Discrete element simulation analysis method for surface microparticle motion under condensation scene

Abstract

The invention relates to the technical field of particle discrete element simulation analysis methods, in particular to a surface microparticle motion discrete element simulation analysis method under a condensation scene. The method comprises the following steps: S1, constructing a preliminary microparticle array; s2, establishing a microparticle search window range based on a microparticle liquid bridge formation condition under a condensation condition, and forming an adjacent microparticle matrix and a contact collision microparticle matrix; s3, forming a liquid bridge force matrix and a contact collision force matrix; s4, other acting force matrixes are imported, a resultant force matrix of the microparticles is calculated on the basis of the liquid bridge force matrix, the contact collision force matrix and the other acting force matrixes, and the resultant force and the movement condition of the microparticles under the condensation scene are calculated according to classical mechanics on the basis of the resultant force matrix; and S5, continuously carrying out iterative simulation calculation, and outputting the movement condition and position information of the microparticles on the acting surface within the total time length. According to the method, the discrete element calculation speed is remarkably increased, and efficient simulation of action surface microparticle motion under the condensation scene is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of particle discrete element simulation analysis methods, and specifically refers to a discrete element simulation analysis method for the movement of surface microparticles in a condensation scenario. Background Technique

[0002] The condensation phenomenon widely exists on the surfaces of refrigeration heat exchangers, outdoor working photovoltaic panels, trough-shaped reflecting mirrors, metal pipe walls, and optical components of laser systems. Due to the sedimentation effect of atmospheric microparticles in the air or the action of sand and dust, the deposition of surface microparticles is inevitably caused. The condensation phenomenon will form a liquid bridge between particles and between particles and the acting surface, generating a liquid bridge force, which exacerbates the deposition and agglomeration of surface microparticles and causes serious negative impacts on the acting surface, such as reducing its working performance and service life. At present, conventional calculation methods such as finite element and finite volume do not fully consider the interaction between condensation and microparticles / acting surfaces, and it is difficult to truly reflect the movement process of surface microparticles in a condensation scenario.

[0003] The discrete element method is a numerical simulation method for studying the movement problems of discontinuous media, which can effectively couple the influence of the condensation effect on the interaction between microparticles and the acting surface, and has now become an important and reliable tool for visualizing the movement process of microparticles. Discrete element calculations include searching for the contacting particles of each particle and the particles that form a liquid bridge with it, and then performing iterative calculations of particle movement. However, the discrete element has defects such as huge computational workload. The computational workload of microparticles is usually between several hundred thousand and several million, and even tens of millions of particle numbers. The search time is too long and the calculation rate is slow, which greatly limits the development and application of discrete element calculations. Therefore, specific methods need to be adopted to achieve fast discrete element simulation calculations to meet the requirements of large-scale microparticle discrete element calculations. Summary of the Invention

[0004] The purpose of this application is to solve the deficiencies of the above background technique and provide a discrete element simulation analysis method for the movement of surface microparticles in a condensation scenario.

[0005] The technical solution of this application is as follows: A discrete element simulation analysis method for the movement of surface microparticles in a condensation scenario is carried out according to the following steps:

[0006] S1. Number the microparticles on the acting surface and construct a preliminary microparticle array;

[0007] S2. Based on the formation conditions of microparticle liquid bridges in the condensation situation, establish the search window range of microparticles, and search and screen the preliminary microparticle array based on the search window range of microparticles to obtain an adjacent microparticle array with liquid bridge force and a contact and collision microparticle array that has no liquid bridge force but has contact and collision, and form an adjacent microparticle matrix and a contact and collision microparticle matrix;

[0008] S3, calculating the liquid bridge force between each microparticle in the adjacent microparticle matrix and the surrounding adjacent microparticles, calculating the contact collision force between each microparticle in the contact collision microparticle matrix and the surrounding contact collision microparticles, forming a liquid bridge force matrix corresponding to the adjacent microparticle matrix based on the liquid bridge force, and forming a contact collision force matrix corresponding to the contact collision microparticle matrix based on the contact collision force;

[0009] S4. Import other force matrices, calculate the resultant force matrix of the microparticles based on the liquid bridge force matrix, the contact collision force matrix and other force matrices, and calculate the resultant force and motion of the microparticles under the condensation scenario according to classical mechanics based on the resultant force matrix;

[0010] S5. Calculate the motion of the microparticles in the next time step according to steps S2 to S4, continuously iterate the simulation calculation, and output the motion and position information of the microparticles on the action surface within the total time.

