CN111259536B - Unit division method for irregular structure and embedded structure entity - Google Patents
Unit division method for irregular structure and embedded structure entity Download PDFInfo
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Abstract
The invention provides a unit division method of irregular structure and embedded structure entities, which comprises the following steps: step S1: determining the range for establishing a geometric entity area and a plane area; step S2: controlling the size of a contact area of the geometric solid area and the plane area; and step S3: generating a 2D plane unit in the plane area; and step S4: and expanding the 2D plane unit and dividing the geometric entity area to generate a 3D entity unit. The method has good applicability to geotechnical engineering with a complex structure, and can quickly generate grid units with good quality.
Description
Technical Field
The invention relates to the field of simulation and simulation research of geotechnical engineering, in particular to a unit partitioning method for irregular structure and embedded structure entities.
Background
In recent years, as underground spaces are more widely used, related construction methods are more and more complicated in order to adapt to more complicated geological environments. The construction method with a more complicated construction process usually has more irregular structures, such as a hole pile method, and the structures of a steel pipe column, a side pile, a top longitudinal beam, a buckling arch, a crown beam and the like are involved in construction. Therefore, when the irregular structure is subjected to grid division, the quality of the irregular structure is difficult to control. The quality of the grid directly affects the correctness of the numerical model result, so that the grid with better quality is required to be divided when the grid is divided.
With the development of computer technology, many kinds of simulation software exist at the present stage. Among them, the Midas GTS NX simulation software is very popular due to its strong preprocessing capability. In the software, for some grid division with irregular structure, the function of a 'mixed grid generator' in 'automatic entity division' carried by the software can be directly adopted. The units divided by the method are in a grid shape with pentahedron units as transition units and tetrahedral and hexahedral units as main units, and the method has the advantages of simple operation, high efficiency, no need of excessive size control on the entity in the middle, and only need of size control on the key part, but has the defect of easy generation of more units with poor quality, wherein the units are mainly the tetrahedral and pentahedron units as the transition units, and the units with poor quality easily generate great influence on the subsequent operation, for example, the operation time is long, the convergence is poor, and the operation result is not accurate enough.
Meanwhile, a 3D entity unit is established in the Midas GTS NX simulation software, or "plane unit extension" may be adopted, that is, a 2D plane unit is generated first, and then the 2D plane unit is extended along a certain direction by using the function of the extension mesh to generate the 3D entity unit. The method has the advantages that regular hexahedral units can be generated, the unit quality in the whole model is good, but the method fails when embedded structures, such as center pillars or middle piles, exist inside the model, and the generated 3D entity units cannot be coupled due to more than one expansion direction. In addition, if the range of the model is large, too many cells are easily generated, and the calculation time is too long in the subsequent calculation.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a unit division method for irregular structure entities and embedded structure entities, which can combine automatic entity division with a plane unit extension method and simultaneously realize the high efficiency of the automatic entity division method and the high quality of the plane unit extension method.
The unit division method of the irregular structure entity and the embedded structure entity provided by the invention comprises the following steps:
step S1: determining the range for establishing a geometric entity area and a plane area;
step S2: controlling the size of a contact area of the geometric solid area and the plane area;
and step S3: generating a 2D plane unit in the plane area;
and step S4: and expanding the 2D plane unit and dividing the geometric entity area to generate a 3D entity unit.
Preferably, the method further comprises the following steps:
step S5: carrying out grid quality inspection on the 3D entity unit, and returning to the step S2 when the 3D entity unit has a free surface;
step S6: and combining grids of the 3D entity units.
Preferably, the contact area comprises a first contact area in which a plane area is in contact with a geometric solid area, and a second contact area in which an expansion direction of the plane area is in contact with the geometric solid area;
the geometric control of the first contact area is used for ensuring that the 3D entity unit generated by adopting an automatic entity division method and the 3D entity unit generated by expanding the plane unit can be mutually coupled on the plane;
the geometric control of the second contact region is used to ensure that a 3D solid element generated using automatic solid segmentation and a planar element extension can be coupled to each other in the extension direction.
Preferably, the step S3 includes performing a grid quality check and a free edge check on the generated 2D plane unit;
the grid quality check includes an aspect ratio check, a skew angle check, and a warp check. Aspect ratio inspection is to examine how much the 2D planar cell shape deviates from a square; the skew angle inspection is to examine how much the shape of the 2D planar cell deviates from a right-angle shape. Warpage evaluation is to evaluate the degree to which the 2D planar cell shape deviates from the plane;
the free edge check is used for ensuring that no free surface appears inside the 2D plane unit when the 2D plane unit is expanded into a 3D entity unit.
Preferably, the generated 3D entity unit is subjected to a mesh quality check in step S5, including checking whether there is a self-preference, and in step S3, the plane area is divided into quadrangles by auxiliary lines with respect to the plane area, thereby generating a 2D plane unit.
