Automatic Modeling Method and System for Finite-Difference Time-Domain Flow Field Analysis of Complex Microchannel Targets

Abstract

This invention discloses an automatic modeling method and system for finite-difference time-domain (FDTD) flow field analysis of complex microchannel targets. The method includes: establishing a geometric model of the microchannel target structure; using ANSYS-APDL to perform tetrahedral mesh generation on the geometric model to obtain tetrahedral meshing information; determining the spatial positions of the two endpoints of the FDTD edge relative to the tetrahedron, inferring the positional relationship between the edge and the tetrahedron; calculating the positional information of the intersection point when the edge intersects the tetrahedron; determining the medium with different material numbers on both sides of the interface; calculating the length information between the intersection point and the two endpoints of the FDTD edge, thereby obtaining the line ratio; assigning material numbers based on the line ratio information; generating the FDTD mesh; and completing the modeling of the complex microchannel structure. This invention effectively solves the problem of difficult modeling of complex microchannel targets, enabling the microchannel flow field analysis platform to efficiently and rapidly construct complex microchannel structures, significantly improving the solution capability.

Description

Technical Field

[0001] This invention belongs to the field of complex microchannel modeling, and specifically relates to an automatic modeling method and system for target time-domain finite difference flow field analysis of complex microchannels. Background Technology

[0002] Microfluidic thermal management technology has attracted widespread attention from scholars both domestically and internationally in recent years due to its high heat transfer coefficient, compact size, and good compatibility with highly integrated chips. This technology typically involves etching microchannels of varying numbers and structures onto a chip substrate, then injecting coolant into the channels via an external system. The coolant's heat absorption capacity helps to remove the heat generated by the chip, thereby achieving heat dissipation.

[0003] In the research and design of microfluidic thermal management technology, simulation tools and research methods play a crucial role. The Finite Difference Time Domain (FDTD) method, due to its significant advantages such as intuitiveness, ease of programming, wide applicability, and inherent parallel processing capabilities, has been widely used in simulation and modeling. However, FDTD faces certain limitations when dealing with complex geometries, particularly in accurately representing irregular shapes and details.

[0004] Therefore, it is particularly important to develop modeling techniques that can effectively deal with complex geometric structures. Only through precise modeling techniques can we accurately capture actual geometric features, improve the reliability and accuracy of simulation results, and provide more refined and realistic simulations for solving complex flow field problems such as microchannels. Summary of the Invention

[0005] The purpose of this invention is to provide an automatic modeling method and system for time-domain finite-difference flow field analysis of complex microchannel targets, which effectively solves the problem of modeling complex microchannel targets, enabling the microchannel flow field analysis platform to efficiently and quickly construct complex microchannel structures and significantly improve the solution capability.

[0006] The technical solutions for achieving the purpose of the present invention are:

[0007] An automated modeling method for time-domain finite-difference flow field analysis of complex microchannel targets includes the following steps:

[0008] Step 1: Establish the geometric model of the microchannel target structure. Use ANSYS-APDL to perform tetrahedral meshing on the geometric model to obtain tetrahedral meshing information, including the tetrahedral number, material number, node number, and the three-dimensional coordinate information of its tetrahedral nodes.

[0009] Step 2: Determine the spatial positions of the two endpoints of the FDTD edge relative to the tetrahedron, deduce the positional relationship between the edge and the tetrahedron, and calculate the positional information of the intersection point when the edge intersects the tetrahedron.

[0010] Step 3: Determine the medium of different material numbers on both sides of the interface, calculate the length information between the intersection point and the two ends of the FDTD edge, and then obtain the line ratio. Allocate material numbers based on the line ratio information, generate the FDTD mesh, and complete the modeling of the complex microchannel structure.

[0011] Furthermore, when an edge intersects a tetrahedron, the position information of the intersection point is calculated as follows:

[0012]

[0013] Where, parameter d = -(x n x A +y n y A +x z z A ), x H ,y H ,z H Let H be the coordinates of the intersection point H of the edge and the interface or boundary surface, x A ,y A ,z A x B ,y B ,z B Let x be the coordinates of two vertices of the interface or boundary surface. n ,y n ,z n The coordinates of the unit normal vector n of the interface or boundary surface of a tetrahedron.

