Method and system for dynamic growth of material points in OTM-FSI simulation based on open system

Abstract

The present invention is a method and system for the dynamic growth of material points in OTM‑FSI simulation based on an open system, and belongs to the field of fluid-solid coupling mechanics technology. In response to the problem that the existing common software causes the fluid-solid coupling simulation to end prematurely due to the lack of fluid, the method of the present invention is as follows: obtaining a two-dimensional or three-dimensional continuous medium problem domain; discretizing the continuous medium problem domain to obtain initial discretized material points and nodes; defining a supplementary domain at the flow field entrance of the continuous medium problem domain, and dynamically generating virtual material points to be activated in the supplementary domain using the Delaunay triangulation algorithm; dynamically activating the virtual material points according to the calculation time, so that the activated material points are dynamically added to the continuous medium problem domain to form new material points and nodes, thereby realizing the dynamic growth of material points in the continuous medium problem domain. The present invention activates virtual material points according to the fluid flow rate at the entrance, realizes the dynamic adaptive growth of material points, ensures calculation accuracy, and effectively improves the overall operating efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of fluid-solid coupling mechanics, and in particular to a method and system for dynamic growth of material points in an open system-based OTM-FSI simulation. Background Art

[0002] Fluid-Structure Interaction (FSI) is a critical issue that exists across a wide range of disciplines, including aerospace / automotive structural engineering, biomedical engineering, naval architecture, offshore and marine engineering. FSI studies the interaction between one or more solid structures and the fluids within or surrounding them. FSI typically involves complex physical phenomena such as extremely large deformations, large temperature gradients, high heating or cooling rates, high-speed impact and geometric distortion, material fission, metal forming, and multiphase transitions.

[0003] When using the traditional Lagrangian finite element method to deal with the above fluid-solid coupling problems, huge mesh distortion or unit splitting make the finite element solution difficult or even lead to solution failure. In order to solve these problems, the finite element calculation often requires continuous mesh re-division. However, this not only greatly increases the calculation time, but for some problems, simply re-dividing the mesh cannot completely solve them.

[0004] The Optimal Transport Meshless Method (OTM) is a Lagrangian meshless method characterized by using optimal transport theory to discretize time and using nodes with position information and material points with material information to discretize space. It is a highly promising and ideal solution for solving highly nonlinear and strong fluid-solid coupling problems. This method not only ensures that the fluid motion and solid motion are solved at the same time phase and how to coordinate the different coordinate systems of the fluid and solid, but also overcomes the problems of how to accurately track the coupling interface and large mesh deformation.

[0005] In fluid-structure interaction simulations, as fluid flows out of the solution region, the material points in the solution region and the material and dynamic information they carry are lost, resulting in discontinuities in the solution flow and causing premature termination of the coupling effect. To prevent premature termination of fluid-structure interaction simulations due to fluid loss, existing commercial software (such as FLUENT and CFX) discretizes the problem domain using hexahedral meshes and pre-creates redundant meshes encompassing the solution region, which incurs computational and memory burdens. Therefore, finding effective solutions to the premature termination of fluid-structure interaction simulations due to fluid loss is of great significance and has promising applications. Summary of the Invention

[0006] In response to the defects existing in the above-mentioned prior art, the present invention aims to provide a method and system for the dynamic growth of material points in OTM-FSI simulation based on an open system, which activates virtual material points according to the fluid flow rate at the inlet to achieve dynamic adaptive growth of material points, covering two dynamic growth situations: the fluid flow rate at the inlet is less affected by the continuous medium problem domain and the fluid flow rate is more affected by the continuous medium problem domain, and solves the problem of premature termination of coupling due to the inability to continuously replenish the fluid into the continuous medium problem domain.

[0007] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention discloses a method for dynamic growth of material points in an open system-based OTM-FSI simulation, comprising the following steps:

[0009] S1: Obtain a two-dimensional or three-dimensional continuum problem domain;

[0010] S2: Discretize the continuous medium problem domain to obtain the initial discretized material points and nodes;

[0011] S3: A supplementary domain is defined at the flow field entrance of the continuous medium problem domain, and the Delaunay triangulation algorithm is used to dynamically generate virtual material points to be activated in the supplementary domain;

[0012] S4: Dynamically activate virtual material points according to the calculation time, so that the activated material points are dynamically added to the continuous medium problem domain to form new material points and nodes, realizing the dynamic growth of material points in the continuous medium problem domain.

