A multi-physical field coupling simulation method for microscale microplastic migration and occurrence

Abstract

The application discloses a kind of microscale microplastic migration occurrence multi-physical field coupling simulation method, belong to ecological environment field.The method aims at solving the problem that existing microplastic migration model ignores interface adsorption process, is difficult to couple the action of multiple physical fields and is not suitable for the problem of insufficient adaptability to heterogeneous environment.Its main points are: in the Lagrangian framework, by constructing seepage field, and comprehensively calculating the stokes drag, dielectrophoresis force and Brownian force suffered by microplastic particles to track its movement, while explicitly introducing the adsorption and desorption between particles and pore wall, to simulate the migration trajectory and occurrence state of microplastic in heterogeneous porous medium.The application provides a high-precision simulation tool for revealing the environmental fate and health risk of microplastics in groundwater systems.

Description

Technical Field

[0001] This invention belongs to the field of ecological environment technology, and in particular relates to a multi-physics field coupling simulation method for the migration and storage of microplastics at the microscale. Background Technology

[0002] Microplastics, as an emerging environmental pollutant widely present from atmospheric clouds to underground aquifer sediments, are difficult to remove effectively by natural groundwater once they enter the underground porous network. They may also adsorb heavy metals and hydrophobic organic pollutants, thereby altering the chemical properties of the soil environment. Therefore, accurately predicting their migration and accumulation behavior in the underground environment is crucial for risk assessment and pollution control. Currently, the application of numerical simulation methods to characterize the spatiotemporal distribution of microplastics faces significant challenges. The solute transport equation framework commonly used in existing technologies treats microplastics as a continuous medium. This method fundamentally ignores the morphological characteristics of microplastics as individual particles, and therefore cannot characterize the physicochemical interactions between particles and porous media interfaces, leading to a substantial deviation between simulation results and actual physical processes.

[0003] To overcome these shortcomings, the Lagrange particle tracking model was introduced to predict the motion of discrete particles. This method can consider the convection-dispersion effects of microplastics and their individual characteristics. However, this model still has serious limitations in practical applications. On the one hand, it ignores the key interfacial forces on microplastics and the polarization effect of the electric field, making it unable to reflect the particle enrichment and migration path changes caused by the electric field gradient. On the other hand, when applied to characterize complex porous systems with high heterogeneity in real soils, the model faces network entanglement problems caused by complex boundary conditions, making the calculation process unstable. Although the DLVO theory provides a theoretical basis for particle adhesion and separation, the calculation of its definition of short-range interfacial forces requires nanometer-scale resolution and detailed mineralogical parameters. The huge computational burden makes it almost impractical to integrate it into macroscopic or pore-scale microplastic transport models. These shortcomings collectively make it difficult for existing simulation technologies to accurately characterize the retention, breakthrough, and re-release processes of microplastics in real heterogeneous pores at the microscopic scale, and to reveal the main physical mechanisms controlling their migration and existence. This greatly limits the practical application value of the models in the accurate diagnosis of contaminated sites, reliable risk prediction, and optimized design of remediation schemes. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a multiphysics coupling simulation method for the migration and storage of microplastics at the microscale. This method significantly improves adaptability to heterogeneous porous environments and can reveal the regulatory mechanisms by which different mineral surface properties, pore structures, and particle characteristics affect migration and storage behavior. It provides a reliable theoretical tool for accurately assessing the environmental fate and health risks of microplastics in groundwater systems and for guiding the formulation of pollution monitoring and remediation strategies.

[0005] To achieve the above objectives, this invention provides a multiphysics coupling simulation method for the migration and storage of microplastics at the microscale, comprising:

[0006] Construct a geometric model of a porous medium containing a heterogeneous pore structure and define the coupled physical fields;

[0007] Within the Lagrange framework, microplastic particles are tracked in the coupled physical field, and the particle tracking process explicitly introduces adsorption and desorption between the particles and the pore walls.

[0008] Based on the particle tracking results, the migration trajectory and occurrence state of the microplastic particles in the porous medium are output.

[0009] Optionally, defining the coupled physical fields includes:

[0010] Based on the incompressible Stokes equations, a seepage field describing the flow of fluid in the porous medium geometric model is constructed.

