KR100932455B1 - Method for post-processing and computer-readable storage medium - Google Patents

Abstract

PURPOSE: A post-processing method of a flow analysis result and a computer readable storage medium are provided to reduce an error of the flow analysis result, and to derive exact and realistic results by amending a smoothed flow surface. CONSTITUTION: Flow rates for central points of each cell are calculated. Flow rates for nodes of each cell are calculated by using the flow rates for the central points of each cell. A location of a reference flow value is extracted by using the flow rates for the central points and the flow rates for the nodes, and flow surfaces are modeled by using the extracted location. Among the modeled flow surfaces, a flow surface which is out of a structure surface is amended.

Description

Post-processing method of flow analysis result and computer-readable storage medium

The present invention relates to a post-processing method and a computer-readable storage medium for flow analysis results, and to a post-processing method and a computer-readable storage medium for flow analysis results that can reduce errors and increase the accuracy in the numerical analysis of the flow will be.

For flow analysis, the structures are generally represented as Stereolithography Tessellation Language (STL) files, and pre-processing is performed on the structures represented as STL files. Pretreatment means, for example, a mesh generation process. After the preprocessing, the equations for flow analysis are calculated using the preprocessed information. For example, after preprocessing, the solver calculates a number of complex partial differential equations for flow numerical analysis. Based on the calculated information, the result is a post-process.

The finite difference method (FDM), the finite element method (FEM), and the finite volume method (FVM) may be used to generate the lattice. have.

In the case of using FDM, the structure is latticed using a hexahedron cell, and automatic lattice is possible at a relatively fast time. For example, when the structure shown in Fig. 1 is gridded in the FDM manner, as shown in Fig. 2, the boundary surface of the boundary region is lattice-shaped. That is, since the boundary region of the structure, in particular, the boundary surface cannot be finely gridded, problems such as a decrease in convergence, loss of excessive pressure, and prediction error in the flow direction may occur. Using FEM or FVM can reduce the error of interpretation of FDM, but automatic lattice is impossible or time-consuming.

In addition, when the flow analysis is performed by the FDM method during the post-processing, and the result is displayed, the step shape is displayed, thereby reducing the accuracy and the realism. Specifically, when the flow rate in each cell in the structure as shown in Figure 4, flow analysis by the FDM method is the result as shown in Figure 5 (see the result by the FDM in Figure 5). In other words, the result is derived in the shape of a staircase. In this case, accuracy and realism are poor, and errors are large.

An object of the present invention is to provide a post-processing method of flow analysis results that can reduce the error of the analysis results of the flow and derive accurate and realistic results in order to solve the problems as described above.

In order to solve the problems as described above, the invention reduces the error of the analysis results of the flow, computer-readable storage for storing a program for executing the post-processing method of the flow analysis results that can produce accurate and realistic results Another purpose is to provide the medium.

The object of the present invention is not limited to the above-mentioned object, and other objects that are not mentioned will be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided a method for post-processing a flow analysis result, which is a method for post-processing a flow analysis result inside a structure, which smoothes a surface of a lattice flow into a plurality of cells. And modifying the smoothed flow surface along the structure surface.

The smoothing may include calculating a flow rate for the center point of each cell, calculating a flow rate for the node of each cell using the flow rate for the center point of each cell, and a flow rate for the center point. And modeling the flow surface by extracting a position of a reference flow value using the flow rate for the node. In this case, the cell may be a hexahedron cell.

In this case, the calculating of the flow rate for the nodes of each cell may include averaging the flow rate of the center points adjacent to each node. In addition, the modeling may include extracting the position of the reference flow rate value on the plurality of grid lines constituting the cell, and configuring a surface having a corner of a point of the extracted position on the grid line.

The modifying may include extracting an intersection point of the structure surface and a three-dimensional orthogonal grid, modeling the structure surface as a surface having an intersection point, and making the flow surface deviating from the surface to the surface. It may include the step of replacing.

Alternatively, the modifying may include receiving information on a surface of the intersection of the structure surface and the three-dimensional orthogonal grid, and using the information, replacing the flow surface deviating from the surface with the surface. can do.

According to another aspect of the present invention, a method for post-processing a flow analysis result according to another aspect of the present invention is a method for post-processing a flow analysis result inside a structure gridized into a plurality of cells, the flow rate for the center point of each cell. Calculating a flow rate for the node of each cell using the flow rate for the center point of each cell and extracting a position of a reference flow rate value using the flow rate for the center point and the flow rate for the node. And modeling the flow surface with a faceted corner of the extracted location. In this case, the cell may be a hexahedron cell.

