Multi-program coupling simulation method and system based on netting model

Abstract

The invention discloses a multi-program coupling simulation method and system based on a netting model. The method comprises the following steps: acquiring an original netting model and a finite element grid, and generating a node table and a unit table according to the original netting model and the finite element grid by adopting a netting grouping method; constructing a plurality of target mesh units according to the node table and the unit table; calculating the hydrodynamic load of each target mesh unit; and performing multi-program coupling simulation on the hydrodynamic load of each target mesh unit based on an external multi-physical field simulation program, and outputting a coupling simulation result.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ocean engineering, and in particular to a multi-program coupling simulation method and system based on a screen model. BACKGROUND

[0002] With the deepening of global marine resource development, the demand for dynamic analysis of large flexible screen structures in the fields of deep-sea aquaculture and marine engineering equipment is increasingly urgent. As a core component of marine aquaculture equipment, the dynamic response of the screen in complex marine environments such as waves and ocean currents directly affects the safety and economy of the entire system.

[0003] The hydrodynamic analysis of the marine screen structure involves multiple disciplines such as fluid mechanics, structural mechanics, and computational mathematics. From the perspective of calculation methods, it mainly includes frequency domain methods based on potential flow theory, time domain methods based on Morison formula, and direct numerical simulation methods based on CFD (CFD, Computational Fluid Dynamics). From the perspective of modeling, it includes mass concentration method, finite element method, finite difference method, etc. From the perspective of software implementation, it involves the collaborative work of ABAQUS (Advanced Simulation for Engineering and Sciences), ANSYS (Analysis System), OpenFOAM (OpenField Operation and Manipulation), Modelica (multi-physical field simulation platform based on Modelica modeling language), etc.

[0004] The existing multi-program coupling simulation method lacks effective multi-software platform data communication mechanism, the time step mismatch problem between different simulation software has not been effectively solved, and numerical oscillation and convergence deficiency may occur during data transmission, resulting in poor simulation efficiency. SUMMARY

[0005] The present application provides a multi-program coupling simulation method and system based on a screen model, which solves the technical problem that the existing multi-program coupling simulation method may easily cause numerical oscillation and convergence deficiency during data transmission, resulting in poor simulation efficiency.

[0006] The first aspect of the present application provides a multi-program coupling simulation method based on a screen model, comprising:

[0007] Obtaining an original netting model and a finite element mesh, and generating a node table and an element table according to the original netting model and the finite element mesh by using a netting grouping method;

[0008] According to the node table and the element table, a plurality of target mesh elements are constructed;

[0009] The hydrodynamic load of each target mesh element is calculated;

[0010] Based on an external multi-physical field simulation program and the hydrodynamic load of each target mesh element, multi-program coupling simulation is performed, and coupling simulation results are output.

[0011] Optionally, the generating a node table and an element table according to the original netting model and the finite element mesh by using a netting grouping method comprises:

[0012] The original netting model is equivalently processed by using a netting grouping method, and equivalent parameters after grouping are output;

[0013] The finite element mesh is given geometric material properties by using the equivalent parameters after grouping, and the finite element mesh with geometric material properties is determined;

[0014] The node table and the element table are extracted in the finite element mesh with geometric material properties.

[0015] Optionally, the constructing a plurality of target mesh elements according to the node table and the element table comprises:

[0016] Each node in the node table is taken as a corresponding initial node, and the number of elements connected to each initial node is counted in the element table, so as to determine the number of connected elements corresponding to each initial node;

[0017] Any initial node corresponding to a connected element number greater than a preset element number threshold value is taken as an effective starting node, and a plurality of element pairs corresponding to each effective starting node are constructed according to a plurality of elements connected to each effective starting node;

[0018] The plurality of element pairs corresponding to each effective starting node are subjected to node extraction, and the end point nodes associated with each element pair corresponding to each effective starting node are output;

[0019] Based on the end point nodes associated with each element pair corresponding to each effective starting node, other element retrieval is performed in the element table, and a set of other elements corresponding to each effective starting node is determined;

[0020] Based on the set of other elements corresponding to each effective starting node, shared nodes corresponding to each effective starting node are determined;

[0021] An effective starting node is adopted, and a plurality of closed net element units are constructed by using the effective starting node, an end node corresponding to the effective starting node, a shared node, and a unit corresponding to the shared node.

[0022] The plurality of closed net element units are de-duplicated to determine a plurality of target net element units.

[0023] Optionally, a multi-program coupling simulation is performed based on the external multi-physical field simulation program, the hydrodynamic load of each target net element unit, and an output coupling simulation result, which includes:

[0024] A load application sub-program is used to convert the hydrodynamic load of each target net element unit into a distributed load according to the unit type matching the net material.

[0025] According to the topological correspondence relationship of each net rope unit corresponding to each target net element unit and the finite element grid, the distributed load is applied to the corresponding net rope unit to determine a plurality of net rope units with applied loads.

[0026] The motion information of the reference point at the current time output by the external multi-physical field simulation program is subjected to a third-order polynomial interpolation to determine the smooth motion parameters of the constraint nodes corresponding to the original net model.

[0027] Based on the smooth motion parameters of the constraint nodes, the distributed load corresponding to each target net element unit, and the mechanical properties of each net rope unit with an applied load, the constraint reaction force of the constraint nodes and the structural dynamic response of each target net element unit are output.

[0028] The current analysis time corresponding to the finite element grid and the current running time corresponding to the external multi-physical field simulation program are counted.

[0029] If the current analysis time is greater than the current running time, the external multi-physical field simulation program is used to calculate new reference point motion information at the current time based on the constraint reaction force.

[0030] The current running time is compared with a preset simulation time.

[0031] If the current running time is less than the preset simulation time, the step of performing a third-order polynomial interpolation on the reference point motion information at the current time output by the external multi-physical field simulation program to determine the smooth motion parameters of the constraint nodes corresponding to the original net model is executed until the current running time is greater than or equal to the preset simulation time.

[0032] According to the current running time greater than or equal to the preset simulation time, the current time reference point motion information, the water dynamic load of each target mesh unit, the structure dynamics response, and the constraint reaction force of the constraint node are coupled to generate a simulation result.

[0033] Optionally, the system further comprises:

[0034] If the current analysis time is less than or equal to the current running time, the spatial posture of the corresponding target mesh unit is adjusted according to the structure dynamics response of each target mesh unit, and a plurality of new target mesh units are determined.

[0035] The water dynamic load of each new target mesh unit is calculated.

[0036] The load application subprogram is executed to convert the water dynamic load of each target mesh unit into a distributed load according to the mesh material matching unit type until the current analysis time is greater than the current running time.

[0037] Optionally, the water dynamic load comprises lift and drag; and the calculation process of the water dynamic load is specifically as follows:

[0038] ;

[0039] ;

[0040] wherein, and are the drag and lift of the target mesh unit respectively; is the sea density; and are the drag coefficient and lift coefficient of the target mesh unit respectively; is the instantaneous speed of the water flow relative to the center point of the target mesh unit; is the coverage area of the target mesh unit.

[0041] The second aspect of the present application provides a multi-program coupled simulation system based on a mesh model, comprising:

[0042] An acquisition module is configured to acquire an original mesh model and a finite element grid, and generate a node table and an element table according to the original mesh model and the finite element grid by using a mesh grouping method;

[0043] A construction module is configured to construct a plurality of target mesh units according to the node table and the element table;

[0044] A calculation module is configured to calculate the water dynamic load of each target mesh unit;

[0045] An emulation module is configured to perform multi-program coupling emulation based on an external multi-physical field emulation program and the hydrodynamic load of each target mesh unit, and output coupling emulation results.

