Marine structure wave dynamic response analysis method based on ABAQUS-OpenFOAM

Abstract

The invention discloses an ocean structure wave dynamic response analysis method based on ABAQUS-OpenFOAM. According to the ocean structure wave dynamic response analysis method based on ABAQUS-OpenFOAM, on the basis of two calculation modules of ABAQUS and OpenFOAM, a fluid-solid coupling algorithm is established, a fluid-solid coupling interface data transmission interface is developed, and a new function of ABAQUS-OpenFOAM coupling analysis is achieved. The method comprises the following steps: firstly, carrying out wave power analysis by utilizing OpenFoam to obtain a pressure field data group of all discrete grid nodes in a fluid calculation area; then, a KDTree is established, and the pressure field data group is subjected to block storage, so that the purpose of quickly retrieving the pressure field data is achieved; and establishing a dynamic analysis model of the ocean structure in the ABAQUS. The wave force at a certain spatial position is quickly obtained by using KDTree, and the wave force is transmitted to ABAQUS through custom subprograms Displ () and Dload () and is applied to the surface of an ocean structure as a boundary condition; and finally, analyzing dynamic response characteristics, including displacement, pore water pressure and effective stress, of the ocean structure under the action of wave impact by utilizing ABAQUS, and further evaluating the stability of the ocean structure.

Description

Technical Field

[0001] The present invention relates to the technical field of marine engineering structure hydrodynamic calculation, and in particular to an ABAQUS-OpenFOAM-based marine structure wave dynamic response analysis method. Background Art

[0002] Computational fluid dynamics (CFD) and computational structural mechanics (CSM) are two independent but closely related fields, each with its own dedicated simulation software. As an open source CFD software, OpenFoam has been widely used in the field of fluid dynamics with its powerful fluid simulation capabilities and flexible customization functions. ABAQUS, on the other hand, occupies an important position in the field of structural simulation with its excellent structural mechanics analysis capabilities and nonlinear solution technology.

[0003] In practical engineering problems, the interaction between fluid and structure is ubiquitous, such as aeroelasticity, fluid-structure coupling vibration, etc., which require simultaneous consideration of the behavior of fluid and structure. There are many fluid-structure coupling problems in geotechnical engineering, such as the safety and stability evaluation of structures in complex marine dynamic environments. Neither ABAQUS nor OpenFOAM has the ability to analyze such problems. Summary of the invention

[0004] In order to solve the problems existing in the above-mentioned prior art, the present invention provides a wave dynamic response analysis method of marine structures based on ABAQUS-OpenFOAM. The present invention is based on two calculation modules of ABAQUS and OpenFOAM, establishes a fluid-solid coupling algorithm, develops a fluid-solid coupling interface data transmission interface, realizes the new function of ABAQUS-OpenFOAM coupling analysis, and provides a new calculation and analysis method for the wave dynamic response characteristics and stability analysis of marine structures.

[0005] The technical solution adopted to achieve the above-mentioned purpose of the present invention is:

[0006] A method for analyzing wave dynamic response of marine structures based on ABAQUS-OpenFOAM includes the following steps:

[0007] S1. Calculate the pressure on the marine structure and the seabed foundation model in the fluid working condition to be simulated according to the OpenFoam software, and obtain the pressure field data group of all OpenFoam grid nodes in the calculation area, the pressure field data group including the spatial coordinates of all OpenFoam grid nodes in the calculation area and the pressure at each OpenFoam grid node;

[0008] S2. Determine the range of the calculation area by calculating the minimum and maximum values ​​of the calculation area in the X, Y, and Z directions, divide the calculation area into 10 parts in each direction, and the entire calculation area is divided into 1000 blocks. Store the OpenFoam grid nodes of the entire calculation area into 1000 blocks in the order of X, Y, and Z, and sort and number the 1000 blocks.