[0013] As a further preferred solution of the above technical solution, in step S2, when discretizing the continuum problem domain, a triangular mesh is used to discretize the two-dimensional continuum problem domain, or a tetrahedral mesh is used to discretize the three-dimensional continuum problem domain.

[0014] As a further preferred embodiment of the above technical solution, in step S3, the step of defining a supplementary domain at the flow field entrance of the continuum problem domain includes:

[0015] S31: Define all nodes at the flow field entrance Domain front as Patch nodes;

[0016] S32: At a distance h from the flow field inlet in the -X direction, add a group of nodes Patchback nodes in the form of Patch nodes, and use the rectangular area formed between the Patch back nodes and the Patch node as the supplementary domain of the fluid, and the supplementary domain dynamically extends in the -X direction as the calculation time increases.

[0017] Further preferably, in step S3, the step of dynamically generating virtual material points to be activated in the supplementary domain using the Delaunay triangulation algorithm is as follows:

[0018] A: Use the Delaunay triangulation algorithm to divide the supplementary domain into a triangular mesh;

[0019] B: Dynamically generate virtual material points to be activated at the center of each triangular mesh.

[0020] As a further preferred solution of the above technical solution, in step S4, the dynamic growth of material points in the continuous medium problem domain is realized, including dynamic growth based on fixed positions and dynamic growth based on dynamic positions.

[0021] Further preferably, the steps of dynamic growth based on a fixed position are as follows:

[0022] C1: Taking the Domain front as the benchmark, when all Patch back nodes move more than h in the X direction and enter the continuous medium problem domain, the virtual material points are activated synchronously;

[0023] C2: Synchronously add a set of Next Patch back nodes to replace the original Patch back nodes at h in the -X direction, and re-perform Delaunay triangulation with the Patch back nodes that have moved to the Domain front to generate a triangular network;

[0024] C3: Dynamically add new material points and nodes to the continuous medium problem domain using the regenerated triangle network.

[0025] Further preferably, the steps of dynamic growth based on dynamic position are as follows:

[0026] D1: When any Patch back nodes enter the continuous medium problem domain through the Domain front in the X direction, it represents the entry of all Patch back nodes and synchronously activates all virtual material points;

[0027] D2: Using this group of Patch back nodes as the base point, add a group of Next Patch backnodes at h in the -X direction, and re-perform Delaunay triangulation with the Patch back nodes to generate a triangular network;

[0028] D3: Dynamically add new material points and nodes to the continuum problem domain using a regenerated triangle network.

[0029] In a second aspect, the present invention further discloses a system for dynamic growth of material points in an open system-based OTM-FSI simulation, the system comprising:

[0030] An acquisition module, used to obtain a two-dimensional or three-dimensional continuous medium problem domain;

[0031] Discretization module, used to discretize the continuous medium problem domain and obtain the initial discretized material points and nodes;

[0032] The expansion and segmentation module is used to expand the supplementary domain at the flow field entrance and segment the supplementary domain to dynamically generate virtual material points to be activated;

[0033] The activation module is used to dynamically activate virtual material points and add the activated material points to the continuous medium problem domain to achieve dynamic growth of material points.

[0034] A further preferred embodiment of the above technical solution is that the expanded segmentation module includes:

[0035] The node definition submodule is used to define all nodes at the Domain front of the flow field entrance;

[0036] The node expansion submodule is used to add nodes in the -X direction at the flow field inlet to form a supplementary domain, and the supplementary domain dynamically extends in the -X direction as the calculation time increases;

[0037] The dynamic triangulation submodule uses the Delaunay triangulation algorithm to divide the supplementary domain into triangular meshes and dynamically generate virtual material points.