[0014] Furthermore, the medium of different material numbers on both sides of the interface is determined, specifically including:

[0015] To determine the relationship between the reference vector and the normal vector: calculate the dot product of the unit normal vector n and the reference vector m. If m·n is greater than 0, it means that the unit normal vector n points to the side with the larger material number; otherwise, it points to the side with the smaller material number.

[0016] Determine the relationship between an edge and its normal vector: Calculate the two vectors of the edge respectively. and The dot product of the vector with the unit normal vector n is such that if the dot product is greater than 0, the line segment corresponding to the vector is located in the material pointed to by the unit normal vector; otherwise, it is in the material on the other side. E and F are the two endpoints E and F of the FDTD mesh edge.

[0017] Furthermore, assigning material numbers based on line ratio information includes: if the edge line accounts for a large proportion in a medium of a certain material number, then the material number is selected to be assigned to the FDTD grid in that direction.

[0018] Furthermore, it also includes: quickly identifying different boundary conditions based on the material number and processing them accordingly.

[0019] Furthermore, the process of quickly identifying and processing different boundary conditions includes: after step approximation, the range for adding boundary conditions is set using meshes with different material numbers; regions with different material numbers in adjacent meshes are identified as boundaries and boundary conditions are set accordingly.

[0020] Furthermore, it also includes: after processing the boundary conditions, performing flow field calculations based on the microchannel flow field simulation method.

[0021] An automated modeling system for time-domain finite-difference flow field analysis of complex microchannel targets includes:

[0022] Tetrahedral meshing elements were used to establish the geometric model of the microchannel target structure. ANSYS-APDL was used to perform tetrahedral meshing on the geometric model to obtain tetrahedral meshing information, including the tetrahedral number, material number, node number, and the three-dimensional coordinate information of its tetrahedral nodes.

[0023] The edge-tetrahedral intersection calculation unit determines the spatial position of the two endpoints of the FDTD edge relative to the tetrahedron, infers the positional relationship between the edge and the tetrahedron, and calculates the positional information of the intersection point when the edge intersects the tetrahedron.

[0024] The complex microchannel structure modeling unit determines the medium of different material numbers on both sides of the interface, calculates the length information between the intersection point and the two ends of the FDTD edge, and then obtains the line ratio. Based on the line ratio information, the material number is assigned, and the FDTD mesh is generated to complete the modeling of the complex microchannel structure.

[0025] An automatic modeling device for time-domain finite-difference flow field analysis of complex microchannel targets includes: a memory, a processor, and a computer program stored in the memory. When the processor executes the computer program, it implements the steps of the automatic modeling method for time-domain finite-difference flow field analysis of complex microchannel targets.

[0026] A computer storage medium storing an executable program, the executable program being executed by a processor to implement the steps of the automatic modeling method for the time-domain finite-difference flow field analysis of complex microchannel targets.

[0027] Compared with the prior art, the significant advantages of this invention are:

[0028] (1) This invention can solve the problem of modeling complex irregular structures by the finite-difference time-domain method, capture the actual geometric features, and improve the reliability and accuracy of simulation results.

[0029] (2) The present invention can achieve a faster modeling speed for complex target structures than the traditional finite difference time-domain method, and reduce the time required for modeling.

[0030] (3) This invention is not only applicable to common microchannel structures, but also can effectively handle microchannel structures with various complex geometries. It has wide applicability and good adaptability, and can meet the needs of different fields and application scenarios. Attached Figure Description

[0031] Figure 1 It is a diagram showing the relationship between vertices and tetrahedrons.

[0032] Figure 2 A schematic diagram of the interface or intersection between an edge and a tetrahedron.

[0033] Figure 3 This is a diagram showing the location of the point. Figure 3 (a) in the diagram is a schematic of H inside triangle ABC. Figure 3 (b) in the diagram is a schematic diagram of H outside triangle ABC.