[0009] S3. Re-dividing the finite element mesh of the marine structure and seabed foundation model using ABAQUS software, taking any finite element mesh node as a given point, taking the spatial coordinates of the given point as an input parameter, calculating the block number of the given point according to the function Number_Block, and determining the block to which the given point belongs;

[0010] The formula for the Number_Block function is as follows:

[0011] Number_Block=(N z -1)*10*10+(N y -1)*10+N x

[0012] Among them, Number_Block is the number of the block to which the given point belongs, (X, Y, Z) is the spatial coordinates of the fixed point, N x 、N y and N z are all natural numbers, N x -X<1,N y -Y<1,N z -Z<1;

[0013] S4, find the nearest point in the block to which the given point belongs, traverse the coordinates of all OpenFoam grid nodes in the block, calculate the distance to the given point, and find the OpenFoam grid node closest to the given point, that is, the nearest point;

[0014] S5, after finding the nearest point, search for the pressure data for the nearest point in the pressure field data group file calculated by the OpenFoam software in S1 according to the spatial coordinates of the nearest point;

[0015] S6, through the ABAQUS custom data exchange interface subroutines Dload() and Disp(), the pressure data of the nearest point is transmitted to ABAQUS;

[0016] S7. Use ABAQUS to perform solid domain calculations and obtain the wave dynamics of marine structures and seabed foundations, including displacement, pore water pressure, and effective stress, by solving the dynamic Biot equations (1)-(5);

[0017] The equilibrium equations and mass conservation equations in three dimensions:

[0018]

[0019] In the formula, u S 、v S and w S are the displacements of the marine structure or seabed foundation in the x, y and z directions respectively; n is the porosity of the marine structure or seabed foundation; σ′ x ,σ′ y and σ′ z are the effective stresses of the marine structure or seabed foundation in the x, y and z directions respectively; τ xy , τ xz and τ yz is the shear stress of the marine structure or seabed foundation in the x, y and z directions; P is the pore fluid pressure; ρ = nρ f +(1-n)ρ s is the average density of the marine structure or seabed foundation; ρ f is the fluid density; ρ s is the density of the marine structure or seabed foundation; β is the compressibility coefficient of the fluid; k is the permeability coefficient; g is the gravitational acceleration; γ w is the density of the fluid; ∈ is the volume strain of the marine structure or seabed foundation.

[0020] Furthermore, the marine structure is a composite breakwater, and the seabed foundation is a sand bed.

[0021] Furthermore, the steps S2-S5 can be performed by establishing a KDTree.

[0022] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0023] 1. At present, there is still a lack of coupled analysis models for wave dynamic response of marine structures in the world. Based on the calculation results of OpenFoam, the present invention obtains the pressure field data group of all discrete grid nodes in the calculation area, reads and blocks the data of the result file in the calculation area, and transmits the pressure to ABAQUS calculation through the custom data exchange interface subroutines Dload() and Disp() of ABAQUS, thereby realizing the coupling of OpenFoam and ABAQUS. This method has high reliability and feasibility.

[0024] 2. Compared with the method of searching for the nearest point by looping through all points, the present invention adopts the method of searching for the nearest point, divides the entire space into 1000 separate blocks, calculates the block where each given point is located according to the function, and searches for the point closest to the given point in the block, so as to quickly find the block where a given point in ABAQUS is located in OpenFoam among tens of millions of units of OpenFoam calculation results.

[0025] 3. The method of the present invention is simple and can be encoded into corresponding software. The software occupies little memory and is easy to promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is an example diagram of the block division of the calculation area of ​​the OpenFoam software.

[0027] Figure 2 Schematic diagram of the composite breakwater and seabed foundation model. Figure 3 Schematic diagram of ABAQUS_FSSI.exe, the program that automatically generates ABAQUS-FSSI-Step1 files.

[0028] Figure 4 Schematic diagram of ABAQUS-FSSI-Step1 file format.

[0029] Figure 5 Schematic diagram of the finite element mesh generated for remeshing the computational domain in ABAQUS software.

[0030] Figure 6 Schematic diagram of the boundary conditions imposed by ABAQUS on the composite breakwater and seabed foundation model.

[0031] Figure 7 Schematic diagram of the submission page for the ABAQUS case.

[0032] Figure 8 This is the dynamic response distribution diagram of the breakwater and seabed under wave load at t=17.65s.