Preferably, the geometric control of the first contact area comprises a first curve on a geometrically solid area and a second curve on a planar area; the sizes of the first curve and the second curve are the same;
the geometric control of the second contact area is arranged on the geometric solid area, and the size of the geometric solid area is the size of the 3D solid unit generated by adopting a plane unit expansion method along the expansion direction
Preferably, in step S1, the ranges of the geometric solid region and the planar region are determined according to the precision of the structure to be simulated and a mesh division method.
Compared with the prior art, the invention has the following beneficial effects:
the method has good applicability to geotechnical engineering with a complex structure, and can quickly generate grid units with good quality; compared with an automatic entity division method, the generated 3D entity unit has higher quality, a large number of entities do not need to be generated, and operations such as entity division, boolean operation and the like are correspondingly reduced; compared with a plane unit expansion method, the method has wider application range, can be applied to a model with an embedded structure (such as a steel pipe column), generates less 3D entity units, and accelerates the calculation time under the same precision.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a flowchart illustrating the steps of a method for partitioning units of irregular structure and embedded structure entities according to an embodiment of the present invention;
fig. 2 to fig. 5 are diagrams illustrating an embodiment of a method for dividing units of irregular structure entities and embedded structure entities according to an embodiment of the present invention.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the concept of the invention. All falling within the scope of the present invention.
Fig. 1 is a flowchart of steps of a method for dividing units of irregular structure and embedded structure entities in an embodiment of the present invention, and as shown in fig. 1, the method for dividing units of irregular structure and embedded structure entities provided by the present invention includes the following steps:
step S1: determining the range for establishing a geometric entity area and a plane area;
in the embodiment of the invention, the mesh partitioning party of the geometric entity area is partitioned by adopting an automatic entity partitioning function in Midas GTS NX simulation software, and the mesh partitioning of the plane area is partitioned by adopting a plane unit extension function in Midas GTS NX simulation software.
And determining the ranges of the geometric entity area and the plane area according to the precision of the structure to be simulated and a grid division method. Therefore, for some plane areas where the plane cell extension cannot be adopted for meshing or the precision requirement is not high, for example, a plane area of an analog structure with a cell size of more than 8m can be subjected to meshing by adopting an automatic entity division method. For example, in the case of a steel pipe column structure in the hole-pile method, since the plane cell expansion method cannot be used, an automatic solid division method may be applied to the steel pipe column structure. In some planar areas where precision is required and a planar cell expansion method can be used, such as a top side rail structure, the top side rail structure is uniform in size in the longitudinal direction and is a main part of the top side rail structure, and therefore, the planar cell expansion method can be used for the top side rail structure.
Step S2: controlling the size of a contact area of the geometric solid area and the plane area;
the 3D solid element generated by the planar element extension method has a well-defined size in its extension direction, and this size is usually determined, known. Therefore, the geometric control can be carried out on the contact area of the geometric solid area and the 3D solid unit generated by the planar unit extension method.
The contact area comprises a first contact area in which the plane area is in contact with the geometric solid area, an expansion direction of the plane area and a second contact area in which the geometric solid area is in contact;
the geometric control of the first contact area is mainly set up at the junction of the geometric solid area and the planar area, and is divided into two curves, one is a first curve on the geometric solid area, and the other is a second curve on the planar area. The sizes of the first curve and the second curve are consistent, so that the unit generated by adopting an automatic entity division method and the 3D entity unit generated by plane unit expansion can be mutually coupled on a plane.
The geometric control at the second contact area is arranged on the geometric solid area, and the size of the dimension is the dimension of the 3D solid unit generated by adopting the plane unit expansion method along the expansion direction, so that the unit generated by adopting the automatic solid division method and the unit generated by adopting the plane unit expansion method can be mutually coupled in the expansion direction.
And step S3: generating a 2D plane unit in the plane area;
and dividing the plane area into regular quadrangles through auxiliary lines, and generating a 2D plane unit by adopting the function of mapping grids (surfaces) in Midas GTS NX. For an area which cannot be divided into regular quadrangles, a 2D plane unit is generated by adopting the function of 'automatic mesh (surface').
And carrying out grid quality inspection and free edge inspection on the generated 2D plane unit.
The grid quality inspection includes an aspect ratio inspection, a skew angle inspection, and a warp inspection. Aspect ratio inspection is to examine how much the 2D planar cell shape deviates from a square; the skew angle inspection is to examine how much the shape of the 2D planar cell deviates from a right-angle shape. Warpage was evaluated to assess the extent to which the 2D planar cell shape deviated from the plane. The smaller the three inspection values, the better the cell quality, the acceptance threshold for the aspect ratio was 8, the acceptance threshold for the twist angle was 45 °, and the acceptance threshold for the warp was 25 °.
The free edge check is used for ensuring that when the 2D plane unit is expanded into a 3D entity unit, no free surface condition exists inside the 2D plane unit.
