solving the anchor chain force, the motion equation of each node is constructed ,in, and Represents the tension caused by the segments on both sides of the node, and represents the internal damping force caused by the segments on both sides of the node, is the underwater weight, For Node i The quality of the anchor chain, is the identity matrix, is the additional mass matrix, For Node i The acceleration of the floating structure is solved to obtain the motion of the floating structure platform and the forces on each anchor chain.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: in response to the shallow water mooring problem, the present invention first calculates the platform deformation energy demand according to the platform structure type, calculates the residual deformation energy of the mooring line configuration scheme based on the deformation energy principle, and preferably selects the mooring scheme with the largest residual deformation energy; then based on the numerical method of viscous flow theory, the overlapping grid method is applied to couple the dynamic simulation method of the mooring cable to check the motion response of the floating structure and the safety factor of the mooring of the preferred scheme, thereby ensuring the safety of the final mooring system scheme; the present invention determines the layout scheme of the mooring system through the scheme design and safety verification process. The entire design process is scientific, logically rigorous, and highly executable, and has guiding significance for practical engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Flowchart of design method for mooring system of floating structure in shallow water conditions; Figure 2 Schematic diagram of calculation principle of mooring stiffness and residual deformation energy of mooring system. DETAILED DESCRIPTION

[0019] The description of the embodiments of this specification should be combined with the corresponding drawings, which should be considered as part of the complete specification. In the drawings, the shape or thickness of the embodiments may be enlarged and indicated for simplification or convenience. Furthermore, the parts of each structure in the drawings will be described separately. It is worth noting that the elements not shown in the drawings or not described in words are in a form known to ordinary technicians in the relevant technical field.

[0020] The description of the embodiments herein and any reference to directions and orientations are only for the convenience of description and are not to be construed as any limitation on the scope of protection of the present invention. The following description of the preferred embodiments may involve combinations of features, which may exist independently or in combination, and the present invention is not particularly limited to the preferred embodiments. The scope of the present invention is defined by the claims.

[0021] like Figure 1 As shown, in the first embodiment of the present invention, the present invention provides a design and analysis method for a floating structure mooring system suitable for shallow water conditions, which is characterized by comprising: Step S1, obtaining the environmental load value of the floating equipment according to the structure type of the floating equipment, the service sea area location and the hydrogeological conditions; Step S2, calculating the horizontal tension at the static equilibrium position according to the environmental load value of the floating equipment, and the hydrodynamic parameters of the platform calculated based on the frequency domain wave radiation / diffraction theory under the potential flow theory framework; Step S3, calculating the functional relationship between the mooring stiffness and the deformation energy requirement of the floating platform according to the platform hydrodynamic parameters and the stiffness range of the shallow water mooring system; Step S4, determining a plurality of different anchor chain parameters, calculating the functional relationship between horizontal tension and horizontal displacement according to the selected anchor chain parameters, and obtaining the stiffness and residual deformation energy of the mooring system at the static equilibrium position based on the functional relationship between horizontal tension and horizontal displacement and the horizontal tension at the static equilibrium position; Step S5, obtaining the deformation energy requirement of the platform according to the stiffness of the mooring system at the static equilibrium position and the functional relationship between the mooring stiffness and the deformation energy requirement of the floating platform, calculating the safety factor according to the platform energy requirement and the residual deformation energy, and selecting the mooring system whose safety factor meets the preset conditions as the system design scheme.

[0022] Furthermore, step S3 further includes: Step S31, calculating the surge motion response amplitude of the platform according to the environmental load value of the floating equipment and the stiffness range of the shallow water mooring system; Step S32, calculating the energy spectrum of the surge motion according to the surge motion response value and the wave action conditions, and then obtaining the meaningful value of the surge motion response; Step S33, based on the deformation energy principle, the deformation energy requirements of the floating equipment under different mooring stiffnesses are calculated, and the functional relationship between the mooring stiffness and the deformation energy requirements of the floating platform is calculated.

[0023] Furthermore, the method of the present invention further comprises: Step S6, based on the numerical solver of viscous flow theory, the overlapping grid method is applied to couple the dynamic simulation method of mooring cables to check the motion response of the floating structure and the safety factor of anchoring of the selected scheme. Based on computational fluid dynamics and concentrated mass method, the platform motion response and anchor chain force analysis are completed, the platform motion and anchor chain force under the action of viscous force are quickly analyzed, and the optimal anchoring scheme is determined.

[0024] Furthermore, step S6 further includes: Step S61, using model building software to build a floating structure model and export the model file; importing the model file into the constructed calculation model, and performing grid division, assigning relevant physical parameters to the imported floating structure model, and designing relevant water depth and wave conditions according to the service sea area location and hydrogeological conditions in step S1, and verifying the accuracy and convergence of the model; Step S62, based on the verified numerical model and the water depth and wave conditions, the anchor chain forces are analyzed using the concentrated mass method for the number of anchor chains and the connection positions used in the target mooring structure design; Step S63, analyzing the maximum force of each anchor chain, finding the mooring structure and the number of anchors that meet the requirements of the mooring force safety factor, and obtaining the optimal mooring solution.