[0033] Fig. 9 This is the displacement time history curve of the upper left corner of the breakwater caisson under wave impact. DETAILED DESCRIPTION

[0034] In order to facilitate ordinary technicians in the field to understand and implement the present invention, the present invention is further described in detail below in conjunction with specific embodiments and application examples. It should be understood that the implementation examples described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0035] Example 1

[0036] 1. Use SolidWorks software to build the marine structure and seabed foundation model and import it into OpenFoam software. Use OpenFoam software to calculate the pressure on the marine structure in the fluid working condition to be simulated, and obtain the pressure field data group of all OpenFoam grid nodes in the calculation area. The pressure field data group includes the spatial coordinates of all OpenFoam grid nodes in the calculation area and the pressure at each OpenFoam grid node;

[0037] S2. Establish KDTree, determine the range of the calculation area by calculating the minimum and maximum values ​​of the calculation area in the X, Y, and Z directions, divide the calculation area into 10 parts in each direction, and the entire space is divided into 1000 blocks. Store the OpenFoam grid nodes of the entire calculation area into 1000 blocks in the order of X, Y, and Z, and sort and number these 1000 blocks.

[0038] S3. Re-dividing the marine structure and the seabed foundation into finite element meshes using ABAQUS software, taking any finite element mesh node as a given point, taking the spatial coordinates of the given point as input parameters, calculating the block number of the given point according to the function Number_Block, and determining the block to which the given point belongs;

[0039] The formula for the Number_Block function is as follows:

[0040] Number_Block=(N z -1)*10*10+(N y -1)*10+N x ,

[0041] Among them, Number_Block is the block number, (X, Y, Z) is the spatial coordinates of the fixed point, N x 、N y and N z are all natural numbers, N x -X<1,N y -Y<1,N z -Z<1.

[0042] In order to facilitate the function Number_Block, an example is given here. Dividing the calculation area of ​​the OpenFoam software into 1000 blocks is too much and not conducive to drawing. Here, the calculation area of ​​the OpenFoam software is divided into 3 parts in each direction. The entire space is divided into 27 blocks, and these 27 blocks are numbered in sequence, such as Figure 1 shown.

[0043] At this time, the formula of the function Number_Block is as follows:

[0044] Number_Block=(N z -1)*3*3+(N y -1)*3+N x ,

[0045] For the spatial coordinates of a given point in ABAQUS software (1.5, 1.5, 1.5), then N x 、N y and N z Both are equal to 2. Substituting into the function Number_Block, Number_Block=14, the given point is located in the 14th block of the calculation area of ​​the OpenFoam software.

[0046] S4. Find the nearest point in the block, traverse all the OpenFoam grid node coordinates in the block, calculate the distance to the given point, and find the OpenFoam grid node closest to the given point, that is, the nearest point.

[0047] S5. After finding the nearest point, search for the pressure of a given point (X, Y, Z) in the pressure field data group calculated by the OpenFoam software according to the spatial coordinates of the nearest point.

[0048] S6. The pressure at the nearest point is transmitted to ABAQUS through the ABAQUS custom data exchange interface subroutines Dload() and Disp().

[0049] S7. Use ABAQUS to perform solid domain calculations and solve the dynamic Biot equation to obtain the wave dynamics of marine structures and seabed foundations, including displacement, pore water pressure and effective stress;

[0050] The equilibrium equations and mass conservation equations in three dimensions:

[0051]

[0052] Where u S 、v S and w S are the displacements of the marine structure or seabed foundation in the x, y and z directions respectively; n is the porosity of the marine structure or seabed foundation; σ′ x ,σ′ y and σ′ z are the effective stresses of the marine structure or seabed foundation in the x, y and z directions respectively; τ xy , τ xz and τ yz is the shear stress of the marine structure or seabed foundation in the x, y and z directions; P is the pore fluid pressure; ρ = nρ f +(1-n)ρs is the average density of the marine structure or seabed foundation; ρ f is the fluid density; ρ s is the density of the marine structure or seabed foundation; β is the compressibility coefficient of the fluid; k is the permeability coefficient; g is the gravitational acceleration; γ w is the density of the fluid; ∈ is the volume strain of the marine structure or seabed foundation.