[0034] Figure 4 It is a vector diagram.

[0035] Figure 5 This is a schematic diagram where an edge passes through a surface and the intersection point is inside the surface.

[0036] Figure 6 yes Figure 5 A schematic diagram of the interface under different conditions. Figure 6 (a) in the diagram is a schematic diagram of the interface between the medium and the moisture. Figure 6 (b) in the diagram is a schematic diagram of the interface between the medium and the air. Figure 6 (c) in the diagram is a schematic diagram of the water-air interface.

[0037] Figure 7 This is a schematic diagram showing the position where the edge does not cross the triangular face. Figure 7 (a) in the diagram is a schematic showing the position of the edge not parallel to the surface. Figure 7 (b) in the diagram is a schematic diagram of the position of the edge parallel to the surface.

[0038] Figure 8 yes Figure 7 A schematic diagram of the interface under different conditions. Figure 8 (a) in the diagram is a schematic diagram of the interface between the medium and the moisture. Figure 8 (b) in the diagram is a schematic diagram of the interface between the medium and the air. Figure 8 (c) in the diagram is a schematic diagram of the water-air interface.

[0039] Figure 9 This is a flowchart of the automatic flow field modeling calculation.

[0040] Figure 10 This is a model diagram of a serpentine microchannel. Figure 10 (a) in the diagram is an ANSYS-APDL modeling diagram. Figure 10 (b) in the figure is the FDTD automatic modeling diagram.

[0041] Figure 11 This is a flow field distribution diagram in the X direction. Figure 11 (a) in the diagram shows the flow field distribution in the COMSOLX direction. Figure 11 (b) in the diagram shows the flow field distribution in the FDTDX direction.

[0042] Figure 12 This is a flow field distribution diagram in the Y direction. Figure 12 (a) in the diagram shows the flow field distribution in the COMSOLY direction. Figure 12 (b) in the diagram shows the flow field distribution in the FDTDY direction.

[0043] Figure 13 This is a graph showing the error comparison calculation. Detailed Implementation

[0044] The present invention will now be described in further detail with reference to the accompanying drawings.

[0045] Combination Figure 9 This invention provides an automatic modeling method for time-domain finite-difference flow field analysis of complex microchannel targets, with the following steps:

[0046] The first step is to establish a microchannel geometric model and use ANSYS-APDL to perform tetrahedral meshing on the geometric structure to obtain the tetrahedral number, material number, node number, and three-dimensional coordinate information of the nodes.

[0047] The second step is to determine the interior points and edges. The process of determining the interior points and edges includes determining the spatial positions of the two endpoints of the FDTD edge relative to the tetrahedron, thereby inferring the relative positional relationship between the edge and the tetrahedron.

[0048] The third step is to calculate the position information of the intersection point when the edge intersects the tetrahedron.

[0049] The fourth step involves calculating the length between the intersection point and the two endpoints of the FDTD mesh edge after obtaining the intersection point, thereby determining the line ratio. Using this line ratio information, the FDTD mesh is generated, enabling accurate construction of complex microchannel structures.

[0050] The fifth step is to quickly identify different boundary conditions and process them accordingly based on the material number generated from the mesh.

[0051] The sixth step is to perform flow field calculations based on the microchannel flow field simulation method after the boundary conditions are identified and added.

[0052] In the first step, a geometric structure model is established, and ANSYS-APDL is used to perform tetrahedral meshing on the geometric structure to obtain the number of the tetrahedrons, material number, node number, and three-dimensional coordinate information of the nodes.

[0053] In the second step, the determination of interior points and edges involves identifying the spatial positions of the two endpoints of the FDTD edge relative to the tetrahedron, thereby inferring the relative positional relationship between the edge and the tetrahedron. Before analyzing the relationship between the edge and the tetrahedron, it is necessary to first determine whether the two endpoints of the edge are located inside the tetrahedron, as these endpoints may be located inside or outside the tetrahedron. The specific determination method is as follows: Figure 1 As shown, it is necessary to calculate the volume of the new tetrahedron formed by any three of the four vertices A, B, C, and D of the tetrahedron from the target point E (a total of four), as well as the volume of the original tetrahedron. By comparing the sum of the volumes of the four new tetrahedrons with the volume of the original tetrahedron, it can be determined whether point E is within the divided tetrahedron.

