Method for establishing fluid-structure interaction wave tank under combined action of wind and wave

Abstract

The application belongs to the technical field of ocean engineering, and proposes a method for establishing a fluid-solid coupling wave tank under the combined action of wind and wave, which comprises the following steps: building a fluid-solid coupling environment, pre-processing the fluid domain and making fluid-solid coupling settings, pre-processing the solid domain and making fluid-solid coupling settings, selecting a fluid-solid coupling scheme, performing fluid-solid coupling calculation and analyzing the calculation results; compared with the prior art, the application realizes flexible construction and efficient solution of the wind-wave coupling environment; the modular architecture not only ensures the calculation stability, but also facilitates the secondary development of key links, is easy to deploy and has strong expandability, and significantly reduces the difficulty of engineering application.

Description

Technical Field

[0001] This invention relates to the field of marine engineering technology, specifically to a method for establishing a fluid-structure interaction wave flume under the combined action of wind and waves that can accurately simulate the fluid-structure interaction of marine structures subjected to wind and waves under different working conditions. It is particularly applicable to the response analysis of flexible vertical structures (such as independent bridge towers, marine meteorological observation towers, and offshore wind turbines) under transient strong nonlinear wind and waves in wind and wave environments, improving the accuracy of structural stress and response prediction and the safety of engineering design. Background Technology

[0002] With the development of marine engineering, renewable energy, and underwater structure construction, a large number of vertical flexible structures are widely used in complex sea conditions. These structures are typically located in the ocean's wave field, and their loading environment exhibits highly coupled characteristics: on the one hand, wind and waves interfere with each other and generate coupling effects during propagation; on the other hand, due to the high flexibility of these structures, significant elastic deformation occurs when subjected to periodic environmental loads. This deformation further disturbs the surrounding fluid and wave fields, altering local flow field characteristics and affecting the structure's dynamic response. These dual effects make the fluid motion near the structure highly complex, and traditional empirical formulas and unidirectional fluid-structure interaction models often fail to accurately characterize its motion and stress properties.

[0003] Waves2Foam is a widely used open-source toolkit in the field of computational fluid dynamics (CFD) for marine and coastal engineering. It is primarily used within the OpenFOAM framework to generate, propagate, and absorb various regular, irregular, and even extreme waves with high precision, and to simulate the interaction between waves and offshore structures. However, because Waves2Foam lacks structural calculation capabilities, it typically simplifies offshore structures as rigid bodies when analyzing them. This significantly limits its applicability and accuracy for structures with high flexibility and requiring knowledge of motion. Furthermore, Waves2Foam does not have built-in mature wind field generation functions, resulting in several limitations when simulating wind-wave coupled conditions.

[0004] While existing research attempts to construct fluid-structure interaction numerical wave tanks, existing tools are expensive, deeply encapsulated, and difficult to redevelop, making it hard to reproduce diverse operating conditions. Furthermore, developing a solver from scratch is extremely labor-intensive and time-consuming. In addition, existing work largely focuses on single wave effects, with less attention paid to the combined effects of wind and waves. To date, a universal, highly portable fluid-structure interaction numerical wave tank capable of accurately analyzing the response of marine structures under various combined wind and wave conditions is still lacking. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes a numerical flume for fluid-structure interaction under the combined effects of wind and waves, built upon the open-source fluid solver waves2Foam, the open-source coupling library preCICE, and the open-source structural solver CalculiX. This numerical platform can effectively capture the mutual coupling behavior of wind and waves during propagation and accurately simulate the dynamic response of structures in complex flow fields, achieving high-precision analysis of fluid-structure interaction problems under the combined effects of wind and waves.

[0006] A method for establishing a fluid-structure interaction wave tank under the combined action of wind and waves, characterized by comprising the following steps:

[0007] Step 1: Build a fluid-structure interaction environment based on waves2Foam-preCICE-CalculiX. Compile and install the fluid solver waves2Foam, the adapter OpenFOAM-adapter, the coupling library preCICE, the structural solver CalculiX, and the adapter CalculiX-adapter on the Linux system.

