Method for researching influence of degree of order of pores on spontaneous imbibition rate of porous medium

Abstract

The invention provides a method for studying the influence of the degree of order of pores on the spontaneous imbibition rate of a porous medium, and relates to plant porous models.The method comprises the steps that firstly, three model structures are constructed, corresponding grids are drawn, and a multiphase flow model, wall surface attributes in the model, a fluid area and a solid area are set; secondly, importing grid files of the three models made by Mesh into Fluent software, setting calculation methods in the three models and physical property parameters of fluid by utilizing Fluent, then respectively calculating, comparing liquid water distribution nephograms of spontaneous imbibition rising of the fluid in the three models, and calculating the liquid water distribution nephograms of spontaneous imbibition rising of the fluid in the three models according to the calculated liquid water distribution nephograms of spontaneous imbibition rising of the fluid in the three models. The method has the advantages that the numerical simulation method is used for exploring the influence of the ordered degree of holes in the porous medium model on the imbibition rate, the complexity of solving the imbibition performance by a mathematical model and an empirical formula is reduced, the numerical simulation result is high in reliability and repeatability, and the method is suitable for large-scale popularization and application. The method is of great significance in further improving the water delivery rate of the porous medium and researching and developing a novel porous medium model.

Description

Technical Field

[0001] The invention relates to prediction and optimization of spontaneous imbibition process in porous medium materials and models, and specifically to a method for using Fluent software to predict the influence of the order degree of pores in a porous medium model on the spontaneous imbibition rate. Background Art

[0002] The transport characteristics and mechanisms of porous media have attracted much attention. Its hydraulic conductivity is closely related to the order of pores. Using numerical simulation methods to explore the influence of the order of pores in porous media models on the imbibition rate can reduce the complexity of mathematical models and empirical formulas for solving imbibition performance, and can flexibly adjust, modify and supplement model parameters according to actual needs, with lower costs and risks. The simulation process has a short cycle and can guide practical production in a timely manner. The numerical simulation results are highly reliable and repeatable, which is of great significance for further improving the water transport rate of porous media and researching and developing new porous media models.

[0003] The most commonly used solution models when using ANSYS Fluent software to perform numerical simulation analysis on capillary action are: CSF model, VOF model, k-ε model or Laminar model, etc.

[0004] (1) CSF model (Continuous Surface Tension Force) is a continuous surface tension model, which is usually used in conjunction with a multiphase flow model. In computational fluid dynamics, the CSF model (continuous surface tension model) is often used to describe the effect of surface force on fluid transport. In essence, this surface force is the capillary driving force. In the CSF model, surface tension is treated as a continuous cross-interface force, and its expression in the momentum equation is equivalent to the volume force term. Based on the continuity equation and momentum equation, numerical calculation and simulation of capillary flow can be achieved. When using the continuous surface tension model, it is usually necessary to select a multiphase flow model, add a variety of fluid medium materials (such as air, water, etc.), then check Surface tension Force Modeling and Continum Surface Force, and then set the surface tension of the relevant liquid.

[0005] (2) VOF model: A type of multiphase flow model. This method simulates the spontaneous imbibition process of liquid water inside a two-dimensional porous model under the action of capillary attraction. The liquid water gradually fills the capillary channel and gradually squeezes the gas in the capillary. Therefore, the VOF model should be used in the process of simulating capillary action.

[0006] (3) k-ε model: The motion state of fluid is usually divided into two modes: laminar flow and turbulence. The main distinction between laminar flow and turbulence is based on the Reynolds number Re. In laminar flow, when the Reynolds number is small, the fluid flow layer is stable; if the Reynolds number is large, the fluid flow is less stable, and small changes in flow velocity are easy to develop and enhance, forming a turbulent and irregular turbulent flow field, namely the k-ε model. The k-ε model is the most representative of the two-equation turbulence models. The standard k-ε model is suitable for simulating fully turbulent flow processes. The pulsation of turbulent instantaneous velocity is usually unpredictable and random, so engineering treatment of such problems is usually based only on the average velocity.