And step S4: expanding the 2D plane unit and dividing the geometric solid to generate a 3D solid unit;
and expanding the 2D plane unit into a 3D entity unit, and simultaneously adopting the function of a mixed grid generator in the automatic entity division function to divide the geometric entity to generate the 3D entity unit.
Step S5: performing grid quality inspection on the generated 3D entity unit;
and performing grid quality check on the generated 3D entity unit, including checking whether a free surface exists and the size of the aspect ratio, the distortion angle and the warpage of the 3D entity unit, wherein the qualification threshold values of the aspect ratio, the distortion angle and the warpage are the same as those described above. When the 3D entity unit has a free surface, the process returns to step S2 to check whether the range and size of the size control are correct.
Step S6: carrying out grid combination on the 3D entity units;
due to the fact that partial structures are disassembled, the grid groups can be combined when the 3D entity units are subjected to grid group combination, the grid groups are tidy, and searching is convenient.
In the embodiment of the invention, compared with an automatic entity division method, the generated 3D entity unit has higher quality, a large number of entities do not need to be generated, and operations such as entity division, boolean operation and the like are correspondingly reduced; compared with a plane unit expansion method, the method has wider application range, can be applied to a model with an embedded structure (such as a steel pipe column), generates less 3D entity units, and accelerates the calculation time under the same precision.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention.
Claims (8)
1. A unit division method for irregular structure and embedded structure entities is characterized by comprising the following steps:
step S1: determining the range for establishing a geometric entity area and a plane area;
step S2: controlling the size of a contact area of the geometric solid area and the plane area;
and step S3: generating a 2D plane unit in the plane area;
and step S4: and expanding the 2D plane unit and dividing the geometric entity area to generate a 3D entity unit.
2. The method for partitioning elements of irregular and embedded structural entities according to claim 1, further comprising the steps of:
step S5: carrying out grid quality inspection on the 3D entity unit, and returning to the step S2 when the 3D entity unit has a free surface;
step S6: and combining grids of the 3D entity units.
3. The method for dividing the unit of the irregular structure and the embedded structure entity according to claim 1, wherein the contact area comprises a first contact area where a plane area is in contact with a geometric entity area and a second contact area where the plane area is extended and the geometric entity area is in contact;
the geometric control of the first contact area is used for ensuring that the 3D entity unit generated by adopting an automatic entity division method and the 3D entity unit generated by expanding the plane unit can be mutually coupled on the plane;
the geometric control of the second contact region is used to ensure that a 3D solid element generated by automated physical segmentation and a planar element extension can be coupled to each other in the extension direction.
4. The method for partitioning units of irregular structure and embedded structure entities according to claim 1, wherein the step S3 comprises performing mesh quality inspection and free edge inspection on the generated 2D plane units;
the grid quality inspection includes an aspect ratio inspection, a skew angle inspection, and a warp inspection. Aspect ratio inspection is to examine how much the 2D planar cell shape deviates from a square; the skew angle inspection is to examine how much the shape of the 2D planar cell deviates from a right-angle shape. Warpage evaluation is to evaluate the degree to which the 2D planar cell shape deviates from the plane;
the free edge check is used for ensuring that no free surface appears inside the 2D plane unit when the 2D plane unit is expanded into a 3D entity unit.
5. The method for partitioning units of irregular and embedded structural entities according to claim 2, wherein the generated 3D physical units are subjected to a grid quality check in step S5, including checking whether free surfaces exist and the size of aspect ratio, distortion angle and warpage of the 3D physical units.
6. The method for partitioning units of irregular structure and embedded structure entities according to claim 1, wherein in step S3, the plane area is partitioned into quadrangles by auxiliary lines for the plane area, thereby generating 2D plane units.
7. The method for cell partition of irregular and embedded structural entities according to claim 3, wherein the geometric control of the first contact area comprises a first curve on a geometric solid area and a second curve on a planar area; the sizes of the first curve and the second curve are the same;
and the geometric control of the second contact area is arranged on the geometric solid area, and the size of the geometric solid area is the size of the 3D solid unit generated by adopting a plane unit expansion method along the expansion direction.
8. The method for partitioning units of irregular and embedded structural entities according to claim 1, wherein in step S1, the ranges of the geometric entity area and the planar area are determined according to the precision of the structure to be simulated and the meshing method.
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| US8111256B2 (en) * | 2008-03-11 | 2012-02-07 | Ford Motor Company | Method of altering a mesh model using model independent dirichlet parametrization |
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| EP1978487A2 (en) * | 2007-04-06 | 2008-10-08 | Hitachi, Ltd. | Numerical analysis mesh generating method and apparatus |
| CN106649903A (en) * | 2015-11-02 | 2017-05-10 | 株洲时代新材料科技股份有限公司 | Hybrid grid partitioning method of truck torsion bar type turnover mechanism finite element model |
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