[0011] The seepage field provides flow field data for particle tracking.

[0012] Optionally, the particle tracking process includes:

[0013] Calculate the Stokes drag force on the microplastic particles in the seepage field;

[0014] The Stokes drag force is determined by the relative velocity between the particles and the fluid and the particle size based on the drag force module.

[0015] Optionally, the particle tracking process also includes:

[0016] Calculate the dielectric force acting on the microplastic particles;

[0017] The dielectric force is generated by a non-uniform electric field and depends on the difference in dielectric properties between the particle and the surrounding medium.

[0018] Optionally, the particle tracking process also includes:

[0019] Calculate the Brownian force acting on the microplastic particles;

[0020] The Brownian force is characterized by a stochastic forcing term under the Langevin framework to simulate the effect of thermal perturbation on particle trajectory.

[0021] Optionally, the particle tracking process further includes: solving the motion equations of the microplastic particles based on the Stokes drag force, the dielectrophoretic force, and the Brownian force, in order to update the position and velocity of the particles.

[0022] Optionally, explicitly introducing adsorption and desorption between particles and pore walls includes:

[0023] During the particle tracking process, the distance between the microplastic particles and the pore wall is determined in real time.

[0024] When the distance reaches the adsorption range, the particles are determined to be captured according to the preset adsorption energy criterion.

[0025] Set the desorption probability for the captured particles to simulate their re-release behavior under changes in flow field or environment.

[0026] Optionally, constructing a porous media geometric model includes: using a method based on real soil structure scanning data to generate heterogeneous porous structures with different porosity and pore connectivity types.

[0027] An electronic device, the electronic device comprising: a processor and a memory storing computer program instructions;

[0028] When the processor executes the computer program instructions, it implements the multiphysics coupling simulation method for microscale microplastic migration and storage.

[0029] A computer storage medium storing computer program instructions, which, when executed by a processor, implement the multiphysics coupling simulation method for microscale microplastic migration and storage.

[0030] Technical Advantages of this Invention: This invention discloses a multiphysics coupling simulation method for the migration and storage of microplastics at the microscale. By constructing an adsorption particle tracking model based on a Lagrange framework, it effectively overcomes the shortcomings of existing technologies in terms of insufficient characterization of interfacial adsorption processes and lack of multiphysics coupling. This method achieves the coupling of hydrodynamic, electric, and thermal disturbance fields at the microscale by comprehensively calculating Stokes drag, dielectrophoresis, and Brownian forces, thereby accurately describing the complex forces and trajectories of microplastic particles in porous media. Simultaneously, the model explicitly incorporates the adsorption and desorption processes between particles and pore walls, making the simulation of microplastic retention and re-release behavior more mechanistically realistic. This technical solution significantly improves adaptability to heterogeneous porous environments, revealing the regulatory mechanisms of different mineral surface properties, pore structures, and particle characteristics on migration and storage behavior. It provides a reliable theoretical tool for accurately assessing the environmental fate and health risks of microplastics in groundwater systems and guiding the formulation of pollution monitoring and remediation strategies. Attached Figure Description

[0031] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0032] Figure 1 This is a conceptual diagram of the adsorbed particle tracking model and multiphysics coupling mechanism for the migration and storage of microplastics at the microscale in this invention.

[0033] Figure 2 The diagrams show the pore potential distribution and the number of adsorbed particles under different porosities in the embodiments of the present invention.

[0034] Figure 3 This is a flowchart illustrating a multiphysics coupling simulation method for the migration and storage of microplastics at the microscale, according to an embodiment of the present invention. Detailed Implementation

[0035] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0036] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0037] This embodiment provides a multiphysics coupling simulation method for the migration and storage of microplastics at the microscale, including:

[0038] Construct a geometric model of a porous medium containing a heterogeneous pore structure and define the coupled physical fields;

[0039] Within the Lagrange framework, microplastic particles are tracked in the coupled physical field, and the particle tracking process explicitly introduces adsorption and desorption between the particles and the pore walls.

[0040] Based on the particle tracking results, the migration trajectory and occurrence state of the microplastic particles in the porous medium are output.

[0041] Furthermore, defining coupled physical fields includes:

[0042] Based on the incompressible Stokes equations, a seepage field describing the flow of fluid in the porous medium geometric model is constructed.