[0046] The third aspect of the present application provides a computer device, comprising a memory and a processor, the memory stores a computer program, and the computer program is executed by the processor to make the processor execute the steps of the multi-program coupling emulation method based on the net model as described in any one of the above aspects.

[0047] The fourth aspect of the present application provides a computer readable storage medium, which stores a computer program, and the computer program is executed to implement the steps of the multi-program coupling emulation method based on the net model as described in any one of the above aspects.

[0048] The fifth aspect of the present application provides a computer program product, which comprises a computer program stored on a non-transitory computer readable storage medium, and the computer program comprises program instructions, wherein when the program instructions are executed by a computer, the computer executes the steps of the multi-program coupling emulation method based on the net model as described in any one of the above aspects.

[0049] From the above technical solutions, the present application has the following advantages:

[0050] The above technical solutions of the present application provide a multi-program coupling emulation method based on a net model, obtain an original net model and a finite element mesh, and generate a node table and an element table according to the original net model and the finite element mesh by using a net group method; a plurality of target mesh units are constructed according to the node table and the element table; the hydrodynamic load of each target mesh unit is calculated; multi-program coupling emulation is performed based on an external multi-physical field emulation program and the hydrodynamic load of each target mesh unit, and coupling emulation results are output; based on the above solutions, the present application optimizes the data organization structure of nodes and elements by using the net group method, so that the calculation of the hydrodynamic load of the target mesh unit is more consistent with the actual stress state, high-quality basic data input is provided for multi-program coupling emulation, the numerical oscillation problem caused by data transmission mismatch in the existing multi-program coupling emulation is effectively solved, and the overall simulation efficiency is significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0051] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiment or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0052] Figure 1A step flow chart of a multi-program coupling simulation method based on a netting model provided for the embodiment one of the present application;

[0053] Figure 2 A schematic diagram of the form of a Panel unit provided for the embodiment one of the present application;

[0054] Figure 3 A force decomposition schematic diagram of a Panel unit provided for the embodiment one of the present application;

[0055] Figure 4 A netting parameter schematic diagram provided for the embodiment one of the present application;

[0056] Figure 5 A netting simulation logic flow chart provided for the embodiment one of the present application;

[0057] Figure 6 A support structure unit and netting unit schematic diagram provided for the embodiment one of the present application;

[0058] Figure 7 A netting deformation schematic diagram provided for the embodiment one of the present application;

[0059] Figure 8 A netting finite element model constructed in ABAQUS provided for the embodiment one of the present application;

[0060] Figure 9 An ABAQUS and external multi-physical field simulation program coupling flow chart provided for the embodiment one of the present application;

[0061] Figure 10 A simulated netting schematic diagram provided for the embodiment one of the present application;

[0062] Figure 11 A square netting gravity test and simulation verification schematic diagram provided for the embodiment one of the present application;

[0063] Figure 12 A node z-axis direction support reaction force timing diagram provided for the embodiment one of the present application;

[0064] Figure 13 A flow schematic diagram of a multi-program coupling simulation method based on a netting model provided for the embodiment one of the present application;

[0065] Figure 14 A structure block diagram of a multi-program coupling simulation system based on a netting model provided for the embodiment two of the present application. DETAILED DESCRIPTION

[0066] This invention provides a multi-program coupled simulation method and system based on a net model, which solves the technical problem that existing multi-program coupled simulation methods are prone to numerical oscillations and insufficient convergence during data transmission, resulting in poor simulation efficiency.

[0067] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0068] Terminology Explanation:

[0069] 1. A panel element is a finite element used in the hydrodynamic analysis of mesh fabric to model and calculate a single mesh (usually a quadrilateral region enclosed by four nodes) as an independent stress element. Panel elements are used to more realistically reflect the overall hydrodynamic properties of the mesh fabric.

[0070] 2. The netting model is a theoretical model used to simulate the force characteristics of net structures (such as fishing nets and aquaculture nets) in fluids. This model treats the netting as being composed of many small panel elements, calculates the lift and drag of each panel element separately, and comprehensively reflects the hydrodynamic response of the entire netting.

[0071] 3. Grouping refers to a simplification method in numerical modeling that combines multiple physical meshes into a single equivalent numerical unit to reduce computational load and improve simulation efficiency. Grouping must ensure equivalence in mass, stiffness, and hydrodynamics.

[0072] 4. DISP Subroutine: A user-defined subroutine (Displacement) in the ABAQUS finite element software, used to control or assign values ​​to the displacement, velocity, and acceleration of specified nodes in the model, enabling data interaction with external programs.

[0073] 5. DLOAD Subroutine: A user-defined load subroutine in ABAQUS (Distributed Load) used to apply custom distributed loads, such as hydrodynamic loads, to elements in the model.

[0074] 6. URDFIL Subroutine: A user-defined results file subroutine in ABAQUS, used to read or output the calculation results of specific nodes or elements during the analysis process, enabling data exchange with external programs.

[0075] 7.FMI standard: Functional Mock-up Interface (FMI) is an international standard for model and data exchange between multi-physical field simulation software, supporting model integration and collaborative simulation between different simulation platforms.

[0076] 8.FMU: Functional Mock-up Unit (FMU) is a portable simulation model file encapsulated based on the FMI standard, containing model description, parameters, algorithms, etc., which can be directly called and integrated between different simulation software supporting FMI.

[0077] Please refer to Figure 1 , Figure 1 A step flowchart of a multi-program coupling simulation method based on a netting model is provided for the first embodiment of the application.

[0078] The application provides a multi-program coupling simulation method based on a netting model, which comprises:

[0079] Step 101: Obtain the original netting model and the finite element grid, and generate the node table and the element table according to the original netting model and the finite element grid by using a netting grouping method.

[0080] The finite element grid is a grid structure formed by dividing a continuous geometric model (such as the original netting model) into a large number of regular or irregular, interconnected "small calculation units" through "discretization" processing, and is the core calculation carrier of finite element analysis (FEA, Finite Element Analysis).

[0081] The original netting model is an initial geometric and physical property representation model of a netting structure (such as a net cage for aquaculture, an ocean protection net, a fishing net, etc.) in the digital simulation or design stage, and is a basic digital carrier for subsequent finite element analysis, hydrodynamic simulation and other engineering applications.

[0082] Further, step 101 can include the following sub-steps S11-S13:

[0083] Step S11: The original netting model is equivalently processed by using a netting grouping method, and the equivalent parameters after grouping are output;

[0084] Step S12: The equivalent parameters after grouping are used to assign geometric material properties to the finite element grid, and the finite element grid to which the geometric material properties are assigned is determined.

[0085] Step S13: The node table and the element table are extracted from the finite element grid to which the geometric material properties are assigned.

[0086] It should be noted that the construction of the netting dynamic model is very important in the hydrodynamic analysis of net cages. In real-world environments, due to the large number of meshes, modeling all netting structures would consume a great deal of computational resources, resulting in low computational efficiency. To improve computational efficiency, a netting grouping method is adopted to merge multiple meshes in the same area into an equivalent unit. The merging process must meet the following equivalence principles: (1) Mass equivalence: Under the same coverage area, the numerical netting and physical netting have the same mass; (2) Stiffness equivalence: Under the same tensile conditions, the stiffness of the merged netting is equal to that of the netting before merging; (3) Hydrodynamic load equivalence: The hydrodynamic loads on the numerical netting and physical netting under the same coverage area should be the same.