[0054] V ABCD =V EABC +V EABD +V EACD +V EBCD (1) If equation (1) is satisfied, then point E is an interior point inside the tetrahedron. If not, then the vertex is outside the tetrahedron. If both vertices of an edge are outside the tetrahedron, then the edge is located outside the microfluidic computational domain, and this case is not considered.

[0055] In the third step, if the edge is not within another medium, it is necessary to determine the different positions of the edge at the tetrahedral interface or boundary surface. For ease of analysis, assume that the two endpoints of an edge of the FDTD mesh are E(x) and E(x). E ,y E ,z E ) and F(x F ,y F ,z F The intersection point of the edge line and the interface or boundary surface is H(x). H ,y H ,z H The three vertices of the triangular interface or boundary are A(x) and A(x). A ,y A ,z A ), B(x) B ,y B ,z B ), C(x)C ,y C ,z C ) and the unit normal vector of the surface is n = (x n ,y n ,z n ),like Figure 2 As shown. Since the coordinates of the three vertices of triangle ABC are known, and according to the definition of the cross product of vectors, the unit normal vector n of triangle ABC can be obtained from any two side vectors, such as:

[0056] The line containing EF intersects the plane ABC containing the triangle, and there must be a point of intersection. Let point H be the point of intersection. Since the coordinates of the three vertices of the tetrahedral triangle are directly obtained from the subdivision file and are known, the normal vector of the face containing the triangle can be easily calculated as n = (x... n ,y n ,z n The details are as follows:

[0057] The analytical equation of the plane containing the triangle can be expressed as:

[0058] x n (xx A )+y n (yy A )+x z (zz A )=0 (4)

[0059] Since the coordinates of the two vertices E and F of the FDTD mesh edge are known, the equation of the line containing EF can be expressed as follows:

[0060] Then, based on the mathematical equations of the line and the plane, the coordinates (x, y) of the intersection point H can be obtained. H ,y H ,z H ), which is represented as follows:

[0061]

[0062] Among them, d = -(x) n x A +y n y A +x z z A Now we know the coordinates of H. After obtaining the coordinates of H, the vector... The size and direction of the intersection point H are known, so the areas of triangles HAB, HBC, and HCA can be easily calculated. To determine whether the intersection point H lies on the face of the triangle defined by vertices A, B, and C, we will calculate the area of ​​all possible new triangles formed by H and any two vertices A, B, and C, and compare them with the area of ​​the original triangle ABC. If the area of ​​the newly formed triangle is equal to the area of ​​the original triangle, then we can deduce that the intersection point H lies on the face of the triangle; otherwise, H does not lie on this face. The intersection point H may be inside or outside the triangle. Figure 3 As shown. Figure 3 As shown in (a), there is S ABC =S HAB +S HBC +S HAC The intersection point H may be inside the triangle, on the side of the triangle, or at a vertex. Thus, the edge may be parallel to the triangle face (on the triangle face) or one vertex of the edge may be at any position on the triangle face.

[0063] In the fourth step, quickly identifying the material affixed by the edge is a prerequisite for modeling. The method for determining the medium with different material numbers on both sides of the interface is as follows, taking the passage through the interface as an example, as shown in the diagram. Figure 4 As shown; the two endpoints of the same edge are E and F, the intersection point of the edge with the interface or boundary surface is H, the three vertices of the triangular interface or boundary surface are A, B, C, and D, and the unit normal vector of the surface is m. For ease of subsequent analysis, the reference vector m always points from the intersection point H to the fourth vertex D of the tetrahedron, and always points to the side with the larger material number. Assume that at this time, the material number on the left side of the interface is larger (5), and the material number on the other side is smaller (4), and the unit normal vector of the surface points to the side with the smaller material number.

[0064] The steps to determine the material affiliation of the two sides of an edge are as follows.