[0011] According to a discrete element simulation analysis method for surface microparticle motion under condensation scenario provided by the present application, step S2 includes the following sub-steps:

[0012] S21, inputting the physical property parameters and size data of the microparticles into a preliminary microparticle array;

[0013] S22. Determine the morphological characteristics of the liquid bridge between the particles and the calculation formula of the liquid bridge volume based on the temperature and humidity of the condensation scenario, the characteristic parameters of the action surface and the properties of the microparticles;

[0014] S23, construct the relationship between the liquid bridge contact radius, the narrowest neck radius of the liquid bridge and the particle spacing;

[0015] S24, according to the conditions for liquid bridge formation, the liquid bridge volume calculation formula and the relationship between the liquid bridge contact radius, the narrowest neck radius of the liquid bridge and the particle spacing are combined to determine the critical particle spacing for liquid bridge formation;

[0016] S25, constructing a microparticle search window range based on the critical particle spacing, searching within the microparticle search window range with the central microparticle as the center, obtaining adjacent microparticles within the microparticle search range, and storing adjacent spacings between the adjacent microparticles and the central microparticle;

[0017] S26, comparing the adjacent spacing with the critical particle spacing, classifying the adjacent microparticles based on the comparison result of the adjacent spacing with the critical particle spacing, screening out the adjacent microparticles having liquid bridge forces with the central microparticles, and the contact collision microparticles in contact with the central microparticles, to form an adjacent microparticle matrix and contact collision microparticles;

[0018] S27, numbering the adjacent microparticles to form an adjacent microparticle matrix, and numbering the contact and collision microparticles to form a contact and collision microparticle matrix.

[0019] According to a discrete element simulation and analysis method for surface microparticle motion under a condensation scenario provided in the present application, in the step S22, the method for determining the liquid bridge volume calculation formula includes: if the microparticle is a hydrophilic microparticle, the liquid bridge is in a hyperbolic shape, and the liquid bridge volume calculation formula is constructed according to the hyperbolic shape; if the microparticle is a hydrophobic microparticle, the liquid bridge is in a convex shape, and the liquid bridge volume calculation formula is constructed according to the convex shape.

[0020] According to a discrete element simulation analysis method for surface microparticle motion under condensation scenario provided by the present application, in step S23, the method for constructing the relationship between the liquid bridge contact radius, the narrowest neck radius of the liquid bridge and the particle spacing includes: constructing the relationship between the liquid bridge contact radius, the narrowest neck radius of the liquid bridge and the particle spacing according to the following formula:

[0021] r c / r0=cosh[D / (2r0)]

[0022] Where: r c ——Liquid bridge contact radius;

[0023] r0——radius of the narrowest neck of the liquid bridge;

[0024] D – distance between particles.

[0025] According to a discrete element simulation analysis method for surface microparticle motion under condensation scenario provided by the present application, in step S24, according to the liquid bridge contact radius and the narrowest neck radius of the liquid bridge being equal, the liquid bridge volume calculation formula and the relationship between the liquid bridge contact radius, the narrowest neck radius of the liquid bridge and the particle spacing are combined to calculate the critical particle spacing according to the following formula:

[0026] D c =(2cosα*r c ) / (1-2sinα)

[0027] Where: D c — critical particle spacing;

[0028] r c ——Liquid bridge contact radius;

[0029] α——Solid-liquid contact angle between microparticles and liquid bridge.

[0030] According to a method for discrete element simulation analysis of surface microparticle motion in a condensation scenario provided by the present application, in the step S25, the method for constructing a microparticle search window range based on the critical particle spacing includes: constructing a microparticle search window range with the sum of the radius of the central microparticle, the maximum microparticle radius, and the critical particle spacing as the search radius.

[0031] According to a method for discrete element simulation analysis of surface microparticle motion in a condensation scenario provided by the present application, in the step S26, the method for classifying adjacent microparticles based on the comparison result of the adjacent spacing and the critical particle spacing includes: if the adjacent spacing is greater than 0 and not greater than the critical particle spacing, it is determined that a liquid bridge can be formed between the adjacent microparticle and the central microparticle, and it is a neighboring microparticle; if the adjacent spacing is not greater than 0, it is determined that the adjacent microparticle and the central microparticle are in contact, and it is a contact collision microparticle.

[0032] According to a method for discrete element simulation analysis of surface microparticle motion in a condensation scenario provided by the present application, in the step S4, the method for calculating the resultant force matrix of microparticles includes: performing vector decomposition on the liquid bridge force matrix, the contact collision force matrix, and other force matrices in the X, Y, and Z directions to obtain the corresponding liquid bridge force vector matrix and contact collision force vector matrix; performing vector decomposition on other forces to obtain the corresponding other force vector matrix; calculating the resultant force matrix of microparticles based on the corresponding liquid bridge force vector matrix, contact collision force vector matrix, and other force vector matrix.

[0033] According to a method for discrete element simulation analysis of surface microparticle motion in a condensation scenario provided by the present application, in the step S3, the method for calculating the liquid bridge force between each microparticle in the neighboring microparticle matrix and the surrounding neighboring microparticles includes: calculating the liquid bridge force according to the following formula:

[0034]

[0035] where: F c ——Liquid bridge force;

[0036] r——Microparticle radius;

[0037] γ——Liquid bridge surface tension coefficient;

[0038] D——Particle spacing;

[0039] A, B, C——Particle and liquid bridge contact empirical parameters, related to the dimensionless liquid bridge volume and the solid-liquid contact angle.