[0087] The equivalent parameters after grouping include the numerical mass diameter d. m Numerical elastic diameter d e Numerical hydrodynamic diameter d h Density S n To satisfy the equivalence between numerical and physical meshes, the physical mesh is d. p The diameter of the net ropes in the grouped net model is divided into three types, namely the numerical mass diameter d. m Numerical elastic diameter d e Numerical hydrodynamic diameter d h The relationship between the diameters of these three types of netting and the diameter of the netting in physical netting is as follows:

[0088] ;

[0089] in, The length of the half-mesh after grouping is L n With physical mesh half-mesh length L p The specific derivation process of the ratio is as follows:

[0090] Based on the mass equivalence assumption, it can be known that, for the same coverage area, the numerical mesh mass M... n With physical mesh quality M p Equal, that is

[0091] ;

[0092] ;

[0093] in, The density of the netting.

[0094] because d can be obtained m With d p The relationship is as follows:

[0095] ;

[0096] For traditional netting, And Then the content in the radical of the above formula can be simplified as:

[0097] ;

[0098] Then we can get:

[0099] ;

[0100] Further, for flexible netting, the netting only bears tensile force, and does not bear bending and compression load, so only the tensile stiffness is calculated. For numerical netting and physical netting with the same coverage area, the tensile stiffness can be expressed as follows:

[0101] ;

[0102] ;

[0103] Since, the simultaneous equations and formula can be obtained:

[0104] ;

[0105] where, is the elastic modulus of the netting material, which is an inherent property of the netting material, reflecting the proportional relationship between stress and strain in the elastic deformation stage, and determining the ability of the netting material to resist elastic tensile deformation; is the tensile stiffness of the physical netting; is the tensile stiffness of the numerical netting.

[0106] Further, for the Screen model, the hydrodynamic coefficient depends on the density, so the density is the same before and after the netting is grouped, which can ensure that the hydrodynamic load is the same. The density of the numerical netting and the physical netting can be obtained by the following formula:

[0107] ;

[0108] ;

[0109] where, Sn p is the density of the physical netting; Sn n is the density of the netting after grouping. From we can get:

[0110] .

[0111] Step 102, constructing a plurality of target mesh units according to the node table and the unit table.

[0112] It should be noted that since the Screen hydrodynamic model (original netting model) is calculated by taking the mesh of the netting as a force unit, and ABAQUS (finite element grid) is modeled by taking the net rope unit as a modeling unit, the Panel unit (target mesh unit) needs to be constructed before the calculation in ABAQUS, which corresponds to the net rope structure unit (net rope unit). Among them, the Panel unit is a module unit independent of ABAQUS, and its information is saved in the dynamic link library called by ABAQUS. The form of the Panel unit is as shown in Figure 2 Figure 2 n1, n2, n3, n4 in the formula are nodes included in the Panel unit, and vectors are diagonal vectors from n1 to n3 and from n2 to n4, respectively, is the normal vector of the Panel unit, and its solving method is as follows:

[0113]

[0114] Further, the unit and node information generated by the ABAQUS model (finite element grid) needs to be read during the construction process, and is rearranged into the Panel unit according to the rules. Each Panel unit obtained is a one-dimensional array with a length of 21, and the specific meaning of each array is shown in Table 1 (Panel unit parameter composition):

[0115] Table 1 Panel unit parameter composition

[0116]

[0117] Specifically, step 102 can include the following sub-steps S21-S27:

[0118] Step S21, taking each node in the node table as a corresponding initial node, and counting the number of units connected to each initial node in the unit table to determine the number of connected units corresponding to each initial node;

[0119] Step S22, taking any initial node corresponding to a number of connected units greater than a preset unit number threshold as an effective starting node, and constructing a plurality of unit pairs corresponding to each effective starting node according to a plurality of units connected to each effective starting node;

[0120] Step S23, extracting nodes from the plurality of unit pairs corresponding to each effective starting node, and outputting the end point nodes associated with each unit pair corresponding to each effective starting node; ​​​

[0121] Step S24, based on the associated end point nodes corresponding to each unit of each effective starting node, other unit retrieval is performed in the unit table to determine the other unit set corresponding to each effective starting node;

[0122] Step S25, based on the other unit set corresponding to each effective starting node, the shared node corresponding to each effective starting node is determined;

[0123] Step S26, a plurality of closed mesh units are constructed by using each effective starting node, and the end point node, the shared node, and the unit corresponding to the shared node corresponding to each effective starting node;

[0124] Step S27, the plurality of closed mesh units are de-duplicated to determine a plurality of target mesh units.

[0125] It should be noted that the process of constructing the Panel unit is shown in Table 2 (Panel unit construction process):

[0126] Table 2 Panel unit construction process

[0127]

[0128] The node table (Node table) represents the node list of the finite element mesh. Each entry contains the node number and the spatial coordinates (optionally containing the velocity). Physically represents the position of the net rope intersection or discretization point.

[0129] The element table (Element table) represents the rod / beam element list of the finite element mesh. Each entry contains the element number and the two node numbers connected by it. Physically represents a section of net rope between two nodes.

[0130] Node_max represents the total number of nodes, which is used to traverse all nodes.

[0131] N(1): The number of the current starting node, which is used as the starting point for the search of the mesh.

[0132] E(1)…E(4) represents the number of the maximum four elements connected to the starting node N(1). Physically, it is the net rope section from N(1).

[0133] nodes(E) represents the end node set of a given element E, which is generally two node IDs.

[0134] Combination [E(n1), E(n2)]: A group of candidate “diagonal supports” or “boundary candidates” is formed by randomly selecting two elements connected to N(1), and there are six possibilities.

[0135] N(2), N(3) are the other end point nodes of E(n1), E(n2) respectively. Physically, they are the adjacent nodes reached by the two ropes extending from N(1).

[0136] X(1) represents the other cell set connected with N(2) and not containing E(n1), E(n2). Physically, it is the optional edge continuing to extend from N(2) along the rope.

[0137] X(2) represents the other cell set connected with N(3) and not containing E(n1), E(n2). Physically, it is the optional edge continuing to extend from N(3) along the rope.

[0138] E(n3), E(n4) represent a pair of cells taken from X(1), X(2) respectively, which are connected with N(2), N(3) and share a common node with each other.

[0139] N(4) represents the common node of E(n3) and E(n4). Physically, it corresponds to the fourth corner of the mesh hole.

[0140] Panel cell represents the quadrilateral mesh cell (target mesh cell) surrounded by four nodes [N(1), N(2), N(3), N(4)] and four cells [E(n1), E(n2), E(n3), E(n4)], which is the basic force calculation unit of the Screen model.

[0141] De-duplication means that the same mesh may be repeatedly discovered by multiple starting nodes or combinations, and needs to be de-duplicated with node set or ordered key as the uniqueness criterion.

[0142] Normalized order / ordered node number represents the node order obtained after the order of Panel vertices is unified (such as counterclockwise and fixed starting point rule) to ensure normal consistency and data consistency.

[0143] Normal vector, center point coordinates, center point velocity, coverage area represent the geometric and kinematic characteristics of Panel, which are used for inflow angle calculation, force direction and size calculation and load application respectively.

[0144] Specifically, the node table and the element table are taken as inputs of the process of constructing the target mesh element, wherein the node table contains the number and initial coordinates (if necessary, containing velocity, for central point interpolation) of each node; the element table contains the number and two nodes connected (beam / rod element) of each element. Then, each node is taken as a "starting node" in turn. Let the current starting node be N(1), and traverse N(1)=1…Node_max. Find all the elements connected with N(1) in the element table, and mark them as E(1), E(2), E(3), E(4) (if there are less than 4, skip the starting node or process according to the boundary rule). Mark the end node set of each E(k) as nodes(E(k)). Take any two from {E(1), E(2), E(3), E(4)} to form a pair, and there are 6 combinations. Mark the nth combination as [E(n1), E(n2)], n=1…6. For the current combination [E(n1), E(n2)]: determine the other end node of the two elements except N(1), and mark them as N(2)=nodes(E(n1))\{N(1)}, N(3)=nodes(E(n2))\{N(1)}.