[0065] (1) Determine the relationship between the reference vector and the normal vector. Calculate the dot product of the unit normal vector n and the reference vector m. If m·n is greater than 0, it means that the unit normal vector n points to the side with the larger material number; otherwise, it points to the side with the smaller material number. Figure 5 The image shows the side with the smaller material number.

[0066] (2) Determine the relationship between the edge line and the normal vector. Calculate the two vectors of the edge line respectively. and The magnitude of the dot product with the unit normal vector n. If the dot product is greater than 0, the line segment corresponding to the vector lies in the material pointed to by the unit normal vector; otherwise, it lies in the material on the other side. Figure 5 In the middle, there is Less than 0, therefore the vector Located in a medium with material number 5, vector Located in a medium with material number 4.

[0067] (3) Calculate the line ratio. The mesh size in the x-direction of the FDTD mesh is known, and the vector... and The length of the line has already been obtained in the previous section. By comparing the two, the line ratio can be obtained, and then the line ratio can be stored in an array.

[0068] (4) Assign material number. Based on the calculated line ratio, if the edge line accounts for a large proportion in a certain material number medium, then select to assign the material number to the FDTD grid in that direction.

[0069] The above only describes the method for determining the positional relationship between the edge and the interface or sub-interface in the x-direction and for calculating the line ratio. This method is also applicable to the y and z directions, and the specific details will not be elaborated further. The purpose of determining the positional relationship between the edge and the boundary surface or sub-interface is to calculate the line ratio in order to perform stepped approximation modeling.

[0070] Based on the above discussion, there are three different positional relationships between the edge line and the interface in the x-direction, which will be explained in detail below:

[0071] (1) An edge passes through a surface and the intersection point lies within the surface, as shown in the diagram. Figure 5 As shown: When the intersection point H is inside the triangle, the edge can be directly identified based on the coordinates of H. If the grid edges are truncated, the lengths of each part of the truncated edge must also be recorded. and The materials used in current microfluidic channel models mainly include media (such as silicon), air, and water. A distinction is made between these materials, illustrated in the diagram. Figure 6 As shown, if Greater than Then the FDTD mesh material is divided into vectors. Points to the material number; otherwise, it is divided into a vector. The material number that points to the material.

[0072] (2) When the edges of the FDTD mesh do not cross the triangular interface, it is divided into... Figure 7 There are two scenarios. One is that one vertex of the edge lies within the plane, and the edge is not parallel to the plane, as follows: Figure 7 As shown in (a), another type is where the edge is parallel to the surface and the vertex lies in the surface, as in (a). Figure 7 (b) shows the material differentiation diagram for the case shown in Figure 7(a). Figure 8 As shown; in this case, only one vertex of the edge is located at the interface or boundary surface, while the rest are located in the medium of the same material number. The line ratio is calculated to be 1, and the FDTD mesh is classified into the class with the larger material number. For Figure 7(b) In the case where one vertex of the edge is located at the interface or boundary surface and is parallel to the plane, we first determine whether it belongs to the case shown in (b) by checking if the dot product of the edge and the surface normal vector is zero. If the dot product is zero, it means that the edge is parallel to the plane. Then, we determine which of the two vertices is located in the plane. For the material partitioning of the FDTD mesh, the edges are classified into the category with the larger material number by default, because it is easier to understand, so the schematic diagram of the medium interface will not be described again.

[0073] In the fifth step, after completing the FDTD mesh modeling of the 3D target model, boundary adaptive meshing can be performed based on the FDTD mesh information of the model. Boundary conditions are typically added at the interface between two materials. Since the material number corresponding to each mesh has been obtained in step four, the FDTD meshes on both sides of the interface can be easily located, and boundary conditions can be set accordingly.

[0074] In the sixth step, after the boundary conditions are set, the FDTD flow field simulation platform can automatically simulate the flow field of the target model.

[0075] To verify the correctness and effectiveness of the present invention, the flow field simulation of a right-angle corner microchannel is analyzed below.

