Structured grid generation method and system of three-period minimal curved surface structure

Abstract

The invention provides a structured grid generation method and system of a three-period minimal curved surface (TPMS) structure. The method comprises the following steps: S1, constructing a full-hexahedron structured grid of a three-period minimal curved surface main structure; s2, intersecting the full-hexahedron structured grid with the filling boundary, and deleting an overrun grid unit to obtain a new grid surface; s3, projecting the new grid surface to the filling boundary to obtain a boundary body-fitted grid; and S4, on the basis of the boundary body-fitted grid, points in the boundary body-fitted grid are generated according to CFD boundary layer calculation requirements. According to the method, the cross-scale generation problem of large-space small unit cells can be easily solved, the generation speed is high, and the data structure is simple. Compared with a traditional tetrahedral unstructured grid, the full-hexahedral grid is beneficial to reducing the number of grids and improving the numerical simulation precision, and can be directly applied to a structured CFD solver.

Description

Technical Field

[0001] The present invention relates to the technical field of computer-aided design, and in particular to a structured grid generation method and system for a three-periodic minimal surface (TPMS) structure. Background Art

[0002] The three-periodic minimal surface (TPMS) structure has the advantages of high strength-to-weight ratio, high specific surface area, self-support and good fluidity. It has great potential in achieving structural lightweighting and improving energy efficiency, and shows important application prospects in industrial fields such as aerospace, energy, automobile, and medical.

[0003] In traditional scientific research and commercial software, TPMS structures typically employ unstructured discretization for CAD geometry and CFD meshes. This approach presents numerous drawbacks: large data volumes, high computational complexity, difficulty controlling mesh quality, and challenges in handling cross-scale applications involving "large spaces and small cells." Furthermore, the integration of multiple software packages often results in high labor costs. These issues severely restrict the design efficiency of TPMS cell-based structures across various industrial sectors.

[0004] A search of patent literature revealed an invention patent with publication number CN111062166A, which discloses a topology optimization method for a porous structure with three-periodic minimal surfaces based on a variable density method. The method comprises the following steps: Step 1: Input the function expression for the three-periodic minimal surface, the design domain, and the optimization target density; Step 2: Based on the design domain and the target density, generate a density distribution and a density-mapped mesh using a variable density topology optimization method; Step 3: Generate a three-periodic minimal surface with dual equivalent parameters based on the density-mapped mesh; Step 4: Extract the intersecting contours of the six covers of the three-periodic minimal surface with dual equivalent parameters to generate a triangular mesh of the cover outlines; Step 5: Track and identify the triangular meshes of the cover outlines, delete illegal meshes, and generate a valid triangular mesh of the six covers; Step 6: Combine the cover triangular meshes with the three-periodic minimal surface with dual equivalent parameters to output an STL file of the optimized three-periodic minimal surface porous structure. The method focuses on topology optimization but does not mention mesh generation or cross-scale scenario processing, which suggests a lack of mesh generation in practical applications.

[0005] In summary, in response to the above-mentioned problems in the existing technology, studying a structured grid generation method and system for a three-periodic minimal surface (TPMS) structure has become a key task that needs to be solved urgently. Summary of the Invention

[0006] In view of the defects in the prior art, the present invention aims to provide a structured grid generation method and system for a triple-periodic minimal surface (TPMS) structure.

[0007] According to the present invention, a structured grid generation method for a three-periodic minimal surface structure includes the following steps:

[0008] Step S1, constructing a full hexahedral structured grid of a three-periodic minimal surface main structure;

[0009] Step S2, intersecting the full hexahedral structured grid with the filling boundary, deleting the excess grid cells, and obtaining a new grid surface;

[0010] Step S3, projecting the new mesh surface onto the filling boundary to obtain a boundary-fitting mesh;

[0011] Step S4: Based on the boundary body-fitting grid and in accordance with the CFD boundary layer calculation requirements, points within the boundary body-fitting grid are generated.

[0012] Preferably, the pipe network formed by the three-periodic minimal surface is divided into multiple Y-shaped three-way units arranged periodically, and each Y-shaped three-way unit is divided into a 3OH topological grid according to the 3OH topological form, and further spliced into a full hexahedral structured grid of the entire three-periodic minimal surface main structure.

