Grid generation method and system for electrical equipment simulation two-dimensional electric-thermal field analysis model

Abstract

The grid generation method and system of the electrical equipment simulation two-dimensional electric-thermal field analysis model, the method comprises: carrying out geometric boundary identification on the initial two-dimensional electric-thermal field analysis STL geometric model, and establishing a signed distance function based on the identified geometric boundary; generating points on the geometric boundary based on the signed distance function and obtaining all newly generated boundary units, completing the grid division of the geometric boundary; on the basis of all newly generated boundary units, the grid division of the geometric interior is carried out by using the inside normal front pushing algorithm based on the signed distance function, and the grid generation is completed. Full-automatic grid division is realized, the automation degree of grid division is improved, the time consumed by grid division is reduced, and the application range and convenience of the algorithm are improved.

Description

Technical Field

[0001] This invention belongs to the field of electrical equipment simulation technology, and relates to a novel mesh generation method and system for a two-dimensional electrothermal field analysis model of electrical equipment simulation. Background Technology

[0002] The finite element method (FEM) or finite volume method (FVMM) is a commonly used numerical calculation method for two-dimensional electrothermal field analysis in electrical equipment simulation. This method can achieve functions such as state prediction and structural optimization of the simulated object, and is widely used in various industries, bringing immeasurable economic value. However, both the FEM and FVMM require discretization of the geometric model for two-dimensional electrothermal field analysis of electrical equipment simulation at the beginning, that is, meshing the geometric model.

[0003] Parametric geometric models offer more accurate and detailed geometric descriptions, and commonly used meshing methods largely revolve around them. Existing commercial simulation software only supports different parametric geometric models based on NURBS. Parametric geometric models are typically obtained through CAD software, such as the 3D modeling software Solidworks, and the geometric descriptions of parametric geometric models constructed by different CAD software still differ. This is why commercial software such as ANSYS needs to develop different CAD geometry interfaces. However, for more general non-parametric geometric models, such as STL (stereolithography) geometric models, existing meshing algorithms and commercial software cannot directly mesh them.

[0004] However, existing meshing methods, including commercial software like ANSYS Mesh, cannot directly mesh STL files. This is because STL itself contains limited geometric information, consisting only of multiple disordered triangular faces and their normals, failing to provide accurate geometric boundary and volume information like parametric models such as NURBS. Existing front-end propagation methods also require manual specification of geometric boundaries, defining the outer boundary as counterclockwise and the inner boundary as clockwise, resulting in low automation and inconvenience. A common solution for meshing STL geometry is to further mesh based on the discrete faces of the non-parametric model; however, this method retains all points of the initial STL model, making it difficult to control node density and resulting in extremely poor mesh quality. Meshing non-parametric geometric models is far more difficult than parametric models. This makes it unsuitable for the numerical simulation calculations of two-dimensional electrothermal field analysis of electrical equipment with complex curves, such as transformer bushing skirts and insulators. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a novel mesh generation method and system for two-dimensional electrothermal field analysis models of electrical equipment simulation. This method identifies geometric features of STL geometric models of electrical equipment with complex curves, such as transformer bushing skirts and insulators, by recognizing key information such as feature edges and surfaces to obtain all boundary information of the original STL geometric model. Based on the identified geometric features, a new geometric description model is reconstructed using a signed distance function, instead of continuing to use discrete elements to describe the geometry. Based on the new geometric description model, a parametric model meshing algorithm (i.e., the inner normal forward propagation algorithm) is used to mesh the model, thus completing mesh generation.

[0006] The present invention specifically adopts the following technical solution.

[0007] A mesh generation method for a two-dimensional electrothermal field analysis model of electrical equipment simulation, the method comprising the following steps:

[0008] Step 1: Identify the geometric boundaries of the initial electrical equipment simulation two-dimensional electrothermal field analysis STL geometric model, and establish a symbolic distance function based on the identified geometric boundaries;

[0009] Step 2: Generate points on the geometric boundary based on the signed distance function and obtain all newly generated boundary elements to complete the mesh generation of the geometric boundary;

[0010] Step 3: Based on all newly generated boundary elements, use the interior normal front advance algorithm based on the signed distance function to perform mesh generation within the geometry, thus completing the mesh generation.

[0011] Preferably, in step 1, all geometric boundaries of the initial electrical equipment simulation two-dimensional electrothermal field analysis STL geometric model are identified, duplicate boundaries are removed, edge elements at the boundaries are found, and a boundary element set composed of geometric boundaries is obtained. Then, a signed distance function is established through this boundary element set.

