JP2001155187A - Automatic mesh generation method for numerical analysis - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic method of generating three dimensional space meshes used for numerical analysis which can automatically generate hexahedral three-dimensional space meshes for numerical analysis even for a large-scale analysis system that includes millions of three-dimensional space meshes or more for numerical analysis, which can reduce the working burden on operator and which is also advantageous in terms of a numerical analysis error. SOLUTION: When a three-dimensional closed space including an optional shape is automatically divided, eight of configuration points of a plurality of interfaces forming the closed space are extracted and the interfaces are reconfigured by four adjacent points of these eight extracted component points. Then the number of division of the closed space is set again so as to equalize the number of division of the opposite sides of the interfaces, and an interface is automatically divided into tetragonal elements. A cross section that is adjacent to one of reconfigured interfaces is generated in a space and this cross section is automatically divided into tetragonal elements, a hexahedral element is formed in a space by using the tetragonal elements which are opposite to each other on the adjacent cross sections. Thus, the hexahedral elements are automatically generated in the closed space.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for generating mesh data for analysis for numerical analysis, and more particularly to a method for generating a three-dimensional spatial mesh. It is generated to reduce the burden on the mesh creation operator.

[0002]

2. Description of the Related Art In a numerical analysis, an actual shape to be analyzed is approximated by nodes and elements and is represented by a grid or a mesh for numerical analysis (hereinafter, mesh). The mesh data includes a node number and coordinate data of the node as node data, an element number and information of a node number constituting the element as element data, and attribute data describing an element analysis condition. There is a limit in creating and editing these mesh data manually by an operator. When creating a two-dimensional mesh or a three-dimensional spatial mesh of a complex analysis system,
It is created using dedicated application software for creating meshes. When creating mesh with application software dedicated to mesh creation, shape creation work,
It can be roughly divided into mesh creation work for numerical analysis. In the work of creating a shape, a boundary line, a boundary surface, and a space element are created. The shape data includes a connection relationship between the shape data and attribute data. Next, in the mesh data creation work for numerical analysis, the number of divisions on the boundary line that configures the shape is set. The boundary surface and the space element are divided according to the boundary line division information, and nodes and element data are created. The automatic element division method on the boundary surface is established by the Deloni method or the like. As for a method of dividing a space, a method of automatically generating a tetrahedral element has been established.

However, an automatic mesh division method for dividing a three-dimensional space by hexahedral elements, which is advantageous in terms of numerical analysis errors, has not been established. Conventionally, when dividing a three-dimensional space into hexahedral elements, the following procedure has been used. First, FIG.
A space element 5 surrounded by a polygonal boundary surface 50 as shown in FIG.
Consider a case where 1 is divided by a hexahedral element. FIG. 5 shows the upper boundary surface 50 of the spatial element 51 shown in FIG. First, the polygonal boundary surface 50 is divided into quadrilateral shapes 52.
A boundary surface 53 facing the boundary surface divided into the quadrilateral shape 52
Is also divided into quadrilateral shapes so that no inconsistency occurs between the boundary surfaces. Next, also regarding the quadrilateral-shaped boundary line, the number of element divisions is set to the boundary line so that the division number 54 of the opposite side is equal, and the space is divided into hexahedral elements. As described above, the operation of dividing the boundary surface forming the space into a quadrilateral shape and the operation of aligning the number of boundary lines so that the division of the boundary line on the opposing boundary surface does not cause inconsistency are determined by the operator. Had been implemented. These tasks were a considerable amount of work for the operator. Furthermore, with the development of hardware technology in recent years, it has become possible to realize numerical analysis using a large-scale mesh exceeding several million nodes in an analysis mesh. Using application software dedicated to mesh creation, several hundreds
To create three-dimensional mesh data covering all nodes,
A large load is placed on the operator.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to automatically convert a three-dimensional mesh for hexahedral numerical analysis into a large-scale analysis system in which the number of three-dimensional meshes for numerical analysis exceeds several million. Another object of the present invention is to provide a method for automatically generating a three-dimensional spatial mesh for numerical analysis, which reduces the work load on the operator and is advantageous in terms of numerical analysis errors.

[0005]

In order to solve the above problem, automatic division is performed by the following algorithm.

(1) Eight points are extracted from constituent points of a boundary surface forming a closed space.

(2) A boundary surface is reconstructed from four of the eight extracted points.

(3) The boundary line of each boundary surface reconfigured in (2) is divided into four boundary lines by four of the eight constituent points extracted. The number of divisions is reset so that the number of divisions of opposing boundary lines becomes equal.

(4) The number of divisions of all the opposing boundary lines constituting the space is reset so as to be equal.

(5) The mesh on the boundary surface is divided into quadrilateral elements.

(6) One of the boundary surfaces is selected, and a section adjacent to the boundary surface is generated in a closed space.

