An interface calculation method and device based on a discrete particle-finite element grid coupling model

Abstract

The application provides an interface calculation method and device based on a discrete particle-finite element grid coupling model. The interface calculation method describes the substances on both sides of the interface by using a discrete particle and a finite element grid method respectively, establishes a coupling calculation model of energy transfer and conversion processes at the interface, and performs computer simulation on diffusion, adsorption, desorption, reaction or heat transfer processes near the interface, so as to study the transfer and conversion processes of energy and substances at the interface or study material performance or catalytic performance, significantly improves the universality of interface calculation, has small prediction deviation of calculation simulation, and has wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of interface interaction research, and particularly relates to an interface calculation method and device based on a discrete particle-finite element grid coupling model. BACKGROUND

[0002] During the process of near space gliding, flying or reentry of a hypersonic vehicle, high temperature gas effect is caused by strong shock wave and viscous friction resistance, which leads to the excitation of internal energy of gas molecules in the shock layer, dissociation and ionization of particles, and further causes complex physical and chemical action processes of the near wall surface of the thermal protection system of the vehicle, which seriously affects the aerodynamic characteristics and aerodynamic thermal environment of the vehicle, and brings great challenges to the heat protection design of the surface material of the vehicle.

[0003] In a gas-solid heterogeneous catalytic reaction or a liquid-solid heterogeneous catalytic reaction, the gas reacts inside and on the surface of the catalyst material, which causes complex endothermic / exothermic and heat transfer processes, resulting in changes in the temperature of the catalyst material, which seriously affects the performance of the catalyst and brings challenges to the development of reaction materials and the design of reaction processes.

[0004] Therefore, gas-solid surface interaction or liquid-solid surface interaction is an important problem in the fields of aerospace and material chemistry, and it has wide application prospects in many fields such as heterogeneous catalysis, adsorption, separation, thermal protection system of hypersonic vehicles, and rarefied gas dynamics. At present, it is very difficult to model and study the energy transfer and conversion processes generated in the complex physical and chemical processes occurring on the gas-solid surface. The existing models have poor accuracy, and it is difficult to conduct in-depth research on each micro-process occurring on the surface.

[0005] At present, the gas-solid surface interaction is mainly processed by the following models and methods. One is to describe the material on one side (or both sides) of the interface with models and methods based on the assumption of continuous medium, such as using computational fluid dynamics method to describe the gas, and then processing the interaction of the two as a kind of boundary condition, such as treating the solid boundary as a slip / no-slip boundary condition or an ideal viscous wall, etc., and simulating with some given assumption parameters.

[0006] CN106055756A discloses a static pressure air floating guide rail system simulation analysis method under the effect of velocity slip, introduces the velocity slip calculation method and boundary condition into the Reynolds equation, and derives the Reynolds equation suitable for compressed gas in microscale; through CFX simulation analysis, the influence of different throttle hole diameters on the gas film thickness can be obtained, the pressure change of the air floating guide rail under different gas film thicknesses, and by comparing with the results simulated by the traditional Reynolds equation, the static characteristics of the guide rail can be more accurately determined. This method is simple and efficient, and is more conducive to guiding the application of static pressure guide rail in practice.

[0007] In the research of the gas-solid surface interaction of hypersonic vehicles, the solid surface is also described by a model based on finite rate reaction, in which the solid wall is regarded as a boundary condition with specific reaction parameters, and the thermal effect of the chemical reaction between the gas and the solid surface is described by parameters such as reaction coefficient and catalytic efficiency. These methods have a given parameter that depends on an empirical / semi-empirical model or limited experimental results, and are not universal, and it is difficult to extend them to different gases, solid materials or different simulation conditions. The prediction deviation and uncertainty of new systems are large.

[0008] Most importantly, the above-mentioned models and methods do not consider the chemical reaction and heat transfer coupling process in the gas-solid surface interaction process, so the transfer and conversion process between different forms of energy cannot be accurately obtained, and the prediction of the heat flow and temperature distribution of the model will also have a large deviation.