[0040] According to a method for discrete element simulation analysis of surface microparticle motion in a condensation scenario provided by the present application, the other forces include gravity, the liquid bridge force between the microparticle and the acting surface, van der Waals force, drag force, and frictional force.

[0041] By analyzing the specific conditions for the formation of liquid bridges under condensation conditions, this application proposes a method for determining the search window range of microparticles, thereby effectively narrowing the search range and frequency of microparticles and achieving efficient identification of adjacent particles and contacting and colliding particles. In addition, this method combines discrete element simulation with GPU matrix operations, constructs a liquid bridge force matrix and a contact and collision force matrix for microparticles, and calculates the actual resultant force matrix of microparticles, significantly improving the speed of discrete element calculations and realizing efficient simulation of the movement of microparticles on the acting surface under condensation scenarios.

[0042] Based on the conditions for the formation of surface microparticle liquid bridges under condensation scenarios, this application screens adjacent microparticles and contacting and colliding microparticles that affect the movement of microparticles. By analyzing the influence of adjacent microparticles and contacting and colliding microparticles on the central microparticle, it can judge the resultant force and movement conditions of the central microparticle, greatly reducing the data for discrete element simulation analysis of microparticles, lowering the difficulty of discrete element simulation analysis of microparticles, and being completely targeted at the movement of microparticles under condensation scenarios, providing a good method for the simulation analysis of the movement of liquid microparticles.

[0043] By constructing the search window range of microparticles based on the liquid bridge formation mechanism, this application can quickly obtain contacting and colliding particles and adjacent particles, shorten the search range, search operation frequency, and calculation cost of microparticles. At the same time, combined with the GPU matrix operation method, it further improves the iterative calculation speed of discrete elements. This application avoids continuously running the search algorithm in conventional discrete element calculations, constantly determining whether to contact other particles and calculating the liquid bridge force between each microparticle. Instead, based on the liquid bridge formation conditions, it establishes a contact and collision particle matrix Pn and an adjacent particle matrix Sn to achieve fast GPU matrix calculation of the discrete element method, and all discrete element calculations are completed in the form of GPU matrices, including physical properties, dimensions, liquid bridge forces, contact and collision forces, and other acting forces. A single computer can achieve fast discrete element simulation of the movement of millions of microparticles. This application considers the influence of condensation heat transfer on microparticles and the acting surface, obtains the actual resultant force matrix of microparticles, and finally uses the conventional discrete element calculation method to complete the fast discrete element simulation of the dynamic process of microparticles on the acting surface under condensation scenarios. Description of the Drawings

[0044] Figure 1 : Schematic diagram of the simulation analysis method flow of this application;

[0045] Figure 2 : Schematic diagram of the method flow for establishing the search window range of microparticles in this application;

[0046] Figure 3 : Schematic diagram of the vector decomposition of the liquid bridge force matrix and the contact and collision force matrix of this application;

[0047] Figure 4: Schematic diagram for constructing other force matrices of the present application;

[0048] Figure 5 : Schematic diagram for vector decomposition of other force matrices of the present application. Detailed implementation manners

[0049] The embodiments of the present application will be described in detail below. The same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present application, but should not be construed as a limitation to the present application.

[0050] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present application.

[0051] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0052] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0053] The present application relates to a discrete element simulation analysis method for the movement of surface microparticles in a condensation scenario, which is used to simulate and analyze the movement of microparticles on the acting surface in a condensation scenario. Condensation will form a liquid film on the surface of the microparticles and the acting surface, and then generate liquid bridges between the particles. These microparticles are affected by various forces on the acting surface. In addition to the force between the microparticle itself and the acting surface, there is also the interaction force between the microparticle and other microparticles. Adjacent microparticles will form liquid bridges on the acting surface, generating liquid bridge forces, which will change the force and movement conditions of the microparticles. In addition, the mutual contact and collision of microparticles will also generate interaction forces, which will also change the force and movement conditions of the microparticles. Therefore, when it is necessary to simulate and analyze the microparticles on the acting surface in a condensation scenario, in addition to analyzing the acting force between the microparticles and the acting surface, it is also necessary to analyze the liquid bridge force and the contact and collision force. The liquid bridge force and the contact and collision force are both interaction forces, that is, the force relationship between the central microparticle and the surrounding microparticles is explored and analyzed. If the force relationship is directly simulated and analyzed, the data and calculation amount involved will be very large, resulting in an extremely complex process of the entire simulation calculation analysis and a very slow calculation speed. The present application constructs a microparticle search window range based on the formation mechanism of the liquid bridge, screens the microparticles that have a direct impact on the central microparticle through the microparticle search window range, and excludes other microparticles that have no impact on the central microparticle, greatly reducing the data range and data volume to be analyzed, and greatly improving the efficiency and rate of the entire simulation analysis calculation.