[0012] Preferably, the symbolic distance function fd(x) is:

[0013]

[0014] Where Ω and Γ represent the geometric interior region and geometric boundary of the STL geometric model for two-dimensional electrothermal field analysis of electrical equipment simulation, respectively.

[0015] When point x is inside the geometry, the signed distance function is negative;

[0016] When point x is on the geometric boundary, the signed distance function is 0;

[0017] The signed distance function is positive when point x is outside the geometry;

[0018] And the absolute value of the function is the distance from point x to the boundary.

[0019] Preferably, when establishing the signed distance function, the method for determining the geometric location of a point is as follows:

[0020] Given the polygon P from the boundary unit set, determine the wind number ω(Q,P) of point Q relative to polygon P. If ω(Q,P) is non-zero, then point Q is inside the polygon, i.e., point Q is inside the geometry. If ω(Q,P) is zero, then further determine the absolute value of the function of point Q. If the absolute value of the function is zero, then point Q is on the geometric boundary. If the absolute value of the function is not zero, then point Q is outside the geometry.

[0021] Preferably, the wind number ω(Q,P) of point Q relative to polygon P is determined as follows:

[0022] Draw a ray λ from point Q along the positive x-axis. Treat the edges of the polygon as a gust of wind, with the wind blowing from the starting point of the edge to the ending point of the edge. Define the wind blowing from below the ray to the top as a positive wind and the wind blowing from above the ray to the bottom as a negative wind.

[0023] Initialize ω(Q,P) = 0;

[0024] 1) If ray λ intersects the wind, and the wind is a positive wind, then equation (2) is satisfied:

[0025]

[0026] Then ω(Q,P)=ω(Q,P)+1;

[0027] 2) If ray λ intersects with the wind, and the wind is a counter-wind, then equation (3) is satisfied:

[0028]

[0029] Then ω(Q,P)=ω(Q,P)-1;

[0030] After accumulating 1) and 2), we obtain the final ω(Q,P), which is the wind number ω(Q,P) of point Q relative to polygon P.

[0031] Among them, P i x and P i y Q represents the x and y coordinates of the i-th point of the polygon, respectively, where n is the number of points in the polygon. x Q y Let x and y be the coordinates of point Q, and sign|*| represent the positive or negative sign of the matrix * determinant.

[0032] Preferably, step 2 specifically includes:

[0033] Step 2.1: Determine the location of the production point on the geometric boundary by using the tangential direction of the boundary curve and the density function value;

[0034] Step 2.2: Correct the position of the point determined in Step 2.1 according to the gradient of the signed distance function to obtain the updated point position;

[0035] Step 2.3: Connect the updated point positions sequentially to obtain the newly generated boundary cell set, thus completing the mesh generation of the geometric boundary.

[0036] Preferably, in step 2.1, it is assumed that n points {P1, P2, P3….P} need to be generated on the boundary curve. n If point A is the starting point of the curve and point B is the ending point of the curve, then P1 is the starting point of the curve. n B is the endpoint of the curve;

[0037] Point P i The position is determined by point P i-1 Point P i-1 Tangential direction Tn i-1 It is determined together with the density function value, specifically:

[0038]

[0039] Among them, P i x and P i y These represent the i-th point P on the curve. i x and y coordinates, Tn i-1 Equal to point P i-1 The curve tangent at point fh is the density function, and the density function value at each point is specified by the user in advance.

[0040] Preferably, in step 2.2, point P is first obtained using equation (5). i The gradient of the sign distance function at point:

[0041]

[0042] Where Δx and Δy are displacements in the x and y directions, respectively;

[0043] fd(P i x ,P i y Let fd be the signed distance function at point P. i The function value at that location;

[0044] [P i dx ,Pi dy [The sign distance function fd at point P] i gradient at;

[0045] Then, the updated point P is obtained based on the gradient. i Location for:

[0046]

[0047] Preferably, in step 3, the inner normal front advancement algorithm based on the signed distance function obtains surface elements within the geometric region based on all newly generated boundary elements, thereby achieving mesh generation within the geometry. The specific algorithm process includes:

[0048] Step 3.1: Take all the newly generated boundary elements as the front, use the signed distance function to establish the normal set Fn of the front, and establish an empty set of surface elements S;

[0049] Step 3.2: Select an edge AB in the Front as the initial edge of the newly generated triangle, and delete the selected edge AB from the Front.