[0038] A further preferred embodiment of the above technical solution is that the activation module includes:

[0039] The retention dynamic growth submodule is used to realize the dynamic growth of material points in the continuum problem domain when all patch back nodes enter the continuum problem domain, taking the Domain front as the benchmark;

[0040] The dynamic growth submodule is used to realize the dynamic growth of material points in the continuous medium problem domain when any Patch backnodes are used in the continuous medium problem domain, taking the Patch back nodes as the base points.

[0041] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0042] 1. Based on the extent to which the fluid velocity at the smooth inlet is affected by the continuous medium problem domain, the method of the present invention specifically proposes two solutions: dynamic growth of material points based on fixed positions and dynamic growth of material points based on dynamic positions. This method adaptively realizes the dynamic growth of material points only in the analysis area, avoiding the computational and memory burden caused by redundant grids.

[0043] While ensuring calculation accuracy, the grid is generated quickly, effectively improving the overall operating efficiency of the system.

[0044] 2. The method of the present invention uses triangular meshes or tetrahedral meshes to discretize the continuous medium problem domain. According to the degree to which the fluid velocity at the inlet is affected by the continuous medium problem domain, the supplementary domain at the flow field inlet is dynamically divided and meshed by Delaunay triangulation, and virtual material points to be activated are generated at the centroid of each dynamically generated mesh. New material points and nodes are dynamically and adaptively added to the continuous medium problem domain according to the calculation time.

[0045] 3. The method of the present invention synchronously updates the material information and dynamic information of the activated material points when the newly added material points enter the calculation domain, and assigns the activated material points the same material properties as the initial entry material points to ensure the conservation of mass and continuity of fluid flow of the entire system, and resets the newly added nodes to ensure that their dynamic information is consistent with the initial conditions of the entry nodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below.

[0047] Figure 1 This is a schematic rendering of the dynamic growth of Delaunay triangulation material points at the entrance of an open system shown in the present invention;

[0048] Figure 2 Schematic diagram of two different material point dynamic growth schemes based on fixed positions and dynamic positions according to the present invention;

[0049] Figure 3 This is a schematic diagram of the update of material information and node dynamics information of a material point shown in the present invention. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. For ordinary technicians in this field, other embodiments can be obtained based on these drawings without paying any creative work.

[0051] Reference Figure 1-3 The present invention provides a method for dynamic growth of material points in an open system-based OTM-FSI simulation, comprising the following steps:

[0052] S1: Obtain a two-dimensional or three-dimensional continuum problem domain;

[0053] In this step, firstly, a solid model is established to determine the scope of the fluid domain and mark the fluid inflow interface.

[0054] S2: Discretize the continuum problem domain. Specifically, use the Delaunay triangulation algorithm to discretize the two-dimensional continuum problem domain, or use a tetrahedral mesh to discretize the three-dimensional continuum problem domain to obtain the initial discretized material points and nodes. For locations where accurate dynamic response calculations are required, local encryption can be performed.

[0055] S3: A supplementary domain is defined at the flow field entrance of the continuous medium problem domain, and the Delaunay triangulation algorithm is used to dynamically generate virtual material points to be activated in the supplementary domain;

[0056] In this step, if Figure 1 As shown in the figure, all nodes at the Domain front of the flow field entrance are defined as Patchnodes. At a distance h in the -X direction from the flow field entrance, a group of nodes Patch backnodes are added in the form of Patch nodes, and the Patch back nodes are given the same dynamic information as the Patch nodes. The rectangular area formed between the Patch backnodes and the Patch node is used as the supplementary domain of the fluid, and this supplementary domain dynamically extends in the -X direction with the calculation time. The Delaunay triangulation algorithm is used to divide the supplementary domain into triangular meshes, and the virtual material points to be activated are dynamically generated at the center of each triangular mesh.

[0057] S4: Dynamically activate virtual material points according to the calculation time, so that the activated material points are dynamically added to the continuous medium problem domain to form new material points and nodes, realizing the dynamic growth of material points in the continuous medium problem domain.

[0058] In this step, the dynamic growth of material points in the continuous medium problem domain is divided into dynamic growth based on fixed position and dynamic growth based on dynamic position, depending on the extent to which the fluid at the flow field inlet is affected by the continuous medium problem domain.