[0043] The seepage field provides flow field data for particle tracking.

[0044] Specifically, the implementation process of this embodiment includes:

[0045] Constructing a seepage field model:

[0046] Microplastic migration occurs under low Reynolds number conditions (typically less than 0.1), where inertial effects are negligible in subsurface porous environments. To capture the microscale hydrodynamic field, this invention employs the incompressible Stokes equations, which govern viscous-dominated creeping flow. The velocity and pressure distributions within complex pore geometries are solved using the incompressible Stokes equations:

[0047] (1);

[0048] (2);

[0049] (3);

[0050] in, u Indicates instantaneous velocity vector (ms) -1 ), p It is fluid pressure (Pa). I Represents the identity tensor. m It is the fluid dynamic viscosity (Pa·s); K It refers to the viscous stress tensor (Pa). F This indicates the physical force (N m) contributed by electrostatics or dielectric electrophoresis. -3 ); r Fluid density (kg m³) -3 The fluid dynamics formula establishes the flow field controlling the migration of microplastics and provides a basis for analyzing the trajectory of microplastic particles within a porous network.

[0051] Furthermore, the particle tracking process includes:

[0052] Calculate the Stokes drag force on the microplastic particles in the seepage field;

[0053] The Stokes drag force is determined by the relative velocity between the particles and the fluid and the particle size based on the drag force module.

[0054] Specifically, the implementation process of this embodiment includes:

[0055] Stokes drag force:

[0056] Hydrodynamic resistance from surrounding water modulates the alignment of particle velocity with the environmental flow and affects their transport and retention. Under typical low Reynolds number conditions in groundwater pores, inertial effects are negligible, and the resistance on spherical particles can be accurately described by Stokes' law:

[0057] (4);

[0058] (5);

[0059] (6);

[0060] in, d p It is the particle diameter (m); v This refers to the local particle velocity vector (ms). -1 ); r p Particle density (kg m³) -3 ); m p It is the particle mass (kg); F drag This represents the hydrodynamic drag (N) acting on the particle; and t p The relaxation time (s) characterizes the particle's ability to respond to the velocity of the surrounding fluid; the drag term describes the main mechanism by which the surrounding fluid transfers momentum to the microplastic, thereby controlling its migration behavior within the pore space.

[0061] Furthermore, the particle tracking process also includes:

[0062] Calculate the dielectric force acting on the microplastic particles;

[0063] The dielectric force is generated by a non-uniform electric field and depends on the difference in dielectric properties between the particle and the surrounding medium.

[0064] Specifically, the implementation process of this embodiment includes:

[0065] Dielectrophoresis: Dielectrophoresis is widely recognized as a crucial mechanism leading to particle enrichment and spatial redistribution at the microscale. The dielectrophoresis force, generated by a non-uniform electric field, drives directional migration and lateral displacement of particles. It is worth emphasizing that this force originates from the difference in dielectric properties between the particles and the surrounding medium. Its classical form is expressed as:

[0066] (7);

[0067] in, F DEP The dielectric force (N) acting on microplastic particles is generated by the spatial gradient in the electric field. e m The dielectric constant (Fm) of the surrounding medium. -1 ); r p Where the particle radius is (m); The gradient (V) of the specified square electric field magnitude 2 m -3 And quantify the degree of non-uniformity of the electric field; Re[K(ω)] Let be the real part of the frequency-dependent Clausius-Mosotti factor, used to describe the degree of dielectric mismatch between the particle and the dielectric; its classical analytical form is as follows:

[0068] (8);

[0069] (9);

[0070] in, Represents the complex permittivity (Fm) -1 ), can be used to characterize microplastic particles or surrounding medium Dielectric response in an alternating electric field; d This refers to electrical conductivity (S m) -1 ); oh It is the angular frequency (rad s) of the applied electric field. -1 ); j Represents the imaginary unit ( j 2 =-1). In groundwater environments, the applied electric field is usually low-frequency or quasi-static. Therefore, a quasi-static approximation can be used for the relevant equations. In weakly negatively charged soil environments, dielectric force can induce dipole polarization within pore channels and directly affect particle trajectories.