[0050] Step 3.3: Calculate the density function value DF at the midpoint of AB. Search for points near AB on the front. The search requirements are: the distance between the point and the midpoint of AB is less than DF, and the triangle formed by the point and AB does not intersect the front edge. Calculate the mass of each triangle formed by the searched point and AB, and select the triangle △ABD with the highest mass to enter the candidate.

[0051] Step 3.4: Calculate the point C required to form the triangle with the highest quality in the normal direction within AB, which together with AB forms triangle △ABC;

[0052] Step 3.5: Compare the quality factors Q of triangles △ABC and △ABD, and add the triangle with the higher quality factor to S;

[0053] Step 3.6: If it is △ABD, add S, and determine whether sides AD and BD are contained in the front. If AD ∈ In the Front section, delete AD and add BD. Then add edge AD to the Front, and the method for determining edge BD is the same as that for AD;

[0054] If triangle ABC is added to S, then sides AC and BC are both added to Front;

[0055] For edges added to Front, calculate their internal normal using the signed distance function and add them to Fn simultaneously.

[0056] Step 3.7: Determine if Front is an empty set. If it is an empty set, output the surface unit set S; otherwise, return to step 3.2.

[0057] A mesh generation system for a two-dimensional electrothermal field analysis model of electrical equipment simulation includes:

[0058] The boundary identification and function construction module is used to identify the geometric boundaries of the initial STL geometric model for two-dimensional electrothermal field analysis, and to establish a symbolic distance function based on the identified geometric boundaries.

[0059] The boundary mesh generation module is used to generate points on the geometric boundary based on the signed distance function and obtain all newly generated boundary cells, thus completing the mesh generation of the geometric boundary;

[0060] The internal mesh generation module is used to generate a mesh for the geometric interior by using an internal normal front advance algorithm based on the signed distance function, based on all newly generated boundary elements.

[0061] A terminal includes a processor and a storage medium; the storage medium is used to store instructions.

[0062] The processor is configured to operate according to the instructions to execute the steps of the method.

[0063] A computer-readable storage medium having a computer program stored thereon that, when executed by a processor, implements the steps of the method.

[0064] The beneficial effects of this invention are compared with those of the prior art:

[0065] This invention addresses the STL geometric model (non-parametric model) for simulating the two-dimensional electrothermal field analysis of electrical equipment with complex curves, such as transformer bushing skirts and insulators. By re-establishing a new geometric description form through the signed distance function and combining it with the mesh generation method of the parametric model, the inner normal forward propagation algorithm, it achieves geometrically adaptive mesh generation of the non-parametric STL model. This method features high automation and requires no manual intervention, thereby improving the computational efficiency of the entire numerical simulation and offering better operability.

[0066] This invention addresses the challenges of existing mesh generation methods for STL geometric models. By establishing a signed distance function, it automatically identifies mesh boundaries and determines the interior and exterior of geometric regions. This eliminates the need for manual specification of geometric region boundaries, achieving fully automated mesh generation, improving the automation level of mesh generation, and reducing the time consumed by mesh generation.

[0067] The symbolic distance function establishment method proposed in this invention can cover any complex 2D structure such as transformer bushing skirts and insulators. Furthermore, it can quickly determine the positional relationship between points and the geometry by judging the wind number, without requiring manual specification of the internal geometric region information. After identifying the geometric boundary using the symbolic distance function, an interior-stepping algorithm is used to generate a mesh inside the geometry, instead of specifying that the outer boundary is clockwise and the inner boundary is clockwise. This avoids manual intervention, improves the automation level of the algorithm, and greatly enhances its application scope and convenience. Attached Figure Description

[0068] Figure 1 A flowchart illustrating the mesh generation method for a two-dimensional electrothermal field analysis model of electrical equipment simulation;

[0069] Figure 2 This is a schematic diagram illustrating the construction principle of the symbolic distance function in this embodiment of the invention;

[0070] Figure 3 This is a schematic diagram illustrating the boundary mesh division principle in this embodiment of the invention.