[0059] First, the process of dynamic growth based on fixed position is as follows, Figure 2 (a) shows:

[0060] 1) Taking the Domain front as the benchmark, when all Patch back nodes move more than h in the X direction, that is, when the Patch back nodes pass through the Domain front and enter the continuous medium problem domain, such as Figure 2 The node shown in (a) x a , then the column of Patch back nodes will be formally added to the continuous medium problem domain and the virtual material points will be activated synchronously;

[0061] 2) At the point h in the -X direction from the Domain front, a set of Next Patch back nodes are added to replace the original Patch back nodes. Delaunay triangulation is then performed again with the Patch back nodes that have moved to the Domain front to generate a triangular network.

[0062] 3) Based on the calculation time, new material points and nodes are dynamically added to the continuous medium problem domain using the regenerated triangle network.

[0063] Second, when the velocity at the inlet is greatly affected by the continuous medium problem domain, the domain front is no longer used as a fixed position for the growth base point of the material point, but the dynamic position is used for the dynamic growth of the material point, such as Figure 2 (b) is shown in the figure. The specific process is as follows:

[0064] 1) When any patch back node enters the continuous medium problem domain through the domain front in the X direction, it means that all patch back nodes have officially entered and all virtual material points are activated synchronously;

[0065] 2) Using this group of Patch back nodes as the base point, add a group of Next Patch back nodes at h in the -X direction, and re-perform Delaunay triangulation on the Next Patch back nodes and the Patch back nodes to generate a triangular network;

[0066] 3) Based on the calculation time, new material points and nodes are dynamically added to the continuous medium problem domain using the regenerated triangle network.

[0067] In the present invention, a material point is used to represent the physical information of a material within a set range of a certain point, and the physical information includes mass and density; a node is used to represent the dynamic information of a certain point, and the dynamic information includes velocity and acceleration.

[0068] The activated material points mentioned above will be given the same material properties as the material points at the initial entrance, and the mass information carried by the material points will be updated synchronously to the total mass of the system to ensure the conservation of mass of the entire system. The newly added nodes will be given the same dynamic information as the entrance nodes at the moment of generation. The newly added nodes move to the entrance through a distance of ℎ. Since there is interaction between the nodes during this process, when the newly added nodes move to the entrance, the acceleration of the nodes may not be 0. At this time, the units generated by the patch nodes and the patch back nodes will have an effect similar to residual stress, such as Figure 3 (a), which is obviously inconsistent with the initial conditions of the inlet. In order to avoid such a situation, as shown in Figure 3 As shown in (b), when the newly added node moves to the entrance, the dynamic information of the newly added node is reset to be consistent with the initial conditions of the entrance.

[0069] Compared with common commercial software such as FLUENT and CFX, the method of the present invention only adaptively performs dynamic growth of material points in the analysis area, avoiding the computational and memory burden caused by redundant grids. Compared with the hexahedral grid division method of common commercial software, the triangular grid adopted in the present invention (tetrahedral grid is used for three-dimensional problems) discretizes the problem domain, and can quickly generate grids while ensuring computational accuracy. When dealing with flow problems related to flow and time, the need for this dynamically growing fluid will be faced. Therefore, the adaptive dynamic growth method of material points of the present invention has reference and guiding significance for the above-mentioned problems.