[0076] The serpentine microchannel structure is composed of two semi-circular channels joined in opposite directions. The total length in the X direction is 7mm, the total length in the Y direction is 7mm, and the thickness in the Z direction is 1mm. The outer radius of the arc is 2mm, and the inner radius is 1mm. The inlet and outlet are located in the Y direction, and their cross-sectional sizes are both... The number of grid cells in the X, Y, and Z directions are 140, 140, and 10, respectively. The FDTD flow field simulation algorithm is selected with a time step of 10. -4 The time was set to 15,000 steps. A fixed flow velocity of u0 (10 mm / s) was applied along the positive Y direction in the XOZ plane. The remaining surfaces were fixed walls. The flow velocities at the center points of the grid in both the X and Y directions were selected for plotting and observation. The FDTD calculation results were compared with those from COMSOL software to obtain the flow field distribution maps in the X and Y directions, as shown below. Figure 11 , 12 As shown, the maximum relative error between the FDTD calculation results and the COMSOL calculation results is approximately 4.5%. Figure 13 As shown.

[0077] This embodiment also provides an automatic modeling system for time-domain finite-difference flow field analysis of complex microchannel targets, including:

[0078] Tetrahedral meshing elements were used to establish the geometric model of the microchannel target structure. ANSYS-APDL was used to perform tetrahedral meshing on the geometric model to obtain tetrahedral meshing information, including the tetrahedral number, material number, node number, and the three-dimensional coordinate information of its tetrahedral nodes.

[0079] The edge-tetrahedral intersection calculation unit determines the spatial position of the two endpoints of the FDTD edge relative to the tetrahedron, infers the positional relationship between the edge and the tetrahedron, and calculates the positional information of the intersection point when the edge intersects the tetrahedron.

[0080] The complex microchannel structure modeling unit determines the medium of different material numbers on both sides of the interface, calculates the length information between the intersection point and the two ends of the FDTD edge, and then obtains the line ratio. Based on the line ratio information, the material number is assigned, and the FDTD mesh is generated to complete the modeling of the complex microchannel structure.

[0081] This embodiment also provides an automatic modeling device for time-domain finite-difference flow field analysis of complex microchannel targets, including: a memory, a processor, and a computer program stored in the memory. When the processor executes the computer program, it implements the steps of the automatic modeling method for time-domain finite-difference flow field analysis of complex microchannel targets.

[0082] This embodiment also provides a computer storage medium storing an executable program, which is executed by a processor to implement the steps of the automatic modeling method for the time-domain finite-difference flow field analysis of complex microchannel targets.

[0083] This invention, based on a finite-difference time-domain flow field analysis platform and incorporating geometric mesh information, automates the solution of intersections between edges and tetrahedrons. It employs a stepped approximation method to process the mesh region, efficiently modeling complex microchannel targets. Furthermore, this technique assigns numbers to different material domains, resolving the adaptive identification and setting of boundary conditions, ensuring the accuracy and completeness of the modeling. This invention effectively solves the difficulty of modeling complex microchannel targets, enabling the microchannel flow field analysis platform to efficiently and rapidly construct complex microchannel structures, significantly improving its solution capabilities.

[0084] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0085] Obviously, those skilled in the art can make various modifications and variations to the embodiments of the present invention without departing from the spirit and scope of the embodiments of the present invention. Thus, if these modifications and variations to the embodiments of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention also intends to include these modifications and variations.

Claims

1. An automatic modeling method for time-domain finite-difference flow field analysis of complex microchannel targets, characterized in that, Including the following steps: Step 1: Establish the geometric model of the microchannel target structure. Use ANSYS-APDL to perform tetrahedral meshing on the geometric model to obtain tetrahedral meshing information, including the tetrahedral number, material number, node number, and the three-dimensional coordinate information of its tetrahedral nodes. Step 2: Determine the spatial positions of the two endpoints of the FDTD edge relative to the tetrahedron, deduce the positional relationship between the edge and the tetrahedron, and calculate the positional information of the intersection point when the edge intersects the tetrahedron. Step 3: Determine the medium of different material numbers on both sides of the interface, calculate the length information between the intersection point and the two ends of the FDTD edge, and then obtain the line ratio. Assign material numbers based on the line ratio information, generate the FDTD mesh, and complete the modeling of the complex microchannel structure. The line ratio refers to the ratio of the calculated length information between the intersection point and the two ends of the FDTD edge.