[0054] Specifically, as Figures 1 to 5 shown, a discrete element simulation analysis method for the movement of surface microparticles in a condensation scenario of the present application is carried out according to the following steps:

[0055] S1. Number the microparticles on the acting surface and construct a preliminary microparticle array;

[0056] Construct a discrete element model of the deposition of microparticles on the acting surface in the initial state. Assume that the number of microparticles deposited on the acting surface is m. Then number the m microparticles on the acting surface, and the numbers range from 1 to m;

[0057] Analyze each microparticle. Assume that the number of the currently analyzed microparticle is 1. Then the 1st microparticle is the central microparticle, and analyze the other microparticles adjacent to the central microparticle;

[0058] S2. Establish a microparticle search window range based on the microparticle liquid bridge formation conditions in the condensation scenario, search and screen the preliminary microparticle array based on the microparticle search window range, obtain an adjacent microparticle array with liquid bridge force and a contact and collision microparticle array without liquid bridge force but with contact and collision, and form an adjacent microparticle matrix and a contact and collision microparticle matrix;

[0059] When analyzing a certain microparticle in this application, taking this microparticle as the central microparticle, diverging and searching around the central microparticle as the center, establishing the range of the microparticle search window based on the formation conditions of the microparticle liquid bridge under the condensation condition, not considering the microparticles outside the range of the microparticle search window, and only the microparticles within the range of the microparticle search window will affect the central microparticle. By screening out the microparticles that affect the central microparticle for analysis, the data volume and the difficulty of simulation analysis can be greatly reduced;

[0060] For the central microparticle of this application, there are two types that can affect the central microparticle. One is the microparticle that can form a liquid bridge with the central microparticle, and this part of the microparticle is the adjacent microparticle. The other part is the microparticle that directly contacts and collides with the central microparticle, and this part of the microparticle is the contact collision microparticle. The adjacent microparticle affects the central microparticle through the liquid bridge force, and the contact collision microparticle affects the central microparticle through the contact collision force;

[0061] After screening out the adjacent microparticles and contact collision microparticles corresponding to the central microparticle, the corresponding adjacent microparticle matrix and contact collision microparticle matrix can be constructed based on the adjacent microparticles and contact collision microparticles. The adjacent microparticle matrix is Pn (with a size of m rows and n columns, the m-th row corresponds to the microparticle numbered m, and the n-th column corresponds to the number of adjacent microparticles of each microparticle. If the number is not enough, it is filled with m + 1), and the contact collision microparticle matrix is Sn (with a size of m rows and n columns, the m-th row corresponds to the microparticle numbered m, and the n-th column corresponds to the number of adjacent microparticles of each microparticle. If the number is not enough, it is filled with m + 1);

[0062] S3. Calculate the liquid bridge force between each microparticle in the adjacent microparticle matrix and the surrounding adjacent microparticles, calculate the contact collision force between each microparticle in the contact collision microparticle matrix and the surrounding contact collision microparticles, form the liquid bridge force matrix corresponding to the adjacent microparticle matrix based on the liquid bridge force, and form the contact collision force matrix corresponding to the contact collision microparticle matrix based on the contact collision force;

[0063] There is a liquid bridge force between each microparticle and the adjacent microparticle. Calculate the liquid bridge force between each microparticle and the adjacent microparticle. Here, the liquid bridge force between the central microparticle and each adjacent microparticle is calculated. As Figure 2 shown, assuming that the adjacent microparticles corresponding to the 1st microparticle are the 5th microparticle, the 8th microparticle, the 11th microparticle, the 12th microparticle..., then the liquid bridge force corresponding to the 1st microparticle is L 1，5 、L 1，8 、L 1，11 、L 1，12 ..., and the liquid bridge force matrix Ln is formed according to this method. AsFigure 3 as shown;

[0064] Similarly, there is a contact and collision force between each microparticle and the contacting and colliding microparticles. Calculate the contact and collision force between each microparticle and the contacting and colliding microparticles. Here, the contact and collision force between the central microparticle and each contacting and colliding microparticle is calculated. As Figure 2 shown, assuming that the contacting and colliding microparticles corresponding to the No. 1 microparticle are the No. 3 microparticle, No. 4 microparticle, No. 9 microparticle, No. 14 microparticle..., then the contact and collision force corresponding to the No. 1 microparticle is M 1，3 、M 1，4 、M 1，9 、M 1，14 ..., and a contact and collision force matrix Mn is formed according to this method. As Figure 3 shown;

[0065] S4. Import other force matrices, calculate the resultant force matrix of the microparticles based on the liquid bridge force matrix, contact and collision force matrix and other force matrices, and calculate the resultant force and motion conditions of the microparticles in the condensation scenario based on the resultant force matrix according to classical mechanics;