[0009] Therefore, it is necessary to develop a new interface calculation method to improve the accuracy of the calculation results. SUMMARY

[0010] In view of the problems in the prior art, the present application provides an interface calculation method and device based on a discrete particle-finite element grid coupling model, which can model and simulate the coupling between multiple processes including physical processes, chemical reactions and heat transfer, and the transfer and conversion process between different forms of energy and matter in the gas-solid surface interaction process. The method can be used in the research of aircraft surface heat-resistant materials, accurate prediction of aerodynamic heat or catalyst reaction kinetics and other fields.

[0011] To achieve this purpose, the present application adopts the following technical solutions:

[0012] In a first aspect, the present application provides an interface calculation method based on a discrete particle-finite element grid coupling model, which comprises the following steps:

[0013] (1) For the interface system, a discrete particle model is established for the gas phase and / or liquid phase on one side of the interface, and a finite element grid model is established for the solid phase on the other side of the interface;

[0014] (2) According to the actual interaction process between the gas phase and / or liquid phase and the solid phase, select any one or at least two combinations of the mass transfer, heat transfer or reaction between the interfaces, and select specific model equations for the interaction process;

[0015] (3) According to the transformation process of matter and / or energy between gas phase and / or liquid phase and solid phase, the correlation between the discrete particle model and the finite element grid model is established based on the model equation in step (3), and the construction of the calculation model is completed;

[0016] (4) The simulation calculation is performed according to the calculation model in step (3).

[0017] The interface calculation method provided by the application describes the discrete particles and the finite element grid according to the types and characteristics of the substances on both sides of the interface, and then selects the model equation according to the diffusion, adsorption, desorption, reaction mechanism, reaction conditions and heat transfer process in the interaction between the particles and the surface. In the model, different forms of energy and the transformation and conversion process between them in the above process are described by parameters. The correlation between these parameters is established between the particles and the grid, so as to construct the coupling calculation model of the transformation and conversion process of energy and matter at the interface. The calculation model considers the correlation between different forms of energy, so as to realize the multi-process coupling simulation including chemical reaction and heat transfer in the surface interaction process.

[0018] Compared with the traditional continuous medium assumption model and method, the interface interaction parameters and boundary conditions of the interface calculation method provided by the application do not need to be supported by empirical or semi-empirical experimental results, have better universality, can be expanded to different gases, solids or liquids, or to different simulation conditions, and can consider the coupling process of reaction, heat transfer and mass transfer at the same time. The simulation calculation is more accurate. Compared with the micro-molecular dynamics simulation, the calculation amount of the application is significantly reduced, and the application can be applied to larger space-time scale. Not only the macroscopic concentration distribution field and temperature distribution field data can be obtained, but also the dynamic evolution process can be obtained. Compared with the traditional MD method, the application can be applied to reaction calculation process.

[0019] Preferably, the discrete particles in the discrete particle model in step (1) include any one or a combination of at least two of point particles, regular geometric structure particles or irregular geometric structure particles, wherein a typical but non-limiting combination is a combination of point particles and regular geometric structure particles, a combination of regular geometric structure particles and irregular geometric structure particles, and a combination of point particles and irregular geometric structure particles.

[0020] Preferably, each particle in the discrete particle represents an atom, a molecule, an atomic cluster or a molecular cluster.

[0021] Preferably, the parameters of the discrete particles in step (1) include any one or a combination of at least two of mass, position, atomic diameter, molecular diameter, translational velocity, thermal velocity, bond energy, dangling bond energy, adsorption heat, rotational energy, vibrational energy, or electronic energy, wherein a typical but non-limiting combination is a combination of mass and position, a combination of atomic diameter and translational velocity, a combination of atomic diameter and thermal velocity, a combination of translational velocity and bond energy, a combination of thermal velocity and dangling bond energy, a combination of bond energy and adsorption heat, a combination of adsorption heat and rotational energy. The more parameters provided in the present application, the more accurate the results of the simulation calculation, but the simulation calculation can also be performed according to other parameters when some parameters are missing.