[0053] The following is an application example of the dynamic characteristics of a small-scale composite breakwater and its sand bed (seabed foundation) under wave loads. The specific steps are as follows:

[0054] 1. Build a composite breakwater and sand bed model. The composite breakwater is divided into two parts: a caisson and a pile of rough stones. The cross section of the caisson is square, and the cross section of the pile of rough stones is an isosceles trapezoid. Use SolidWorks software to build a model of the composite breakwater and seabed foundation. The composite breakwater and seabed foundation model is as follows: Figure 2 shown.

[0055] 2. Import the composite breakwater and sand bed model into OpenFoam software, use OpenFoam software to mesh the composite breakwater and sand bed model in the fluid domain, and then set the wave parameters on OpenFoam software according to the working conditions to be simulated, as shown in Table 1 below:

[0056] Table 1 Wave and calculation model material parameters

[0057] Wave form medium H(cm) d(m) T(s) <![CDATA[G(N / m 2 )]]> ν k(m / s) n <![CDATA[d 50 (mm)]]> Sr Second-order Stokes waves Wave 5 0.32 2.2 Sand bed <![CDATA[5.0×10 8 ]]> 0.33 <![CDATA[2.3×10 -3 ]]> 0.3 0.8 0.98 Rough Stone Pile <![CDATA[1.0×10 9 ]]> 0.24 <![CDATA[1.6×10 -1 ]]> 0.33 27 0.99 Caisson <![CDATA[1.0×10 9 ]]> 0.38 0 0 - 1

[0058] 3. Run OpenFoam software for calculation to obtain the pressure field data group of the composite breakwater and sand bed model in the calculation area at each calculation time point.

[0059] 4. Set the coupling file. First, use the automatic generation program ABAQUS_FSSI.exe of the ABAQUS-FSSI-Step1 file. The interface is as follows: Figure 3 As shown. Figure 3 The interface states: coupling mode (Openfoam), time interval and path of OPENFOAM results. The automatically generated file format is as follows: Figure 4 shown.

[0060] 5. Import the composite breakwater and sand bed model into ABAQUS software and re-divide the mesh. The mesh division of the structure and sand bed in the calculation domain of ABAQUS software is as follows: Figure 5 Then set the material parameters of the sand bed, caisson and rough stone (same as Table 1 above), set the analysis steps, set the boundary conditions, and apply loads to the composite breakwater and sand bed model. The boundary conditions are set as follows Figure 6 shown.

[0061] 6. Use ABAQUS to perform solid domain calculations and obtain results such as displacement, pore water pressure, and effective stress. When submitting a job in ABAQUS, specify the data interface program file path ABAQUS_FSSI_version5_final.for (the code content in the file is the content of steps S2-S5). During the calculation process, the DLOAD and DISP subroutines can be automatically called to call the OpenFOAM calculation results. The ABAQUS submission interface is as follows Figure 7 shown.

[0062] 7. Then you can use ABAQUS to continue post-processing the calculation results. The example of post-processing the one-way coupling calculation results in ABAQUS is as follows: Figure 8 and Fig. 9 shown.

[0063] Figure 8 The dynamic response distribution (σ′) of the breakwater and sand bed under wave load at t = 17.65s is shown. x ,σ′ y ,σ′ z , τ xz and P). Figure 8 It can be seen that at t = 17.65s, the dynamic pore pressure P caused by waves in the seabed and rubble piles below the wave crest is significant. The dynamic pore pressure P in the sand bed below the wave crest is positive, indicating that the wave penetration force is downward and the seabed is in a compacted state. x The distribution diagram shows that due to the impact of the wave force to the right, the breakwater always has a tendency to slide to the right. x The left side of the rubble pile is stretched, forming a stretching zone; the right side of the rubble pile is σ′ x It is compressed, forming a compression zone. σ′ at the interface between the left and right sides of the caisson and the rubble pile z and σ′ y Obviously larger than other places. From the dynamic τ xz The distribution diagram shows that due to the impact of wave force, a large shear stress concentration area is formed at the interface between the lower left side of the caisson and the rubble pile. If it is large enough, it may cause shear failure of the breakwater. From the above analysis, it can be seen that the influence of waves on the pore water pressure and effective stress in the sand foundation and breakwater is very significant.

