CFD-DEM coupling simulation method for high-viscosity fluid stirring

Abstract

The invention provides a CFD-DEM coupling simulation method for high-viscosity fluid stirring. The CFD-DEM coupling simulation method is suitable for solid-liquid stirring simulation of high-viscosity hydroxyl-terminated polybutadiene and superfine silicon dioxide particles. The method mainly comprises the following steps: establishing a solid-liquid stirring three-dimensional model, and importing ANSYS software to perform boundary extraction and grid division operation; the file obtained after grid division is imported into FLUENT software, and then the boundary grid file is imported into EDEM software; setting a material parameter, a viscosity model and the like of the high-viscosity fluid in FLUENT software, and setting a material parameter, a generation quantity and a generation speed of particles, a rotating speed of a stirring paddle and the like in EDEM software; a UDF script is read in FLUENT software, a coupling switch of EDEM software is turned on, bidirectional coupling simulation of simulation data exchange is carried out on solid-liquid stirring, a simulation result is obtained, and analysis and research are carried out on high-viscosity fluid flow field characteristics and a solid particle dispersion mechanism. A bidirectional coupling CFD-DEM simulation method is adopted to simulate stirring of high-viscosity fluid, and reference is provided for related research.

Description

Technical Field

[0001] The present invention relates to the technical field related to stirring of high-viscosity fluid and silicon dioxide particles, and in particular to a CFD-DEM coupled simulation method for stirring high-viscosity fluid. Background Art

[0002] Solid rocket engines are core power components for aerospace equipment such as missiles and launch vehicles. The liner of a solid rocket engine is a critical functional layer between the propellant and the shell, providing bonding, sealing, and corrosion resistance. Its performance directly impacts the engine's reliability and lifespan. The solid-liquid composite mixing process of hydroxy-terminated polybutadiene (HTPB), the primary binder for the liner, and ultrafine silica particles (nano-SiO2) is the core step in preparing a high-performance liner mother liquor. Summary of the Invention

[0003] The purpose of the present invention is to simulate the stirring of high-viscosity fluids by using a bidirectionally coupled CFD-DEM simulation method, and therefore a CFD-DEM coupled simulation method for stirring high-viscosity fluids is proposed.

[0004] A CFD-DEM coupled simulation method for stirring high-viscosity fluids, the inventive method comprising the following contents:

[0005] Step (1): For the solid-liquid mixing of high-viscosity fluid and ultrafine silica particles for the production and preparation of solid rocket engine liner mother liquor, the CFD-DEM coupling simulation method is used to analyze the influence of the fluid flow field on the particle dispersion effect. In the CFD-DEM coupling, the Euler-Lagrange method is used to treat the particles as discrete phases. The motion trajectory of the particles is tracked according to Newton's second law, and the rotational angular momentum of the particles is calculated according to the angular momentum equation. The three-dimensional model of the stirring paddle, stirring tank and fluid calculation domain is established using modeling software to provide a geometric basis for the subsequent numerical simulation of the flow field.

[0006] Step (2): Import the three-dimensional model of the impeller, stirring tank, and fluid calculation domain constructed in step (1) into ANSYS software for pre-processing, perform Boolean operations on the model, and divide and extract the geometric boundaries. In the meshing module, mesh the model, define the partitioning method, boundary size adjustment, boundary layer expansion, etc., and locally densify the mesh of key parts (such as the edge of the impeller blade and near the wall of the stirring tank) to enhance the ability to capture the interaction area between fluid and particles;

[0007] Step (3): import the .msh file after meshing in step (2) into FLUENT software, load and display the corresponding geometric structure, and export the Boundary.msh mesh file for EDEM software;

[0008] Step (4): Import the Boundary.msh mesh file of step (3) into the EDEM software as a geometric model in the EDEM software, add and set the material properties of the particles and the model, including elastic modulus, density, Poisson's ratio, etc. In addition, it is necessary to define the contact parameters between particles and between particles and the model;

[0009] Step (5): Import the particle model based on the particle information from step (4), create a new geometric model (plane, cube or cylinder) to define the location of particle generation, define the "particle factory" and the particle input form (total number or total mass), particle generation speed, etc. Set and define the rotation speed of the stirring paddle model;

[0010] Step (6): For all the processing operations in steps (4) and (5), set the time step and submit them to the system for calculation to generate the corresponding particle model and stably distribute it at the bottom of the stirring tank under the action of gravity, which serves as the initial state of the stirring simulation;

[0011] Step (7): Set up the geometric model imported into the FLUENT software in step (3). The viscosity model in the stirring tank needs to be determined according to the flow state of the fluid, and the flow state of the fluid is generally determined according to the Reynolds number R e Make a judgment, combine the model geometric parameters, fluid material parameters and calculate the Reynolds number value according to the formula, and select the corresponding viscosity model. For laminar fluid state, the laminar model can be used, for transitional flow fluid state, the SST k-ω model can be used, and for turbulent fluid state, the k-ε model can be used.