[0013] Preferably, step S1 includes the following sub-steps:

[0014] Step S1.1, dividing the pipe network formed by the three-periodic minimal surface into a plurality of periodically arranged Y-shaped three-way units;

[0015] Step S1.2: Each Y-shaped three-way unit is divided into three rotationally symmetrical branches, which are connected at the Y-shaped interface to form a 3OH topology;

[0016] In step S1.3, each branch pipe is divided into a full hexahedral structured grid using the OH topology form, and then the end faces of each branch pipe are butted together to form a full hexahedral structured grid of a modularly filled three-periodic minimal surface main structure.

[0017] Preferably, step S1.3 includes the following sub-steps:

[0018] In step S1.3.1, fill the area near the pipe wall of each branch with an O-shaped grid, and fill the void in the middle of the O-shaped grid with an H-shaped grid. Set the number of grid cells in the H-shaped grid's flow direction cross section to 2n × 2n, and the number of grid cells in the O-shaped grid's circumferential direction to 8n, with the grid cells in the inner ring of the O-shaped grid corresponding to the grid cells in the outer ring of the H-shaped grid. Set the number of radial grid cells in the O-shaped grid to m, and the number of grid cells in the O-shaped grid's flow direction cross section to 8n × m. Finally, set the number of grid cells in the OH topology grid of each branch along the flow direction to k, to obtain the OH topology grid for each branch.

[0019] In step S1.3.2, the end faces of the OH topological grid of each branch pipe are bent halfway at an angle of 120° and spliced into a Y shape, and a 3OH topological form is formed at the Y-shaped interface to obtain a fixed, modular 3OH topological grid that fills each Y-shaped tee unit.

[0020] Preferably, in step S1.3.2, the number of H-shaped grid units obtained from the three branch sections of the Y-shaped interface is n×2n, and the number of O-shaped grid units obtained is 4n×m. The O-shaped grids are docked with the O-shaped grids, and the H-shaped grids are docked with the H-shaped grids to obtain a fully hexahedral structured grid in the 3OH topological form of the Y-shaped three-way unit.

[0021] Preferably, in step S2, the out-of-limit grid cells include grid cells that exceed the filling boundary, grid cells that overlap with the filling boundary, and grid cells that are within the filling boundary and have a distance from the filling boundary less than a set threshold.

[0022] Preferably, in step S2, the operation of deleting the excess grid units includes: trimming scattered grid units or trimming a whole grid block.

[0023] Preferably, step S3 includes the following sub-steps:

[0024] Step S3.1, calculating the average value of the external normal vectors of the new mesh surface at each mesh point;

[0025] Step S3.2, calculating the external normal vector of each surface element of the filling boundary;

[0026] Step S3.3, emit a cubic polynomial curve from the new mesh surface, the starting point of the curve is tangent to the external normal vector of the new mesh surface, the curve gradually bends and projects to the filling boundary, and the direction is tangent to the external normal vector of the filling boundary to obtain a boundary-fitting mesh.

[0027] Preferably, step S4 includes the following sub-steps:

[0028] Step S4.1: For each curve, insert 15 points in the grid according to a geometric progression, and change the curve into a 16-segment broken line. The size of the first segment is half of the mainstream grid size, and the size of the last segment is set to 0.01 mm.

[0029] In step S4.2, the boundary body-fitting grid is divided at the 15 breakpoints in step S4.1, and the boundary body-fitting grid is divided into 16 layers to obtain a boundary body-fitting grid that can meet the requirements of CFD boundary layer calculation.

[0030] The present invention also provides a structured grid generation system for a three-periodic minimal surface structure, comprising:

[0031] Module M1, constructs a full hexahedral structured grid of the three-periodic minimal surface main structure;

[0032] Module M2 intersects the full hexahedral structured grid with the filling boundary, deletes the excess grid cells, and obtains the new grid surface;

[0033] Module M3 projects the new mesh surface onto the filling boundary to obtain a boundary-fitting mesh;

[0034] Module M4 generates points within the boundary-fitting grid based on the boundary-fitting grid and according to the CFD boundary layer calculation requirements.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. This invention uses a fully hexahedral grid. Compared to tetrahedral unstructured grids, it requires fewer grids, smaller data volumes, and a simpler data structure. This not only improves numerical simulation accuracy but also can be applied to structured CFD solvers.

