A Multi-Spring Calculation Method and System for Cumulative Deformation and Frequency Evolution of Marine Suction Bucket Foundations

Abstract

A multi-spring calculation method and system for the cumulative deformation and frequency evolution of offshore suction barrel foundations belongs to the field of numerical simulation calculation technology for offshore wind turbines. This method establishes a multi-spring calculation model of the suction barrel structure-soil interaction and embeds it into an offshore wind turbine suction barrel foundation model for calculating the deformation and frequency evolution of the overall structure under complex environmental loads. First, a multi-spring model of the suction barrel structure-soil interaction is established in MATLAB, and then coupled with an offshore wind turbine module established in COMSOL. In COMSOL, the displacement data of the suction barrel structure is calculated based on the input environmental load and output to MATLAB. Then, the structure-soil interaction force data is calculated in MATLAB and transmitted back to COMSOL for interactive iteration. This invention establishes a simplified offshore wind turbine model of mass point-tower-foundation for analyzing the overall structural deformation and natural frequency evolution of offshore suction barrel foundations under combined wind, wave, and current loads.

Description

Technical Field

[0001] This invention relates to a multi-spring calculation method and system applicable to the cumulative deformation and frequency evolution of offshore suction barrel foundations, belonging to the field of offshore wind turbine numerical simulation calculation technology. Background Technology

[0002] With the development of green energy, sustainable energy accounts for a significant proportion of global energy consumption. Currently, offshore wind power is developing rapidly, resulting in various foundation types, such as gravity foundations, monopiles, suction caissons, jacket foundations, and floating foundations. Compared to other foundations, suction caissons offer significant advantages in installation and recycling, making them a popular foundation type for offshore wind turbines. During operation, offshore wind turbines are primarily affected by gravity and environmental loads (wind, waves, and currents), generating vertical and lateral loads and overturning moments at the top of the foundation.

[0003] Currently, existing calculation schemes for spring models of offshore wind turbine suction tank foundations generally only use one set of springs to simulate soil-structure interaction under combined loads, which cannot address the following issues: uneven stress distribution in the soil around the suction tank; unequal normal stiffness of the soil around the suction tank at failure; and inaccurate quantification of the overturning moment generated by the soil under the suction tank cover. These problems make it difficult to accurately analyze the dynamic response of the suction tank structure under combined wind, wave, and current loads. Therefore, accurately reconstructing the stress field around the suction tank structure has become an urgent problem to be solved.

[0004] This invention proposes a multi-spring calculation method to solve the above problems: Py and Tz springs are divided into multiple groups to simulate the non-uniform soil stress field around the caisson; the coupling effect between each group of Py and Tz springs is considered to reflect the unequal stiffness of the soil outside the caisson; the position of the Qz spring is corrected according to the soil stress state under the caisson cover, and its contribution to overturning resistance is calculated. Furthermore, the above analysis method is developed into MATLAB, and by coupling it with the offshore wind turbine suction bucket foundation model in COMSOL, the evolution analysis of the cumulative deformation and natural frequency of the overall structure is realized. Summary of the Invention

[0005] The technical problem to be solved by this invention is to propose a multi-spring calculation method and system for the cumulative deformation and frequency evolution of offshore suction barrel foundations. The proposed multi-spring analysis scheme for suction barrel-soil interaction can realize the deformation and frequency evolution calculation of the overall structure of offshore wind turbine-suction barrel foundation under complex environmental loads such as wind, waves, and currents.

[0006] The technical solution adopted in this invention is:

[0007] A multi-spring calculation method for the cumulative deformation and frequency evolution of a marine suction barrel foundation includes the following steps:

[0008] In the finite element analysis software, an overall model of the suction bucket foundation of the offshore wind turbine is established. Then, the environmental load is input, and the displacement data of the suction bucket structure is calculated by combining the input suction bucket structure-soil interaction force.

[0009] A multi-spring model of the interaction between the suction bucket structure and the soil was constructed, and the interaction forces at the interface between the suction bucket structure and the soil were solved by combining the displacement data transmitted by the finite element analysis software.

[0010] Update the environmental load information based on the load-time history relationship, repeat the above two steps to iterate the data, and realize the load-displacement-soil resistance calculation under multiple time histories.

[0011] Based on the obtained displacement data, cumulative deformation analysis of the offshore suction barrel foundation was performed, and based on the obtained stiffness data, frequency evolution calculation of the offshore suction barrel foundation was performed.

[0012] In the above technical solution, the overall model for establishing the offshore wind turbine suction barrel foundation includes: simplifying the upper blade-nacelle as a mass point acting on the top of the wind turbine tower; and building a finite element analysis model of the tower, suction barrel main pipe, and suction barrel structure according to the Euler-Bernoulli beam element theory.