(7) The generated cross section is mesh-divided into quadrilateral elements.

(8) A hexahedral element is generated from quadrilateral elements that are opposed on adjacent cross sections.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An automatic mesh generation method according to the present invention is shown in FIGS.

In the configuration of the present invention, a boundary surface 2 forming the closed space 1, a closed curve 3 forming the boundary surface 2, a boundary line 4 forming the closed curve 3, an end point 5 of the boundary line 4, and a closed curve 3 are enclosed. First area 6, second area 7, number of divisions of each boundary line 8, closed space 1
Among the end points 5 described above, the extracted node 60, the boundary surface 61 reconstructed by the extracted node 60, the number of divisions of the opposite side 10,
The center of gravity 100 of the closed space 1 is set.

FIG. 1 shows a boundary surface 2 constituting a closed space 1 and a boundary surface 12 of a closed space 11 adjacent to the space element 1. The closed curve 3 constituting the boundary surface 2 is composed of a plurality of boundary lines 4, and eight of the end points 5 of the boundary line are extracted by automatic judgment. In the determination, for example, the distance from the center of gravity 100 of the closed space 1 to the end point 5 is determined, and eight points are extracted from the farthest points. A boundary surface is reconstructed at four of the extracted nodes 6. Reconstruct boundary surfaces for all closed spaces. FIG. 2 shows the closed surface 2 and the closed surface 12 among the reconstructed closed surfaces. For the opposing side 21 of the closed curve, the division number 8 of each boundary line is searched, and the division number is automatically reset according to the maximum division number. The number of divisions 8 is searched and reset for all the opposing sides 21 and the number of divisions between the opposing sides 21 is set to be equal. Then, the mesh on the boundary surface 2 is formed into a quadrilateral element. For mesh generation, for example, mapping methods such as
Use the ry fit method.

FIG. 3 shows a method of generating a hexahedral element for the spatial element 1 after generating a rectangular element on the boundary surface. A cross section 31 can be formed between the boundary surface 22 facing the boundary surface 2 and the dividing nodes on the boundary line, and the number of divisions of the opposing sides forming the cross section is equal to the boundary surfaces 2 and 12. When the quadrilateral element is divided on the cross section 3, a hexahedral element can be generated in space by the boundary surface 2 and the quadrilateral elements 71 and 72 on the cross section 31. By repeating this, a hexahedral element can be automatically generated in the space element 1. For all analysis systems, hexahedral elements can be automatically generated as spatial elements by the above method.

[0018]

According to the first to fourth aspects, even if the three-dimensional spatial mesh for numerical analysis is a large-scale analysis system exceeding several million points, the hexahedron is advantageous in terms of numerical analysis error. Can automatically generate a three-dimensional spatial mesh for numerical analysis, which has the effect of reducing the operator's work load.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of determining a four-divided point of a closed curve according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of quadrilateral element division on a boundary surface according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram of a hexahedral element division of a spatial element according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram of a conventional hexahedral element division of a space element.

FIG. 5 is an explanatory diagram of a conventional hexahedral element division of a space element.

[Explanation of symbols]

1 ... spatial element, 2 ... boundary surface forming spatial element 1, 3 ...
Closed curve forming the boundary surface 2, 4 ... Boundary line forming the closed curve 3, 5 ... End point of the boundary line 4, 6 ... First areas 6, 8 surrounded by the closed curve 3, ... Division number of each boundary line, 9 ... 4 divided points of the closed curve, 10 ... number of divisions of the opposite side.

Claims (4)

[Claims] 1. A method for automatically dividing a three-dimensional closed space including an arbitrary shape, wherein eight points are extracted from constituent points of a plurality of boundary surfaces constituting the closed space, and adjacent points among the eight points are extracted.
Reconstruct the boundary surface at four points, reset the number of divisions so that the number of divisions on the opposite side of the boundary surface is equal, automatically divide the reconstructed boundary surface with quadrilateral elements, Generates a cross section adjacent to one of the boundary surfaces in the space, automatically divides the cross section with a quadrilateral element, and generates a hexahedral element in the space between adjacent quadrilateral elements on the adjacent cross section An automatic grid generation method for automatically generating a hexahedral element in the closed space. 2. The automatic grid generation method according to claim 1, wherein
As a method of extracting eight points from a plurality of constituent points constituting a space, an automatic grid generation method in which the distance from the center of gravity of the space to the constituent points is determined, and eight points are selected from the farthest points. 3. The automatic grid generation method according to claim 1, wherein
An automatic grid generation method using a conformal mapping method as a method for generating a quadrilateral element on a reconstructed boundary surface. 4. The automatic grid generation method according to claim 1, wherein
An automatic grid generation method using a boundary fit method as a method for generating a quadrilateral element on a reconstructed boundary surface.