[0066] Other forces include gravity, liquid bridge force between the microparticle and the acting surface, van der Waals force, drag force and frictional force. Other forces are the forces of the microparticle itself and the interaction forces between the microparticle and the acting surface. After obtaining other forces, the obtained other forces can be imported into the preliminary microparticle array to construct other force matrices; for example, other forces involved in this application include gravity Fg, liquid bridge force Fl between the microparticle and the acting surface, van der Waals force Fv, drag force Fd and frictional force Ff, then an other force matrix Xn with m rows and n columns can be constructed, and 0 is used to fill in if the quantity is not enough. Specifically, as Figure 4 shown;

[0067] So far, the other force matrix, liquid bridge force matrix and contact and collision force matrix have been obtained, and the forces on the microparticles are clear. Calculate the resultant force matrix of the microparticles based on the liquid bridge force matrix, contact and collision force matrix and other force matrices, and the resultant force matrix of each microparticle can be obtained. After obtaining the resultant force matrix of the microparticles, based on classical mechanics, that is, the resultant force is the product of mass and acceleration, the resultant force and motion conditions of the microparticles in the condensation scenario can be determined;

[0068] S5. Calculate the motion conditions of the microparticles at the next time step according to steps S2 to S4, continuously perform iterative simulation calculations, and output the motion conditions and position information of the microparticles on the acting surface within the total duration.

[0069] In some embodiments of the present application, this embodiment optimizes the above step S2. Specifically, as Figure 2 shown, step S2 includes the following sub-steps:

[0070] S21. Input the physical property parameters and size data of the microparticles into the preliminary microparticle array;

[0071] The physical property parameters and size data of the microparticles in this embodiment include the microparticle density, particle size, initial velocity, solid-liquid contact angle, elastic modulus, and Poisson's ratio of the microparticles. In the actual application process, it is not limited to the above parameters, and the above physical property parameters and size data can be obtained by looking up tables (after obtaining the material of the microparticles and the material of the acting surface, the microparticle density, particle size, initial velocity, solid-liquid contact angle, elastic modulus, and Poisson's ratio can be obtained by looking up tables);

[0072] S22. Determine the morphological characteristics of the liquid bridge between the particles and the calculation formula for the liquid bridge volume based on the temperature and humidity of the condensation scenario, the characteristic parameters of the acting surface, and the microparticle properties;

[0073] The morphological characteristics of the liquid bridge are directly related to the calculation formula for the liquid bridge volume. If the microparticles are hydrophilic microparticles, the liquid bridge is in a hyperbolic shape, and the calculation formula for the liquid bridge volume is constructed according to the hyperbolic shape. The calculation formula is:

[0074] V L = πD(2r0 2 + r c 2 ) / 3 Formula 1

[0075] Where: V L ——Liquid bridge volume;

[0076] D——Particle spacing;

[0077] r c ——Liquid bridge contact radius (the liquid bridge radius corresponding to the liquid bridge wetting the particle);

[0078] r0——Radius of the narrowest neck of the liquid bridge;

[0079] If the microparticles are hydrophobic microparticles, the liquid bridge is in a convex shape, and the calculation formula for the liquid bridge volume is constructed according to the convex shape;

[0080] Or the morphological characteristics of the liquid bridge can be directly obtained through a microscope, and the relative relationship between the liquid bridge volume, particle spacing, liquid bridge contact radius, and the radius of the narrowest neck of the liquid bridge is constructed through the observed morphological characteristics of the liquid bridge, that is, the calculation formula for the liquid bridge volume;

[0081] S23. Construct the relationship between the liquid bridge contact radius, the radius of the narrowest neck of the liquid bridge, and the particle spacing;

[0082] Construct the relationship between the liquid bridge contact radius, the radius of the narrowest neck of the liquid bridge, and the particle spacing according to the following formula:

[0083] r c / r0=cosh[D / (2r0)] Formula 2

[0084] Where: r c ——Liquid bridge contact radius;

[0085] r0——radius of the narrowest neck of the liquid bridge;

[0086] D – particle spacing;

[0087] S24, according to the conditions for liquid bridge formation, the liquid bridge volume calculation formula and the relationship between the liquid bridge contact radius, the narrowest neck radius of the liquid bridge and the particle spacing are combined to determine the critical particle spacing for liquid bridge formation;

[0088] The critical interparticle spacing is calculated as follows:

[0089] D c =(2cosα*r c ) / (1-2sinα) Formula 3

[0090] Where: D c — critical particle spacing;

[0091] r c ——Liquid bridge contact radius;

[0092] α——solid-liquid contact angle between microparticles and liquid bridge;

[0093] The condition for liquid bridge formation is actually to set the maximum spacing of the liquid bridge. There are many ways to set this formation condition. In this embodiment, it is assumed that the liquid bridge contact radius r c The particle spacing at this time is equal to the radius r0 of the narrowest neck of the liquid bridge, and is set as the critical particle spacing, that is,

[0094] r c = r0 Formula 4

[0095] By combining equations 1, 2, and 4, we can substitute them into equation 3 to solve for the critical particle spacing D. c ;

