Magnetorheological fluid particle motion simulation method based on CFD-DEM coupling

Abstract

The invention discloses a magnetorheological fluid particle motion simulation method based on CFD-DEM coupling. Comprising the following steps: 1) constructing a magnetorheological fluid three-dimensional simulation model by using three-dimensional modeling software and exporting a. Stp file; 2) performing grid division on a fluid domain of the three-dimensional simulation model to generate a. Msh file; (3) a magnetorheological fluid three-dimensional simulation model is imported into DEM simulation software, and basic simulation parameters and the like are set; 4) importing an API magnetic model; 5) importing the. Msh file and the coupling file into the CFD simulation software, and coupling the CFD simulation software and the DEM simulation software; 6) initializing CFD and DEM simulation software environments, and then setting a solving time step length; and 7) starting simulation, carrying out multi-physics field coupling on the CFD model and the DEM model through the coupling file, carrying out fluid mechanics and discrete phase calculation in CFD simulation software, and exporting a particle motion track and a variable change process in DEM software. The device can simulate the microstructure evolution and movement trend of the magnetic particles in the magnetorheological fluid under the action of a magnetic field, and is good in stability and high in accuracy.

Description

Technical Field

[0001] This invention relates to the field of fluid mechanics, specifically to a simulation method for the motion of magnetorheological fluid particles based on CFD-DEM coupling. Background Technology

[0002] Under the influence of an external magnetic field, ferromagnetic particles in a magnetorheological fluid align themselves along the magnetic field lines to form particle chains. Changing the magnetic induction intensity of the external magnetic field alters the interactions between these particle chains. With the continuous maturation of modern smart materials technology, the dynamically changing rheological properties of magnetorheological fluids under an applied magnetic field give them broad application prospects.

[0003] Currently, the simulation of magnetorheological fluid performance mostly uses molecular dynamics methods. Given the initial position and velocity of each particle, the interaction force between particles is calculated based on the potential energy function, and then Newton's equations of motion are solved to obtain the evolution trajectory of the system over time. The microscopic state composed of the particle's position, force, energy, and velocity is then averaged over time to obtain physical quantities such as the system's pressure, structure, and mechanical properties, thus explaining the properties and behavior of the research object.

[0004] Because the simulation of magnetorheological fluid particle motion involves multiple physical fields such as gravity, fluid resistance, magnetic fields, and interparticle interactions, the potential functions available for molecular dynamics are very limited for such complex multi-component systems, and the accuracy of these potential functions varies significantly across different simulation systems. Furthermore, magnetorheological fluids can rapidly transform from low-viscosity Newtonian fluids into semi-solid, low-flowability, high-viscosity Bingham plastics under an external magnetic field. Their excellent mechanical properties have led to their widespread application in engineering scenarios, but their microscopic mechanisms (such as micron-scale particle rotational orientation, chain-like arrangement, and changes in compressive / shear stress in chain-like structures) are limited by experimental detection methods and cannot be effectively detected. Summary of the Invention

[0005] The purpose of this invention is to provide a simulation method for the motion of magnetorheological fluid particles based on CFD-DEM coupling. The CFD-DEM multiphysics coupling simulation method can accurately simulate the motion trend of magnetorheological fluid particles, and provide assistance in the particle rotation, chain structure formation and stress evolution process.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A simulation method for particle motion in magnetorheological fluids based on CFD-DEM coupling includes the following steps: Step 1: Use 3D modeling software to construct a 3D simulation model of the magnetorheological fluid, and export the 3D simulation model as a .stp file; Step 2: Mesh the fluid domain of the 3D simulation model and generate an .msh file; Step 3: Import the .stp file of the magnetorheological fluid 3D simulation model into the DEM simulation software, set the basic simulation parameters, set the interaction models between particles and between particles and geometry, and then import the API magnetic force model. The API magnetic force model includes the interaction force model between magnetic particles and the force model of magnetic particles under the action of an external magnetic field. By importing the API magnetic force model into the DEM simulation software, the above two forces are applied to the particles, realizing the rotation of magnetic particles under the action of a magnetic field and the rotation and displacement generated by the interaction of magnetic particles. Step 4: Import the .msh file and coupling file from Step 2 into the CFD simulation software to couple the CFD and DEM simulation software; Step 5: After initializing the CFD and DEM simulation software environment, set the solution time step; Step 6: Start the simulation. Couple the CFD model and the DEM model using a coupling file to perform multiphysics calculations. Perform fluid dynamics and discrete phase calculations in the CFD simulation software, and export the particle motion trajectory and variable change process in the DEM software.