[0145] Further, search for other elements connected with N(2) and N(3) respectively in the element table, and get two sets: X(1)={elements connected with N(2)}\{E(n1), E(n2)}, X(2)={elements connected with N(3)}\{E(n1), E(n2)}; enumerate the element pairs of X(1) and X(2), and find a pair of elements with "common nodes": if X(1)[i] and X(2)[j] share the same node N(4), then let E(n3)=X(1)[i] and E(n4)=X(2)[j], and the common node is N(4). After finding the above pair, a closed Panel element (a mesh hole) can be formed by four elements [E(n1), E(n2), E(n3), E(n4)] and four nodes [N(1), N(2), N(3), N(4)]. Remove the duplicate Panels from all Panel candidate sets obtained by different starting nodes and different combinations; remove or process according to the given tolerance for the boundary or degenerate cases (cannot be closed into quadrilateral / colinear / overlap). For each Panel retained, calculate and store its normalized data (such as sorted node number, normal vector, central point coordinates and velocity, coverage area, etc.) according to subsequent needs, and organize it into a one-dimensional array with a length of 21 according to Table 1. In the step of finding all the elements connected with N(1) in the element table, it is assumed that the regular mesh node is usually connected with 4 rods / beams; if the connection degree ≠4 in actual engineering, the corresponding boundary and fault tolerance strategy needs to be used.

[0146] In the present embodiment, in the node table (containing node number, initial coordinates, etc.) and the element table (containing element number and connected node number), all nodes are first traversed as starting nodes, the connected elements of each starting node are found from the element table, the starting nodes with four connected elements are screened out (less than four are skipped), and the connected element set corresponding to each valid starting node is output; for the connected element set of each valid starting node, six kinds of element pairs are formed by combining the elements two by two, and the six kinds of element pairs corresponding to each starting node are output; for each kind of element pair, another endpoint node in addition to the starting node is extracted from the two elements to obtain two endpoint nodes, and the two endpoint nodes corresponding to each element pair are output; for the two endpoint nodes, other elements connected to each other and excluding the current element pair are retrieved from the element table to obtain two element sets, and the two element sets are output; the element pairs in the two element sets are enumerated, and the element pairs sharing the same node are found, and the closed Panel element is formed by the starting node, the two endpoint nodes, the common node and the corresponding four elements, and the Panel candidate set is output; the Panel candidate set is de-duplicated to eliminate duplicate Panels and boundary and degenerate cases (such as unable to close into quadrilateral, collinear, coincident, etc.), and the screened Panel element is output; for each Panel element after screening, its normalized data (such as sorted node number, normal vector, center point coordinates and speed, coverage area, etc.) is calculated and stored, organized into a one-dimensional array with a length of 21, and the sorted Panel element data is output.

[0147] Step 103, calculate the hydrodynamic load of each target mesh element.

[0148] It should be noted that the hydrodynamic load includes lift and drag. In the Screen model, each mesh element (Panel element) of the netting is taken as an independent force element. The average drag and lift on the element depend on the model solidity of the netting, the Reynolds number and the direction and speed of the incident flow. The incident angle θ of the flow is the angle between the incident velocity and the normal direction of the Panel element, as shown in the Panel element force decomposition diagram. The drag direction is the same as the flow direction, the lift direction is perpendicular to the flow direction, and the plane formed by the lift and drag directions is perpendicular to the plane of the Panel element. The lift-drag coefficient is determined according to the experimental data of the netting in steady flow, and is related to the solidity S of the netting. The physical meaning of the overall solidity of the netting represents the ratio of the projected area of the solid netting to the area of the mesh, and for an ideal knotless square netting, the solidity can be expressed as: p Figure 3 The Panel element force decomposition diagram is shown. The drag direction is the same as the flow direction, the lift direction is perpendicular to the flow direction, and the plane formed by the lift and drag directions is perpendicular to the plane of the Panel element. The lift-drag coefficient is determined according to the experimental data of the netting in steady flow, and is related to the solidity S of the netting. The physical meaning of the overall solidity of the netting represents the ratio of the projected area of the solid netting to the area of the mesh, and for an ideal knotless square netting, the solidity can be expressed as: n

[0149] ;

[0150] where d​​w D is the diameter of the netting, L is the half length of the panel element, and V is the relative velocity of the water flow. Figure 4 The parameters of the netting are shown in the schematic diagram. For some Screen models, the solidity can be expressed in the following simplified form:

[0151] ;

[0152] Further, in calculating the hydrodynamic load of the Panel element, the relative water flow velocity and direction at the center point of the Panel element are taken. The lift and drag on each Panel element are shown in the schematic diagram of the force decomposition of the Panel element, and their calculation formulas are as follows: Figure 3

[0153] ;

[0154] ;

[0155] wherein, and are the drag and lift of the target mesh element, respectively; is the sea density; and are the drag coefficient and lift coefficient of the target mesh element, respectively; is the instantaneous velocity of the water flow relative to the center point of the target mesh element; is the coverage area of the target mesh element.

[0156] ;

[0157] wherein, r is the water flow velocity decay rate, which is because the water flow passing through the upstream netting will have a decay effect on the downstream velocity, and the decay rate can be obtained by the following formula:

[0158] ;

[0159] Further, for the values of and in the Screen model, the following method is used to express, wherein, and are the drag coefficient and lift coefficient of the Panel element in the Screen model, and R e is the Reynolds number.

[0160] ;

[0161] , ;

[0162] ;

[0163] ​ ;

[0164] ;

[0165] ;

[0166] ;

[0167] ;

[0168] ;

[0169] For the present model, the solidity S n and the Reynolds number R e need to satisfy the following conditions

[0170] ;

[0171] wherein, is the Reynolds number dependent drag coefficient of the cylinder; is the relative flow velocity; is the kinematic viscosity coefficient of the fluid; the incident angle θ p of the water flow; is the normal force coefficient; is the tangential force coefficient; is the reference drag coefficient; is the tangential force coefficient when the normal angle of the Panel unit is ; is the intermediate lift coefficient; is the drag coefficient of the Panel unit in the Screen model when the incident angle of the water flow is ; is the lift coefficient of the Panel unit in the Screen model when the incident angle of the water flow is .

[0172] It is worth mentioning that, please refer to Figure 5 , the basic flow of the ABAQUS to calculate the hydrodynamic load of the netting is shown in Figure 3 (the logic flow chart of the netting simulation), wherein the steps performed by the external dynamic link library are in the red dashed box.

[0173] Step 104, based on the external multi-physical field simulation program, the hydrodynamic load of each target mesh unit is simulated by multi-program coupling, and the coupling simulation result is output.

[0174] Specifically, step 104 can include the following sub-steps S41-S49:

[0175] Step S41, the load application subprogram converts the hydrodynamic load of each target mesh unit into a distributed load according to the unit type matched with the netting material;

[0176] Step S42, the distributed load is applied to the corresponding net string unit according to the topological correspondence of each target mesh unit and each net string unit corresponding to the finite element grid, and the net string unit with multiple applied loads is determined;

[0177] Step S43, the third-order polynomial interpolation is performed on the reference point motion information output by the external multi-physical field simulation program at the current time, and the smooth motion parameters of the constraint nodes corresponding to the original netting model are determined;

[0178] Step S44, based on the smooth motion parameters of the constraint nodes, the distributed load corresponding to each target mesh unit, and the mechanical properties of each net string unit with applied load, the constraint reaction force of the constraint node and the structural dynamics response of each target mesh unit are output;

[0179] Step S45, the current analysis time corresponding to the finite element grid and the current running time corresponding to the external multi-physical field simulation program are counted;

[0180] Step S46, if the current analysis time is greater than the current running time, the external multi-physical field simulation program is used to calculate new reference point motion information at the current time according to the constraint reaction force;

[0181] Step S47, compare the current running time with the preset simulation time;

[0182] Step S48, if the current running time is less than the preset simulation time, jump to execute the step of performing third-order polynomial interpolation on the reference point motion information output by the external multi-physical field simulation program at the current time to determine the smooth motion parameters of the constraint nodes corresponding to the original netting model until the current running time is greater than or equal to the preset simulation time;

[0183] Step S49, according to the multiple reference point motion information at the current time determined when the current running time is greater than or equal to the preset simulation time, the multiple hydrodynamic loads of each target mesh unit, the multiple structural dynamics responses, and the multiple constraint reaction forces of the constraint nodes, a coupling simulation result is generated.