[0013] The multi-spring model for the interaction between the suction bucket structure and the soil includes:

[0014] The interaction between the suction bucket structure and the soil is described by a resistance-displacement spring and decomposed into three parts: py spring, tz spring, and Qz spring. These parts are used to solve for the horizontal soil stress, sidewall friction resistance, and soil resistance under the bucket cover of the suction bucket structure, respectively.

[0015] The constructed py spring is decomposed according to the law of equal energy, and its uniform distribution along the circumference of the barrel is used to describe the non-uniform horizontal stress field of the suction barrel structure under the combined loads of wind, waves and current.

[0016] The decomposed Py springs are paired with corresponding Tz springs, and the horizontal soil resistance results obtained from each Py spring are input into the corresponding Tz spring calculation to restore the non-uniform stiffness mode of the soil around the suction bucket structure under combined load.

[0017] The position of the Qz spring is adjusted in real time based on the soil resistance distribution under the lid, which is used to solve the contribution of the soil resistance under the lid to the overturning moment of the suction bucket structure under combined load.

[0018] Furthermore, the horizontal, vertical, and rotational displacement data of the suction bucket structure were extracted to conduct a cumulative deformation analysis of the offshore suction bucket foundation.

[0019] Furthermore, a complete offshore wind turbine model excluding the lower suction barrel foundation was built in finite element analysis software. The stiffness data of the suction barrel head in the horizontal, vertical, and rotational directions calculated by the multi-spring model were extracted and input into the bottom of the tower of the complete turbine model to carry out frequency evolution calculation of the offshore suction barrel foundation.

[0020] Furthermore, the finite element analysis software used is COMSOL, and a multi-spring model is built using MATLAB. An interface for data interaction between MATLAB and COMSOL modules is established, which is responsible for receiving and distributing the displacement data calculated in COMSOL, and transmitting the force data solved by itself to COMSOL.

[0021] A multi-spring calculation system for the cumulative deformation and frequency evolution of offshore suction barrel foundations, applying the method described above, includes:

[0022] The offshore wind turbine-suction tank structure coupling module is used to calculate displacement data based on the environmental load information of the offshore wind turbine and the soil resistance borne by the suction tank structure.

[0023] The suction bucket structure-soil interaction module is used to calculate the interaction force at the suction bucket structure-soil interface by combining a multi-spring model with displacement data.

[0024] The data transmission iteration module is used to realize the interaction of displacement data and interaction force data between the offshore wind turbine-suction tank structure coupling module and the suction tank structure-soil interaction module, so as to achieve iteration;

[0025] The cumulative deformation analysis and frequency evolution calculation module is used to extract the horizontal, vertical, and rotational displacement data of the suction barrel structure calculated by the offshore wind turbine-suction barrel structure coupling module, to carry out cumulative deformation analysis of the offshore suction barrel foundation, and to extract the stiffness data of the suction barrel head in the horizontal, vertical, and rotational directions calculated by the suction barrel structure-soil interaction module. Combined with the complete offshore wind turbine model excluding the lower suction barrel foundation, the frequency evolution calculation of the offshore suction barrel foundation is carried out.

[0026] According to a specific example of the present invention, the multi-spring calculation method for the cumulative deformation and frequency evolution of offshore wind turbine barrel foundations proposed in this invention is an integrated coupling calculation method for offshore wind turbine-suction barrel foundation-soil, which may include the following steps:

[0027] a. Using MATLAB programming, establish an interface for data interaction with the COMSOL module, responsible for receiving and distributing the displacement data of the suction bucket foundation calculated in the COMSOL module, and then solving the structure-soil interaction force in the MATLAB module based on the displacement data and transmitting it to the COMSOL module;

[0028] b. Using the Euler-Bernoulli theory, establish an overall model of the offshore wind turbine suction bucket foundation in COMSOL, then input the environmental loads generated by wind, waves, currents, etc., and combine the suction bucket structure-soil interaction force calculated in step a to calculate the displacement data of the suction bucket structure.

[0029] The following sub-steps are used:

[0030] b1. The upper blade-nacelle configuration is simplified to a mass point acting on the top of the wind turbine tower;

[0031] b2. Based on the geometric dimensions of the tower, the main pipe of the suction tank, and the suction tank structure, build a finite element analysis model in COMSOL;

[0032] b3. Based on the open MATLAB function interface in COMSOL, receive the structure-soil force data received from the interface in step a, and apply it to the suction bucket structure;

[0033] b4.COMSOL calculates the displacement data of the overall structure based on environmental load information and soil resistance data of the suction bucket structure;

[0034] c. Based on MATLAB programming, a multi-spring calculation scheme for the interaction between the suction bucket structure and soil was built, and the interaction force at the interface between the suction bucket structure and soil was solved by combining the displacement data transmitted by COMSOL.