[0012] (7.1), the Reynolds number calculation formula used is as follows, where ρ is the fluid density, n is the impeller speed, D is the impeller diameter, and μ is the fluid viscosity;

[0013] (7.2) The formula used to determine the fluid flow state is as follows, and it needs to be determined based on the calculated Reynolds number value;

[0014] Step (8): Based on the settings in step (7), define the material parameters of the high-viscosity fluid, including density and viscosity, and define the rotation speed, rotation axis coordinates, and fluid parameters of the computational fluid domain. Read the UDF script and couple it with the EDEM software to achieve two-way exchange of simulation data.

[0015] The core value of analyzing the simulation results lies in the use of multi-physics field coupling technology to overcome the bottleneck of traditional experimental methods in intuitively revealing the coupling mechanism between complex flow fields and particle motion, providing theoretical support for the optimized design of mixing equipment. This simulation method accurately captures the laminar shear, vortex diffusion and particle collision, and the dynamic equilibrium process of agglomeration and dispersion unique to high-viscosity fluids, and analyzes the influence of agitator type, size parameters, and operating conditions on particle dispersion, sedimentation rate, and energy dissipation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a technical flow chart of a CFD-DEM coupled simulation method for high-viscosity fluid stirring;

[0017] Figure 2 Diagram of the experimental setup for stirring high-viscosity fluid with ultrafine silica particles; DETAILED DESCRIPTION

[0018] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings and implementation examples. However, the scope of protection of the present invention is not limited by the specific implementation methods. Obviously, the implementation examples described are only part of the implementation examples of the present invention, not all of the implementation examples.

[0019] like Figure 1 The following is a technical implementation flow chart, which specifically includes the following contents:

[0020] like Figure 2 The figure shows an experimental setup for mixing high-viscosity fluids with ultrafine silica particles. In the figure, 1 is the power unit, 2 is the support device, and 3 is the stirring paddle structure (31 is the stirring shaft, and 32 is the stirring blade). Based on this, a three-dimensional model of solid-liquid mixing was established, and the stirring model was constructed to actual size using 3D modeling software. The computational fluid domain within the stirring tank was divided into the area near the stirring blade. Unstructured meshing was used in this area to accommodate the complex geometric structure and accurately capture the complex flow of the HTPB fluid.

[0021] For the solid-liquid mixing of high-viscosity fluids and ultrafine silica particles for the production and preparation of solid rocket engine liner mother liquor, the CFD-DEM coupling simulation method is used to analyze the influence of the fluid flow field on the particle dispersion effect. In the CFD-DEM coupling, the Euler-Lagrange method is used to treat the particles as discrete phases, track the motion trajectory of the particles according to Newton's second law, and calculate the rotational angular momentum of the particles according to the angular momentum equation. The modeling software is used to establish a three-dimensional model of the stirring paddle, stirring tank and fluid calculation domain, providing a geometric basis for the subsequent numerical simulation of the flow field. The stirring paddle can be of different types and with different size parameters;

[0022] The constructed 3D model of the impeller, mixing tank, and fluid computational domain was imported into ANSYS for pre-processing. Boolean operations were performed on the model to extract the geometric boundaries. The model was meshed in the meshing module, defining the partitioning method, boundary size adjustment, and boundary layer expansion. The mesh was locally encrypted in key areas (such as the edges of the impeller blades and near the mixing tank walls) to enhance the ability to capture the interaction areas between fluid and particles.

[0023] Import the meshed .msh file into FLUENT software, load and display the corresponding geometric structure, and export the Boundary.msh mesh file for EDEM software;

[0024] Import the Boundary.msh mesh file into the EDEM software as a geometric model in the EDEM software. Add and set the material properties of the particles and the model, including elastic modulus, density, Poisson's ratio, etc. In addition, it is necessary to define the contact parameters between particles and between particles and the model.

[0025] Import the particle model based on the particle information, create a new geometric model (plane, cube or cylinder) to define the location of particle generation, define the "particle factory" and the particle input form (total number or total mass), particle generation speed, etc. Set and define the rotation speed of the stirring paddle model;

[0026] After setting the time step, submit the system for calculation to generate the corresponding particle model and stably distribute it at the bottom of the mixing tank under the action of gravity, which serves as the initial state of the mixing simulation;

[0027] The geometric model imported into FLUENT software is set up. The viscosity model in the stirred tank needs to be determined according to the flow state of the fluid, and the flow state of the fluid is generally determined by the Reynolds number R e Make a judgment, combine the model geometric parameters, fluid material parameters and calculate the Reynolds number value according to the formula, and select the corresponding viscosity model. For laminar fluid state, the laminar model can be used, for transitional fluid state, the SST k-ω model can be used, and for turbulent fluid state, the k-ε model can be used;

[0028] Define the material parameters of high-viscosity fluids, including density and viscosity, and define the rotational speed, rotation axis coordinates, and fluid parameters of the computational fluid domain. Read in the UDF script and couple it with the EDEM software to achieve two-way exchange of simulation data.