[0071] Figure 4 This is a schematic diagram of the initial STL geometric model in this embodiment of the invention;

[0072] Figure 5 This is a schematic diagram of the boundary recognition results in this embodiment of the invention;

[0073] Figure 6 This is the symbolic distance function constructed based on the boundary in this embodiment of the invention;

[0074] Figure 7 This is the boundary mesh division result in this embodiment of the invention;

[0075] Figure 8 This is the result of the inner normal of the initial frontier in this embodiment of the invention;

[0076] Figure 9 The results of the internal normal front advancement algorithm iteration and internal mesh generation process in this embodiment of the invention are shown. Detailed Implementation

[0077] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, other embodiments obtained by those skilled in the art without creative effort are all within the protection scope of this invention.

[0078] like Figure 1As shown, Embodiment 1 of the present invention provides a mesh generation method for a two-dimensional electrothermal field analysis model of electrical equipment simulation, used for mesh generation of a two-dimensional electrothermal field analysis model of electrical equipment simulation. In a preferred but non-limiting embodiment of the present invention, the method includes the following steps 1-3:

[0079] Step 1: Identify the geometric boundaries of the initial two-dimensional electrothermal field analysis STL geometric model, and establish a symbolic distance function based on the identified geometric boundaries;

[0080] More preferably, all geometric boundaries of the initial two-dimensional electrothermal field analysis STL geometric model are identified, and duplicate boundaries are removed. The edge elements on the boundary (edge ​​elements on the geometric boundary: unique and not shared by two triangular faces) are found to obtain a set of boundary elements composed of geometric boundaries. Then, a signed distance function is established through this set of boundary elements.

[0081] This invention proposes a two-dimensional electrothermal field analysis model for simulating electrical equipment with complex curves, such as transformer bushing skirts and insulators, which can meet the requirements of numerical simulation calculations for their complex 2D structures. To demonstrate the adaptability of this invention to arbitrary complex 2D structures, [the following is used as an example]. Figure 4-9 The shape is used as an example, and those skilled in the art will understand that the example will have the same effect when replaced with the shape of electrical equipment with complex curves, such as transformer bushing skirts or insulators.

[0082] The initial STL geometric model, boundary recognition results, and the symbolic distance function constructed based on the boundary are as follows: Figure 4 , Figure 5 and Figure 6 As shown.

[0083] This invention reconstructs the STL geometric model using a sign distance function and describes the geometry in the form of a mathematical function. The sign distance function (SDF) fd is shown in the following equation.

[0084]

[0085] Where Ω and Γ represent the geometric interior region and geometric boundary of the STL geometric model, respectively.

[0086] When point x is inside the geometry, the signed distance function is negative;

[0087] When point x is on the geometric boundary, the signed distance function is 0;

[0088] When point x is outside the geometry, the signed distance function is positive;

[0089] And the absolute value of the function is the distance from point x to the boundary.

[0090] like Figure 2 As shown, when establishing the signed distance function, the method for determining the geometric position of a point is as follows:

[0091] Given polygon P from the boundary element set, determine the wind number ω(Q,P) of point Q relative to polygon P. ω If (Q, P) is non-zero, then point Q is inside the polygon, that is, point Q is inside the geometry. ω If (Q,P) is zero, then further determine the absolute value of the function at point Q. If the absolute value of the function is zero, then point Q is on the geometric boundary; if the absolute value of the function is not zero, then point Q is outside the geometry.

[0092] The number of winds of point Q relative to polygon P ω The method for determining (Q,P) is as follows:

[0093] Draw a ray λ from point Q along the positive x-axis. The sides of the polygon are like a gust of wind, with the wind blowing from the starting point of the side to the ending point.

[0094] Initialize ω(Q,P) = 0;

[0095] 1) If the wind intersects the ray and is a positive wind (i.e., blowing from below the ray to above), then equation (2) is satisfied, and ω(Q,P)=ω(Q,P)+1:

[0096]

[0097] 2) If the wind intersects the ray and is a counter-wind (i.e., blowing from above to below the ray), then the following condition is met:

[0098]

[0099] Then ω(Q,P)=ω(Q,P)-1;

[0100] The final result is obtained by accumulating steps 1) and 2). ω (Q, P) represents the number of winds relative to point Q and polygon P. ω (Q,P);

[0101] Among them, P i x and P i y Q represents the x and y coordinates of the i-th point of the polygon, respectively, where n is the number of points in the polygon. x Q y Let x and y be the coordinates of point Q, and sign|*| represent the positive or negative sign of the matrix * determinant.

