Anisotropic porous medium three-dimensional structure generation method based on random growth method

Abstract

The invention provides a three-dimensional porous medium generation method based on a random generation method, and belongs to the technical field of three-dimensional structure generation. The method comprises the following steps of: firstly, specifying porous medium parameters needing to be generated by a user; secondly, placing a growth core in the porous medium domain, and growing until the required porosity is met; and thirdly, smoothing the edge of the porous medium by using a filter. And finally, modeling the porous medium data. Compared with a computed tomography technology and a focused ion beam scanning electron microscope technology, the method has the advantages that the three-dimensional porous medium structures with similar quality can be obtained without professional instruments, and the three-dimensional porous medium structures meeting requirements can be generated in a very short time; a user can obtain a required three-dimensional porous medium structure by adjusting different parameters.

Description

Technical Field

[0001] The present invention belongs to the technical field of three-dimensional structure generation, and relates to a method for generating an anisotropic three-dimensional porous medium structure based on a random generation method. Background Art

[0002] A porous medium is a substance composed of multiple materials. The solid part in this substance is called the skeleton, and the remaining part is called the pore. The pores can be connected, and according to whether they are connected or not, they can be divided into open-cell materials and closed-cell materials. The distribution of pores in the porous medium is full of uncertainty. Porous media have a wide range of applications in life and production. The soil and rocks in geological exploration and oil extraction are porous media; the catalytic beds, filters, and adsorbents in chemical production are a kind of porous media; the thermal protection structure sandwich on the outer surface of aerospace aircraft is also a porous media; the internal structure of plant leaves is also a porous media. The flow of fluids (liquids or gases) inside the porous medium is affected by various factors such as the shape, distribution position, connectivity, and size of the pores, and the flow process of the fluid has complex characteristics. In addition to common experiments, numerical simulation research has also become an important link. To conduct numerical research, first, a physical model of the porous medium must be obtained.

[0003] In the existing three-dimensional structure generation technologies of porous media, there are computerized tomography (CT) and focused ion beam scanning electron microscopy (FIB-SEM) and other methods to scan the porous medium to generate the porous medium. However, these methods have many technical problems and high costs. For example, the internal structure of the porous medium is very complex, and the resolution of the CT technology and the FIB-SEM technology is limited by the performance of the equipment, and it is difficult to capture all the microscopic structure information; due to the limited imaging depth of the CT technology and the FIB-SEM, for large-volume porous media, it is impossible to perform complete imaging and reconstruction of the internal structure; the FIB-SEM requires cutting and preparation of the sample, and the CT requires scanning of the sample. These pre-treatment processes are cumbersome and complex; the results obtained by FIB-SEM and CT scanning must undergo complex data processing before they can be converted into a three-dimensional model; the FIB-SEM and CT equipment are expensive, require maintenance costs and professional technical personnel for operation and maintenance, and the characterization cost of the sample is also very high. In view of the above problems of the FIB-SEM and CT, the present invention provides a method for generating an anisotropic three-dimensional structure of a porous medium based on a random generation method. Summary of the Invention

[0004] According to the above technical problems existing in the three-dimensional reconstruction of porous media, a method for generating three-dimensional porous media based on the random generation method is proposed. This method mainly constructs three-dimensional porous media by using the methods of random growth and controlling the growth probabilities in different directions, and generates the point information of the three-dimensional porous media.

[0005] To achieve the above object, the technical means adopted by the present invention are as follows:

[0006] A method for generating three-dimensional porous media based on the random generation method, the method: First, the user specifies the parameters of the porous media to be generated. Second, growth nuclei are placed in the porous media domain and grown until the required porosity is satisfied.

[0007] Third, use a filter to smooth the edges of the porous media. Finally, model the porous media data. Specifically, it includes the following steps:

[0008] The first step is that the user specifies the parameters of the porous media to be generated. The porous media parameters include the side length of the porous media region, the porosity of the porous media, the generation probability of the initial growth nuclei, and the growth probabilities in each direction. Specifically:

[0009] Step 1.1, the user specifies the side length of the porous media region to determine the size of the porous media.

[0010] Step 1.2, the user specifies the porosity of the porous media. The porosity refers to the ratio of the pore volume in the porous media to the total volume of the porous media.

[0011] Step 1.3, the user specifies the generation probability of the initial growth nuclei of the porous media.

[0012] Step 1.4, the user specifies the initial growth nuclei of the porous media, and the growth probabilities in multiple directions such as above, below, left, right, front, and back for each growth nucleus. This probability is the same for all initial growth nuclei and growth nuclei.

[0013] The second step is to calculate the number of initial growth nuclei according to the parameters obtained in the first step, place the initial growth nuclei at random positions in the porous media domain, and grow until the required porosity is satisfied. Specifically:

[0014] Step 2.1, construct a cube region as the porous media region. The cube region is composed of a series of points. Each point has its own coordinates and a corresponding value of 0 or 1. 0 represents that there is a pore at this point, and 1 represents that there is a solid at this point. The values of all points in the porous media region are initially set to 0.