[0184] Optionally, it further comprises:

[0185] If the current analysis time is less than or equal to the current running time, adjust the spatial posture of the corresponding target mesh unit according to the structural dynamics response of each target mesh unit to determine multiple new target mesh units;

[0186] Calculate the hydrodynamic load of each new target mesh unit;

[0187] The jump execution adopts a load application subroutine to convert the hydrodynamic load of each target mesh unit into a distributed load according to the mesh material matching unit type until the current analysis time is greater than the current running time.

[0188] It should be noted that the net model constructed in ABAQUS is mainly divided into two parts, one is the net model, and the other is the support model. The mass and geometric properties of the net are determined by the net grouping method, and the unit type of the net is set according to the net of different materials. For example, for metal net, this kind of net itself has a certain bending strength, beam element can be selected to construct the model, and the unit type code is B31; for flexible net made of high polymer material, truss element can be selected for modeling, and the unit type code is T3D2. When loading the load for these two models, it should be noted that the DLOAD subroutine can apply linear load to the beam element, and load body load to the truss element, so when modeling specifically for different elements, the appropriate load type should be selected according to the properties of the element. For the support structure, the main purpose of this part is to transfer the load on the net to the reference point, and its inertia property does not participate in the calculation of the model, so when constructing the model, beam element is used to model this part of the element, and the mass of the material is set to 0.1 kg / m3 to achieve the purpose of ignoring the mass effect in numerical calculation. For its elastic modulus, it can be set to the elastic modulus of steel, which is 209GPa. Figure 6 ABAQUS constructs the net and its support structure, which shows the model of part of the net and the support structure in the ABAQUS model, the red part is the support structure, and the black net line is the net model, Figure 7 ABAQUS constructs the net and its support structure, which shows the deformation of the net after being subjected to load.

[0189] Further, ABAQUS needs to communicate data with external programs through subprograms, and the application realizes real-time communication of ABAQUS and external multi-physical field simulation programs in time sequence by writing subprograms and supporting dynamic link library programs for secondary development of ABAQUS, and solves the problems of data communication and step-by-step cooperation in coupled calculation. Among them, DISP (Displacement, displacement control), DLOAD (Distributed Load, load application) and URDFIL (User Results Definition File, result reading) three core subprograms are adopted, combined with Windows API (Windows Application Programming Interface, Windows application programming interface) and shared memory technology, to establish a two-way communication bridge between ABAQUS and external programs, and then solve the problems of net cloth hydrodynamic force and device overall motion in the floating net cage device. DISP is used to specify the displacement constraint of a node or node set; DLOAD is used to apply distributed load (such as pressure, body force, etc.) on the element or element surface; URDFIL is used to customize variables and data output to the result file (.fil).

[0190] Further, in the ABAQUS net cloth model, a constraint node (reference point) is set, and the displacement, velocity and acceleration of the node are controlled by the DISP subprogram to keep consistent with the reference point in the external program, such as Figure 8 The net cloth finite element model constructed in ABAQUS. The net cloth hydrodynamic load will be loaded as an external force into the system, but this external load is not directly loaded into the multi-body motion system in the external multi-physical field simulation program, but first acts on the net cloth, and the net cloth moves under the action of force and generates internal force, which is transmitted to the constraint node through the finite element structure. The constraint node will generate a corresponding constraint reaction force due to the control of the motion behavior of the external multi-physical field simulation program, and the constraint reaction force of the node can be read through the ABAQUS subprogram URFIL and transmitted to the external multi-physical field simulation program as an external force to load into the platform motion system. Since the constraint reaction force transmitted to the external multi-physical field simulation program is obtained through the internal force generated by the motion response, the constraint reaction force contains the influence of inertia force, and thus the coupling of the inertia characteristics of the net cloth and the external multi-physical field simulation program is realized.

[0191] Further, please refer to Figure 9In the process of coupling the external multi-physical field simulation program and ABAQUS, data communication and step coordination are also achieved through dynamic link library and the API of Windows system. In the initialization process, ABAQUS reads the virtual grid data and matches with the finite element units and nodes, and after confirming the consistency, the initialization is completed, and ABAQUS enters into standby state, waiting for the external multi-physical field simulation program to send a calculation instruction after the initialization is completed. ABAQUS and the external multi-physical field simulation program each set a reference point in the model (generally, the position of the device at zero time of the device model constructed by the external multi-physical field simulation program is located at the coordinate origin, which is the center of the waterline surface of the platform in the present application), and the motion conditions (including 6 degrees of freedom displacement, velocity and acceleration) of the reference point in the ABAQUS model and the external multi-physical field simulation program model are completely consistent. The external multi-physical field simulation program simultaneously initializes and uploads the displacement, velocity and acceleration information (i.e. the current motion information of the reference point) of the reference point to the shared memory, and sends a command to inform ABAQUS system that the update is completed and the calculation can be performed. After receiving the signal sent by the external multi-physical field simulation program, ABAQUS enters into the calculation state, starts to calculate the motion response of the netting under the action of the water dynamic load and the inertia load generated by its own motion, and transmits the load to the reference point through the beam element connected with the reference point. It should be noted that since ABAQUS uses a variable step calculation method in the calculation, i.e. ABAQUS sets the calculation step according to its own convergence characteristics, therefore, when setting the working condition, the ABAQUS time step should not be greater than the external multi-physical field simulation program time step, and in fact, when judging whether to be coupled with the external multi-physical field simulation program, it is confirmed by judging whether the current ABAQUS time step is greater than or equal to the current external multi-physical field simulation program time step, i.e. the current analysis time T A ≥ current running time T MABAQUS sends a signal to the external multi-physics simulation program that the load has been uploaded and the next time step calculation can be performed to complete the coupling. This coupling method allows ABAQUS to calculate without limiting its variable step size, releasing the solving performance of ABAQUS during calculation and improving the convergence of the model. Among them, the external multi-physics simulation program refers to the model / software independent of ABAQUS, for example, 1) self-programmed model / software, such as self-developed model / software based on Fortran, C++, Modelica, etc. Programming languages; 2) open source simulation software, such as OpenFAST (Open-source Simulation Tool for Advanced Wind Turbine Systems), WEC-Sim (Wave Energy Converter Simulator); 3) commercial simulation software, such as OrcaFlex (OrcaFlex Offshore Dynamics Simulation Software).

[0192] Specifically, the hydrodynamic load of the Panel unit is mapped to the finite element unit (netting unit), and is applied through the DLOAD subroutine: the Beam unit (B31) applies a line load, and the Truss unit (T3D2) applies a body load, to obtain the netting unit with applied load, and the equivalent diameter d of the netting group after considering the group is h For load calculation. Then, the external program outputs the reference point motion information (displacement U, velocity V, acceleration A), and since ABAQUS uses variable step size and the external program uses fixed step size, interpolation processing is needed, and a third-order polynomial is used to fit the motion parameters between two time steps.