[0007] Furthermore, the three-dimensional simulation model of the magnetorheological fluid in step one is constructed as a solid, which facilitates subsequent mesh generation. Saving the three-dimensional simulation model as a .stp file can preserve the model's geometry, properties, material, and other information, making it easier to import the model into DEM simulation software and ensuring data compatibility.

[0008] Furthermore, in step two, the meshing should treat the solid parts of the 3D model as a fluid domain and mesh them accordingly. The meshing process is as follows: Figure 2 As shown.

[0009] Furthermore, in step three, the particles in the DEM simulation software are set to spherical particles with a diameter of 4 μm. The interaction models between particles and between particles and the geometry are set to Hertz-Mindlin no-slip models. A static particle factory generation method is used. After the particles have freely fallen and accumulated, the entire model simulation file is exported and the time is reset to 0. Then, an API magnetic model is added to this model and coupled with the CFD simulation software. The DEM simulation software model is as follows: Figure 3 As shown.

[0010] Furthermore, the API magnetic model described in step three is written in C++ in Visual Studio software and a .dll file is generated. After importing the .dll file into the DEM simulation path folder, the DEM simulation software can be opened to load the API magnetic model.

[0011] Furthermore, the coupling file described in step four is written in C++. First, for each CFD grid cell, the volume fraction occupied by particles within it is calculated to obtain the local porosity of that cell. This porosity is then incorporated into the continuity and momentum equations, thus writing the particle's influence on the fluid into the fluid control equations. Next, for each particle, based on the fluid velocity information of its CFD grid cell and its adjacent nodes, the local fluid velocity at the particle's center is obtained through interpolation. Finally, the force exerted by the fluid on the particle is calculated based on the selected drag model and applied to the particle. Since particle motion in magnetorheological fluids involves the coupling effects of multiple physical fields such as fluid resistance, magnetic fields, and gravitational fields, the types of potential functions available in traditional molecular dynamics simulations are limited, and their accuracy varies significantly across different simulation systems. The above-described coupled simulation method can more intuitively reveal the evolution process of particle microstructure and its motion trends.

[0012] Furthermore, in step four, the coupling file is imported into the CFD simulation software. The DEM model and the CFD model are coupled in a multiphysics manner through the coupling file. The generation of a discrete phase in the CFD simulation software indicates successful coupling.

[0013] Furthermore, the initialization of the CFD and DEM simulation software environment and the setting of the solution time step in step five are crucial to whether the subsequent simulation results converge.

[0014] Furthermore, in step six, the fluid dynamics and discrete phase calculations performed in the CFD simulation software require checking whether the coupling interface in the DEM simulation software is working. If the calculation results do not converge, the boundary conditions or the solution time step need to be redefined until the calculation results converge. If the calculation results still do not converge after redefining the boundary conditions or the solution time step, the mesh needs to be re-generated to make the mesh more reasonable. After the calculation results converge, the particle motion simulation animation is output, exporting the particle motion trajectory and variable change process. The initial state of the particle coupling simulation is as follows: Figure 4 As shown, the particle motion results are as follows Figure 5 As shown.

[0015] This invention employs the above technical solutions, combining C++ programming, fluid mechanics, particle computational mechanics, and multiphysics coupling simulation. It primarily addresses the difficulty in obtaining the real-time motion and structural evolution of magnetorheological fluid particles through experiments. By using CFD-DEM multiphysics coupling simulation to obtain particle motion trajectories, it simulates the microstructural evolution and motion trends of magnetic particles in magnetorheological fluids under the influence of a magnetic field. This provides assistance for the quantitative analysis of particle evolution processes, reduces the economic cost of experiments, and shortens the research cycle.