[0008] Step 2: Perform preprocessing on the fluid domain and configure fluid-structure interaction settings, specifically including:

[0009] Step 2-1: Generate wave field, set relaxation region, define spectral parameters, configure boundary conditions and initial flow field;

[0010] Step 2-2: At the inlet definition of the fluid domain, firstly, create Inlet1 below for wave generation and Inlet2 above for wind generation during flow field generation. In Inlet1, various custom waves can be generated using analytical solutions from linear or nonlinear wave theory. The free surface rise at a certain position x and time t is represented as:

[0011] (1), where, Represents Airy linear waves, Stokes waves of various orders, and custom waves;

[0012] Within the Inlet2 boundary, OpenFOAM's built-in custom boundary type, codedFixedValue, allows for direct input of a given wind speed time history. Furthermore, it enables the construction of a continuous and smooth wind speed profile shape function using relative wind speed values ​​measured by a finite number of anemometers through cubic natural spline interpolation.

[0013] (2), where, This represents the coefficients of each segment of the natural spline. These coefficients are obtained by solving a tridiagonal linear equation system containing only the relationship between adjacent nodes using wind speed data. The second derivative of each node is then obtained by substituting these second derivatives back into the cubic polynomial formula of each segment to obtain the Stokes waves of various orders and custom waves. This represents the wind profile function between the i-th wind speed sampling point and the (i+1)-th wind speed sampling point;

[0014] Steps 2-3: At the outlet definition of the fluid domain, firstly, create Outlet1, located below, for absorbing waves, when generating the flow field. Define the relaxation zone of Outlet1 using the relaxation zone definition function built into waves2Foam. The outlet Outlet2, located above, for the wind field, is handled in the same way as a general outlet.

[0015] Steps 2-4: Define the controlDict and precisionDict files in the system folder under the example directory to prepare for fluid-structure interaction. The settings of other parameters and files are the same as for unidirectional fluid-structure interaction.

[0016] Steps 2-5: Calculate the structural forces using the forces function in controlDict; collect wind speed time history using probe; collect wind speed profiles using sampledSets;

[0017] Step 3: Preprocess the solid domain and configure the fluid-structure interaction settings, including:

[0018] Step 3-1: Geometric modeling, mesh generation, material property definition, boundary condition setting, and load application prepare the input file for structural analysis;

[0019] Step 3-2: Define the config.yml file to prepare for fluid-structure interaction;

[0020] Step 4: Select a fluid-structure interaction scheme and edit the precision-configure.xml file;

[0021] Step 5: Perform fluid-structure interaction calculations and analyze the results.

[0022] Step 4 of this invention includes:

[0023] Step 4-1: Define the two solvers involved in the fluid-structure interaction as waves2Foam and CalculiX;

[0024] Step 4-2: When mapping the fluid dynamics of the flow field in waves2Foam to CalculiX, select the conservation mapping; when mapping the structural displacements in CalculiX to waves2Foam, select the uniform mapping.

[0025] Step 4-3: Select a data mapping method, including nearest neighbor mapping, nearest projection mapping, linear unit interpolation, nearest neighbor gradient and radial basis function interpolation, choose one;

[0026] Step 4-4: Select the data communication method for the two solvers, waves2Foam and CalculiX, including MPI-based communication and TCP / IP-based mesh communication. Choose one.

[0027] Steps 4-5: Select the serial / parallel scheme for the two solvers, waves2Foam and CalculiX, including explicit serial, explicit parallel, implicit serial, and implicit parallel, and choose one.

[0028] Steps 4-6: Select a fluid-structure interaction acceleration algorithm, including constant under-relaxation, dynamic Aitken under-relaxation, and quasi-Newton schemes; choose one.

[0029] Steps 4-7: Define the coordinates of the observation point and collect the displacement of the structure under the action of wind and waves.

[0030] Step 5 of this invention specifically includes: running two solvers simultaneously, reading the precision-configure.xml file into preCICE, performing fluid-structure interaction calculations, and exporting wind speed time history data, wind profile data, structural stress time history data, and structural displacement data for comparison with experiments.

[0031] This invention boasts several significant advantages in its technical implementation. Firstly, the system employs a combination of waves2Foam's built-in wave module and OpenFOAM's coded boundaries, enabling the rapid construction of highly customized wind-wave coupling scenarios. Secondly, the open-source architecture based on the preCICE coupler and the CalculiX solver ensures the stability of the core computational modules while providing flexible support for customized development of key processes through standard interfaces. Thirdly, the entire toolchain is composed entirely of open-source components, exhibiting low environment dependency and ease of portability. This reduces user configuration complexity while maintaining excellent architectural scalability and practical engineering applicability. Attached Figure Description

[0032] Appendix Figure 1 This is a schematic diagram of data transmission in the fluid-structure interaction numerical flume based on waves2Foam-preCICE-CalculiX for wind and wave analysis established in this invention.