[0035] The multi-spring calculation scheme includes the following sub-steps:

[0036] c1. The interaction between the suction bucket structure and the soil is described by a resistance-displacement spring and decomposed into three parts: py spring, tz spring, and Qz spring, which are used to solve the horizontal soil stress, side wall friction resistance, and soil resistance under the bucket cover of the suction bucket structure, respectively.

[0037] c2. Decompose the py spring constructed in c1 according to the law of equal energy, so that it is uniformly distributed along the circumference of the barrel to describe the non-uniform horizontal stress field of the suction barrel structure under the combined load of wind, waves and current.

[0038] c3. Pair the Py springs decomposed in c2 with the corresponding Tz springs, and input the horizontal soil resistance results obtained from the Py springs into the Tz spring calculation to restore the non-uniform stiffness mode of the soil around the suction bucket structure under combined load.

[0039] c4. The position of the Qz spring is adjusted in real time according to the soil resistance distribution under the bucket lid, which is used to solve the contribution of the soil resistance under the bucket lid to the overturning moment of the suction bucket structure under the combined load.

[0040] d. Transfer the force data calculated in step c to the COMSOL module through the MATLAB data processing interface built in step a. Repeat steps b and c to iterate the data until all calculation time steps are completed, so as to realize the load-displacement-soil resistance calculation under multiple time histories.

[0041] e. By extracting the horizontal, vertical, and rotational displacement data of the suction bucket structure from COMSOL, a cumulative deformation analysis of the offshore wind turbine suction bucket foundation is conducted.

[0042] f. Build a complete offshore wind turbine model in COMSOL (excluding the lower suction barrel foundation). Based on the calculation results of steps b and c, extract the stiffness data of the suction barrel head in the horizontal, vertical, and rotational directions, and input them into the bottom of the tower of the COMSOL model. Use the COMSOL finite element model to solve for the frequency of the offshore wind turbine suction barrel foundation.

[0043] The beneficial effects of this invention are: (1) Due to the adoption of the soil spring grouping design, it can reflect the uneven distribution of soil resistance around the suction bucket when it is horizontally loaded, and at the same time, the calculation results of the horizontal resistance are transferred to the Tz spring calculation. This scheme can calculate the complex stress state of large-diameter rigid foundations such as suction buckets when they are horizontally loaded. (2) Through the multi-spring calculation scheme of structure-soil interaction under combined load, a finite element model of the mutual coupling of offshore wind turbine-suction bucket structure-soil is established. It can be used for the cumulative deformation analysis of offshore wind turbine suction bucket foundation, and can also be used for the frequency evolution calculation of the overall structure, providing a feasible calculation scheme for the calculation of the dynamic response of offshore wind turbine suction bucket foundation. (3) This invention forms a complete calculation solution through the mutual coupling of COMSOL and MATLAB. In the COMSOL module, geometric modeling can be performed for different wind turbine models and suction bucket foundation sizes. In the MATLAB module, structure-soil interaction models can be developed for different soil conditions, which improves the applicability of the entire calculation scheme and is a broad application solution. Attached Figure Description

[0044] The above description is only an overview of the technical solution of the present invention. In order to introduce the key technical means of the present invention in more detail and clearly, the following figures and specific embodiments provide a more detailed overview of the present invention.

[0045] Figure 1 This is a basic flowchart of a multi-spring calculation method for the cumulative deformation and frequency evolution of the suction barrel foundation of an offshore wind turbine.

[0046] Figure 2 This is a schematic diagram of a multi-spring model of the interaction between the suction bucket structure and the soil.

[0047] Figure 3This is a comparison chart of the cumulative rotation of the suction bucket structure, the load secant stiffness, and the centrifuge test results, calculated with and without considering the coupling between the py and tz springs. Specific implementation methods

[0048] The multi-spring calculation system for the cumulative deformation and frequency evolution of the suction barrel foundation of an offshore wind turbine, as exemplified by this invention, mainly includes an offshore wind turbine-suction barrel structure coupling module, a suction barrel structure-soil interaction module, and a COMSOL-MATLAB data transmission iteration module, etc. The corresponding analysis method includes the following steps and features.

[0049] The first step is to calculate the wind, wave, and current loads on the offshore wind turbine based on the environmental conditions and the model of the turbine.