[0016] The beneficial effects of the method of the present invention are: it can simulate the microstructure evolution and motion trend of magnetic particles in magnetorheological liquids under the action of a magnetic field, with good stability and high accuracy. It can ensure the calculation accuracy when adding different models, making the simulation preparation work simpler, greatly improving the simulation efficiency and shortening the research cycle. Attached Figure Description

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments; Figure 1 This is a flowchart of the simulation method for the evolution and motion of magnetorheological fluid particle structure based on CFD-DEM coupling according to the present invention.

[0018] Figure 2 This is a cross-sectional view of the mesh division in the embodiment.

[0019] Figure 3 This is a diagram of the DEM simulation model in the embodiment.

[0020] Figure 4 This is the initial state diagram of particle coupling simulation in the embodiment.

[0021] Figure 5 This is a diagram showing the particle motion results in the embodiment. Detailed Implementation

[0022] A simulation method for particle motion in magnetorheological fluids based on CFD-DEM coupling includes the following steps: S1: Use 3D modeling software to construct a 3D simulation model of the magnetorheological fluid, and export the 3D simulation model as a .stp file; The three-dimensional simulation model of the magnetorheological fluid is constructed as a solid, which facilitates subsequent mesh generation. Saving the three-dimensional simulation model as a .stp file can preserve the model's geometry, properties, material, and other information, making it easy to import the model into DEM simulation software and ensuring data compatibility.

[0023] S2: Mesh the fluid domain of the 3D simulation model and generate an .msh file; Meshing should treat the solid parts of the 3D model as a fluid domain and mesh them accordingly. Figure 2 As shown.

[0024] S3: Import the .stp file of the magnetorheological fluid 3D simulation model into the DEM simulation software, set the basic simulation parameters, set the interaction models between particles and between particles and geometry, and then import the API magnetic force model on this basis. The API magnetic force model includes the interaction force model between magnetic particles and the force model of magnetic particles under the action of an external magnetic field. By importing the API magnetic force model into the DEM simulation software, the above two forces are applied to the particles to realize the rotation of magnetic particles under the action of a magnetic field and the rotation and displacement generated by the interaction of magnetic particles. Further, in this step, the particles in the DEM simulation software are set to spherical particles with a diameter of 4 μm. The interaction models between particles and between particles and the geometry are set to Hertz-Mindlin no-slip models. A static particle factory generation method is used. After the particles have freely fallen and accumulated, the entire model simulation file is exported and the time is reset to 0. Then, an API magnetic model is added to this model and coupled with the CFD simulation software. The DEM simulation software model is as follows: Figure 3 As shown; Furthermore, the API magnetic model is written in C++ in Visual Studio software and a .dll file is generated. After importing the .dll file into the DEM simulation path folder, the DEM simulation software can be opened to load the API magnetic model.

[0025] S4: Import the .msh file and coupling file from step S2 into the CFD simulation software to couple the CFD and DEM simulation software; this step uses the coupling file to couple the DEM model and the CFD model in a multiphysics manner, and the generation of a discrete phase in the CFD simulation software indicates successful coupling. Furthermore, the coupling file is written in C++. First, for each CFD grid cell, the volume fraction of particles within it is calculated to obtain the local porosity of that cell. This porosity is then incorporated into the continuity and momentum equations, thus integrating the particle's influence on the fluid into the fluid control equations. Next, for each particle, based on the fluid velocity information of its CFD grid cell and adjacent nodes, the local fluid velocity at the particle's center is obtained through interpolation. Finally, the force exerted by the fluid on the particle is calculated based on the selected drag model and applied to the particle. Since particle motion in magnetorheological fluids involves the coupling effects of multiple physical fields such as fluid resistance, magnetic fields, and gravitational fields, the types of potential functions available in traditional molecular dynamics simulations are limited, and their accuracy varies significantly across different simulation systems. The aforementioned coupled simulation method can more intuitively reveal the evolution process and motion trends of particle microstructures.

[0026] S5: Set the solution time step after initializing the CFD and DEM simulation software environment; This step is crucial for whether the subsequent simulation results converge.