[0064] Fig. 9 The displacement time history curve of the upper left corner of the breakwater caisson under wave impact is shown. Fig. 9 It can be seen that under the action of wave loads, although the displacements in both horizontal and vertical directions have only slight fluctuations, they can still be captured by the established numerical model, indicating that the established model has a high resolution for the calculation of structural displacements.

Claims

1. A method for analyzing the wave dynamic response of marine structures based on ABAQUS-OpenFOAM, characterized in that The steps include: S1. Calculate the pressure on the marine structure and the seabed foundation model in the fluid working condition to be simulated according to the OpenFoam software, and obtain the pressure field data group of all OpenFoam grid nodes in the calculation area, the pressure field data group including the spatial coordinates of all OpenFoam grid nodes in the calculation area and the pressure at each OpenFoam grid node; S2. Determine the range of the calculation area by calculating the minimum and maximum values ​​of the calculation area in the X, Y, and Z directions, divide the calculation area into 10 parts in each direction, and the entire calculation area is divided into 1000 blocks. Store the OpenFoam grid nodes of the entire calculation area into 1000 blocks in the order of X, Y, and Z, and sort and number the 1000 blocks. S3. Re-dividing the finite element mesh of the marine structure and seabed foundation model using ABAQUS software, taking any finite element mesh node as a given point, taking the spatial coordinates of the given point as an input parameter, calculating the block number of the given point according to the function Number_Block, and determining the block to which the given point belongs; The formula for the Number_Block function is as follows: Number_Block=(N z -1)*10*10+(N y -1)*10+N x Among them, Number_Block is the number of the block to which the given point belongs, (X, Y, Z) is the spatial coordinates of the fixed point, N x 、N y and N z are all natural numbers, N x -X<1,N y -Y<1,N z -Z<1; S4, find the nearest point in the block to which the given point belongs, traverse the coordinates of all OpenFoam grid nodes in the block, calculate the distance to the given point, and find the OpenFoam grid node closest to the given point, that is, the nearest point; S5, after finding the nearest point, search for the pressure data for the nearest point in the pressure field data group file calculated by the OpenFoam software in S1 according to the spatial coordinates of the nearest point; S6, through the ABAQUS custom data exchange interface subroutines Dload() and Disp(), the pressure data of the nearest point is transmitted to ABAQUS; S7. Use ABAQUS to perform solid domain calculations and obtain the wave dynamics of marine structures and seabed foundations, including displacement, pore water pressure, and effective stress, by solving the dynamic Biot equations (1)-(5); The equilibrium equations and mass conservation equations in three dimensions: In the formula, u S 、v S and w S are the displacements of the marine structure or seabed foundation in the x, y and z directions respectively; n is the porosity of the marine structure or seabed foundation; σ′ x ,σ′ y and σ′ z are the effective stresses of the marine structure or seabed foundation in the x, y and z directions respectively; τ xy , τ xz and τ yz is the shear stress of the marine structure or seabed foundation in the x, y and z directions; P is the pore fluid pressure; ρ = nρ f +(1-n)ρ s is the average density of the marine structure or seabed foundation; ρ f is the fluid density; ρ s is the density of the marine structure or seabed foundation; β is the compressibility coefficient of the fluid; k is the permeability coefficient; g is the gravitational acceleration; γ w is the density of the fluid; ∈ is the volume strain of the marine structure or seabed foundation.

2. The method for analyzing wave dynamic response of marine structures based on ABAQUS-OpenFOAM according to claim 1, characterized in that: The marine structure is a composite breakwater, and the seabed foundation is a sand bed.

3. The method for coupling ABAQUS with OpenFoam according to claim 1, characterized in that: The steps S2-S5 can be performed by establishing a KDTree.

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