[0050] The second step is to build an Euler-Bernoulli beam element model of the offshore wind turbine suction bucket foundation in COMSOL, and solve for the corresponding displacement data based on the load information of the offshore wind turbine and the soil resistance borne by the suction bucket structure.

[0051] Furthermore, the calculation steps of the Euler-Bernoulli beam element model used in this invention are as follows:

[0052] (1) Input the environmental loads calculated in step one into COMSOL;

[0053] (2) Receive the soil resistance calculation results of the suction bucket structure transmitted by the MATLAB module;

[0054] (3) Based on the Euler-Bernoulli beam element theory, the stress-strain relationship is processed to solve the displacement data of the offshore wind turbine and suction bucket structure;

[0055] The third step involves using MATLAB programming to construct a Py spring for calculating the horizontal load-displacement relationship, a Tz spring for calculating the sidewall friction-displacement relationship, and a Qz spring for calculating the vertical soil resistance-displacement relationship. Based on the energy equivalence principle, the Py spring is decomposed and coupled with its corresponding Tz spring. The overall spring distribution is as follows: Figure 2 As shown.

[0056] Furthermore, this invention uses the API RP 2A standard to calculate the py curve of horizontal load-displacement relationship, the tz curve of sidewall friction-displacement relationship, and the Qz curve of vertical soil resistance-displacement relationship.

[0057] The fourth step involves calibrating the parameters required for the multi-spring calculation method constructed in the third step, based on factors such as geological conditions, soil type, soil unit weight, average soil particle size, relative soil density, soil internal friction angle, soil depth, suction bucket diameter and length, and suction bucket structure-soil interface contact friction angle. These parameters are then input into the MATLAB calculation program.

[0058] The fifth step is to set up a MATLAB data transmission interface to couple the COMSOL finite element analysis software. This interface will transfer the lateral soil resistance, wall friction, soil resistance under the lid, and overturning moment of the suction bucket calculated by MATLAB to the COMSOL finite element module, and will also receive the displacement data solved by the COMSOL module.

[0059] Furthermore, the multi-spring analysis method established in this invention is used to construct a solution module for the interaction between a suction bucket structure and soil. Based on the py, tz, and Qz springs that describe the soil resistance-displacement relationship, the specific calculation steps are as follows:

[0060] (1) Based on the spring parameters calibrated in step four, complete the construction of the entire calculation framework;

[0061] (2) Distribute the displacement data of the suction bucket structure received by the coupling interface, including the vertical displacement, horizontal displacement and rotation angle of the suction bucket;

[0062] (3) Receive the displacement data obtained in the second step and decompose it, allocate it to the displacement data interfaces of different groups of py and tz springs, and calculate the horizontal soil stress and sidewall friction of the suction bucket obtained by each group of springs.

[0063] (4) Combine the horizontal soil stress and sidewall friction obtained from each group in (3) to calculate the total horizontal soil resistance and sidewall friction of the suction bucket structure.

[0064] (5) Input the displacement data into the Qz spring calculation module to solve the vertical soil resistance and overturning moment of the suction bucket structure;

[0065] (6) Transfer the horizontal soil resistance, sidewall friction, vertical soil resistance and overturning moment calculated in (4) and (5) to the COMSOL finite element solution module in the second step;

[0066] Step 6: Based on the load-time history relationship obtained in Step 1, update the environmental load information and repeat Steps 2 through 5.

[0067] Step 7: Extract displacement data of the offshore wind turbine suction barrel structure from the COMSOL module and perform deformation analysis of the overall structure.

[0068] Step 8: Build a complete offshore wind turbine model in COMSOL (excluding the lower suction barrel foundation), extract the stiffness data of the suction barrel head in the horizontal, vertical and rotational directions based on the calculation results, and input them into the bottom of the tower of the COMSOL model to carry out frequency evolution calculation of the offshore wind turbine suction barrel foundation.

[0069] Figure 3 The effectiveness of the proposed calculation scheme was verified. By comparing the results with those from centrifuge testing, it was found that the calculation scheme considering the coupling effect between the Py and Tz springs can accurately predict the deformation and stiffness changes of the suction bucket foundation under cyclic loading. Simultaneously, a comparison was made with calculations that did not consider the coupling effect between the Py and Tz springs. It was found that ignoring the influence of the Py spring on the Tz spring overestimates the rotation angle of the suction bucket and underestimates its stiffness evolution, demonstrating the rationality and effectiveness of the proposed calculation scheme.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes or alterations made by those skilled in the art using the disclosed technical content shall fall within the protection scope of the present invention.