[0037] 2. This invention achieves fast generation speed and good mesh quality through the careful design of Y-shaped grid topology. This modular design is good at handling cross-scale application scenarios of "large space, small cell".

[0038] 3. The boundary-fitting mesh clipping, projection, and filling techniques employed in this invention maintain the fully hexahedral mesh form desired for CFD. This technique is simple, easy to implement, and computationally inefficient, making it suitable for large-scale mesh generation. Furthermore, if the clipping step is modified to clip entire mesh blocks (rather than individual cells), the technique can be used with structured CFD solvers. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0040] Figure 1 Schematic diagram of a full hexahedral structured grid of the TPMS main structure in an embodiment of the present invention;

[0041] Figure 2 A schematic diagram of a Y-shaped topology of a modular design in an embodiment of the present invention;

[0042] Figure 3 Schematic diagram of mesh clipping, projection, and filling at the filling boundary in an embodiment of the present invention. DETAILED DESCRIPTION

[0043] The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0044] Based on previous research on TPMS structures, this paper proposes a fully hexahedral mesh generation method and system for triple-periodic minimal surfaces (TPMS) structures. This technology easily addresses the cross-scale generation challenge of "large space, small cell" with fast generation speed and simple data structure. Compared with traditional tetrahedral unstructured meshes, fully hexahedral meshes help reduce the number of meshes, improve numerical simulation accuracy, and can be directly applied to structured CFD solvers.

[0045] Example 1:

[0046] This embodiment provides a structured grid generation method for a three-periodic minimal surface (TPMS) structure, comprising the following steps:

[0047] Step S1, constructing a full hexahedral structured grid of a three-periodic minimal surface main structure.

[0048] Specifically, the originally complex pipe network formed by the three-periodic minimal surface is divided into multiple periodically arranged Y-shaped tee units. Each Y-shaped tee unit is divided into a 3OH topological grid according to the 3OH topological form, and further spliced into a full hexahedral structured grid of the entire three-periodic minimal surface main structure.

[0049] In this embodiment, by dividing the pipe network into periodically arranged identical modules and filling them with fixed, modular grids, rapid modular grid generation is achieved in the cross-scale application scenario of "large space, small cell".

[0050] Figure 1 Schematic diagram of a full hexahedral structured grid of the TPMS main structure (excluding the filling area boundary) in an embodiment of the present invention.

[0051] like Figure 1 As shown, step S1 includes the following sub-steps:

[0052] Step S1.1, dividing the pipe network formed by the three-periodic minimal surface into a plurality of periodically arranged Y-shaped three-way units.

[0053] In step S1.2, each Y-shaped tee unit is divided into three rotationally symmetrical branches, which are connected at the Y-shaped interface, thereby dividing the pipe network into periodically arranged identical modules to form a 3OH topology.

[0054] In step S1.3, each branch pipe is divided into a full hexahedral structured grid using the OH topology form, and then the end faces of each branch pipe are butted together to form a full hexahedral structured grid of a modularly filled three-periodic minimal surface main structure.

[0055] Specifically, step S1.3 includes the following sub-steps:

[0056] In step S1.3.1, the area near the pipe wall of each branch is filled with an O-shaped grid, and the void in the middle of the O-shaped grid is filled with an H-shaped grid; the number of grid cells in the flow cross section of the H-shaped grid is set to 2n×2n (in this embodiment, n is 8), and the number of circumferential grid cells of the O-shaped grid is set to 8n, and the grid cells of the inner circle of the O-shaped grid and the outer circle of the H-shaped grid correspond one to one; the number of radial grid cells of the O-shaped grid is set to m (for solid simulation, m can be 8, and for fluid simulation, m can be 24), then the number of grid cells in the flow cross section of the O-shaped grid is 8n×m; finally, the number of grid cells of the OH topological grid of each branch along the flow direction (branch axial direction) is set to k (in this embodiment, k is 8), and the OH topological grid of each branch is obtained.