[0193] Further, the displacement, velocity, and acceleration of the constraint node are controlled through the DISP subroutine, and the displacement, velocity, and acceleration must be transmitted simultaneously to avoid ABAQUS calculation speed mutation leading to non-convergence, and the constraint node motion is completely consistent with the reference point motion in the external program. The netting produces structural dynamic response under the excitation of hydrodynamic load and constraint motion, and the inertial effect is automatically included through the ABAQUS structural dynamic equation, and the internal force of the structure is transmitted to the constraint node through the finite element grid.

[0194] Further, the constraint reaction force of the constraint node is read through the URDFIL subroutine, wherein the constraint reaction force has already included the influence of the inertial force, realizing the coupling of the netting and the inertial characteristics of the external program.

[0195] Finally, it is judged whether T A ≥T MABAQUS current time ≥ external program current time) determines the coupling opportunity, ABAQUS can keep its variable step length characteristics, improve the solving performance and convergence. When T A ≥ T M , ABAQUS sends a signal to the external program that the load has been uploaded, and the next time step calculation can be performed. Using Windows API and shared memory technology to realize two-way communication, through dynamic link library (DLL) to execute Panel unit construction, hydrodynamic load calculation and other steps. The external multi-physical field simulation program receives the constraint reaction force data, loads the constraint reaction force as an external load into the platform motion system, calculates the reference point motion information (T M = T M + ΔT), and the external program uploads the new motion information to the shared memory and sends a signal to ABAQUS system that the update is complete and the calculation can be performed. Repeat the above steps until T M reaches the preset simulation time T max , output the integrated net deformation history (consisting of all structural dynamic responses generated by the iteration process), Panel unit hydrodynamic load time history (consisting of all hydrodynamic loads generated by the iteration process), constraint reaction force time history data (consisting of all constraint reaction forces generated by the iteration process), and system motion response data (consisting of all current time reference point motion information generated by the iteration process), thereby obtaining the complete coupling simulation results (i.e. coupling simulation results).

[0196] It should be noted that ABAQUS can only assign displacement information when calling the DISP subroutine to assign motion information to the reference point, and ABAQUS will calculate the current time node speed and acceleration on its own, but this calculation has a certain probability to cause the model in ABAQUS to have a sudden change in speed, i.e. infinite acceleration, which makes the calculation not converge, especially in the net structure involved in this study, the node motion is relatively loose, and this non-convergence is particularly prominent. Therefore, when assigning DISP to ABAQUS, the displacement, velocity and acceleration of the reference point need to be transmitted to ABAQUS to solve the above problem. At this time, due to the previous coupling method, i.e. ABAQUS variable step length, the external multi-physical field simulation program fixed step length will bring the problem of how to determine the displacement, velocity and acceleration of the ABAQUS model corresponding to the external multi-physical field simulation program time step. In this patent, a third-order polynomial is defined to fit the displacement, velocity and acceleration of ABAQUS between two time steps of the external multi-physical field simulation program, and the specific method is as follows:

[0197] The reference point acceleration is defined as follows:

[0198] ;

[0199] wherein a0, a1, a2, a3 are undetermined coefficients, t is time, the velocity and displacement of the reference point satisfy the integral formula, and the following formula is obtained:

[0200] ;

[0201] ;

[0202] wherein V(t) is the velocity of the reference point, U(t) is the displacement of the reference point, C1 and C2 are undetermined constants. The displacement, velocity and acceleration of the previous time output by the external multi-physical field simulation program are defined as U1, V1, A1, and the displacement, velocity and acceleration of the next time output by the external multi-physical field simulation program are defined as U2, V2, A2, and the step size of the external multi-physical field simulation program is Δt. U1, V1, A1, U2, V2, A2 are substituted into the formula, the formula and the formula, and the following formula is obtained:

[0203] ;

[0204] The values of a0, C1 and C2 are determined in the above formula, and the above formula is simplified and linearized to obtain:

[0205] ;

[0206] wherein , , ,

[0207] The above problem is converted into solving the coefficient vector Therefore, it can be solved by the following formula:

[0208] ;

[0209] wherein is a coefficient matrix containing each power term of the time step Δt; is a vector of boundary conditions and known quantities; after obtaining the coefficient vector, the displacement, velocity and acceleration of the corresponding time in ABAQUS can be obtained by , and

[0210] In this embodiment, the lift and drag of the Panel unit are converted into distributed loads, which are applied to the corresponding net rope unit according to the topological correspondence relationship between the Panel and the net rope, to obtain the net rope unit subjected to the load (the distributed load is the core external force input for the stress analysis of the net structure); the current time reference point motion information output by the external multi-physical field simulation program is obtained through the DISP subroutine of ABAQUS (this information is used as the initial value of the next time reference point motion information in the next time step of the external multi-physical field simulation program, and the current time reference point motion information is updated in the next time step of the external multi-physical field simulation program) to realize the coupling between the external multi-physical field simulation program and ABAQUS. M ​The third-order polynomial interpolation method is used to determine the smooth motion parameters (displacement, velocity, acceleration) of the constraint nodes corresponding to the Screen model; the distributed load on the net element under the applied load (i.e. the transformed form of the hydrodynamic load of the Panel element), the synchronous motion parameters of the constraint nodes, and the mechanical properties of the net element are combined to calculate the constraint reaction force of the constraint node, and the structural dynamic response (such as deformation and internal force distribution) of the Panel element is obtained, and the deformation of the net cloth in the structural dynamic response directly adjusts the spatial posture of each Panel element (including the normal vector angle and the center point coordinate), so that the state of the Panel element changes; the constraint reaction force data is transmitted to the external multi-physical field simulation program through the URDFIL subroutine of ABAQUS and the shared memory technology; if the current analysis time T A is less than the current iteration time T M , the following process is repeated: first, the motion information of the fixed reference point is obtained through the DISP subroutine to maintain the constraint boundary, then the spatial posture of each Panel element is adjusted (the normal vector and the center point coordinate are updated) based on the structural dynamic response (deformation) of the Panel element obtained in the last round of calculation, and the hydrodynamic load (lift, drag and normal vector) of the Panel element is recalculated based on the updated Panel element, then the new hydrodynamic load is converted into a distributed load by the DLOAD subroutine and applied to the corresponding net element, and then the constraint reaction force and the structural dynamic response (further correction of deformation and Panel element state) of the Panel element are recalculated based on the new distributed load and the motion parameters of the constraint node, and finally the updated constraint reaction force is transmitted through the URDFIL subroutine; in this way, the spatial posture of the Panel element, the hydrodynamic load of the Panel element, the distributed load of the net element, and the constraint reaction force of the constraint node are continuously updated until T A >T M ; if T A >T M , the external multi-physical field simulation program loads the converged constraint reaction force, calculates the motion response and updates the reference point motion information, then matches the motion state of each Panel element after the updated motion information is interpolated by the third-order polynomial, drives the net cloth to produce deformation corresponding to the motion state, and forms new state Panel elements; based on the new state Panel elements, the new basic data of each Panel element based on the Screen model, such as lift, drag and normal vector, are recalculated, and the DLOAD subroutine is used again to convert the distributed load according to the material matching of the net cloth to apply it to the corresponding net element, and T M =T M +ΔT, which drives the net cloth to a new round of stress analysis and forms a closed loop coupling; when T M ≥Tmax When the preset simulation duration is reached, the constraint reaction forces of all the constraint nodes, the constraint reaction force data of the external program, and the system motion data (i.e., the reference point motion information in the iteration process) are integrated to obtain the final coupling simulation result.