[0007] For the study of the spontaneous imbibition process of different ordered micropore models in this method, the VOF model is used, where:

[0008] The continuity equation is:

[0009] The momentum equation is (finally is the source term of the momentum equation caused by surface tension):

[0010]

[0011] The energy equation is (the four terms on the right are the energy changes caused by heat conduction, liquid evaporation, viscous loss and radiation):

[0012]

[0013] This study intends to use numerical simulation methods to explore the effect of pore order on the spontaneous imbibition of porous media models, and to provide predictions and guidance for experimental methods to regulate the pore order of porous materials. Summary of the invention

[0014] The purpose of the present invention is to solve the problems in the prior art and to propose a method for studying the influence of pore order on the spontaneous imbibition rate of porous media.

[0015] Based on Monte Carlo fractal theory, on a two-dimensional plane, the minimum particle cross-sectional area Smin, the maximum particle cross-sectional area Smax and the fractal dimension Df can be calculated by simply giving the ratio of the minimum cross-sectional area to the maximum cross-sectional area Smin / Smax of the particle, the area fraction Ф of the particle and the average area Sav of the particle.

[0016]

[0017] Given a random number Ri, we can get a series of Si

[0018]

[0019] The convergence condition is set as

[0020]

[0021] The order of the hole can be represented by a vector v pointing from the origin to the unit hemisphere, so the hole orientation distribution can be described by the probability density function p(v) per unit area on the hemisphere. The second-order orientation tensor Ot (Orientation tensor) is used to describe the characteristics of the orientation distribution, which is defined as follows:

[0022]

[0023] Where: vi is the i-th component of the orientation vector v, and dA is the infinitesimal area around v. Similarly, the fourth-order orientation tensor is defined as:

[0024]

[0025] From formula (6), we can see that the orientation tensor is symmetric and semi-positive. In the principal coordinate system composed of its eigenvectors {V1, V2, V3}, it can be written as a diagonal matrix with the diagonal elements being the eigenvalues ​​λ1, λ2, λ3. According to the normalization condition, λ1+λ2+λ3=1, and it is usually agreed that λ≥λ2≥λ3≥0. The size of the eigenvalue can reflect the orientation to a certain extent. The largest eigenvalue is usually 1 and is called the degree of orientation. The higher the degree of orientation, the more parallel the holes are.

[0026] Therefore, it is known that the order of the pores in the porous medium model can be described by the matrix (direction tensor) of the probability distribution function. The components of this tensor are further used to draw the orientation ellipse of the pore, where the direction of the major axis of the ellipse represents the overall orientation of the pore, and the size of the major axis represents the overall orientation degree of the pore. The narrower the ellipse, the higher the overall order of the pore. Adopting the principle of random non-overlapping placement, all solids are randomly placed non-overlappingly in a square area of ​​a given area A to obtain a porous medium model with increasing order. Create three different geometric shapes that gradually transition from spherical beads to long ellipsoids from porous media (change the aspect ratio of the ellipse from 1:1 (80*80um) to 1:2 (80*160um) and 1:4 (40*160um)). The pore models used in this scheme according to the above method are:

[0027] The 59 walls of the randomly arranged and disorderly placed solids are 80um circles;

[0028] Randomly generate an ellipse with a solid wall of 40*160um;

[0029] Randomly generate solid walls with an ellipse of 80*160um.

[0030] The steps include:

[0031] S1: Establish multiple two-dimensional pore models, the upper surfaces of the multiple models are connected to the atmosphere and set as the outlet boundary, the model also includes liquid and gas, the volume fraction of the liquid is 0, the volume fraction of the gas is 1, the lower surface of the model is the water inlet surface, set as the inlet boundary, the volume fraction of the liquid is 1, and the volume fraction of the gas is 0, then divide the multiple two-dimensional porous models into grids, use local encryption for the boundary layer, and export the grid mesh file as the input file of the fluid calculation software Fluent.

[0032] S2: Start FLUENT and import the mesh;

[0033] S3: Define the model;

[0034] S4: Setting boundary conditions and calculation methods;

[0035] S5: Initial condition setting.