2. The automatic modeling method for time-domain finite-difference flow field analysis of complex microchannel targets according to claim 1, characterized in that, When an edge intersects a tetrahedron, the location information of the intersection point is calculated as follows: Where, parameter d = -(x n x A +y n y A +x z z A ), x H ,y H ,z H Let H be the coordinates of the intersection point H of the edge and the interface or boundary surface, x A ,y A ,z A x B ,y B ,z B Let x be the coordinates of two vertices of the interface or boundary surface. n ,y n ,z n The coordinates of the unit normal vector n of the interface or boundary surface of the tetrahedron.

3. The automatic modeling method for time-domain finite-difference flow field analysis of complex microchannel targets according to claim 1, characterized in that, The determination of the medium with different material numbers on both sides of the interface includes: To determine the relationship between the reference vector and the normal vector: Calculate the dot product of the unit normal vector n and the reference vector m. If m·n is greater than 0, the unit normal vector n points to the side with the larger material number; otherwise, it points to the side with the smaller material number. To determine the relationship between the edge line and the normal vector: Calculate the two vectors of the edge line respectively. and The dot product of the vector with the unit normal vector n is such that if the dot product is greater than 0, the line segment corresponding to the vector with a dot product greater than 0 with the unit normal vector n is located in the material pointed to by the unit normal vector; otherwise, it is in the material on the other side. E and F are the two endpoints E and F of the FDTD mesh edge.

4. The automatic modeling method for time-domain finite-difference flow field analysis of complex microchannel targets according to claim 1, characterized in that, Also includes: Based on the material number, quickly identify different boundary conditions and perform corresponding processing.

5. The automatic modeling method for time-domain finite-difference flow field analysis of complex microchannel targets according to claim 4, characterized in that, The process of quickly identifying and processing different boundary conditions includes: after step approximation, the range for adding boundary conditions is set by using meshes with different material numbers. Regions with different material numbers in adjacent meshes are identified as boundaries and boundary conditions are set.

6. The automatic modeling method for time-domain finite-difference flow field analysis of complex microchannel targets according to claim 4, characterized in that, Also includes: After processing the boundary conditions, the flow field is calculated using the microchannel flow field simulation method.

7. An automatic modeling system for time-domain finite-difference flow field analysis of complex microchannel targets based on the method of any one of claims 1-6, characterized in that, include: Tetrahedral meshing elements were used to establish the geometric model of the microchannel target structure. ANSYS-APDL was used to perform tetrahedral meshing on the geometric model to obtain tetrahedral meshing information, including the tetrahedral number, material number, node number, and the three-dimensional coordinate information of its tetrahedral nodes. The edge-tetrahedral intersection calculation unit determines the spatial position of the two endpoints of the FDTD edge relative to the tetrahedron, infers the positional relationship between the edge and the tetrahedron, and calculates the positional information of the intersection point when the edge intersects the tetrahedron. The complex microchannel structure modeling unit determines the medium of different material numbers on both sides of the interface, calculates the length information between the intersection point and the two ends of the FDTD edge, and then obtains the line ratio. The material number is assigned based on the line ratio information, and the FDTD mesh is generated to complete the modeling of the complex microchannel structure. The line ratio refers to the ratio of the calculated length information between the intersection point and the two ends of the FDTD edge.

8. An automatic modeling device for time-domain finite-difference flow field analysis of complex microchannel targets, characterized in that, include: A memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the automatic modeling method for the analysis of the target time-domain finite-difference flow field of complex microchannels as described in any one of claims 1-6.

9. A computer storage medium, characterized in that, The computer storage medium stores an executable program, which is executed by a processor to implement the steps of the automatic modeling method for the analysis of complex microchannel target time-domain finite difference flow field as described in any one of claims 1-6.

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