[0211] It is worth mentioning that the present application realizes efficient modeling of the net structure and accurate calculation of the hydrodynamic load, supports real-time coupling with a multi-physical field simulation platform, and improves the simulation efficiency and accuracy of complex marine equipment. The experimental and simulation results are highly consistent, verifying the effectiveness and practicality of the present application.

[0212] For net dynamics verification, the present application will use ABAQUS to model the experimental model in previous research, and compare the simulation results with the experimental data to verify the feasibility and accuracy of ABAQUS for net dynamics simulation. The experimental model of the present application uses the simulation experiment conducted by Lee et al. The experimental model is shown in the simulation net schematic diagram, which is a square net with a mesh length L = 100 mm, and the horizontal and vertical directions are meshed. The displacements of the four corners of the net are fixed, and 1.5 kg, 0.5 kg and 0.7 kg weights are hung at F1, F2 and F3 positions, and the motion and convergence of the model are observed. The net material is nylon, and its basic properties are shown in Table 3. Since the original experiment only gives the stiffness of 15000 N / m, and the Young's modulus of the model needs to be given in the calculation of ABAQSU, after conversion, the Young's modulus value is 119.37 GPa. Figure 10

[0213] Table 3 Physical properties of the net

[0214]

[0215] Since the calculation step (step) adopted is the "Dynamic, Implicit" mode, the simulation is actually a dynamic change process. As shown in Figure 11 , the final deformation state of the net model and the experimental deformation state are shown. It can be seen that the deformation result of the simulation is basically the same as that of the experiment. As shown in Figure 12 , the support reaction force of the fixed end of the upper left and upper right corners changes with time. The net is subjected to gravity from the beginning, and after several oscillations for 12 s, it tends to be stable, and the support reaction force of the upper left and upper right corners along the z-axis direction is 6.19 N and 7.05 N, respectively. Since the model is symmetric about the x-axis, the z-axis direction support reaction force of the lower left and right corners is the same as that of the upper left and right corners. The total support reaction force is 26.48 N, which is the same as the actual gravity.

[0216] ​As a comparison of technical effects, reference can be made in combination with the prior art. In the prior art, the traditional Morison formula method regards the net rope as an elongated rod structure for water dynamic calculation, and cannot accurately reflect the overall fluid mechanics characteristics of the net structure, resulting in a large deviation between the calculation results and the actual stress condition. The Screen model is adopted in the present application, the net is regarded as an independent Panel stress unit, the lift and drag force characteristics of the net in the fluid can be more realistically simulated, and the accuracy of the water dynamic load calculation is significantly improved.

[0217] In the prior art, commercial finite element software such as ABAQUS mainly models based on the net rope unit, while the Screen water dynamic model needs to take the net Panel unit as the calculation object, and there is a lack of effective conversion mechanism between the two. The Panel unit automatic generation algorithm based on the node and unit topological relationship is proposed in the present application, which can automatically convert the net rope unit model into the Panel unit model, and solves the technical problem of mismatching modeling methods.

[0218] In the prior art, when the net-cum-float-fluid multi-physical field coupling simulation is carried out, there is a lack of effective data communication mechanism between different simulation software, especially when the ABAQUS variable step length is inconsistent with the fixed step length of the external program, numerical instability or calculation non-convergence problems are prone to occur. The real-time bidirectional data exchange and step-by-step cooperation of ABAQUS and external simulation programs are realized through the self-developed subprograms (DISP, DLOAD, URDFIL) combined with Windows API and shared memory technology. In the prior art, when the system-level simulation is carried out, the net load is often simplified as a concentrated force directly applied to the float, and the inertia characteristics and structural dynamics response of the net itself are ignored, resulting in inaccurate system dynamics analysis results. The structural internal force generated by the stress of the net is transmitted to the reference point through the finite element structure by the constraint node and load transmission mechanism in the present application, and the inertia force influence is naturally included in the constraint reaction force, realizing the real coupling of the inertia characteristics of the net and the system. In the prior art, when the ABAQUS variable step length is coupled with the fixed step length of the external program, directly transmitting the motion information at discrete time points is easy to cause velocity mutation and acceleration infinity, causing calculation non-convergence, especially in the net-like flexible structure. The third-order polynomial interpolation method is adopted in the present application to smoothly fit the displacement, velocity and acceleration between two time steps, effectively avoiding numerical oscillation and convergence problems. By solving the above technical problems, the present application provides a complete technical solution for accurate modeling, efficient simulation and system-level coupling analysis of large marine net structures, and has important engineering application value.

[0219] Specifically, refer to Figure 13The application is based on the node and unit topological relationship of the net rope unit, four units connected with each node are searched, recombined into a Panel unit according to specific rules, a one-dimensional array with a length of 21 is established to store the Panel unit information, the automatic conversion from the net rope unit model to the Panel unit model can be realized, and the modeling method mismatch problem is solved. A ≥T M The criterion controls the coupling time sequence, thereby solving the multi-software platform data communication difficulty and time step mismatch problem, and ensuring the stability of the coupled calculation. The constraint node is set in ABAQUS, the motion thereof is controlled through the DISP subroutine to be synchronized with the reference point of the external program, the netting load is transmitted to the constraint node through the finite element structure to generate a constraint counterforce, the counterforce naturally contains the inertial force effect and is transmitted to the external program, the real coupling of the netting and the inertial characteristics of the system can be realized, and the precision loss of the traditional concentrated force simplification method is avoided. Meanwhile, the application defines a three-order polynomial expression of the reference point acceleration , the polynomial coefficients are solved through the known two time step boundary conditions, the smooth interpolation of the displacement, velocity and acceleration is realized, thereby effectively avoiding the velocity mutation and numerical oscillation problem in the flexible net-like structure, and ensuring the calculation convergence. According to the material characteristics of the netting, different unit types are selected: the metal netting adopts a Beam unit (B31) to bear the bending, the flexible netting adopts a Truss unit (T3D2) to bear the tension only, and the support structure adopts a beam unit with a mass of 0.1 kg / m³ to transmit the load, the calculation precision and convergence of the finite element model can be improved, and the mechanical characteristics of different material nettings can be adapted. In addition, the application standardizes the Panel unit information into a 21-bit one-dimensional array, contains the unit number, node number, normal vector, center point coordinate, velocity and other key parameters, is convenient for the dynamic link library calling and data management, thereby improving the data processing efficiency and facilitating the information exchange between different software modules.

[0220] Compared with the prior art, the Panel unit method of the Screen model is adopted instead of the traditional Morison formula, the mesh is taken as an independent stress unit for hydrodynamic calculation, and the lift and drag characteristics of the netting and the fluid flow effect can be accurately reflected. The seamless coupling of the variable step of ABAQUS and the fixed step of the external multi-physical field simulation program is realized for the first time by combining the DISP, DLOAD and URDFIL subprograms developed independently with the Windows API and shared memory technology, and the numerical instability problem caused by the difficulty of data communication between different simulation software and the mismatch of time steps in the prior art is solved. Especially, the third-order polynomial interpolation method and the constrained node load transfer mechanism adopted in the application not only ensure the smoothness of the motion information transmission, but also realize the real coupling of the inertia characteristics of the netting and the overall dynamics of the system, compared with the processing method of simplifying the netting load as a concentrated force in the prior art, the accuracy of the system-level dynamics analysis is fundamentally improved.

[0221] In the embodiment of the application, a multi-program coupling simulation method based on a netting model is provided, an original netting model and a finite element grid are obtained, a node table and an element table are generated according to the original netting model and the finite element grid by using a netting grouping method, a plurality of target mesh units are constructed according to the node table and the element table, the hydrodynamic load of each target mesh unit is calculated, multi-program coupling simulation is performed based on an external multi-physical field simulation program and the hydrodynamic load of each target mesh unit, and the coupling simulation result is output. Based on the above scheme, the data organization structure of the nodes and the elements is optimized by the netting grouping method, the hydrodynamic load calculation of the target mesh unit is more in line with the actual stress state, high-quality basic data input is provided for multi-program coupling simulation, the numerical oscillation problem caused by data transmission mismatch in the existing multi-program coupling simulation is effectively solved, and the overall simulation efficiency is significantly improved.