[0096] S25, constructing a microparticle search window range based on the critical particle spacing, searching within the microparticle search window range with the central microparticle as the center, obtaining adjacent microparticles within the microparticle search range, and storing adjacent spacings between the adjacent microparticles and the central microparticle;

[0097] The critical particle spacing is the maximum spacing that may form a liquid bridge. Based on the critical particle spacing, the microparticle search window range can be constructed. In this embodiment, the microparticle search window range can be constructed according to the sum of the central microparticle radius, the maximum microparticle radius and the critical particle spacing as the search radius, that is, the microparticle search window range is (R+R max +Dc ), where R is the radius of the central microparticle, and R max is the radius of the largest particle among all microparticles, and D c is the critical particle spacing;

[0098] The range of the microparticle search window can also be determined in other ways. For example, taking 2R max +D c as the range of the microparticle search window. It should be noted that the particle spacing corresponds to the edge spacing of the microparticles, rather than the spacing between the centers of the particles;

[0099] After obtaining the range of the microparticle search window, draw a circle with the center of the central microparticle as the center and the range of the microparticle search window as the search radius. All the microparticles within this circular range are the above-mentioned adjacent microparticles. Adjacent microparticles are the microparticles that may affect the central microparticle. Since the range of the microparticle search window is searched with the center of the central microparticle as the center, and whether there is an influence between microparticles is judged based on the spacing between microparticles, the range of the microparticle search window is set to encompass a relatively large range;

[0100] S26. Compare the adjacent spacing with the critical particle spacing, classify the adjacent microparticles based on the comparison result of the adjacent spacing and the critical particle spacing, and screen out the neighboring microparticles that have a liquid bridge force with the central microparticle and the contact and collision microparticles that are in contact with the central microparticle to form a neighboring microparticle matrix and contact and collision microparticles;

[0101] Adjacent microparticles are divided into three types. One is the neighboring microparticles that have a liquid bridge force with each other, one is the contact and collision microparticles that are in contact and collision with each other, and the last one is the non-interacting microparticles that have neither a liquid bridge force nor a contact and collision. The specific screening method is as follows: If the adjacent spacing is greater than 0 and not greater than the critical particle spacing, it is judged that a liquid bridge can be formed between the adjacent microparticle and the central microparticle, and it is a neighboring microparticle; if the adjacent spacing is not greater than 0, it is judged that the adjacent microparticle and the central microparticle are in contact with each other, and it is a contact and collision microparticle; as for the adjacent spacing greater than the critical particle spacing, it is a non-interacting microparticle, and non-interacting microparticles are not considered in this embodiment;

[0102] S27. Number the neighboring microparticles to form a neighboring microparticle matrix, and number the contact and collision microparticles to form a contact and collision microparticle matrix;

[0103] The specific forms of the neighboring microparticle matrix and the contact and collision microparticle matrix are shown in Figure 2 and 3 as shown.

[0104] In some other embodiments of the present application, this embodiment optimizes the above step S3. Specifically, the method for calculating the liquid bridge force between each microparticle in the adjacent microparticle matrix and the surrounding adjacent microparticles in this embodiment is as follows: Calculate the liquid bridge force according to the following formula:

[0105]

[0106] Where: F c —— Liquid bridge force;

[0107] r —— Particle radius;

[0108] γ —— Liquid bridge surface tension coefficient;

[0109] D —— Particle spacing;

[0110] A, B, C —— Particle and liquid bridge contact empirical parameters, related to the dimensionless liquid bridge volume and the solid-liquid contact angle, obtained by looking up the table.

[0111] The method for calculating the contact and collision force between each microparticle in the contact and collision microparticle matrix and the surrounding contact and collision microparticles in this embodiment is as follows: Calculate the contact and collision force according to the Hertz-Mindlin-JKR model according to the following formula:

[0112]

[0113] Where: —— Normal contact and collision force between particle i and particle j;

[0114] —— Tangential contact and collision force between particle i and particle j;

[0115] —— Tangential contact and collision force between particles;

[0116] k n —— Normal elastic coefficient;

[0117] k t —— Tangential elastic coefficient;

[0118] c n —— Normal damping coefficient;

[0119] c t —— Tangential damping coefficient;

[0120] δ n —— Normal deformation;

[0121] —— Tangential deformation;

[0122] ——Relative velocity between particle i and particle j;

[0123] ——Sliding velocity vector;

[0124] ——Unit vector from particle i to particle j;

[0125] μ s ——Coefficient of friction between particles;

[0126] ——Tangential unit vector of n.