[0036] S6: Post-processing of results.

[0037] In the above method for studying the effect of pore order on the spontaneous imbibition rate of porous media, the steps of importing the grid include:

[0038] S1: Execute the Mesh command in the main menu and import the msh mesh file.

[0039] S2: Check the mesh. If there is a negative volume mesh in the result, re-mesh it. If there is no negative volume mesh in the result, proceed to the next step:

[0040] S3: When reading the uniform circular tube model into a mesh file, the number of meshes is between 587850 and 778850.

[0041] In the above method for studying the effect of pore order on the spontaneous imbibition rate of porous media, the steps of setting boundary conditions and calculation methods include:

[0042] S1: Execute the General command in the structure tree, the General (overall model settings) panel pops up, select the Transient command and check the Gravity command;

[0043] S2: Fill in -9.81m / s2 in the Z parameter, fill in 0 in the gravitational acceleration in the X and Y directions, and then set the multiphase flow model: execute the Multiphase button in the model setting panel Models, the Multiphase Model dialog box pops up, fill in 2 in Number of Eulerian Phases, check Impicit Body Force, execute the Phases command under Multiphase in the model setting panel Models, the Phase dialog box pops up, in the Phase-1 dialog box, select water in Phase Material, in the Phase-2 dialog box, select diesel-liquid in Phase Material, and set the surface tension between the air and water phases to 0.072N / m, fill in 2 in Number of Eulerian Phases, check Impicit Body Force, and finally start the energy equation on the operation panel, the k-epsilon (2eqn) equation in the viscosity model, and activate the transient model Transient;

[0044] S3: Set materials: Click Setting Up Physics→Materials→Create / Edit in the main menu to pop up the Create / Edit Materials dialog box. Click the Fluent Database button to pop up the Fluent Database Materials dialog box, select water-liquid and diesel-liquid, and click the Copy button to confirm.

[0045] In the above method for studying the effect of pore order on spontaneous imbibition rate of porous media, the steps of defining the model include:

[0046] S1: Select the Boundaries command to start the boundary condition panel;

[0047] S2: In the boundary condition panel, set the parameters of the inlet, select Magnitude in Velocity Specification Method, Normal to Boundary, check Absolute in Reference Frame, set VelocityMagnitude to 2 [m2 / s], Specification Method to Intensity and Viscosity Ratio, set Turbulent Intensity to 5, Turbulent Viscosity Ratio to 10, set the boundary type of the surface to wall, wall motion to Specific wall, relative to adjative cell zone, shearcondition to Specific Shear, Routhness models to standard, and set the Routhness Constant solid wall roughness to 0.5.

[0048] In the above method for studying the effect of pore order on the spontaneous imbibition rate of porous media, the steps of setting the initial conditions include:

[0049] S1: Select the Sohing-Initialization command, the Solution Initialization panel pops up, select Standard Initialization in Initiallzation Methods, and set the volume percentage of the water phase to 1;

[0050] S2: Select the Initialize command to initialize the parameters of the calculation area, and use Patch to perform global patching before running the calculation; select the Run Calculation command, the Run Calculation panel pops up, and set the automatic saving of dat files in the Fluent calculation activity options, which means that Fluent automatically saves a dat file to the storage location every time it completes the calculation of 10 time steps;

[0051] S3: Before calculation, set the average height of the liquid water surface as the monitoring variable, add Report Files and save them to a specific storage location; set the time step to 1.0X 10-7s-5.0X 10-6s; set the number of steps to 1000-10000, set the maximum number of iterations in each time step to 1000-10000, and select the Cakulate command to start the calculation.

[0052] In the above method for studying the effect of pore order on the spontaneous imbibition rate of porous media, the steps of result processing include:

[0053] S1: Enter CFD-Post perimeter and display cloud map;

[0054] S2: Read the dat file of Fluent under the corresponding working conditions, and use the Graphics option in Fluent to obtain the volume distribution cloud map of the liquid water phase in the two-dimensional porous model.