[0027] S6: Start simulation. Couple the CFD model and DEM model with a multiphysics coupling file. Perform fluid dynamics and discrete phase calculations in the CFD simulation software. Export the particle motion trajectory and variable change process in the DEM software. In CFD simulation software, the calculation of fluid dynamics and discrete phases requires checking whether the coupling interface in the DEM simulation software is working. If the calculation results do not converge, the boundary conditions or the solution time step need to be redefined until the calculation results converge. If the calculation results still do not converge after redefining the boundary conditions or the solution time step, the mesh needs to be re-generated to make the mesh more reasonable. After the calculation results converge, the particle motion simulation animation is output, exporting the particle motion trajectory and variable change process. The initial state of the particle coupling simulation is as follows. Figure 4 As shown, the particle motion results are as follows Figure 5 As shown.

Claims

1. A simulation method for particle motion in magnetorheological fluids based on CFD-DEM coupling, characterized in that, Includes the following steps: Step 1: Use 3D modeling software to construct a 3D simulation model of the magnetorheological fluid, and export the 3D simulation model as a .stp file; Step 2: Mesh the fluid domain of the 3D simulation model and generate an .msh file; Step 3: Import the .stp file of the magnetorheological fluid 3D simulation model into the DEM simulation software, set the basic simulation parameters, set the interaction models between particles and between particles and geometry, and then import the API magnetic force model. The API magnetic force model includes the interaction force model between magnetic particles and the force model of magnetic particles under the action of an external magnetic field. Step 4: Import the .msh file and coupling file from Step 2 into the CFD simulation software to couple the CFD and DEM simulation software; Step 5: After initializing the CFD and DEM simulation software environment, set the solution time step; Step 6: Start the simulation. Couple the CFD model and the DEM model using a coupling file to perform multiphysics calculations. Perform fluid dynamics and discrete phase calculations in the CFD simulation software, and export the particle motion trajectory and variable change process in the DEM software.

2. The method for simulating the motion of magnetorheological fluid particles based on CFD-DEM coupling according to claim 1, characterized in that, In step one, the construction of the three-dimensional simulation model of the magnetorheological fluid is all solid. The three-dimensional simulation model is saved as a .stp file, which includes the model's geometry, properties, and material information.

3. The method for simulating the motion of magnetorheological fluid particles based on CFD-DEM coupling according to claim 1, characterized in that, In step three, the particles are set to spherical particles with a particle size of 4 μm in the DEM simulation software. The interaction models between particles and between particles and geometry are set to Hertz-mindlin no-slip models. The static generation method of the particle factory is adopted. After the particles have freely fallen and accumulated, the entire model simulation file is exported and the time is reset to 0. Then, the subsequent steps are carried out based on this model.

4. The method for simulating the motion of magnetorheological fluid particles based on CFD-DEM coupling according to claim 1, characterized in that, The API magnetic model described in step three is written in C++ in Visual Studio software and a .dll file is generated. After importing the .dll file into the DEM simulation path folder, the DEM simulation software can be opened to load the API magnetic model.

5. The method for simulating the motion of magnetorheological fluid particles based on CFD-DEM coupling according to claim 1, characterized in that, The coupling file described in step four is written in C++ programming language. First, for each CFD mesh cell, the volume fraction of particles inside it is calculated to obtain the local porosity of the cell. The porosity is introduced into the continuity equation and momentum equation to write the influence of particles on the fluid into the fluid control equation. Then, for each particle, based on the fluid velocity information of its CFD mesh cell and its adjacent nodes, the local fluid velocity at the center of the particle is obtained by interpolation method. Based on the selected drag force model, the force of the fluid on the particle is calculated and finally applied to the particle.

6. The method for simulating the motion of magnetorheological fluid particles based on CFD-DEM coupling according to claim 1, characterized in that, Step four involves multiphysics coupling between the DEM model and the CFD model using a coupling file. Generating a discrete phase in the CFD simulation software indicates successful coupling.

7. The method for simulating the motion of magnetorheological fluid particles based on CFD-DEM coupling according to claim 1, characterized in that, In step six, when performing fluid dynamics and discrete phase calculations in the CFD simulation software, check whether the coupling interface in the DEM simulation software is in working condition. If the calculation results do not converge, the boundary conditions or the solution time step need to be redefined until the calculation results converge. If the calculation results still do not converge after redefining the boundary conditions or the solution time step, the mesh needs to be re-generated to make the mesh more reasonable. After the calculation results converge, output the particle motion simulation animation and export the particle motion trajectory and variable change process.

Images