[0102] For example, for Figure 2Point Q and polygon P are in the diagram. P3 and P4 are on ray λ. Upward arrows represent forward winds, and downward arrows represent reverse winds. Edges without arrows do not affect the wind count. Initialize ω(Q,P) = 0. Edges E1, E4, and E6 are forward winds, such that ω(Q,P) = ω(Q,P) + 3, resulting in ω(Q,P) = 3. Edges E2 and E5 are reverse winds, such that ω(Q,P) = ω(Q,P) - 2, resulting in ω(Q,P) = 1, which is not equal to 0. Therefore, Q is inside polygon P.

[0103] In addition, establishing the distance function requires calculating the distance from point Q to P. This step can be performed by referring to common methods for calculating the distance from a point to a line segment.

[0104] Step 2: Generate points on the geometric boundary based on the signed distance function and obtain all newly generated boundary elements to complete the mesh generation of the geometric boundary;

[0105] Step 2 involves dividing the boundary points into meshes, such as... Figure 3 As shown, step 2 specifically includes:

[0106] Step 2.1: Determine the location of the production point on the geometric boundary by using the tangential direction of the boundary curve and the density function value;

[0107] More preferably, suppose that n points {P1, P2, P3, ..., P} need to be generated on the boundary curve. n},A(x a ,y a Point B(x) is the starting point of the curve. b ,y b If A is the endpoint of the curve, then P1 is the starting point of the curve. n B is the endpoint of the curve.

[0108] Point P i The position is determined by point P i-1 Point P i-1 Tangential direction Tn i-1 and density function value fh(x) i-1 ,y i-1 Jointly decided:

[0109]

[0110] Among them, P i x and P i y These represent the i-th point P on the curve. i x and y coordinates, Tn i-1 Equal to point P i-1The curve tangent at the point is fh, which is a density function. It is defined to calculate the density of the distribution of nodes at different locations in the solution domain. Its function value is always positive. This function is specified by the user.

[0111] For example, if a user desires a uniform mesh, they can define fh(x,y) = C, where C is a positive constant, representing the target mesh density, such as... Figure 4-9 The example shown uses a value of 0.1.

[0112] Step 2.2: Correct the position of the point determined in Step 2.1 according to the gradient of the signed distance function to obtain the updated point position;

[0113] More preferably, obtaining points on the boundary involves two steps: the first step is to obtain... Figure 3 The second step involves pulling the dashed line point back to the boundary. The point obtained in step 2.1 may be on the boundary, but to ensure the robustness of the program, the second step is executed after each point is generated to ensure it is always on the boundary.

[0114] Specifically, point P obtained through step 2.1 i The location may not be on the curved edge, such as... Figure 3 As shown by the dashed circle, it needs to be moved to the curved edge of the geometric boundary.

[0115] First, point P is obtained using equation (5). i Gradient of SDF:

[0116]

[0117] Where Δx and Δy are small displacements in the x and y directions, respectively, [P] i dx ,P i dy [] is the distance function fd at point P i The gradient at point P is obtained. The updated point P is then calculated. i Location for:

[0118]

[0119] Step 2.3: Set {P1, P2, P3….P n By connecting them sequentially, a new set of edge cells can be generated, thus completing the mesh generation of the boundary.

[0120] In practice, the boundary mesh generation results are as follows: Figure 7 As shown.

[0121] Step 3: Based on all newly generated boundary elements, use the interior normal front advance algorithm based on the signed distance function to perform mesh generation within the geometry, thus completing the mesh generation.

[0122] Step 2 yields discrete edge elements on the geometric edges, and then surface elements are obtained within the geometric region.

[0123] This invention proposes a novel front-end propulsion method based on the inner normal direction, namely, the inner normal front-end propulsion algorithm based on the signed distance function.

[0124] First, take all the boundary cells obtained in the previous step as the initial front, and use the signed distance function to obtain the inner normal of each cell (the outer normal is opposite to the inner normal).

[0125] Then, select one of the front edges AB in the front, and calculate the position of point C required to form the triangle with the highest quality in its inner normal direction, and require that it does not intersect with the front edge;

[0126] Then, find points that are close to each other on the boundary to form triangle △ABD. Compare the mass of triangle △ABC and triangle ABD, and use the one with the higher mass as the final triangle unit.

[0127] Finally, update the frontier and its normal, and check if the frontier is empty. If it is empty, stop the loop; otherwise, continue iterating.