[0055] Compared with the prior art, the present invention has the following advantages:

[0056] (1) Using computational fluid dynamics (Fluent) numerical simulation software, it is concluded that the spontaneous imbibition rate of the porous media model becomes faster as the degree of pore order increases.

[0057] (2) By establishing two-dimensional micropore models with different degrees of order, a method for using computational fluid dynamics software to simplify the study of the effect of pore order on the spontaneous imbibition process of liquid in porous media models is provided. This method is of great significance for further improving the spontaneous imbibition rate of porous media, designing the microstructure of directional pore materials, and researching and developing new models of porous media.

[0058] In summary, the present invention provides a research method based on Fluent to explore the influence of the degree of pore order on the spontaneous imbibition process of liquid in a porous medium model, which is of great significance for further improving the spontaneous imbibition rate of porous media, designing the microstructure of ordered pore materials, and researching and developing new models of porous media. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 It is a numerical simulation flow diagram of the present invention;

[0060] Figure 2 It is a schematic diagram of a two-dimensional geometric model of the present invention;

[0061] Figure 3 It is a schematic diagram of the liquid water distribution cloud map at different time steps of the model 1 of the present invention;

[0062] Figure 4 is a schematic diagram of liquid water distribution cloud diagrams at different time steps of model 2 of the present invention;

[0063] Figure 5 It is a schematic diagram of the liquid water distribution cloud diagram at different time steps of the model three of the present invention;

[0064] Figure 6 It is a schematic diagram comparing the liquid water distribution cloud diagrams of different models at the same time step of the present invention. DETAILED DESCRIPTION

[0065] Reference Figure 1-6 , a method to study the effect of pore order on the spontaneous imbibition rate of porous media. The overall steps of numerical simulation are as follows Figure 1 As shown, the following steps are included:

[0066] In the first step, GeoDict was used to create cells that conform to the microstructure of porous media by randomly arranging ellipses. The pore size, porosity and pore direction were input. Randomly creating cells can eliminate the deviation of the ellipse cluster direction and generalize the results along the vertical (spontaneous imbibition flow) direction. In the two-dimensional plane of the imbibition cross section, the longitudinal direction is the spontaneous imbibition direction, that is, ideally all pores are arranged along the longitudinal direction with an order of 100%. Changing the pore direction changes the order. The order represents the consistency of the axial arrangement of the pores in a certain direction. The ordered pore geometric model was analyzed using the image recognition software ImageJ, and the distribution ratio of the pore arrangement at each angle was statistically calculated with the help of the OrientationJ plug-in to achieve qualitative and quantitative characterization of the order. Then, the pore order was analyzed using the OrientationJ Analysis tool. The pixel structure tensor was calculated by calculating the pixel intensity gradient in the x and y directions within a Gaussian shape window of a specified size. The local pore orientation at each pixel was defined by the minimum eigenvector of the structure tensor. In the HSB (hue, saturation and brightness) mode, different hues of the image represent different orientations of different pores, and color saturation and brightness represent coherence and source image, respectively. Finally, the OrientationJDistribution tool is used to quantitatively analyze the proportion of holes oriented at various angles. The orientation degree of holes within ±90° is calculated using the following formula:

[0067]

[0068] Where: β is the hole orientation ratio in the θ direction.

[0069] The model size: the cell created by GeoDict represents a porous medium with a porosity of 70%, and the two-dimensional shape is a square; the size is 1000um*1000um; the cells (1) to (3) show the gradual transition from a granular porous medium to a fibrous ordered porous medium. The ellipse sizes (small diameter * large diameter) of the three model units are: (1) the solid wall is 80um circles (59) randomly arranged and disordered; (2) the solid wall is 80*160um ellipses randomly generated; (3) the solid wall is 40*160um ellipses randomly generated; by changing the aspect ratio of the ellipse from 1:1 (80*80μm) to 1:4 (40*160um), a series of microstructures were formed, and porous models with order ranging from 30%, 50% to 70% were created. The same size setting of multiple models is to ensure that the volume flow rate of the average inlet surface of the fluid is equal; the upper surfaces of the three models are connected to the atmosphere and set as the outlet boundary, the volume fraction of the liquid is 0, and the volume fraction of the gas is 1; the lower surface is the water inlet surface, set as the inlet boundary, the volume fraction of the liquid is 1, and the volume fraction of the gas is 0.