[0025] The design process of the floating platform mooring system under shallow water conditions is further described in detail below.

[0026] Process 1. Design of mooring system in shallow water conditions.

[0027] Step 1: Take a floating platform as an example, and consider the environmental load under working condition as follows: wind speed V w Flow rate V c ; The wave is irregular, the spectrum is JONSWAP spectrum, and the peak rise factor γ , the peak frequency is w p , the significant wave height is H s Based on the structural type and scale parameters of the platform, according to the formula Calculate wind loads where C w , C s , C h , A They are wind force coefficient, platform shape coefficient, platform height coefficient and vertical projection area of ​​the platform windward surface; flow load ,in C ss , C d , A c , A f They are the flow coefficient, drag coefficient, the total projected area of ​​cylindrical components under the waterline, and the total projected area of ​​flat components under the waterline; the platform hydrodynamic parameters, including the added mass, are calculated based on the frequency domain wave radiation / diffraction theory under the potential flow theory framework. A , Radiation Damping B and wave excitation force F .

[0028] Step 2: Consider system stiffness for shallow water moorings K Generally below 2000kN / m, according to the formula Calculate the surging motion response amplitude RAO of the platform with mooring stiffness ranging from 0 to 2000 kN / msurge (Right now X component in the first direction), where M For platform quality, X is the motion response of the platform. Combined with the wave action conditions S w ( w ) Calculate the energy spectrum of the oscillatory motion , get the 1 / 10 meaningful value corresponding to the longitudinal motion ,in Calculation of deformation energy requirements of floating structures based on deformation energy principle , and the relationship curve between the mooring stiffness and the deformation energy demand of the floating platform under the action of irregular waves is obtained.

[0029] Step 3: According to the horizontal tension value of the static equilibrium position calculated in step 1, it is mainly wind load and flow load, that is, T 0 = F H = F w + F cs , design an anchoring system with impact resistance. Select anchor chains of different specifications and materials, and draw the functional relationship between horizontal tension and horizontal displacement as follows: . According to different anchor chain parameters (diameter, length, wet weight, axial stiffness, breaking force), the relationship curve between horizontal tension and horizontal displacement of anchor chain is drawn. The mooring stiffness of the mooring system is obtained based on the static analysis method of the mooring line. and residual deformation energy ( Figure 2 ).in, x 0 , T 0 are the deformation and horizontal tension of the mooring system at the static equilibrium position, x m is the deformation of the mooring system at the extreme position.

[0030] Step 4: Refer to the mooring stiffness parameters in step 3 K , combined with the relationship curve between the mooring stiffness and the deformation energy requirement of the floating platform in step 2, the platform energy requirement can be obtained E P , calculate the safety factor k = E M / E P , ( k The most dangerous working condition of the mooring system is the swaying motion of the floating structure. Analogously to the dynamic stability problem of the floating structure with large inclination angle, refer to the CCS offshore platform stability code and take k= 1.4), ifk > 1.4 Satisfy the design requirements of the mooring system. If not, redesign the anchor chain parameters in step 3, calculate the safety factor until the design requirements are met, and determine the design plan of the mooring system.

[0031] Process 2. Platform motion response and anchor chain force analysis.

[0032] Step 1: Use classic examples to verify the accuracy of the established numerical model. After verification, use the three-dimensional model building software to export the STL model file according to the floating platform parameters, use the overlapping grid technology (to avoid the problem of negative volume caused by the movement of the dynamic grid) to simulate the rigid body motion, import the STL model file into the overlapping grid area, and divide the overlapping grid area and the background grid area. Assign the corresponding physical parameters (floating structure mass, anchor chain mass, anchor point position, anchor chain length, axial stiffness, etc.) to the floating platform and anchor chain respectively, and assign corresponding boundary conditions; use the VOF method to express the gas and liquid phases: , (in For the i The volume fraction of the fluid, is the gas density, is the liquid density, is the gas viscosity, is the dynamic viscosity of the liquid). After the model parameters are set, the working conditions that can characterize the typical characteristics of the dynamic response of the floating structure-mooring system are selected, and various grid sizes are set to verify the grid convergence of the numerical model (to ensure that the grid size has little effect on the results).