Claims

1. A multi-spring calculation method for the cumulative deformation and frequency evolution of a marine suction-type barrel foundation, characterized in that, Includes the following steps: In the finite element analysis software, an overall model of the suction bucket foundation of the offshore wind turbine is established. Then, the environmental load is input, and the displacement data of the suction bucket structure is calculated by combining the input suction bucket structure-soil interaction force. A multi-spring model of the interaction between the suction bucket structure and the soil was constructed, and the interaction forces at the interface between the suction bucket structure and the soil were solved by combining the displacement data transmitted by the finite element analysis software. Update the environmental load information based on the load-time history relationship, repeat the above two steps to iterate the data, and realize the load-displacement-soil resistance calculation under multiple time histories. Based on the obtained displacement data, cumulative deformation analysis of the offshore suction barrel foundation is performed, and based on the obtained stiffness data, frequency evolution calculation of the offshore suction barrel foundation is performed. The multi-spring model for the interaction between the suction bucket structure and the soil includes: The interaction between the suction bucket structure and the soil is described by a resistance-displacement spring and decomposed into three parts: py spring, tz spring, and Qz spring. These parts are used to solve for the horizontal soil stress, sidewall friction resistance, and soil resistance under the bucket cover of the suction bucket structure, respectively. The constructed py spring is decomposed according to the law of equal energy, and its uniform distribution along the circumference of the barrel is used to describe the non-uniform horizontal stress field of the suction barrel structure under the combined loads of wind, waves and current. The decomposed Py springs are paired with corresponding Tz springs, and the horizontal soil resistance results obtained from each Py spring are input into the corresponding Tz spring calculation to restore the non-uniform stiffness mode of the soil around the suction bucket structure under combined load. The position of the Qz spring is adjusted in real time based on the soil resistance distribution under the lid, which is used to solve the contribution of the soil resistance under the lid to the overturning moment of the suction bucket structure under combined load.

2. The multi-spring calculation method for cumulative deformation and frequency evolution of offshore suction barrel foundations according to claim 1, characterized in that, The overall model for establishing the offshore wind turbine suction barrel foundation includes: simplifying the upper blade-nacelle as a mass point acting on the top of the wind turbine tower; and building a finite element analysis model of the tower, suction barrel main pipe, and suction barrel structure according to the Euler-Bernoulli beam element theory.

3. The multi-spring calculation method for cumulative deformation and frequency evolution of offshore suction barrel foundations according to claim 1, characterized in that, Extract horizontal, vertical, and rotational displacement data of the suction bucket structure to conduct cumulative deformation analysis of the offshore suction bucket foundation.

4. The multi-spring calculation method for cumulative deformation and frequency evolution of offshore suction barrel foundations according to claim 1, characterized in that, A complete offshore wind turbine model excluding the lower suction barrel foundation was built in finite element analysis software. The stiffness data of the suction barrel head in the horizontal, vertical, and rotational directions calculated by the multi-spring model were extracted and input into the bottom of the tower of the complete turbine model to carry out frequency evolution calculation of the offshore suction barrel foundation.

5. The multi-spring calculation method for cumulative deformation and frequency evolution of offshore suction barrel foundations according to claim 1, characterized in that, The finite element analysis software used is COMSOL. A multi-spring model is built using MATLAB, and an interface is established between MATLAB and COMSOL modules for data interaction. This interface is responsible for receiving and distributing the displacement data calculated in COMSOL, and transmitting the force data it solves to COMSOL.

6. A multi-spring calculation system for the cumulative deformation and frequency evolution of a marine suction barrel foundation using the method described in any one of claims 1-5, characterized in that, include: The offshore wind turbine-suction tank structure coupling module is used to calculate displacement data based on the environmental load information of the offshore wind turbine and the soil resistance borne by the suction tank structure. The suction bucket structure-soil interaction module is used to calculate the interaction force at the suction bucket structure-soil interface by combining a multi-spring model with displacement data. The data transmission iteration module is used to realize the interaction of displacement data and interaction force data between the offshore wind turbine-suction tank structure coupling module and the suction tank structure-soil interaction module, so as to achieve iteration; The cumulative deformation analysis and frequency evolution calculation module is used to extract the horizontal, vertical, and rotational displacement data of the suction barrel structure calculated by the offshore wind turbine-suction barrel structure coupling module, to carry out cumulative deformation analysis of the offshore suction barrel foundation, and to extract the stiffness data of the suction barrel head in the horizontal, vertical, and rotational directions calculated by the suction barrel structure-soil interaction module. Combined with the complete offshore wind turbine model excluding the lower suction barrel foundation, the frequency evolution calculation of the offshore suction barrel foundation is carried out.

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