[0070] The three two-dimensional porous models are meshed, the boundary layer is locally encrypted, and the mesh files are exported as input files for the fluid calculation software Fluent.

[0071] The second step is to start FLUENT and import the mesh. (1) In Windows, execute "Start" → "All Programs" → ANSYS2021 → FluidDynamics → Fluent 2021 to start Fluent 2021. (2) Click File → Read → Mesh in the main menu to import the .msh mesh file. Check the mesh. If there is a negative volume mesh in the result, re-mesh it. If there is no negative volume mesh in the result, proceed to the next step. The uniform circular tube model reads the mesh file, and the number of meshes is between 587850 and 778850.

[0072] Step 3: Define the model

[0073] (1) Click the General button in the command structure tree to pop up the General (overall model setting) panel. Select Transient for Time in Solver. Check Gravity, enter -9.81m / s2 in Z, and enter 0 in the gravity acceleration in the X and Y directions. Set the multiphase flow model: Double-click the Multiphase button in the Models panel to pop up the Multiphase Model (multiphase flow model) dialog box. Enter 2 in Number of Eulerian Phases and check Impicit Body Force. Double-click the Phases button under Multiphase in the Models panel to pop up the Phase (multiphase flow setting) dialog box. In the Phase-1 dialog box, select water as Phase Material. In the Phase-2 dialog box, select diesel-liquid as Phase Material. Click the OK button to confirm and close the dialog box. Set the surface tension between the air and water phases to 0.072N / m. Enter 2 in Number of Eulerian Phases, check Impicit Body Force, and click the OK button to confirm and close the dialog box. Start the energy equation on the operation panel, the k-epsilon (2eqn) equation in the viscosity model, and activate the transient model Transient.

[0074] (2) Set materials: Click Setting Up Physics→Materials→Create / Edit in the main menu to pop up the Create / Edit Materials dialog box. Click the Fluent Database button to pop up the Fluent Database Materials dialog box, select water-liquid and diesel-liquid, and click the Copy button to confirm.

[0075] Step 4: Set boundary conditions and calculation methods

[0076] (1) Click Physics → Zones → Boundaries in the main menu to open the boundary condition panel.

[0077] (2) In the boundary condition panel, set the parameters of the inlet. Select Magnitude, Normal to Boundary in Velocity Specification Method, check Absolute in Reference Frame, set Velocity Magnitude to 2 [m2 / s], Specification Method to Intensity and Viscosity Ratio, set Turbulent Intensity to 5, and Turbulent Viscosity Ratio to 10. Set the boundary type of the surface to wall, wall motion to Specific wall, relative to adjative cell zone, shear condition to Specific Shear, Routhness models to standard, and Routhness Constant solid wall roughness to 0.5.

[0078] Step 5, initial condition setting: Click Sohing-Initialization in the main menu, and the Solution Initialization panel pops up. Select Standard Initialization in Initialization Methods, and set the volume percentage of the water phase to 1. Click the Initialize button to initialize the parameters of the calculation area, and use Patch to perform global patching before running the calculation; click SoMing→Run Calculation in the main menu, and the Run Calculation panel pops up. Set the automatic saving of dat files in Fluent's calculation activity options. Automatic saving of dat files means that every time Fluent completes the calculation of 10 time steps, it automatically saves a dat file to the storage location; before calculation, set the average height of the liquid water surface as the monitoring variable, and add Report Files to save to a specific storage location; set the time step to 1.0X 10-7s-5.0X 10-6s; set the number of steps to 1000-10000, set the maximum number of iterations in each time step to 1000-10000, and click Cakulate to start the calculation.