[0033] Appendix Figure 2 This is a schematic diagram of the dimensions and wall definition of the fluid-structure interaction numerical water tank in an embodiment of the present invention.

[0034] Appendix Figure 3 This is a schematic diagram of the wind speed time history probe position, wind speed profile acquisition position, and wave height meter position in an embodiment of the present invention.

[0035] Appendix Figure 4 This is a time history diagram of wind speed after the wind and waves have stabilized in an embodiment of the present invention.

[0036] Appendix Figure 5 This is a wind speed profile after the wind and waves have stabilized in an embodiment of the present invention.

[0037] Appendix Figure 6 This is a wave height time history diagram after the wind and waves have stabilized in an embodiment of the present invention.

[0038] Appendix Figure 7 This is a time history diagram of the structural stress after the wind and waves have stabilized in an embodiment of the present invention.

[0039] Appendix Figure 8 This is a time history diagram of the displacement of the top of the structure after the wind and waves have stabilized in an embodiment of the present invention. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0041] This invention proposes a numerical flume for combined wind and wave action based on the fluid solver waves2Foam, the coupling library preCICE, and the structural solver CalculiX. The specific data transmission method is as follows: Figure 1 As shown, this numerical platform can effectively capture the mutual coupling behavior of wind and waves during propagation and accurately simulate the dynamic response of structures in complex flow fields, achieving high-precision analysis of fluid-structure interaction problems under the combined action of wind and waves. Example

[0042] This example uses a flexible, upright cylinder in a wind and wave field. Key parameters of the fluid domain in a fluid-structure interaction numerical water tank are as follows: Figure 2 As shown, the water tank is 7.8m long, 3m wide, and 3.6m high, with a water depth of 0.6m. The relaxation zone is 1.1m behind the Inlet, and the damping zone is 2.7m in front of the Outlet. The waves are regular waves with a wave height of 0.04m and a wave period of 0.8s. The wind speed is steady with an amplitude of 3.144m / s. The wind speed profile is theoretically an exponential profile, but the measured data does not completely coincide with the theoretical value. Spline function interpolation is used for fitting. Figure 3 As shown, a wave height meter (WG) is set up 0.5m in front of the structure, and a wind speed time history probe (WP) is set up 2m above the wave height meter. A series of wind profile sample points (WS) are set up between WG and WP to collect wind profiles.

[0043] Key parameters of the fluid-structure interaction numerical cooling tank structural domain: A typical experimental structure consisting of a flexible vertical cylinder with an aluminum core, aerodynamic shape, and counterweight. Key parameters used for simulation include an equivalent elastic modulus of 194 MPa and an equivalent density of 792 kg / m³. 3 Damping ratio 0.65%, diameter 0.15m and height 2.4m.

[0044] Key choices for the fluid-structure interaction (FSI) scheme in numerical flume: the data mapping method is nearest projection mapping, the communication method is based on MPI, the serial-parallel scheme is implicit parallelism, and the FSI acceleration algorithm adopts quasi-Newton acceleration.

[0045] like Figure 4 As shown, although the wind speed fluctuated slightly, it was in line with expectations; Figure 5 As shown, through spline function interpolation, the wind profile in waves2Foam can fit the experimental data well; as Figure 6 As shown, the wave height is basically consistent with the experimental value.

[0046] To further verify the accuracy of the method presented in this example, the calculation results were compared with experimental results under the same wind and wave conditions. The comparison results are as follows: Figure 7 , Figure 8 ,in, Figure 7 Comparison of the forces exerted by wind and waves; Figure 8 The comparison of the displacement of the flexible upright cylinder under the action of wind and waves shows that the calculation results of the fluid-structure interaction numerical water tank in this example are in good agreement with the experimental results. It can accurately calculate the wave force on the flexible structure and the displacement of the flexible structure under the action of wind and waves.

[0047] Compared with the prior art, the present invention has the following advantages: (1) By combining the mature wave library of waves2Foam with the programmable boundary condition type codedFixedValue of OpenFOAM, the system can efficiently construct and reproduce a variety of customized wind-wave joint environments. (2) Relying on widely verified open source solvers such as waves2Foam, preCICE and CalculiX, while ensuring the stability of the core solver, its modular design and open interface provide a standardized secondary development space for key links. (3) Based on a fully open source toolchain, the system has less dependence on the environment and strong portability, which reduces the deployment threshold and programming burden for users, while maintaining the scalability and engineering practicality of the overall architecture.