[0222] Please refer to Figure 14 , Figure 14 The structure block diagram of a multi-program coupling simulation system based on a netting model is provided for the second embodiment of the application.

[0223] The multi-program coupling simulation system based on a netting model provided by the application comprises:

[0224] The obtaining module 1401 is configured to obtain an original netting model and a finite element grid, generate a node table and an element table according to the original netting model and the finite element grid by using a netting grouping method.

[0225] The construction module 1402 is configured to construct a plurality of target mesh units according to the node table and the element table.

[0226] The calculation module 1403 is configured to calculate the hydrodynamic load of each target mesh unit.

[0227] The simulation module 1404 is configured to perform multi-program coupling simulation based on an external multi-physical field simulation program and the hydrodynamic load of each target net element, and output a coupling simulation result.

[0228] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described system and modules can refer to the corresponding processes in the foregoing method embodiments, which will not be described here.

[0229] The embodiment of the present application further provides a computer device, which comprises a memory and a processor, and the memory stores a computer program; when the computer program is executed by the processor, the processor executes the steps of the multi-program coupling simulation method based on the net element model according to any one of the foregoing embodiments.

[0230] The embodiment of the present application further provides a computer readable storage medium, which stores a computer program / instruction; when the computer program / instruction is executed by a processor, the steps of the multi-program coupling simulation method based on the net element model according to any one of the foregoing embodiments are implemented.

[0231] The embodiment of the present application further provides a computer program product, which comprises a computer program / instruction; when the computer program / instruction is executed by a processor, the steps of the multi-program coupling simulation method based on the net element model according to any one of the foregoing embodiments are implemented.

[0232] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than limit them; those skilled in the art should understand that: the technical solutions recorded in the foregoing embodiments can still be modified, or some technical features can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method of multi-procedure coupling simulation based on a net model, characterized by, The method comprises the following steps: obtaining an original net model and a finite element mesh, and generating a node table and an element table according to the original net model and the finite element mesh by using a net grouping method; constructing a plurality of target net elements according to the node table and the element table; calculating the hydrodynamic load of each target net element; performing multi-program coupling simulation based on an external multi-physical field simulation program and the hydrodynamic load of each target net element, and outputting a coupling simulation result.

2. The mesh model based multi-procedure coupling simulation method of claim 1, wherein, The method of generating a node table and an element table according to the original net model and the finite element mesh by using a net grouping method comprises the following steps: performing equivalent processing on the original net model by using a net grouping method, and outputting equivalent parameters after grouping; assigning geometric material properties to the finite element mesh by using the equivalent parameters after grouping, and determining the finite element mesh with geometric material properties; extracting a node table and an element table from the finite element mesh with geometric material properties.

3. The mesh model based multi-procedure coupling simulation method of claim 1, wherein, The method of constructing a plurality of target net elements according to the node table and the element table comprises the following steps: taking each node in the node table as a corresponding initial node, and determining the number of connected elements of each initial node by counting the number of connected elements of each initial node in the element table; taking any initial node with a number of connected elements greater than a preset element number threshold as an effective starting node, and constructing a plurality of element pairs corresponding to each effective starting node according to a plurality of elements connected to each effective starting node; extracting nodes from a plurality of element pairs corresponding to each effective starting node, and outputting end point nodes associated with each element pair corresponding to each effective starting node; performing other element retrieval in the element table based on the end point nodes associated with each element pair corresponding to each effective starting node, and determining a set of other elements corresponding to each effective starting node; determining shared nodes corresponding to each effective starting node based on the set of other elements corresponding to each effective starting node; constructing a plurality of closed net elements by using each effective starting node, end point nodes, shared nodes, and elements corresponding to the shared nodes corresponding to each effective starting node; determining a plurality of target net elements by removing duplicates from a plurality of closed net elements.

4. The mesh model based multi-procedure coupling simulation method of claim 1, wherein, The method of performing multi-program coupling simulation based on an external multi-physical field simulation program and the hydrodynamic load of each target net element, and outputting a coupling simulation result comprises the following steps: converting the hydrodynamic load of each target net element into distributed load by using a load application sub-program according to the element type matching the net material; applying the distributed load on corresponding net elements by matching the topology of each net element corresponding to each target net element and the finite element mesh, and determining a plurality of net elements with applied load; determining the smooth motion parameters of the constraint nodes corresponding to the original net model by performing third-order polynomial interpolation on the reference point motion information output by the external multi-physical field simulation program at the current time. outputting constraint reaction forces of the constraint nodes and structural dynamic responses of the target mesh units based on the smooth motion parameters of the constraint nodes, the distributed loads corresponding to the target mesh units, and mechanical properties of the cable units of the applied loads; statistically recording a current analysis time corresponding to the finite element mesh and a current running time corresponding to the external multi-physical field simulation program; if the current analysis time is greater than the current running time, using the external multi-physical field simulation program to calculate new current-time reference point motion information according to the constraint reaction forces; comparing the current running time with a preset simulation time; if the current running time is less than the preset simulation time, jumping to execute the step of performing third-order polynomial interpolation on the current-time reference point motion information output by the external multi-physical field simulation program to determine the smooth motion parameters of the constraint nodes corresponding to the original swimsuit model until the current running time is greater than or equal to the preset simulation time; generating coupling simulation results according to the current-time reference point motion information determined when the current running time is greater than or equal to the preset simulation time, the water dynamic loads of the target mesh units, the structural dynamic responses, and the constraint reaction forces of the constraint nodes.

5. The mesh model based multi-procedure coupling simulation method of claim 4, wherein, Further comprising: if the current analysis time is less than or equal to the current running time, adjusting spatial postures of the target mesh units according to the structural dynamic responses of the target mesh units to determine new target mesh units; calculating water dynamic loads of the new target mesh units; jumping to execute the step of converting the water dynamic loads of the target mesh units into distributed loads according to the swimsuit material matching unit type by using the load application sub-program until the current analysis time is greater than the current running time.

6. The mesh model based multi-procedure coupling simulation method of claim 1, wherein, The water dynamic loads include lift and drag, and the calculation process of the water dynamic loads specifically includes: ； ； wherein, and are the drag and lift forces on the target mesh unit, respectively; is the sea density; and are the drag and lift coefficients of the target mesh unit, respectively; is the instantaneous velocity of the water flow relative to the center point of the target mesh unit; is the footprint area of the target mesh unit.

7. A multi-program coupling simulation system based on a net model, characterized by, Further comprising: an acquisition module configured to acquire an original swimsuit model and a finite element mesh, and generate a node table and an element table according to the original swimsuit model and the finite element mesh by using a swimsuit grouping method; a construction module configured to construct target mesh units according to the node table and the element table; a calculation module configured to calculate water dynamic loads of the target mesh units; a simulation module configured to perform multi-program coupling simulation based on an external multi-physical field simulation program and the water dynamic loads of the target mesh units, and output coupling simulation results.

8. A computer device, comprising: The computer program is executed to implement the multi-program coupling simulation method based on a swimsuit model.

9. A computer readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed to implement the multi-program coupling simulation method based on a swimsuit model.

10. A computer program product, characterised in that, The computer program product comprises a computer program stored on a non-transitory computer-readable storage medium, the computer program comprising program instructions, wherein the program instructions, when executed by a computer, cause the computer to perform the method of multi-program coupling simulation based on the netting model according to any one of claims 1-6.

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