[0015] Step 2.2, randomly place initial growth nuclei at random positions in the porous medium region according to the parameters in Step 1.3 within the cube region, and change the values at the positions where these initial growth nuclei are located to 1. The number of initial growth nuclei in this step is calculated from the generation probability of the initial growth nuclei specified by the user in the first step.

[0016] Step 2.3, generate a random number, and compare this random number with the growth probability in each direction of each initial growth nucleus. If the random number is greater than the growth probability in that direction and the value at the position in that direction is not 1, then change the value at that position to 1, and at the same time these points become new growth nuclei.

[0017] Step 2.4, repeat Step 2.3 until all the initial growth nuclei in the porous medium region have been subjected to Step 2.3.

[0018] Step 2.5, count the number of points with a value of 0 in the porous medium region at this time, calculate the ratio of the number of points with a value of 0 to the number of all points. If the porosity requirement in Step 1.2 is satisfied, then proceed to Step Three; otherwise, repeat Step 2.3.

[0019] The third step is to smooth the edge of the porous medium using a filter.

[0020] The fourth step is to package it into a CSV format file.

[0021] Furthermore, in Step 1.4, if the growth probability in each direction is the same, it is an isotropic porous medium; if the growth probability in each direction is different, it is an anisotropic porous medium.

[0022] The beneficial effects of the present invention are as follows:

[0023] (1) Compared with computer tomography (CT) and focused ion beam scanning electron microscopy (FIB-SEM), the present invention can obtain a three-dimensional porous medium structure with similar quality without using professional instruments.

[0024] (2) In terms of the size, porosity, anisotropy, etc. of the porous medium, the present method can be defined by the user. By adjusting different parameters, the user can obtain the required three-dimensional porous medium structure.

[0025] (3) Compared with computer tomography (CT) and focused ion beam scanning electron microscopy (FIB-SEM), the present invention can generate a three-dimensional porous medium structure that meets the requirements only in a very short time. Description of the Drawings

[0026] Figure 1 It is a schematic diagram of the growth probability of each growth nucleus in 26 directions;

[0027] Figure 2 A flowchart of a method for generating a three-dimensional structure of an anisotropic porous medium based on a random growth method provided by the present invention;

[0028] Figure 3 An image of the initial growth nuclei generated by the present invention on a section of the porous medium;

[0029] Figure 4 An image of a section of the porous medium after one round of growth is shown;

[0030] Figure 5 An image of a section of the porous medium that meets the porosity requirement;

[0031] Figure 6 An image of a section of the porous medium after filtering;

[0032] Figure 7 A three-dimensional isotropic porous medium generated by this method;

[0033] Figure 8 A three-dimensional anisotropic porous medium generated by this method. Detailed implementation mode

[0034] The present invention will be further described below in conjunction with specific implementation cases.

[0035] Step 1: The user specifies the parameters of the porous medium to be generated. Specifically:

[0036] Step 1.1: The user specifies the side length a of the porous medium region, which is used to determine the size of the porous medium.

[0037] Step 1.2: The user specifies the porosity of the porous medium The porosity refers to the ratio of the pore volume in the porous medium to the total volume of the porous medium.

[0038] Step 1.3: The user specifies the initial growth nucleus generation probability P0 of the porous medium.

[0039] Step 1.4: As shown in Figure 1 , the user specifies the growth probability P of the porous medium initial growth nucleus in each of the 28 directions such as up, down, left, right, front, and back i (i = 1, 2,..., 28). If the growth probability in each direction is the same, it is an isotropic porous medium. If the growth probability in each direction is different, it is an anisotropic porous medium.

[0040] Step 2: According to the parameters in Step 1, growth nuclei are placed in the porous medium region and grown until the required porosity is met. Specifically:

[0041] Step 2.1: Construct a cubic region with a size of a*a*a as the porous medium region. There are a total of a points in the porous medium region, and each point has its own coordinates (i, j, k) and a corresponding value of 0 or 1. 0 represents a pore at that point, and 1 represents a solid at that point. The values of all points in the porous medium domain are initially set to 0. 3 Step 2.2: Randomly generate P0*a initial growth nuclei within the cubic region, and change the values of the positions where these initial growth nuclei are located to 1.

[0042] Step 2.3: Generate a random number and compare this random number with the growth probability P in each direction of an initial growth nucleus (i = 1, 2,..., 28). If the random number is greater than P, and the value of the position in this direction is not 1, then change the value of this position to 1, and at the same time, these points become new growth nuclei. 3 Step 2.4: Repeat Step 2.3 until all growth nuclei in the region have been executed Step 2.3. Figure 3 Figure shows an image of a cross-section after the generation of the initial growth nuclei.