[0127] After calculating the liquid bridge force and contact collision force of each microparticle, they can be stored in the adjacent microparticle matrix and contact collision microparticle matrix to form the required liquid bridge force matrix Ln and contact collision force matrix Mn. Adding the already obtained other force matrix Xn, at this point, the above matrices can be vectorially decomposed. The liquid bridge force matrix Ln, contact collision force matrix Mn, and other force matrix Xn are vectorially decomposed in the X, Y, and Z directions to obtain the corresponding liquid bridge force vector matrices LnX, LnY, LnZ and contact collision force vector matrices MnX, MnY, MnZ, as shown in Figure 3 shown; the other forces are vectorially decomposed to obtain the corresponding other force vector matrices XnX, XnY, XnZ, as shown in Figure 4 and 5 shown;

[0128] Ln = LnX * i + LnY * j + LnZ * z Equation Nine

[0129] Mn = MnX * i + MnY * j + MnZ * z Equation Ten

[0130] Xn = XnX * i + XnY * j + XnZ * z Equation Eleven

[0131] Based on the corresponding liquid bridge force vector matrix, contact collision force vector matrix, and other force vector matrix, calculate the resultant force matrix of the microparticles. The calculation formula is as follows:

[0132] FnX = LnX + MnX + XnX Equation Twelve

[0133] FnY = LnY + MnY + XnY Equation Thirteen

[0134] FnZ = LnZ + MnZ + XnZ Equation Fourteen

[0135] According to Formula XII, Formula XIII, and Formula XIV, the resultant force of the microparticles in each direction can be calculated to form the resultant force matrix of the microparticles. Based on the resultant force matrix, the resultant force and motion of the microparticles in the condensation scenario are calculated according to classical mechanics. The resultant forces of the central microparticle numbered m in the X, Y, and Z directions are respectively the sum of all the unit values in the m-th row of the matrices FnX, FnY, and FnZ. The calculation formula is as follows:

[0136]

[0137] u x = u x + d t * a x 、u y = u y + d t * a y 、u z = u z + d t * a z Formula XVI

[0138] S x = S x + u x * d t 、S y = S y + u y * d t 、S z = S z + u z * d t Formula XVII

[0139] Where: m s —— The mass of the central microparticle;

[0140] a x —— The x-direction acceleration of the central microparticle;

[0141] a y —— The y-direction acceleration of the central microparticle;

[0142] a z —— The z-direction acceleration of the central microparticle;

[0143] u x —— The x-direction velocity of the central microparticle;

[0144] u y —— The y-direction velocity of the central microparticle;

[0145] u z —— The z-direction velocity of the central microparticle;

[0146] S x—— The x-direction displacement of the central microparticle;

[0147] S y —— The y-direction displacement of the central microparticle;

[0148] S z —— The z-direction displacement of the central microparticle;

[0149] dt - The time step.

[0150] The above method calculates the motion of the microparticle in one time step. The iterative calculation can be continuously performed according to the above method to output the motion and position information of the microparticle on the acting surface within the total duration.

[0151] The above shows and describes the basic principle, main features and advantages of this application. Those skilled in the art should understand that this application is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principle of this application. Without departing from the spirit and scope of this application, this application will have various changes and improvements, and these changes and improvements all fall within the scope of this application claimed. The scope of protection claimed by this application is defined by the appended claims and their equivalents.

Claims

1. A discrete element simulation analysis method for surface microparticle motion under condensation scenario, characterized by: Follow these steps: S1. Number the microparticles on the action surface and construct a preliminary microparticle array; S2. Based on the conditions for the formation of micro-particle liquid bridges under condensation conditions, a micro-particle search window range is established, and a preliminary micro-particle array is searched and screened based on the micro-particle search window range to obtain a neighboring micro-particle array with liquid bridge forces and a contact collision micro-particle array with no liquid bridge forces but contact collisions, thereby forming a neighboring micro-particle matrix and a contact collision micro-particle matrix; S3, calculating the liquid bridge force between each microparticle in the adjacent microparticle matrix and the surrounding adjacent microparticles, calculating the contact collision force between each microparticle in the contact collision microparticle matrix and the surrounding contact collision microparticles, forming a liquid bridge force matrix corresponding to the adjacent microparticle matrix based on the liquid bridge force, and forming a contact collision force matrix corresponding to the contact collision microparticle matrix based on the contact collision force; S4. Import other force matrices, calculate the resultant force matrix of the microparticles based on the liquid bridge force matrix, the contact collision force matrix and other force matrices, and calculate the resultant force and motion of the microparticles under the condensation scenario according to classical mechanics based on the resultant force matrix; S5. Calculate the motion of the microparticles in the next time step according to steps S2 to S4, continuously iterate the simulation calculation, and output the motion and position information of the microparticles on the action surface within the total time.