[0079] Step 6: Post-processing of results: (1) Enter CFD-Post and display the cloud map, where (a) the cloud map of liquid water distribution of different models at different time steps is compared. Figure 3As shown; (b) Comparison of liquid water distribution cloud maps of different models at different time steps. Figure 4 As shown; (c) Comparison of liquid water distribution cloud maps of different models at different time steps. Figure 5 (2) Read the dat file of Fluent under the corresponding working condition, and use the Graphics option in Fluent to obtain the volume distribution cloud map of the liquid water phase in the two-dimensional porous model. The liquid water distribution cloud maps of different models at the same time step are compared. Figure 6 As shown in Figure 3, numerical simulation shows that in porous media, as the degree of pore order increases, the spontaneous imbibition rate increases accordingly.

[0080] It is known from common technical knowledge that the present invention can be implemented by other embodiments that do not deviate from its spirit or essential features. Therefore, the above disclosed embodiments are only illustrative in all respects and are not exclusive. All changes within the scope of the present invention or within the scope equivalent to the present invention are included in the present invention.

Claims

1. A method for studying the effect of pore order on the spontaneous imbibition rate of porous media, characterized in that: The following steps are involved: S1: Establishing a plurality of two-dimensional hole models, wherein the process of establishing the plurality of two-dimensional hole models comprises: Step 1: Use GeoDict to create cells that conform to the microstructure of porous media by randomly arranging ellipses. Input the pore size, porosity and pore direction. Randomly creating cells can eliminate the deviation of the ellipse cluster direction and generalize the results along the spontaneous imbibition flow direction. In the two-dimensional plane diagram of the imbibition cross section, the longitudinal direction is the spontaneous imbibition direction, that is, ideally all pores are arranged along the longitudinal direction with an order of 100%. Changing the pore direction means changing the order, which represents the consistency of the axial arrangement of the pores in a certain direction. Step 2: Use the image recognition software ImageJ to analyze the ordered pore geometry model, and use the OrientationJ plug-in to count the distribution ratio of pores at various angles to achieve qualitative and quantitative characterization of the degree of order; The third step is to use the tool to analyze the pore order. The structure tensor of the pixel is calculated by calculating the pixel intensity gradient in the x and y directions within a Gaussian shape window of a specified size. The local pore orientation at each pixel is defined by the minimum eigenvector of the structure tensor. In HSB mode, different tones of the image represent different orientations of different pores, and color saturation and brightness represent coherence and source image, respectively. Step 4: Use the OrientationJ Distribution tool to quantitatively analyze the proportion of holes at various orientation angles, and count the orientation of holes within ±90°. The calculation formula is: Wherein: β is the pore orientation ratio in the θ direction; each of the two-dimensional pore models includes an area model of the same size and a pore model of different shapes, and the area model ensures that the volume flow rate of the average inlet surface of the fluid is equal; the upper surfaces of the multiple models are connected to the atmosphere and are set as the outlet boundary, and the model also includes liquid and gas, the volume fraction of the liquid is 0, and the volume fraction of the gas is 1, and the lower surface of the model is the water inlet surface, which is set as the inlet boundary, the volume fraction of the liquid is 1, and the volume fraction of the gas is 0, and then the multiple two-dimensional porous models are divided into grids, the boundary layer is locally encrypted, and the grid mesh file is exported as the input file of the fluid calculation software Fluent. S2: Start FLUENT and import the mesh; S3: Define the model; S4: Setting boundary conditions and calculation methods; S5: Initial condition setting. S6: Post-processing of results.

2. A method for studying the effect of pore order on spontaneous imbibition rate of porous media according to claim 1, characterized in that: The cell created by GeoDict represents a porous medium with a porosity of 70%. The shape of the area model is a square; the size is 1000um*1000um. The number of the two-dimensional pore models is set to three. The ellipse sizes of the three two-dimensional pore models are shown in the form of small diameter*large diameter, respectively: The 59 randomly arranged and disordered solid walls are 80 μm circular; Randomly generate an ellipse with a solid wall of 40*160um; The randomly generated solid wall is an 80*160um ellipse; By varying the ellipse aspect ratio from 1:1 to 1:4, a range of microstructures were formed, creating porous models with ordering levels ranging from 30%, 50% to 70%.