[0033] Step 2: Based on the verified numerical model, the water depth, wave and other conditions in step 1 are used to analyze the anchor chain stress using the concentrated mass method for the number of anchor chains and the connection positions used in the specific target mooring structure design. The concentrated mass method divides the anchor chain into multiple nodes with mass, and each node is connected by a massless spring. i Tension in the segment ,in is the elastic modulus, is the anchor chain diameter, internal damping force ,in is the internal damping coefficient, is the strain rate, the interaction between the mooring line and the seabed ,in, is the seabed stiffness coefficient, is the seabed damping coefficient, is the seafloor elevation, is the node coordinate, the lateral drag force ,in, is the lateral drag coefficient, tangential drag ,in is the tangential resistance coefficient. After solving the above anchor chain force, the motion equation is constructed on this basis. ,in, and Represents the tension caused by the segments on both sides of the node, and represents the internal damping force caused by the segments on both sides of the node, is the underwater weight, For Node i The quality of the anchor chain, is the identity matrix, is the additional mass matrix, For Node i The acceleration of the floating structure is solved to obtain the motion of the floating structure platform and the forces on each anchor chain.

[0034] Step 3: According to the loads of each anchor chain obtained in step 2, analyze whether the force of each anchor chain meets the requirements of the safety factor of anchoring force (the ratio of the breaking strength of the mooring cable to the maximum tension). If it does not meet the requirements, return to step 2 to redesign the anchor chain. If it meets the requirements, the target mooring scheme is obtained.

[0035] In response to the shallow water mooring problem, the present invention first calculates the platform deformation energy demand according to the platform structure type, calculates the residual deformation energy of the mooring line configuration scheme based on the deformation energy principle, and optimizes the mooring scheme with the largest residual deformation energy; then based on the numerical method of viscous flow theory, the overlapping grid method is applied to couple the dynamic simulation method of the mooring cable to verify the motion response of the floating structure and the safety factor of the mooring of the preferred scheme, thereby ensuring the safety of the final mooring system scheme; the present invention determines the layout scheme of the mooring system through the scheme design and safety verification process. The entire design process is scientific, logically rigorous, and highly executable, and has guiding significance for practical engineering applications.

Claims

1. A design and analysis method for a floating structure mooring system suitable for shallow water conditions, characterized in that: include: Step S1, obtaining the environmental load value of the floating equipment according to the structure type of the floating equipment, the service sea area location and the hydrogeological conditions; Step S2, calculating the horizontal tension at the static equilibrium position according to the environmental load value of the floating equipment, and the hydrodynamic parameters of the platform calculated based on the frequency domain wave radiation / diffraction theory under the potential flow theory framework; Step S3, calculating the functional relationship between the mooring stiffness and the deformation energy requirement of the floating platform according to the platform hydrodynamic parameters and the stiffness range of the shallow water mooring system; Step S4, determining a plurality of different anchor chain parameters, calculating the functional relationship between horizontal tension and horizontal displacement according to the selected anchor chain parameters, and obtaining the stiffness and residual deformation energy of the mooring system at the static equilibrium position based on the functional relationship between horizontal tension and horizontal displacement and the horizontal tension at the static equilibrium position; Step S5, obtaining the deformation energy requirement of the platform according to the stiffness of the mooring system at the static equilibrium position and the functional relationship between the mooring stiffness and the deformation energy requirement of the floating platform, calculating the safety factor according to the platform energy requirement and the residual deformation energy, and selecting the mooring system whose safety factor meets the preset conditions as the system design scheme.

2. A design and analysis method for a floating structure mooring system suitable for shallow water conditions according to claim 1, characterized in that: The step S1 further includes: the environmental load value of the floating equipment includes wind load and flow load, wherein the calculation formula of the wind load is: ,in C w , C s , C h , A , V w They are wind force coefficient, platform shape coefficient, platform height coefficient, vertical projection area of ​​the platform windward surface and wind speed; flow load ,in C ss , C d , A c , A f , V c They are the flow coefficient, drag coefficient, the total projected area of ​​cylindrical components under the waterline, the total projected area of ​​flat plate components under the waterline and the flow velocity.

3. The design and analysis method for a floating structure mooring system suitable for shallow water conditions according to claim 1 is characterized in that: The step S2 further comprises: The horizontal tension value at the static equilibrium position calculated according to the environmental load value of the floating equipment is: ; Calculate the platform hydrodynamic parameters, including the added mass, based on the frequency domain wave radiation / diffraction theory in the potential flow theory framework A , Radiation Damping B and wave excitation force F .

4. A design and analysis method for a floating structure mooring system suitable for shallow water conditions according to claim 1, characterized in that: The step S3 further comprises: Step S31, calculating the surge motion response amplitude of the platform according to the environmental load value of the floating equipment and the stiffness range of the shallow water mooring system; Step S32, calculating the energy spectrum of the surge motion according to the surge motion response value and the wave action conditions, and then obtaining the meaningful value of the surge motion response; Step S33, based on the deformation energy principle, the deformation energy requirements of the floating equipment under different mooring stiffnesses are calculated, and the functional relationship between the mooring stiffness and the deformation energy requirements of the floating platform is calculated.