[0128] Mesh generation is performed using an inner normal front propagation algorithm based on the signed distance function, as shown in the following algorithm:

[0129] Step 3.1: Initialize data. Use all newly generated boundary elements as the front, establish the normal set Fn of the front, and create an empty set of surface elements S;

[0130] Step 3.2: Select the front edge AB to be advanced. Select an edge AB in the Front as the initial edge of the newly generated triangle. Usually, the selected edge can be the first edge or the shortest edge in the Front, and then delete the selected edge AB from the Front.

[0131] Step 3.3: Find the optimal point on the front. Calculate the density function value DF at the midpoint of AB (in practice, the user pre-specifies the density function value at a point, and inputting the point location will output the preset value). Search for points near AB on the front, with the following requirements: the distance between the point and the midpoint of AB is less than DF, and a triangle is formed (the triangle should not intersect the front). Calculate the mass of each triangle formed by the searched point and AB, and select the triangle △ABD with the highest mass as a candidate.

[0132] Step 3.4: Create a new point to form the optimal triangle. Calculate the required point position C for this triangle, which, together with AB, forms triangle △ABC. That is, calculate the point C required to form the highest quality triangle within AB along the normal direction.

[0133] Step 3.5: Form new triangular units. Compare the quality factors Q of triangles △ABC and △ABD. The quality factor determines whether the triangle is distorted. The closer the triangle is to an equilateral triangle, the higher its quality factor. Add the triangle with the higher quality factor to S.

[0134] More preferably, the quality factor is calculated as follows:

[0135] For △ABC, let the quality factor Q be:

[0136] Q = η·β

[0137] Where η is the shape quality factor of △ABC:

[0138]

[0139] Where AB represents the vector consisting of points A and B, and ||AB|| is the length of line segment A to B.

[0140] β is the density mass factor between △ABC and the target triangle (determined by the density function):

[0141] β=β1·β2

[0142]

[0143]

[0144] Where ρ1 and ρ2 are the values ​​of the density function at the midpoints of edges AC and CB, respectively, and min represents taking the smallest value.

[0145] Step 3.6: Update the front and normal set Fn.

[0146] If triangle ABD is added to S, determine whether edges AD and BD are contained in the front. If AD ∈ the front, delete AD from the front and add BD to the front. If... Then add edge AD to the Front, and the method for determining edge BD is the same as that for AD;

[0147] If triangle ABC is added to S, then sides AC and BC are both added to Front;

[0148] Edges added to the Front need to have their internal methods calculated and added to Fn simultaneously;

[0149] The method for calculating the internal normal vector is as follows:

[0150] Starting from the center point A of the edge, extend the line segment AB to any side of the edge to obtain point B. The line segment AB must be perpendicular to the edge. Then, use the signed distance function of point B to determine the direction of the normal vector. If the function is negative, it means B is inside the geometry, and the internal normal vector is from A to B. If the function is positive, it means B is outside the geometry, and the internal normal vector is from B to A. When the function is zero, B is on the geometric boundary, and therefore there is no normal vector.

[0151] Step 3.7: Determine if Front is an empty set. If it is, output the face set S; otherwise, return to step 3.2.

[0152] In practical implementation, the initial frontier's inward normal direction result is as follows: Figure 8 As shown, the results of the algorithm iteration and internal mesh generation process are as follows: Figure 9 As shown.

[0153] Embodiment 2 of the present invention provides a mesh generation system for a two-dimensional electrothermal field analysis model of electrical equipment simulation, comprising:

[0154] The boundary identification and function construction module is used to identify the geometric boundaries of the initial two-dimensional electrothermal field analysis STL geometric model and establish a symbolic distance function based on the identified geometric boundaries.

[0155] The boundary mesh generation module is used to generate points on the geometric boundary based on the signed distance function and obtain all newly generated boundary cells, thus completing the mesh generation of the geometric boundary;

[0156] The internal mesh generation module is used to generate a mesh for the geometric interior by using an internal normal front advance algorithm based on the signed distance function, based on all newly generated boundary elements.

[0157] A terminal includes a processor and a storage medium; the storage medium is used to store instructions.

[0158] The processor is configured to operate according to the instructions to execute the steps of the method.

[0159] A computer-readable storage medium having a computer program stored thereon that, when executed by a processor, implements the steps of the method.

[0160] The beneficial effects of this invention are compared with those of the prior art:

[0161] This invention addresses the STL geometric model (non-parametric model) for two-dimensional electrothermal field analysis in electrical equipment simulation. It re-establishes a new geometric description form through the signed distance function and combines it with the mesh generation method of the inner normal forward propagation algorithm for parametric models. This achieves geometrically adaptive mesh generation for the non-parametric STL model, which has high automation characteristics and requires no manual intervention, thereby improving the computational efficiency of the entire numerical simulation and providing better operability.