[0057] In step S1.3.2, the end faces of the OH topological grid of each branch pipe are bent halfway at an angle of 120° and spliced into a Y shape, and a 3OH topological form is formed at the Y-shaped interface to obtain a fixed, modular 3OH topological grid that fills each Y-shaped tee unit.

[0058] Figure 2 A schematic diagram of a Y-shaped topology of a modular design in an embodiment of the present invention.

[0059] like Figure 2 As shown in the figure, the Y-shaped topology adopts a three-channel symmetrical connection structure at the intersection of the pipe network branches of the three-periodic minimal surface main structure.

[0060] Specifically, the three branch sections of the Y-shaped interface are divided into H-shaped grid units of n×2n and O-shaped grid units of 4n×m. The O-shaped grids are docked with the O-shaped grids, and the H-shaped grids are docked with the H-shaped grids to obtain a fully hexahedral structured grid in the 3OH topological form of the Y-shaped three-way unit.

[0061] The fully hexahedral nature of this embodiment enables the minimum dihedral angle of the grid to be controlled above 40° and the dihedral angles of most grids to be close to 90°, thereby improving the grid quality; the structured nature enables the nodes to be connected into hexahedral units simply by the order of arrangement, without the need to store the vertex numbers of each hexahedral unit and the numbers of adjacent units, reducing the storage capacity by approximately 65% compared to a tetrahedral unstructured grid of the same spatial resolution.

[0062] Step S2: intersect the full hexahedral structured grid with the filling boundary, delete the excess grid cells, and obtain a new grid surface.

[0063] Figure 3 Schematic diagram of mesh clipping, projection, and filling at the filling boundary in an embodiment of the present invention.

[0064] like Figure 3 As shown, the out-of-limit grid cells include grid cells that exceed the filling boundary, grid cells that coincide with the filling boundary, and grid cells that are within the filling boundary and whose distance from the filling boundary is less than a set threshold.

[0065] In this embodiment, the threshold is set using the side length of a mainstream grid unit.

[0066] Furthermore, the operation of deleting the out-of-limit grid cells includes: trimming scattered grid cells or trimming an entire grid block. If a whole grid block is trimmed, the method of this embodiment is applicable to a structured CFD solver.

[0067] Step S3, projecting the new mesh surface onto the filling boundary to obtain a boundary-fitting mesh;

[0068] Specifically, step S3 includes the following sub-steps:

[0069] Step S3.1, calculating the average value of the external normal vectors of the new mesh surface at each mesh point.

[0070] Specifically, for each grid point, the external normal vectors of all surface grid cells containing the grid point are calculated. The external normal vector of each surface cell is The calculation formula is In the formula is the coordinate vector of any vertex p1 of the face unit, is the coordinate vector of the two vertices p2 and p3 adjacent to the face unit and point p1; in order to ensure that the calculated normal vector Outward, we also need to calculate the normal vector from point p1 The number of times the ray in the direction passes through the new mesh surface (excluding point p r ), if the number of times it passes is an even number (including 0), then The direction is correct, otherwise Reverse; finally calculate the external normal vectors of all surface grid cells containing the grid point The average value of .

[0071] Step S3.2, calculate the external normal vector of each surface element of the filling boundary.

[0072] Specifically, the external normal vector The calculation formula is the same as step S3.1, In the formula is the coordinate vector of any vertex p1 of the face unit, is the coordinate vector of the two vertices p2 and p3 adjacent to the face unit and point p1; in order to ensure that the calculated normal vector Outward, we also need to calculate the normal vector from point p1 The number of times the ray in the direction passes through the filling boundary (excluding point p1). If the number of times is an even number (including 0), then The direction is correct, otherwise Reverse.

[0073] In step S3.3, a cubic polynomial curve is emitted from the new mesh surface. The starting point of the curve is tangent to the external normal vector of the new mesh surface. The curve gradually bends and projects to the filling boundary. The direction is tangent to the external normal vector of the filling boundary at that location. Thus, a layer of boundary-fitting mesh is obtained, which is further segmented in step S4.