[0071] Furthermore, the particle tracking process also includes:

[0072] Calculate the Brownian force acting on the microplastic particles;

[0073] The Brownian force is characterized by a stochastic forcing term under the Langevin framework to simulate the effect of thermal perturbation on particle trajectory.

[0074] Specifically, the implementation process of this embodiment includes:

[0075] An improved model for adsorbed particle tracking: thermal fluctuations manifest as Brownian motion at the microscale, which significantly alters the trajectory of microplastics even under creep flow conditions. The intensity of the Brownian motion of microplastics is quantified by the Stokes-Einstein relation:

[0076] (10);

[0077] in, D The diffusion coefficient (m) 2 s -1 ), k B Boltzmann constant (JK) -1 ), T Represents absolute temperature (K). Within the Langevin framework, the stochastic forcing term, based on the diffusion coefficient and thermal fluctuations, characterizes the thermal random perturbations experienced by particles at the microscale. Its typical expression is as follows:

[0078] (11);

[0079] (12);

[0080] (13);

[0081] in, F Brownian Random thermal force (N) acting on a particle. Δt The time increment (s) is used for calculation. or It is a normally distributed random variable with a mean of zero and a variance of 1, following a standard Gaussian distribution N(0,1); coefficients c It is the Stokes drag coefficient (kg s) -1 The Brownian contribution is used to characterize the hydrodynamic drag exerted on particles by the fluid-carrying agent. For particles smaller than 10 μm or under high-temperature conditions, the random thermal perturbations caused by the Brownian contribution become particularly significant.

[0082] Furthermore, the particle tracking process also includes: solving the motion equations of the microplastic particles based on the Stokes drag force, the dielectrophoretic force, and the Brownian force, in order to update the position and velocity of the particles.

[0083] Specifically, the implementation process of this embodiment includes:

[0084] The overall dynamics of microplastic particles within a porous network are controlled by the combined effects of Stokes drag, Brownian motion, and dielectrophoresis. Therefore, the governing equations for microplastics are expressed as:

[0085] (14);

[0086] in, q This represents the particle position vector (m). dq / dt The velocity of the particle is (m / s); F ext The external force (N) acting on the particle includes various forces such as gravity, Brownian motion, or dielectric force. F ext / m p The acceleration imparted by these external forces was quantified (m / s). -2 This supplements the advection transport process determined by the current carrier.

[0087] Furthermore, the explicit introduction of adsorption and desorption between particles and pore walls includes:

[0088] During the particle tracking process, the distance between the microplastic particles and the pore wall is determined in real time.

[0089] When the distance reaches the adsorption range, the particles are determined to be captured according to the preset adsorption energy criterion.

[0090] Set the desorption probability for the captured particles to simulate their re-release behavior under changes in flow field or environment.

[0091] Furthermore, the construction of the porous media geometric model includes: using a method based on real soil structure scanning data to reconstruct heterogeneous pore structures with different porosity and pore connectivity types. The porosity parameters are preset to 0.4, 0.5, and 0.6, corresponding to different pore structure models. The model is configured to simulate the transport process of microplastics in the pore structure, outputting the spatial retention distribution and occurrence state data of microplastics. The spatial retention distribution and occurrence pattern of microplastics show a trend of gradually weakening with increasing porosity. The total number of adsorbed particles under each combination of porosity and pore type is statistically analyzed to quantify the influence of structural heterogeneity and connectivity on the overall retention behavior.

[0092] Specifically, the implementation process of this embodiment includes:

[0093] The above model constitutes a coupled framework that synthesizes the main driving forces acting on particles within the microporous structure, while explicitly introducing the adsorption effect of the pore walls. The above discussion presents a groundbreaking adsorption particle tracking model proposed in this invention. This model couples Stokes drag, Brownian waves, and dielectrophoretic forces within a Lagrangian framework, and explicitly considers the adsorption and desorption processes at the particle-pore wall interface. Based on this coupling mechanism, a multiphysics coupled model suitable for the migration and storage of microplastics at the microscale is constructed, providing a high-precision simulation tool for characterizing the true trajectory of microplastics in heterogeneous porous networks within groundwater systems.

[0094] An electronic device, the electronic device comprising: a processor and a memory storing computer program instructions;

[0095] When the processor executes the computer program instructions, it implements the multiphysics coupling simulation method for microscale microplastic migration and storage.