[0043] Step 2.5: Count the number of points with a value of 0 in the porous medium domain at this time, calculate the ratio of the number of points with a value of 0 to the total number of points. If it meets the requirement, proceed to Step Three; otherwise, repeat Step 2.3. The final obtained structural cross-section is as shown in i (i = 1, 2,..., 28), and if the random number is greater than P, and the value of the position in this direction is not 1, then change the value of this position to 1, and at the same time, these points become new growth nuclei. i Step 2.5: Count the number of points with a value of 0 in the porous medium domain at this time, calculate the ratio of the number of points with a value of 0 to the total number of points. If it meets the requirement, proceed to Step Three; otherwise, repeat Step 2.3. The final obtained structural cross-section is as shown in Figure 4 Figure shows an image of a cross-section after this step.

[0044] Step 2.6: Repeat Step 2.3 until all growth nuclei in the region have been executed Step 2.3.

[0045] Step 2.7: Count the number of points with a value of 0 in the porous medium domain at this time, calculate the ratio of the number of points with a value of 0 to the total number of points. If it meets the requirement, proceed to Step Three; otherwise, repeat Step 2.3. The final obtained structural cross-section is as shown in then proceed to Step Three, otherwise, repeat Step 2.3. The final obtained structural cross-section is as shown in Figure 5 shown.

[0046] Step Three: Use a filter to smooth the edge of the porous medium. Scan the generated three-dimensional porous medium structure with a 3*3 filter, count the values of the 9 elements in the filter, and replace all 9 elements with the value that appears more frequently. The final obtained structural cross-section is as shown in Figure 6 shown.

[0047] Step Four: Package it into a CSV format file.

[0048] The above-described embodiments only represent the implementation manners of the present invention, but should not be construed as limiting the scope of the present invention. It should be noted that for those skilled in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A method for generating a three-dimensional structure of an anisotropic porous medium based on a random growth method, characterized in that The method includes the following steps: In the first step, the user specifies the parameters of the porous medium to be generated, which include the side length of the porous medium region, the porosity of the porous medium, the initial growth nucleus generation probability, and the growth probabilities in each direction; In the second step, based on the parameters obtained in the first step, the number of initial growth nuclei is calculated through computation, and the initial growth nuclei are placed at random positions within the porous medium domain and grown until the required porosity is satisfied. Specifically: Step 2.1, construct a cube region as the porous medium region. The cube region consists of a series of points, each point having its own coordinates and a corresponding value of 0 or 1. 0 represents a pore at that point, and 1 represents a solid at that point. The values of all points within the porous medium region are initially set to 0; Step 2.2, randomly place the initial growth nuclei at random positions within the porous medium region according to the parameters in Step 1.3, and change the values of the positions where these initial growth nuclei are located to 1. The number of initial growth nuclei in this step is calculated from the initial growth nucleus generation probability specified by the user in the first step; Step 2.3, generate a random number, and compare this random number with the growth probability in each direction of each initial growth nucleus. If the random number is greater than the growth probability in that direction and the value of the position in that direction is not 1, then change the value of that position to 1, and at the same time, these points become new growth nuclei; Step 2.4, repeat Step 2.3 until all the initial growth nuclei within the porous medium region have been subjected to Step 2.3; Step 2.5, count the number of points with a value of 0 within the porous medium region at this time, calculate the ratio of the number of points with a value of 0 to the total number of points. If the porosity requirement in Step 1.2 is satisfied, then proceed to the third step; otherwise, repeat Step 2.3; In the third step, use a filter to smooth the edges of the porous medium to obtain a three-dimensional structure of the anisotropic porous medium.

2. The method for generating a three-dimensional structure of an anisotropic porous medium based on the random growth method according to claim 1, characterized in that, After obtaining the three-dimensional structure of the anisotropic porous medium in the third step described above, it can also be packaged into a CSV format file.

3. A method for generating a three-dimensional structure of an anisotropic porous medium based on the random growth method, characterized in that, Specifically, the first step described above: Step 1.1, the user specifies the side length of the porous medium region to determine the size of the porous medium; Step 1.2, the user specifies the porosity of the porous medium. The porosity refers to the ratio of the pore volume in the porous medium to the total volume of the porous medium; Step 1.3, the user specifies the initial growth nucleus generation probability of the porous medium; Step 1.4, the user specifies the initial growth nuclei of the porous medium, and the growth probabilities in the up, down, left, right, front, back, and other multiple directions for each growth nucleus. This probability is the same for all initial growth nuclei and growth nuclei.

4. A method for generating a three-dimensional structure of an anisotropic porous medium based on the random growth method according to claim 3, characterized in that, In Step 1.4 described above, if the growth probability in each direction is the same, it is an isotropic porous medium; if the growth probability in each direction is different, it is an anisotropic porous medium.

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