[0074] Step S4: Based on the boundary body-fitting grid and in accordance with the CFD boundary layer calculation requirements, points within the boundary body-fitting grid are generated. Specifically, the steps include:

[0075] In step S4.1, for each curve obtained in step S3, insert 15 points in the grid in a geometric progression to change the curve into a 16-segment broken line. The size of the first segment (away from the filling boundary) is approximately half the size of the mainstream grid, and the size of the last segment (close to the filling boundary) is set to 0.01 mm or the value required for the boundary layer CFD solution in the specific problem.

[0076] In step S4.2, the layer of boundary-fitting mesh obtained in step S3 is split at the 15 breakpoints in step S4.1, and the original layer of boundary-fitting mesh is split into 16 layers, thereby obtaining a boundary-fitting mesh that can meet the requirements of CFD boundary layer calculation.

[0077] The above method can maintain the full hexahedral mesh form expected by CFD, the steps are simple and easy to implement, the calculation amount is small, and it is also suitable for large-scale mesh generation. The full hexahedral structured mesh of the three-periodic minimal surface structure can also be combined with polyhedral unstructured meshes of other structures to form a hybrid mesh. Polyhedral unstructured meshes of other structures include unstructured meshes formed by combining one or more of tetrahedral units, quadrangular pyramid (also known as pyramid) units, triangular prism units, hexahedral units, and other polyhedral units, as well as Cartesian meshes mainly composed of full regular hexahedrons or regular hexahedrons, and combinations of unstructured meshes and Cartesian meshes. The combination includes node-matched connection, node mismatched or partially matched splicing, overlap, and the combined use of these combination methods.

[0078] Example 2:

[0079] The present invention also provides a structured grid generation system for a three-periodic minimal surface structure. The structured grid generation system for a three-periodic minimal surface structure can be implemented by executing the process steps of the structured grid generation method for a three-periodic minimal surface structure. That is, those skilled in the art can understand the structured grid generation method for a three-periodic minimal surface structure as a preferred implementation of the structured grid generation system for a three-periodic minimal surface structure.

[0080] Specifically, the structured grid generation system of the three-periodic minimal surface structure includes:

[0081] Module M1, constructs a full hexahedral structured grid of the three-periodic minimal surface main structure;

[0082] Module M2 intersects the full hexahedral structured grid with the filling boundary, deletes the excess grid cells, and obtains the new grid surface;

[0083] Module M3 projects the new mesh surface onto the filling boundary to obtain a boundary-fitting mesh;

[0084] Module M4 generates points within the boundary-fitting grid based on the boundary-fitting grid and according to the CFD boundary layer calculation requirements.

[0085] Module M1 includes the following submodules:

[0086] Module M1.1 divides the pipe network formed by the three-periodic minimal surface into multiple Y-shaped three-way units arranged periodically.

[0087] In module M1.2, each Y-shaped tee unit is divided into three rotationally symmetrical branches, which are connected at the Y-shaped interface, thereby dividing the pipe network into periodically arranged identical modules, forming a 3OH topology.

[0088] Module M1.3 divides each branch pipe into a full hexahedral structured grid using the OH topology form, and then connects the end faces of each branch pipe to form a full hexahedral structured grid with a modularly filled three-periodic minimal surface main structure.

[0089] Specifically, module M1.3 includes the following submodules:

[0090] Module M1.3.1, fills the area near the pipe wall of each branch with an O-shaped grid, and fills the void in the middle of the O-shaped grid with an H-shaped grid; sets the number of grid cells in the flow cross section of the H-shaped grid to 2n×2n (in this embodiment, n is 8), sets the number of circumferential grid cells of the O-shaped grid to 8n, and the grid cells of the inner circle of the O-shaped grid correspond one to one with the grid cells of the outer circle of the H-shaped grid; sets the number of radial grid cells of the O-shaped grid to m (for solid simulation, m can be 8, for fluid simulation, m can be 24), then the number of grid cells in the flow cross section of the O-shaped grid is 8n×m; finally, sets the number of grid cells of the OH topological grid of each branch along the flow direction (branch axial direction) to k (in this embodiment, k is 8), and obtains the OH topological grid of each branch.

[0091] Module M1.3.2, bend the end face of the OH topology grid of each branch pipe into half an angle of 120° and splice them into a Y shape, and splice them at the Y-shaped interface to form a 3OH topology form, obtaining a fixed, modular 3OH topology grid filling each Y-shaped tee unit.