[0070] The detailed description of the above embodiments is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the invention. Based on the embodiments of the present invention, they are only used to illustrate the technical solution of the present invention and are not limiting. Other modifications or equivalent substitutions made by ordinary technicians in this field to the technical solution of the present invention should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for dynamic growth of material points in OTM-FSI simulation based on open systems, characterized by: The following steps are involved: S1: Obtain a two-dimensional or three-dimensional continuum problem domain; S2: Discretize the continuous medium problem domain to obtain the initial discretized material points and nodes; S3: A supplementary domain is defined at the flow field entrance of the continuous medium problem domain, and the Delaunay triangulation algorithm is used to dynamically generate virtual material points to be activated in the supplementary domain; The steps to define a supplementary domain at the flow inlet of a continuum problem domain include: S31: Define all nodes at the flow field entrance Domain front as Patch nodes; S32: At a distance h from the flow field inlet in the -X direction, a group of nodes Patch backnodes are added in the form of Patch nodes. The rectangular area formed between the Patch back nodes and the Patch node is used as the supplementary domain of the fluid, and the supplementary domain is dynamically extended in the -X direction as the calculation time increases. The steps for dynamically generating virtual material points to be activated in the supplementary domain using the Delaunay triangulation algorithm are as follows: A: Use the Delaunay triangulation algorithm to divide the supplementary domain into a triangular mesh; B: Dynamically generate virtual material points to be activated at the center of each triangular mesh; S4: Dynamically activate virtual material points according to the calculation time, so that the activated material points are dynamically added to the continuous medium problem domain to form new material points and nodes, realizing the dynamic growth of material points in the continuous medium problem domain; The realization of dynamic growth of material points in the continuous medium problem domain includes dynamic growth based on fixed positions and dynamic growth based on dynamic positions; The steps for dynamic growth based on a fixed position are as follows: C1: Taking the Domain front as the benchmark, when all Patch back nodes move more than h in the X direction and enter the continuous medium problem domain, the virtual material points are activated synchronously; C2: Synchronously add a set of Next Patch back nodes to replace the original Patch back nodes at h in the -X direction, and re-perform Delaunay triangulation with the Patch back nodes that have moved to the Domain front to generate a triangular network; C3: Dynamically adding new material points and nodes to the continuum problem domain using the regenerated triangle network; The steps for dynamic growth based on dynamic position are as follows: D1: When any Patch back nodes enter the continuous medium problem domain through the Domain front in the X direction, it represents the entry of all Patch back nodes and synchronously activates all virtual material points; D2: Using this group of Patch back nodes as the base point, add a group of Next Patch back nodes at h in the -X direction, and re-perform Delaunay triangulation with the Patch back nodes to generate a triangular network; D3: Dynamically add new material points and nodes to the continuum problem domain using a regenerated triangle network.

2. The method for dynamic growth of material points in open system-based OTM-FSI simulation according to claim 1, characterized in that: In step S2, when discretizing the continuum problem domain, a triangular mesh is used to discretize the two-dimensional continuum problem domain, or a tetrahedral mesh is used to discretize the three-dimensional continuum problem domain.

3. A system for dynamic growth of material points in OTM-FSI simulation based on an open system, used to execute the method for dynamic growth of material points in OTM-FSI simulation based on an open system according to claim 1 or 2, characterized in that: The system includes: An acquisition module, used to obtain a two-dimensional or three-dimensional continuous medium problem domain; Discretization module, used to discretize the continuous medium problem domain and obtain the initial discretized material points and nodes; The expansion and segmentation module is used to expand the supplementary domain at the flow field entrance and segment the supplementary domain to dynamically generate virtual material points to be activated; The activation module is used to dynamically activate virtual material points and add the activated material points to the continuous medium problem domain to achieve dynamic growth of material points.

4. The system for dynamic growth of material points in open system-based OTM-FSI simulation according to claim 3, characterized in that: The extended meshing module includes: The node definition submodule is used to define all nodes at the Domain front of the flow field entrance; The node expansion submodule is used to add nodes in the -X direction at the flow field inlet to form a supplementary domain, and the supplementary domain dynamically extends in the -X direction as the calculation time increases; The dynamic triangulation submodule uses the Delaunay triangulation algorithm to divide the supplementary domain into triangular meshes and dynamically generate virtual material points.

5. The system for dynamic growth of material points in OTM-FSI simulation based on open system according to claim 4, characterized in that: The activation modules include: The retention dynamic growth submodule is used to realize the dynamic growth of material points in the continuum problem domain when all patch back nodes enter the continuum problem domain, taking the Domain front as the benchmark; The dynamic growth submodule is used to realize the dynamic growth of material points in the continuous medium problem domain with Patch back nodes as the base points when any Patch back nodes are used in the continuous medium problem domain.

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