[0162] This invention addresses the challenges of existing mesh generation methods for STL geometric models. By establishing a signed distance function, it automatically identifies mesh boundaries and determines the interior and exterior of geometric regions. This eliminates the need for manual specification of geometric region boundaries, achieving fully automated mesh generation, improving the automation level of mesh generation, and reducing the time consumed by mesh generation.

[0163] The proposed method for establishing the signed distance function can cover any complex 2D structure and can quickly determine the positional relationship between points and geometry by judging the wind number, without the need for manual specification of information about the internal geometric region. After identifying the geometric boundary by establishing the signed distance function, an interior-stepping algorithm is used to generate a mesh into the geometric interior, instead of specifying that the outer boundary is clockwise and the inner boundary is clockwise. This avoids manual intervention, improves the automation level of the algorithm, and greatly enhances its application scope and convenience.

[0164] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

[0165] Computer-readable storage media can be tangible devices capable of holding and storing instructions for use by an instruction execution device. Computer-readable storage media can be, for example—but not limited to—electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination of the foregoing. The computer-readable storage media used herein are not to be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0166] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0167] Computer program instructions used to perform the operations of this disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing the status information of the computer-readable program instructions to implement various aspects of this disclosure.

[0168] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A mesh generation method for a two-dimensional electrothermal field analysis model of electrical equipment simulation, characterized in that: The method includes the following steps: Step 1: Identify the geometric boundaries of the initial electrical equipment simulation two-dimensional electrothermal field analysis STL geometric model, and establish a symbolic distance function based on the identified geometric boundaries; Step 2: Based on the signed distance function, generate points on the geometric boundary and obtain all newly generated boundary elements, completing the mesh generation of the geometric boundary. Specifically, this includes: Step 2.1: Determine the location of the production point on the geometric boundary by using the tangential direction of the boundary curve and the density function value; Suppose that the boundary curve needs to generate n points { P 1, P 2, P 3…. P n If point A is the starting point of the curve and point B is the ending point of the curve, then... P 1 is the starting point A of the curve. P n B is the endpoint of the curve; point P i The position is determined by the point P i-1 ,point P i-1 tangential direction Tn i-1 It is determined together with the density function value, specifically: （4） wherein, and respectively represent the coordinates of the i-th point on the curve, i P i x , y Tn i-1 is equal to the tangent of the curve at the point P i-1 fh is a density function, the value of the density function at each point being specified in advance by the user;​​​​ Step 2.2: Correct the position of the point determined in Step 2.1 according to the gradient of the signed distance function to obtain the updated point position; Step 2.3: Connect the updated point positions sequentially to obtain the newly generated boundary cell set, thus completing the mesh generation of the geometric boundary; Step 3: Based on all newly generated boundary elements, use the interior normal front advance algorithm based on the signed distance function to perform mesh generation within the geometry, thus completing the mesh generation.

2. The mesh generation method for the two-dimensional electrothermal field analysis model of electrical equipment simulation according to claim 1, characterized in that: In step 1, all geometric boundaries of the initial electrical equipment simulation two-dimensional electrothermal field analysis STL geometric model are identified, duplicate boundaries are removed, edge elements at the boundaries are found, and a boundary element set composed of geometric boundaries is obtained. Then, a signed distance function is established through this boundary element set.

3. The mesh generation method for the two-dimensional electrothermal field analysis model of electrical equipment simulation according to claim 2, characterized in that: The symbol distance function fd (x) is: （1） wherein , are the geometric inner region and the geometric boundary of the STL geometry model for the electrical equipment simulation two-dimensional electric-thermal field analysis, respectively. When the point x The signed distance function is negative inside the geometry. When a point x The signed distance function is 0 at geometric boundaries; When a point x The signed distance function is positive when outside the geometry. and the function absolute value is the point x distance to the border.

4. The mesh generation method for the two-dimensional electrothermal field analysis model of electrical equipment simulation according to claim 3, characterized in that: When establishing the signed distance function, the geometric location of a point is determined as follows: Polygons are obtained from the boundary unit set. P， Determined point Q Relative to polygons P The number of wind ,if If it is non-zero, then the point Q A point is located inside a polygon. Q Within the geometry, if If it is zero, then further determine the point. Q The absolute value of a function; if the absolute value of the function is zero, then the point... Q On the geometric boundary, if the absolute value of the function is not zero, then the point... Q Outside of geometry.