[0092] Specifically, module M3 includes the following submodules:

[0093] Module M3.1 calculates the average value of the external normal vector of the new mesh surface at each mesh point.

[0094] Specifically, for each grid point, the external normal vectors of all surface grid cells containing the grid point are calculated. The external normal vector of each surface cell is The calculation formula is In the formula is the coordinate vector of any vertex p1 of the face unit, is the coordinate vector of the two vertices p2 and p3 adjacent to the face unit and point p1; in order to ensure that the calculated normal vector Outward, we also need to calculate the normal vector from point p1 The number of times the ray in the direction passes through the new mesh surface (excluding point p r ), if the number of times it passes is an even number (including 0), then The direction is correct, otherwise Reverse; finally calculate the external normal vectors of all surface grid cells containing the grid point The average value of .

[0095] Module M3.2 calculates the external normal vectors of each element on the filled boundary surface.

[0096] Specifically, the external normal vector The calculation formula is the same as module M3.1, In the formula is the coordinate vector of any vertex p1 of the face unit, is the coordinate vector of the two vertices p2 and p3 adjacent to the face unit and point p1; in order to ensure that the calculated normal vector Outward, we also need to calculate the normal vector from point p1 The number of times the ray in the direction passes through the filling boundary (excluding point p1). If the number of times is an even number (including 0), then The direction is correct, otherwise Reverse.

[0097] Module M3.3 emits a cubic polynomial curve from the new mesh surface. The starting point of the curve is tangent to the external normal vector of the new mesh surface. The curve gradually bends and projects to the filling boundary. The direction is tangent to the external normal vector of the filling boundary at that location. Thus, a layer of boundary-fitting mesh is obtained, which is further segmented in module M4.

[0098] Module M4 specifically includes:

[0099] Module M4.1: For each curve obtained in Module M3, insert 15 points in the grid in geometric progression, and change the curve into a 16-segment broken line. The size of the first segment (away from the fill boundary) is about half the size of the mainstream grid, and the size of the last segment (near the fill boundary) is set to 0.01 mm or the value required for the boundary layer CFD solution in the specific problem.

[0100] Module M4.2 divides the one-layer boundary-fitting mesh obtained in module M3 at the 15 breakpoints in module M4.1, dividing the original one-layer boundary-fitting mesh into 16 layers, thereby obtaining a boundary-fitting mesh that can meet the requirements of CFD boundary layer calculations.

[0101] Those skilled in the art will appreciate that, in addition to implementing the system and its various devices, modules, and units provided by the present invention in purely computer-readable program code, it is entirely possible to implement the same functions of the system and its various devices, modules, and units provided by the present invention in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system and its various devices, modules, and units provided by the present invention can be considered a hardware component, and the devices, modules, and units included therein for implementing various functions can also be considered as structures within the hardware component; the devices, modules, and units for implementing various functions can also be considered as both software modules implementing the method and structures within the hardware component.

[0102] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. The embodiments of this application and the features in the embodiments may be combined with each other in any manner unless there is a conflict.

Claims

1. A structured grid generation method for a three-periodic minimal surface structure, characterized in that: The following steps are involved: Step S1, constructing a full hexahedral structured grid of a three-periodic minimal surface main structure; Step S2, intersecting the full hexahedral structured grid with the filling boundary, deleting the excess grid cells, and obtaining a new grid surface; Step S3, projecting the new mesh surface onto the filling boundary to obtain a boundary-fitting mesh; Step S4: Based on the boundary body-fitting grid and in accordance with the CFD boundary layer calculation requirements, points within the boundary body-fitting grid are generated.

2. The structured grid generation method of a three-periodic minimal surface structure according to claim 1, characterized in that: In step S1, the pipe network formed by the three-periodic minimal surface is divided into a plurality of periodically arranged Y-shaped three-way units, each Y-shaped three-way unit is divided into a 3OH topological grid according to the 3OH topological form, and further spliced into a full hexahedral structured grid of the entire three-periodic minimal surface main structure.