[0096] A computer storage medium storing computer program instructions, which, when executed by a processor, implement the multiphysics coupling simulation method for microscale microplastic migration and storage.

[0097] This invention discloses a multiphysics coupling simulation method for the migration and storage of microplastics at the microscale. By constructing an adsorption particle tracking model based on a Lagrange framework, it effectively overcomes the shortcomings of existing technologies in terms of insufficient characterization of interfacial adsorption processes and lack of multiphysics coupling. This method achieves the coupling of hydrodynamic, electric, and thermal disturbance fields at the microscale by comprehensively calculating Stokes drag, dielectrophoresis, and Brownian forces, thereby accurately describing the complex forces and trajectories of microplastic particles in porous media. Simultaneously, the model explicitly incorporates the adsorption and desorption processes between particles and pore walls, making the simulation of microplastic retention and re-release behavior more mechanistically realistic. This technical solution significantly improves adaptability to heterogeneous porous environments, revealing the regulatory mechanisms of different mineral surface properties, pore structures, and particle characteristics on migration and storage behavior. It provides a reliable theoretical tool for accurately assessing the environmental fate and health risks of microplastics in groundwater systems and guiding the formulation of pollution monitoring and remediation strategies.

[0098] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A multiphysics coupling simulation method for the migration and storage of microplastics at the microscale, characterized in that, include: Construct a geometric model of a porous medium containing a heterogeneous pore structure and define the coupled physical fields; Within the Lagrange framework, microplastic particles are tracked in the coupled physical field, and the particle tracking process explicitly introduces adsorption and desorption between the particles and the pore walls. Based on the particle tracking results, the migration trajectory and occurrence state of the microplastic particles in the porous medium are output. The construction of a porous media geometric model includes: generating heterogeneous pore structures with different porosity and pore connectivity types using a method based on real soil structure scanning data; wherein the porosity parameters are preset to 0.4, 0.5, and 0.6, corresponding to different pore structure models; the pore structure model is configured to simulate the transport process of microplastics in the pore structure, outputting the spatial retention distribution and occurrence state data of microplastics, and counting the total number of adsorbed particles under each combination of porosity and pore type to quantify the influence of structural heterogeneity and connectivity on the overall retention behavior; The particle tracking process also includes: Calculate the dielectric force acting on the microplastic particles; The dielectric force is generated by a non-uniform electric field and depends on the difference in dielectric properties between the particle and the surrounding medium. The particle tracking process also includes: Calculate the Brownian force acting on the microplastic particles; The Brownian force is characterized by a stochastic forcing term under the Langevin framework to simulate the effect of thermal perturbation on particle trajectory. The particle tracking process also includes: solving the motion equations of the microplastic particles based on the Stokes drag force, the dielectric force, and the Brownian force, in order to update the position and velocity of the particles; Explicitly introduced adsorption and desorption between particles and pore walls include: During the particle tracking process, the distance between the microplastic particles and the pore wall is determined in real time. When the distance reaches the adsorption range, the particles are determined to be captured according to the preset adsorption energy criterion. Set the desorption probability for the captured particles to simulate their re-release behavior under changes in flow field or environment.

2. The multiphysics coupling simulation method for the migration and storage of microplastics at the microscale as described in claim 1, characterized in that, Defining coupled physical fields includes: Based on the incompressible Stokes equations, a seepage field describing the flow of fluid in the porous medium geometric model is constructed. The seepage field provides flow field data for particle tracking.

3. The multiphysics coupling simulation method for the migration and storage of microplastics at the microscale as described in claim 2, characterized in that, The particle tracking process includes: Calculate the Stokes drag force on the microplastic particles in the seepage field; The Stokes drag force is determined by the relative velocity between the particles and the fluid and the particle size based on the drag force module.

4. An electronic device, characterized in that, The electronic device includes: a processor and a memory storing computer program instructions; When the processor executes the computer program instructions, it implements the multiphysics coupling simulation method for microscale microplastic migration and storage as described in any one of claims 1-3.

5. A computer storage medium, characterized in that, The computer storage medium stores computer program instructions, which, when executed by a processor, implement the multiphysics coupling simulation method for microscale microplastic migration and storage as described in any one of claims 1-3.

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