5. The design and analysis method for a floating structure mooring system suitable for shallow water conditions according to claim 1 is characterized in that: The step S3 further comprises: Step S31, due to the system stiffness of the shallow water mooring K Below 2000kN / m, according to the formula Calculate the surging motion response amplitude RAO of the platform with mooring stiffness ranging from 0 to 2000 kN / m surge ,Right now X The component in the surge direction is A For additional quality, B is the radiation damping, F The wave excitation force, M For platform quality, X is the motion response of the platform, for X Find the differential, To find the second order differential; Step S32: Based on the surging motion response value and the incident wave spectrum S w ( w ) Calculate the energy spectrum of the oscillatory motion , get the 1 / 10 meaningful value corresponding to the longitudinal motion ,in ; Step S33, calculating the deformation energy requirement of the floating structure based on the deformation energy principle , the functional relationship between the mooring stiffness and the deformation energy demand of the floating platform under the action of irregular waves is calculated.

6. A design and analysis method for a floating structure mooring system suitable for shallow water conditions according to claim 1, characterized in that: The step S4 further comprises: Select multiple sets of anchor chain parameters, and calculate the functional relationship between horizontal tension and horizontal displacement according to the selected multiple sets of anchor chain parameters: , the mooring stiffness of the mooring system is obtained by calculating the horizontal tension at the static equilibrium position and residual deformation energy ,in, x 0. T 0 are the deformation and horizontal tension of the mooring system at the static equilibrium position, x m is the deformation of the mooring system at the extreme position.

7. A design and analysis method for a floating structure mooring system suitable for shallow water conditions according to claim 1, characterized in that: The step S5 further comprises: According to the mooring stiffness parameters obtained in step S4 K And the functional relationship between the mooring stiffness and the deformation energy demand of the floating platform in step 2, the deformation energy demand of the platform is calculated E P , calculate the safety factor based on the platform deformation energy requirement and residual deformation energy k =E M / E P ,in k= 1.4, if k > 1.4, the corresponding mooring scheme shall be taken as the alternative mooring system design scheme.

8. The design and analysis method for a floating structure mooring system suitable for shallow water conditions according to claim 1, characterized in that: The method further comprises: Step S6, based on the numerical solver of viscous flow theory, the overlapping grid method is applied to couple the dynamic simulation method of the mooring cable to check the motion response of the floating structure and the safety factor of the anchoring of the selected scheme, complete the platform motion response and anchor chain force analysis, quickly analyze the platform motion and anchor chain force under the action, and determine the optimal anchoring scheme.

9. A design and analysis method for a floating structure mooring system suitable for shallow water conditions according to claim 8, characterized in that: The step S6 further comprises: Step S61, using model building software to build a floating structure model and export the model file; importing the model file into the constructed calculation model, and performing grid division, assigning relevant physical parameters to the imported floating structure model, and designing relevant water depth and wave conditions according to the service sea area location and hydrogeological conditions in step S1, and verifying the accuracy and convergence of the model; Step S62, based on the verified numerical model and the water depth and wave conditions, the anchor chain forces are analyzed using the concentrated mass method for the number of anchor chains and the connection positions used in the target mooring structure design; Step S63, analyzing the maximum force of each anchor chain, finding the mooring structure and the number of anchors that meet the requirements of the mooring force safety factor, and obtaining the optimal mooring solution.

10. A design and analysis method for a floating structure mooring system suitable for shallow water conditions according to claim 9, characterized in that: The analysis of the anchor chain stress by using the concentrated mass method in step S62 includes: The concentrated mass method divides the anchor chain into multiple nodes with mass, and each node is connected by a massless spring. i Tension in the segment ,in is the elastic modulus, is the anchor chain diameter, , and For Node i +1 and node i The global position vector of Direction by Node i Point to Node i +1, is the anchor chain strain value; internal damping force ,in is the internal damping coefficient, is the strain rate; the interaction between the mooring cable and the seabed ,in, The anchor chain is stretched to its full length. is the anchor chain diameter, is the seabed stiffness coefficient, is the seabed damping coefficient, is the seafloor elevation, is the node coordinate, for Find the differential, for z Unit vector of direction; lateral drag force ,in, is the water density, , is the node speed, is the anchor chain diameter, is the lateral drag coefficient; tangential drag ,in is the tangential resistance coefficient; after solving the anchor chain force, the motion equation of each node is constructed ,in, and Represents the tension caused by the segments on both sides of the node, and represents the internal damping force caused by the segments on both sides of the node, is the underwater weight, For Node i The quality of the anchor chain, is the identity matrix, is the additional mass matrix, For Node i The acceleration of the floating structure is calculated by solving the motion equation to obtain the motion of the floating structure platform and the forces on each anchor chain.

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