The method may further include modifying the modeled flow surface along a structure surface.

In this case, the modifying may include extracting an intersection point of the structure surface and a three-dimensional orthogonal grid, modeling the structure surface as a surface having an intersection point, and modeling the flow surface deviating from the surface. It may include a step of replacing.

Alternatively, the modifying may include receiving information on a surface of the intersection of the structure surface and the three-dimensional orthogonal grid, and using the information, replacing the flow surface deviating from the surface with the surface. can do.

A computer readable storage medium according to another aspect of the present invention stores a program for executing the method of post-processing the flow analysis result described above.

Specific details of other embodiments are included in the detailed description and the drawings.

According to the present invention, it is possible to reduce the error of the analysis results of the flow, and to obtain accurate and realistic flow analysis results.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various forms, and only the embodiments are to make the disclosure of the present invention complete, and the general knowledge in the technical field to which the present invention belongs. It is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined only by the scope of the claims. Meanwhile, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In this specification, the singular also includes the plural unless specifically stated otherwise in the phrase. As used herein, “comprises” and / or “comprising” refers to the presence of one or more other components, steps, operations and / or elements. Or does not exclude additions.

Hereinafter, the post-processing method of the flow analysis result according to an embodiment of the present invention will be described, but the present invention is not limited to the order described below, it is merely illustrative.

A post-processing method of flow analysis results according to an embodiment of the present invention will be described with reference to FIGS. 5 to 12. 5 is a conceptual diagram illustrating a post-processing method of a flow analysis result according to an exemplary embodiment of the present invention, and FIGS. 6 to 9 are conceptual diagrams for explaining a process of smoothing a flow surface, and FIGS. Therefore, conceptual diagrams for explaining the process of modifying the flow surface.

First, when a Streolithography Tessellation Language (STL) file for a structure is mesh generated by an FDM method (hexahedral cell) and analyzed, the analysis result is represented in a stepped shape as shown in FIG. 5 (see FIG. 5). See output by FDM). To increase the accuracy and realism of these results, first smooth the flow surface. Then, the smoothed flow surface is modified along the structure outer surface. Hereinafter, with reference to the drawings will be described in more detail.

First, the process of smoothing the flow surface will be described in detail with reference to FIGS. 6 to 9.

Referring to FIG. 6, when the structure is divided (or lattice) into, for example, a hexahedron cell, part of it is shown two-dimensionally.

First, the flow rate is calculated at the center point of each cell (ie, the center of the cube cell in three dimensions). The flow rate may refer to the cell volume occupancy of the fluid. For example, the flow rate at the center point C1 of the first cell is 0.0 (no fluid is present in the first cell), and at the center point C2 of the second cell the flow rate is 0.5 (the fluid in the second cell occupies 0.5 of the volume of the second cell). Flow rate is 0.8 (the fluid occupies 0.8 of the volume of the third cell) at the zoom center point C3 of the third cell, and the flow rate is 1.0 (at the fourth cell) at the center point C4 of the fourth cell. Fluid fills the fourth cell).

Next, the flow rate of the node (or grid point) of each cell is calculated using the flow rate information of the center points C1 to C4 of each cell. For example, the flow rate of the node A5 may be an average value of the flow rates of the center points C1 to C4 of each cell. In other words, the flow rate of the node A5 is (0.0 + 0.5 + 0.8 + 1.0) /4=0.58. In this way, the flow rate to each node A1 to A9 is calculated. For example, the flow rate of the node A1 may be calculated using the flow rate information of the center point C1 and the center point of other cells not shown. In the present exemplary embodiment, the flow rate of each node is calculated by averaging the flow rates of the center points, but the present invention is not limited thereto and may be calculated by other formulas or methods. 7 is an enlarged picture.