3. The structured grid generation method of a three-periodic minimal surface structure according to claim 2, characterized in that: The step S1 includes the following sub-steps: Step S1.1, dividing the pipe network formed by the three-periodic minimal surface into a plurality of periodically arranged Y-shaped three-way units; Step S1.2: Each Y-shaped three-way unit is divided into three rotationally symmetrical branches, which are connected at the Y-shaped interface to form a 3OH topology; In step S1.3, each branch pipe is divided into a full hexahedral structured grid using the OH topology form, and then the end faces of each branch pipe are butted together to form a full hexahedral structured grid of a modularly filled three-periodic minimal surface main structure.

4. The structured grid generation method for a three-periodic minimal surface structure according to claim 3, characterized in that: The step S1.3 includes the following sub-steps: In step S1.3.1, fill the area near the pipe wall of each branch with an O-shaped grid, and fill the void in the middle of the O-shaped grid with an H-shaped grid. Set the number of grid cells in the H-shaped grid's flow direction cross section to 2n × 2n, and the number of grid cells in the O-shaped grid's circumferential direction to 8n, with the grid cells in the inner ring of the O-shaped grid corresponding to the grid cells in the outer ring of the H-shaped grid. Set the number of radial grid cells in the O-shaped grid to m, and the number of grid cells in the O-shaped grid's flow direction cross section to 8n × m. Finally, set the number of grid cells in the OH topology grid of each branch along the flow direction to k, to obtain the OH topology grid for each branch. In step S1.3.2, the end faces of the OH topological grid of each branch pipe are bent halfway at an angle of 120° and spliced into a Y shape, and a 3OH topological form is formed at the Y-shaped interface to obtain a fixed, modular 3OH topological grid that fills each Y-shaped tee unit.

5. The structured grid generation method of a three-periodic minimal surface structure according to claim 4, characterized in that: In the step S1.3.2, the number of H-shaped grid units obtained from the three branch sections of the Y-shaped interface is n×2n, and the number of O-shaped grid units obtained is 4n×m. The O-shaped grids are docked with the O-shaped grids, and the H-shaped grids are docked with the H-shaped grids to obtain a fully hexahedral structured grid in the 3OH topological form of the Y-shaped three-way unit.

6. The structured grid generation method of a three-periodic minimal surface structure according to claim 1, characterized in that: In step S2, the out-of-limit grid cells include grid cells that exceed the filling boundary, grid cells that overlap with the filling boundary, and grid cells that are within the filling boundary and are less than a set threshold distance from the filling boundary.

7. The structured grid generation method of a three-periodic minimal surface structure according to claim 6, characterized in that: In step S2, the operation of deleting the excess grid cells includes: trimming scattered grid cells or trimming an entire grid block.

8. The structured grid generation method of a three-periodic minimal surface structure according to claim 1, characterized in that: The step S3 includes the following sub-steps: Step S3.1, calculating the average value of the external normal vectors of the new mesh surface at each mesh point; Step S3.2, calculating the external normal vector of each surface element of the filling boundary; Step S3.3, emit a cubic polynomial curve from the new mesh surface, the starting point of the curve is tangent to the external normal vector of the new mesh surface, the curve gradually bends and projects to the filling boundary, and the direction is tangent to the external normal vector of the filling boundary to obtain a boundary-fitting mesh.

9. The structured grid generation method of a three-periodic minimal surface structure according to claim 1, characterized in that: The step S4 includes the following sub-steps: Step S4.1: For each curve, insert 15 points in the grid according to a geometric progression, and change the curve into a 16-segment broken line. The size of the first segment is half of the mainstream grid size, and the size of the last segment is set to 0.01 mm. Step S4.2, dividing the boundary body-fitting grid at the 15 breakpoints in step S4.1, dividing the boundary body-fitting grid into 16 layers, and obtaining a boundary body-fitting grid that can meet the requirements of CFD boundary layer calculation.

10. A structured grid generation system for a three-periodic minimal surface structure, characterized in that: include: Module M1, constructs a full hexahedral structured grid of the three-periodic minimal surface main structure; Module M2, intersecting the full hexahedral structured grid with the filling boundary, deleting the excess grid cells, and obtaining a new grid surface; Module M3, projects the new mesh surface onto the filling boundary to obtain a boundary-fitting mesh; Module M4 generates points within the boundary body-fitting grid based on the boundary body-fitting grid and in accordance with CFD boundary layer calculation requirements.

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