5. The mesh generation method for the two-dimensional electrothermal field analysis model of electrical equipment simulation according to claim 4, characterized in that: Points Q Relative to the polygon P The number of winds The determination is made in the following manner: By point Q Along x Draw a ray in the positive direction of the axis Consider the edge of a polygon as a wind, the direction of the wind is from the start point of the edge to the end point of the edge, define the wind from below to above of the ray as positive wind, and the wind from above to below of the ray as reverse wind; Initialization ; 1) if the ray intersects the wind and the wind is a positive wind, i.e. equation (2) is satisfied: （2） then ; 2) if the ray intersects the wind and the wind is adverse, i.e. equation (3) is satisfied: （3） then ; The final result is obtained by accumulating the results of 1) and 2) i.e. the point Q relative to the polygon P number of winds ; in, and Representing the polygons respectively i The x and y coordinates of each point For point Q of x , y coordinate, The sign represents the positive or negative sign of the matrix determinant.

6. The mesh generation method for the two-dimensional electrothermal field analysis model of electrical equipment simulation according to claim 1, characterized in that: Step 2.2 is first solved by equation (5) P i Gradient of the signed distance function: （5） wherein and is x , y displacement in the direction of fd P i x P i y ) is the signed distance function fd at point P i the function value at point​​ is a signed distance function fd at point P i gradient at point Then the updated point is obtained according to the gradient P i Position is: （6）。 7. The mesh generation method for the two-dimensional electrothermal field analysis model of electrical equipment simulation according to claim 1, characterized in that: In step 3, the inner normal front advancement algorithm based on the signed distance function obtains surface elements within the geometric region based on all newly generated boundary elements, thereby achieving mesh generation within the geometry. The specific algorithm process includes: Step 3.1: Treat all newly generated boundary cells as the frontier. Front Construct the normal set of the front using the signed distance function. Fn Establish an empty set of surface units. S ; Step 3.2, select one edge AB as the initial edge of the newly generated triangle from the edges in Front and delete the selected edge AB from the edges in Front ; Step 3.3, calculate the value of density function DF at the midpoint of AB, search the points near AB, the search requires that the distance between the point and the midpoint of AB is less than DF, and the triangle formed by the point and AB does not intersect with the front Front edge, calculate the mass of each triangle formed by the searched point and AB, select the triangle △ABD with the highest mass into the candidate; Front ​ Step 3.4: Calculate the point C required to form the triangle with the highest quality in the normal direction within AB, which together with AB forms triangle △ABC; Step 3.5, compare mass factors of triangles ABC and ABD Q add the triangle with the higher mass factor to S ; Step 3.6: If it is △ABD, add... S Determine whether edges AD and BD are contained within the boundary. Front If AD Front Then in Front Delete AD, and Front Add BD if AD Front Then in Front Add edge AD, and the method for determining edge BD is the same as that for AD; If △ABC joins S, then both edges AC and BC are added Front ; For edges that are added Front , the inner normal is computed using the signed distance function and added Fn synchronously; Step 3.7, Judgment Front Is it an empty set? If it is an empty set, output the face unit set. S Otherwise, return to step 3.

2.

8. A grid generation system for electrical equipment simulation two-dimensional electro-thermal field analysis model for implementing the method according to any one of claims 1 to 7, characterized in that: The system includes: The boundary identification and function construction module is used to identify the geometric boundaries of the initial STL geometric model for two-dimensional electrothermal field analysis, and to establish a symbolic distance function based on the identified geometric boundaries. The boundary meshing module is configured to generate points on the geometric boundary based on a signed distance function and obtain all newly generated boundary cells, so as to complete meshing of the geometric boundary. The internal meshing module is configured to perform meshing of the geometric interior by using an internal normal front propagation algorithm based on the signed distance function on the basis of all the newly generated boundary cells, so as to complete mesh generation. 9.A terminal, comprising a processor and a storage medium; characterized in that: The storage medium is configured to store instructions; The processor is configured to operate according to the instructions to perform the steps of the method according to any one of claims 1-7.

10. A computer readable storage medium having stored thereon a computer program, characterized in that, The program is executed by the processor to implement the steps of the method according to any one of claims 1-7.

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