Next, the position of the reference flow value (Iso-value) is extracted using the flow rate information of the center points C1 to C4 of each cell and the flow rate information of each node A1 to A9. Here, the reference flow rate is a value that can be variably set by the user. For example, when 0.5 is used as an example, the flow rate information of the center points C1 to C4 of each cell and the flow rate information of each node A1 to A9 are used. On the plurality of grid lines constituting the cell, a position having a reference flow rate value of 0.5 is extracted. That is, as shown in Fig. 6, positions P1, P2, P3, and P4 which are 0.5 on each lattice line are extracted. Then, each position P1, P2, P3, P4 is connected to smooth the flow surface. That is, the flow surface is modeled using the positions P1, P2, P3 and P4. Although shown in two dimensions in FIG. 6, the present invention is performed in three dimensions, so that the flow surface is modeled as a plane. That is, the flow surface is modeled as a surface that edges location points with reference flow values on the grid.

At this time, since the flow surface should be a closed curve (closed surface in the actual 3D), a virtual cell is used as shown in FIG. 8 for this purpose.

Specifically, as shown in FIG. 7, the flow rate of the center point of each cell (the value described in the center of the rectangle in FIG. 7) is calculated, and the flow rate of the node (lattice point) of each cell (the rectangle in FIG. 7) is calculated using these values. After calculating the value described at the vertex of, a plurality of virtual cells are added to represent the flow surface of the closed curve. In this case, as shown in FIG. 7, the plurality of virtual cells may be added so as to surround the surface of the structure, that is, the surface of the structure does not leave the outside of the virtual cell. Since no flow rate exists in the virtual cell, the flow rate of the outer node of each virtual cell is set to 0.0.

The position of the reference flow value 0.5 is extracted by using the flow rate information of the node of the virtual cell, the flow rate information of the center points C1 to C4 of each cell described above, and the flow rate information of each node A1 to A9. Through this process, the flow surface is smoothed to the closed surface as shown in FIG. 8.

However, since the virtual cell is used, the flow surface is present in the virtual cell. That is, as shown in FIG. 5, the flow surface is smoothed out of the structure surface (see flow surface smoothing in FIG. 5). This is because there is no flow in the virtual cell, but the virtual cell is introduced to smooth the flow surface of the closed surface. Therefore, to correct this part, the flow surface along the structure surface must be modified again. That is, as can be seen from FIG. 9 in contrast to FIG. 8, the portion where the flow surface is extended by the virtual cell should be modified (deleted) along the structure surface. The following describes the process of modifying the flow surface along the structure surface to obtain the final result shown in FIG. 9 from the result shown in FIG. 8.

First, information about the structure surface is obtained.

To this end, as shown in FIG. 10, the intersection point of the grating lines LL_1, LL_2, and LL_3 constituting an arbitrary cell CE (hereinafter, referred to as an example of a hexahedron cell) and the structure surface BS ( P1, P2, P3, and P4 are first extracted and the intersections P1, P2, P3, and P4 are connected. As a result, as shown in FIG. 11, the surface LS which makes the intersection P1, P2, P3, P4 the edge is produced | generated. That is, the structure surface BS is modeled as the surface LS whose edges P1, P2, P3, and P4 are the edges.

The grid lines LL_1, LL_2, and LL_3 may be, for example, grid lines constituting a three-dimensional orthogonal grid, and the distance between the grid lines LL_1, LL_2, and LL_3 may be adjusted. As the spacing of the lattice lines LL_1, LL_2, and LL_3 decreases, the accuracy in the numerical analysis of the flow may be improved. In addition, when the cell CE is not a cube, it may not be a three-dimensional orthogonal grid.

The above-described process will be described in more detail with reference to FIG. 12.

As shown in FIG. 12, when the surface BS of the structure is a curved surface, a stepped shape is formed when interpreted by the prior art, for example, the FDM method, but when smoothed by the method according to an embodiment of the present invention, the structure By smoothing the outer surface BS of the structure using the intersection of the outer surface BS and the lattice lines, an error due to the stepped lattice can be reduced, and accurate numerical analysis can be performed.

As such, by using the surface LS in which the surface BS of the structure is modeled (or smoothed), the flow surface deviating from the surface LS is deleted. In other words, the flow surface is replaced with the modeled plane LS (see output of FIG. 5).

On the other hand, as shown in FIG. 13, as in the region A of the structure, when the surface of the structure is severely bent, the intersection of the surface of the structure and one cell becomes four. As such, when there are many intersections, it may be difficult to distinguish between the inside and the outside of the surface. In addition, in order to model the surface, since the surface is a closed curve (two-dimensional closed curve), the modeled result should also be a closed curve, but it is difficult to determine what intersections should be used to achieve the closed curve. In this case, therefore, as shown in FIG. 14, some of the intersections may be ignored and the remaining ones may be subsequently modeled.