3. A method for studying the effect of pore order on spontaneous imbibition rate of porous media according to claim 1, characterized in that: The steps to import a mesh are: S1: Execute the Mesh command in the main menu and import the msh mesh file. S2: Check the mesh. If there is a negative volume mesh in the result, re-mesh it. If there is no negative volume mesh in the result, proceed to the next step: S3: When reading the uniform circular tube model into a mesh file, the number of meshes is between 587850 and 778850.

4. The method for studying the effect of pore order on spontaneous imbibition rate of porous media according to claim 1, characterized in that: The steps to set boundary conditions and calculation methods include: S1: Execute the General command in the structure tree, the General overall model setting panel pops up, select the Transient command and check the Gravity command; S2: Fill in -9.81m / s2 in the Z parameter, fill in 0 in the gravitational acceleration in the X and Y directions, and then set the multiphase flow model: execute the Multiphase button in the model setting panel Models, the Multiphase Model dialog box pops up, fill in 2 in Number of Eulerian Phases, check Impicit Body Force, execute the Phases command under Multiphase in the model setting panel Models, the Phase multiphase flow setting dialog box pops up, in the Phase-1 dialog box, select water in Phase Material, in the Phase-2 dialog box, select diesel-liquid in Phase Material, and set the surface tension between the air and water phases to 0.072N / m, fill in 2 in Number of EulerianPhases, check Impicit Body Force, and finally start the energy equation on the operation panel, the k-epsilon equation in the viscosity model, and activate the transient model Transient; S3: Set materials: Click Setting Up Physics→Materials→Create / Edit in the main menu to pop up the Create / Edit Materials dialog box. Click the Fluent Database button to pop up the Fluent DatabaseMaterials dialog box, select water-liquid and diesel-liquid, and click the Copy button to confirm.

5. The method for studying the effect of pore order on spontaneous imbibition rate of porous media according to claim 1, characterized in that: The steps to define a model include: S1: Select the Boundaries command to start the boundary condition panel; S2: In the boundary condition panel, set the parameters of the inlet, select Magnitude in Velocity Specification Method, Normal to Boundary, check Absolute in Reference Frame, set VelocityMagnitude to 2 [m2 / s], Specification Method to Intensity and Viscosity Ratio, set Turbulent Intensity to 5, Turbulent Viscosity Ratio to 10, set the boundary type of the surface to wall, wall motion to Specific wall, relative to adjative cell zone, shearcondition to Specific Shear, Routhness models to standard, and set the Routhness Constant solid wall roughness to 0.

5.

6. A method for studying the effect of pore order on spontaneous imbibition rate of porous media according to claim 1, characterized in that: The steps of initial condition setting include: S1: Select the Sohing-Initialization command, the Solution Initialization initialization setting panel pops up, select Standard Initialization in Initiallzation Methods, and set the volume percentage of the water phase to 1; S2: Select the Initialize command to initialize the parameters of the calculation area, and use Patch to perform global patching before running the calculation; select the Run Calculation command to pop up the Run Calculation panel, and set the automatic saving of dat files in the calculation activity options of Fluent, which means that every time Fluent completes the calculation of 10 time steps, it automatically saves a dat file to the storage location; S3: Before calculation, set the average height of the liquid water surface as the monitoring variable, add Report Files and save them to a specific storage location; set the time step to 1.0X 10-7s-5.0X 10-6s; set the number of steps to 1000-10000, set the maximum number of iterations in each time step to 1000-10000, and select the Cakulate command to start the calculation.

7. A method for studying the effect of pore order on spontaneous imbibition rate of porous media according to claim 1, characterized in that: The steps of result processing include: S1: Enter CFD-Post perimeter and display cloud map; S2: Read the dat file of Fluent under the corresponding working conditions, and use the Graphics option in Fluent to obtain the volume distribution cloud map of the liquid water phase in the two-dimensional porous model.

Images