[0029] The core value of analyzing the simulation results lies in the use of multi-physics field coupling technology to overcome the bottleneck of traditional experimental methods in intuitively revealing the coupling mechanism between complex flow fields and particle motion, providing theoretical support for the optimized design of mixing equipment. This simulation method accurately captures the laminar shear, vortex diffusion and particle collision, and the dynamic equilibrium process of agglomeration and dispersion unique to high-viscosity fluids, and analyzes the influence of agitator type, size parameters, and operating conditions on particle dispersion, sedimentation rate, and energy dissipation.

[0030] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that some local modifications or changes may be made without departing from the principles and essential features of the present invention, all of which fall within the scope of protection of the present invention. Therefore, from all perspectives, the embodiments should be considered as exemplary and non-limiting, and the scope of the present invention is determined by the appended claims. The present invention does not cover parts that are identical to or can be implemented using existing technologies.

Claims

1. A CFD-DEM coupled simulation method for high viscosity fluid stirring, characterized in that: The method comprises the following steps: Step (1): Solid-liquid mixing of high-viscosity fluid and ultrafine silica particles is performed for the production and preparation of solid rocket engine liner mother liquor. The CFD-DEM coupling simulation method is used to analyze the influence of the fluid flow field on the particle dispersion effect. In the CFD-DEM coupling, the Euler-Lagrange method is used to treat the particles as discrete phases, the motion trajectory of the particles is tracked according to Newton's second law, and the rotational angular momentum of the particles is calculated according to the angular momentum equation; a three-dimensional model of the stirring paddle, stirring tank and fluid calculation domain is established using modeling software to provide a geometric basis for the subsequent numerical simulation of the flow field; Step (2): importing the three-dimensional model of the stirring paddle, stirring tank and fluid calculation domain constructed in step (1) into ANSYS software for pre-processing, performing Boolean operations on the model, dividing and extracting the geometric boundaries; meshing the model in the meshing module, defining the partitioning method, boundary size adjustment and boundary layer expansion, etc., locally encrypting the mesh of key parts (such as the edge of the stirring paddle blade and near the wall of the stirring tank) to enhance the ability to capture the area where the fluid and particles interact; Step (3): import the .msh file after meshing in step (2) into FLUENT software, load and display the corresponding geometric structure, and export the Boundary.msh mesh file for EDEM software; Step (4): Import the Boundary.msh mesh file of step (3) into the EDEM software as a geometric model in the EDEM software, add and set the material properties of the particles and the model, including elastic modulus, density, Poisson's ratio, etc. In addition, it is necessary to define the contact parameters between particles and between particles and the model; Step (5): Import the particle model of the particle information of step (4), create a new geometric model (plane, cube or cylinder) to define the location of particle generation, define the "particle factory" and the particle input form (total number or total mass), particle generation speed, etc.; set and define the rotation speed of the stirring paddle model; Step (6): For all the processing operations in steps (4) and (5), set the time step and submit them to the system for calculation to generate the corresponding particle model and stably distribute it at the bottom of the stirring tank under the action of gravity, which serves as the initial state of the stirring simulation; Step (7): Set up the geometric model imported into the FLUENT software in step (3). The viscosity model in the stirring tank needs to be determined according to the flow state of the fluid, and the flow state of the fluid is generally determined according to the Reynolds number R e Make a judgment, combine the model geometric parameters, fluid material parameters and calculate the Reynolds number value according to the formula, and select the corresponding viscosity model. For laminar fluid state, the laminar model can be used, for transitional fluid state, the SST k-ω model can be used, and for turbulent fluid state, the k-ε model can be used; (7.1), the Reynolds number calculation formula used is as follows, where ρ is the fluid density, n is the impeller speed, D is the impeller diameter, and μ is the fluid viscosity; (7.2) The formula used to determine the fluid flow state is as follows, and it needs to be determined based on the calculated Reynolds number value; Step (8): For the settings in step (7), define the material parameters of the high-viscosity fluid, including density and viscosity, and define the rotation speed, rotation axis coordinates and fluid parameters of the fluid domain for the computational fluid domain; read in the UDF script and couple it with the EDEM software to achieve two-way exchange of simulation data and obtain simulation analysis results.

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