However, the present invention is not limited thereto, and the smoothing step of the outer surface may be omitted when the outer surface (or interface) of the structure is not lattice by the FDM method in the pretreatment step. In addition, information about the intersection of the surface outside the structure and the three-dimensional orthogonal grid and the surface LS is generated in a pre-process step, and the information may be simply received and used in the flow analysis step of the present invention. .

On the other hand, the post-processing method of the flow analysis result according to the embodiment of the present invention described above can be implemented in a general-purpose digital computer that can be written in a program that can be executed in a computer, and operating the program using a computer-readable storage medium. Can be.

In addition, the post-processing method according to the embodiment of the present invention described above may be recorded and / or stored in a computer-readable storage medium through various means. Computer-readable storage media include magnetic storage media (e.g., ROMs, floppy disks, hard disks, etc.), optical read media (e.g., CD-ROMs, DVDs, etc.) and carrier waves (e.g., transmission over the Internet). Storage media such as

Those skilled in the art will appreciate that the present invention can be embodied in other specific forms without changing the technical spirit or essential features of the present invention. For example, a program for realizing the control method of the present invention may be implemented in various forms such as a recording medium in which a program is recorded. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive. The scope of the present invention is shown by the following claims rather than the detailed description, and all changes or modifications derived from the claims and their equivalents should be construed as being included in the scope of the present invention.

1 and 2 are exemplary views for explaining a lattice method according to the prior art.

3 and 4 are conceptual views for explaining the post-processing method of the flow analysis result according to the prior art.

5 is a conceptual diagram illustrating a post-processing method of flow analysis results according to an exemplary embodiment of the present invention.

6 to 9 are conceptual diagrams for explaining a process of smoothing a flow surface.

10 to 14 are conceptual diagrams for describing a process of modeling a structure surface.

(Explanation of symbols for the main parts of the drawing)

C1, C2, C3, C4: Center point CE: Cell

P1, P2, P3, P4: Intersection LL_1, LL_2, LL_3: Grid lines

Claims (13)

In the method of post-processing the flow analysis results in a structure gridized into a plurality of cells, Calculating a flow rate for the center point of each cell; Calculating a flow rate for the node of each cell using the flow rate for the center point of each cell; Extracting a position of a reference flow value using the flow rate for the center point and the flow rate for the node, and modeling the flow surface using the extracted position; And Modifying the flow surface outside of the structured surface of the modeled flow surface. delete The method of claim 1, wherein calculating the flow rate for the node of each cell And averaging the flow rates of the center points adjacent to each node. The method of claim 1, wherein the modeling step Extracting the position of the reference flow rate value on a plurality of grid lines constituting the cell; And a step of constructing a surface having a corner at a point of the extracted position on the grid line. The method of claim 1, And said cell is a hexahedron cell. The method of claim 1, wherein the modifying step Extracting an intersection point of the structure surface with a three-dimensional orthogonal grid; Modeling the surface of the structure as a face with the intersection of corners; And replacing said flow surface leaving said face with said face. The method of claim 1, wherein the modifying step Receiving information about a surface of an intersection of the structure surface and a three-dimensional orthogonal grid line; Using said information to replace said flow surface leaving said face with said face. In the method of post-processing the flow analysis results in a structure gridized into a plurality of cells, Calculating a flow rate for the center point of each cell; Calculating a flow rate for the node of each cell using the flow rate for the center point of each cell; And Post-processing the flow analysis result comprising extracting the position of the reference flow value using the flow rate for the center point and the flow rate for the node, and modeling the flow surface with a surface having the corner of the extracted position Way. The method of claim 8, And modifying the modeled flow surface along the structure surface. 10. The method of claim 9, wherein said modifying Extracting an intersection point of the structure surface with the grid lines constituting the cell; Modeling the surface of the structure as a face with the intersection of corners; And replacing said flow surface leaving said face with said face. 10. The method of claim 9, wherein said modifying Receiving information about a surface of the structure at the intersection of the grid line constituting the cell with an edge; Using said information to replace said flow surface leaving said face with said face. The method of claim 8, And said cell is a hexahedron cell. A computer-readable storage medium having stored thereon a program for executing the post-processing method of the flow analysis result according to any one of claims 1 to 4.

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