2. The discrete element simulation analysis method for surface microparticle motion under condensation scenario according to claim 1, characterized in that: The step S2 comprises the following sub-steps: S21, inputting the physical property parameters and size data of the microparticles into a preliminary microparticle array; S22. Determine the morphological characteristics of the liquid bridge between the particles and the calculation formula of the liquid bridge volume based on the temperature and humidity of the condensation scenario, the characteristic parameters of the action surface and the properties of the microparticles; S23, construct the relationship between the liquid bridge contact radius, the narrowest neck radius of the liquid bridge and the particle spacing; S24, according to the conditions for liquid bridge formation, the liquid bridge volume calculation formula and the relationship between the liquid bridge contact radius, the narrowest neck radius of the liquid bridge and the particle spacing are combined to determine the critical particle spacing for liquid bridge formation; S25, constructing a microparticle search window range based on the critical particle spacing, searching within the microparticle search window range with the central microparticle as the center, obtaining adjacent microparticles within the microparticle search range, and storing adjacent spacings between the adjacent microparticles and the central microparticle; S26, comparing the adjacent spacing with the critical particle spacing, classifying the adjacent microparticles based on the comparison result of the adjacent spacing with the critical particle spacing, screening out the adjacent microparticles having liquid bridge forces with the central microparticles, and the contact collision microparticles in contact with the central microparticles, to form an adjacent microparticle matrix and contact collision microparticles; S27, numbering the adjacent microparticles to form an adjacent microparticle matrix, and numbering the contact and collision microparticles to form a contact and collision microparticle matrix.

3. The discrete element simulation analysis method for surface microparticle motion under condensation scenario according to claim 2, characterized in that: In step S22, the method for determining the liquid bridge volume calculation formula includes: if the microparticles are hydrophilic microparticles, the liquid bridge is in a hyperbolic shape, and the liquid bridge volume calculation formula is constructed according to the hyperbolic shape; if the microparticles are hydrophobic microparticles, the liquid bridge is in a convex shape, and the liquid bridge volume calculation formula is constructed according to the convex shape.

4. The discrete element simulation analysis method for surface microparticle motion under condensation scenario according to claim 2, characterized in that: In step S23, the method for constructing the relationship between the liquid bridge contact radius, the narrowest neck radius of the liquid bridge and the particle spacing includes: constructing the relationship between the liquid bridge contact radius, the narrowest neck radius of the liquid bridge and the particle spacing according to the following formula: r c / r0=cosh[D / (2r0)] Where: r c ——Liquid bridge contact radius; r0——radius of the narrowest neck of the liquid bridge; D – distance between particles.

5. The discrete element simulation analysis method for surface microparticle motion under condensation scenario according to claim 2, characterized in that: In step S24, according to the liquid bridge contact radius and the narrowest neck radius of the liquid bridge being equal, the liquid bridge volume calculation formula and the relationship between the liquid bridge contact radius, the narrowest neck radius of the liquid bridge and the particle spacing are combined to calculate the critical particle spacing according to the following formula: D c =(2cosα*r c ) / (1-2sinα) Where: D c — critical interparticle spacing; r c ——Liquid bridge contact radius; α——Solid-liquid contact angle between microparticles and liquid bridge.

6. The discrete element simulation analysis method for surface microparticle motion under condensation scenario according to claim 2, characterized in that: In step S25, the method for constructing a microparticle search window range based on the critical particle distance includes: constructing a microparticle search window range with the sum of the central microparticle radius, the maximum microparticle radius and the critical particle distance as the search radius.

7. The discrete element simulation analysis method for surface microparticle motion under condensation scenario according to claim 2, characterized in that: In step S26, the method for classifying adjacent microparticles based on the comparison result of the adjacent spacing and the critical particle spacing includes: if the adjacent spacing is greater than 0 and not greater than the critical particle spacing, it is judged that a liquid bridge can be formed between the adjacent microparticle and the central microparticle, and it is a neighboring microparticle; if the adjacent spacing is not greater than 0, it is judged that the adjacent microparticle and the central microparticle are in contact with each other, and it is a contact collision microparticle.

8. The discrete element simulation analysis method for surface microparticle motion under condensation scenario according to claim 1, characterized in that: In step S4, the method for calculating the resultant force matrix of the microparticles includes: performing vector decomposition on the liquid bridge force matrix, the contact collision force matrix and other force matrices in the three directions of X, Y and Z to obtain the corresponding liquid bridge force vector matrix and the contact collision force vector matrix; performing vector decomposition on other forces to obtain the corresponding other force vector matrices; and calculating the resultant force matrix of the microparticles based on the corresponding liquid bridge force vector matrix, the contact collision force vector matrix and other force vector matrices.

9. The discrete element simulation analysis method for surface microparticle motion under condensation scenario according to claim 1, characterized in that: In step S3, the method for calculating the liquid bridge force between each microparticle in the adjacent microparticle matrix and the surrounding adjacent microparticles includes: calculating the liquid bridge force according to the following formula: Among them: F c ——Liquid bridge force; r——particle radius; γ——Surface tension coefficient of liquid bridge; D – particle spacing; A, B, C are empirical parameters of the contact between particles and liquid bridge, which are related to the dimensionless liquid bridge volume and the solid-liquid contact angle.

10. The discrete element simulation analysis method for surface microparticle motion under condensation scenario according to claim 1, characterized in that: The other forces include gravity, liquid bridge force between microparticles and the surface of action, van der Waals force, drag force and friction force.

Images