Claims

1. A method for constructing a fluid-structure interaction wave tank under the combined action of wind and waves, characterized in that, Includes the following steps: Step 1: Build a fluid-structure interaction environment based on waves2Foam-preCICE-CalculiX. Compile and install the fluid solver waves2Foam, the adapter OpenFOAM-adapter, the coupling library preCICE, the structural solver CalculiX, and the adapter CalculiX-adapter on the Linux system. Step 2: Perform preprocessing on the fluid domain and configure fluid-structure interaction settings, specifically including: Step 2-1: Generate wave field, set relaxation region, define spectral parameters, configure boundary conditions and initial flow field; Step 2-2: At the inlet definition of the fluid domain, firstly, create Inlet1 below for wave generation and Inlet2 above for wind generation during flow field generation. In Inlet1, various custom waves can be generated using analytical solutions from linear or nonlinear wave theory. The free surface rise at a certain position x and time t is represented as: (1), where, Represents Airy linear waves, Stokes waves of various orders, and custom waves; Within the Inlet2 boundary, the given wind speed time history is directly input using the custom boundary type codedFixedValue provided by OpenFOAM. A continuous and smooth wind speed profile shape function is constructed using relative wind speed values ​​measured by a finite number of anemometers and cubic natural spline interpolation. (2), where, This represents the coefficients of each segment of the natural spline. These coefficients are obtained by solving a tridiagonal linear equation system containing only the relationship between adjacent nodes using wind speed data. The second derivative of each node is then obtained by substituting these second derivatives back into the cubic polynomial formula of each segment to obtain the Stokes waves of various orders and custom waves. This represents the wind profile function between the i-th wind speed sampling point and the (i+1)-th wind speed sampling point; Steps 2-3: At the outlet definition of the fluid domain, firstly, create Outlet1, located below, for absorbing waves, when generating the flow field. Define the relaxation zone of Outlet1 using the relaxation zone definition function built into waves2Foam. The outlet Outlet2, located above, for the wind field, is processed in the same way as the outlet. Steps 2-4: Define the controlDict and precisionDict files in the system folder under the example directory to prepare for fluid-structure interaction. The parameters and file settings are consistent with those for unidirectional fluid-structure interaction. Steps 2-5: Calculate the structural forces using the forces function in controlDict; collect wind speed time history using probe; collect wind speed profiles using sampledSets; Step 3: Preprocess the solid domain and configure the fluid-structure interaction settings, including: Step 3-1: Geometric modeling, mesh generation, material property definition, boundary condition setting, and load application prepare the input file for structural analysis; Step 3-2: Define the config.yml file to prepare for fluid-structure interaction; Step 4: Select a fluid-structure interaction scheme and edit the precision-configure.xml file; Step 5: Perform fluid-structure interaction calculations and analyze the results.

2. The method for establishing a fluid-structure interaction wave tank under the combined action of wind and waves according to claim 1, characterized in that, Step 4 includes: Step 4-1: Define the two solvers involved in the fluid-structure interaction as waves2Foam and CalculiX; Step 4-2: When mapping the fluid dynamics of the flow field in waves2Foam to CalculiX, select the conservation mapping; when mapping the structural displacements in CalculiX to waves2Foam, select the uniform mapping. Step 4-3: Select a data mapping method, including nearest neighbor mapping, nearest projection mapping, linear unit interpolation, nearest neighbor gradient and radial basis function interpolation, choose one; Step 4-4: Select the data communication method for the two solvers, waves2Foam and CalculiX, including MPI-based communication and TCP / IP-based mesh communication. Choose one. Steps 4-5: Select the serial / parallel scheme for the two solvers, waves2Foam and CalculiX, including explicit serial, explicit parallel, implicit serial, and implicit parallel, and choose one. Steps 4-6: Select a fluid-structure interaction acceleration algorithm, including constant under-relaxation, dynamic Aitken under-relaxation, and quasi-Newton schemes; choose one. Steps 4-7: Define the coordinates of the observation point and collect the displacement of the structure under the action of wind and waves.

3. The method for establishing a fluid-structure interaction wave tank under the combined action of wind and waves according to claim 1, characterized in that, Step 5 specifically includes: running two solvers simultaneously, reading the precision-configure.xml file into preCICE, performing fluid-structure interaction calculations, and exporting wind speed time history data, wind profile data, structural stress time history data, and structural displacement data for comparison with experiments.

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