[0022] Preferably, the finite element mesh model in step (1) includes a two-dimensional surface mesh model or a three-dimensional mesh model.

[0023] Preferably, the original structure of the solid phase includes any one or a combination of at least two of a regular geometric surface, an irregular geometric surface, a solid structure, a porous material structure, or a particle packing structure, wherein a typical but non-limiting combination is a combination of a regular geometric surface and an irregular geometric surface, a combination of an irregular geometric surface and a solid structure, a combination of an irregular geometric surface and a particle packing structure, a combination of a solid structure and a particle packing structure, a combination of a particle packing structure and a porous material structure.

[0024] Preferably, the parameters of the finite element mesh model in step (1) include mesh shape, mesh size, material density, material specific heat capacity, material thermal conductivity, material surface emissivity, mesh absorbed heat, mesh emitted heat, and material temperature.

[0025] Preferably, the parameters of the finite element mesh model further include the size of the reaction site and the shape of the reaction site.

[0026] Preferably, the parameters of the finite element mesh model further include the size of the adsorption site and the shape of the adsorption site.

[0027] The size and shape of the reaction site in the present application include the description and data coordinates of points, lines, surfaces, and bodies in space.

[0028] Preferably, the mass transfer in step (2) includes any one or a combination of at least two of diffusion, adsorption, or desorption, wherein a typical but non-limiting combination is a combination of diffusion and adsorption, a combination of diffusion and desorption, a combination of adsorption and desorption, a combination of diffusion, adsorption, and desorption.

[0029] Preferably, the heat transfer includes any one or a combination of at least two of thermal radiation, thermal conduction or thermal convection, wherein typical but non-limiting combinations are a combination of thermal radiation and thermal conduction, a combination of thermal radiation and thermal convection, a combination of thermal conduction and thermal convection, a combination of thermal radiation, thermal convection and thermal conduction.

[0030] Preferably, the reaction includes any one or a combination of at least two of a gas phase and / or liquid phase reaction, a gas-solid catalytic reaction, a liquid-solid catalytic reaction or a gas-liquid-solid three-phase catalytic reaction, such as a combination of a gas-liquid reaction and a gas-solid catalytic reaction, a combination of a gas-solid catalytic reaction and a liquid-solid catalytic reaction, a combination of a gas-gas reaction or a liquid-liquid reaction.

[0031] The interaction processes between the discrete particles in the present application are not particularly specified, and the transfer and conversion processes of matter and energy can be modeled according to a specific physical and chemical mechanism model. Similarly, the energy transfer and conversion processes within the solid material grid are not particularly specified, and can be processed according to a given heat transfer process model.

[0032] Preferably, the calculation model of step (3) uses real space-time scales or dimensionless scales.

[0033] Preferably, the energy includes any one or a combination of at least two of kinetic energy, potential energy, chemical energy, electromagnetic energy, radiation energy or thermal energy, wherein typical but non-limiting combinations are a combination of kinetic energy and potential energy, a combination of kinetic energy and radiation energy, a combination of potential energy and chemical energy, a combination of chemical energy and electromagnetic energy, a combination of electromagnetic energy and thermal energy.

[0034] Preferably, the association of energy between the discrete particle model and the finite element grid model in step (3) includes that the energy change of each grid in each time step includes a first energy change and a second energy change. The first energy change is a first energy action of the discrete particle on the grid in the time step; and the second energy change is a second energy action of the adjacent grid on the grid.

[0035] When the discrete particles of the present application interact with the grid, the energy exchange between the particles and the grid affects the temperature change of the grid, and the temperature change of the grid affects the diffusion, adsorption, reaction or desorption processes of the particles on the grid, so the two processes are coupled.

[0036] According to the mechanism and process of physical and chemical reactions, energy will be transferred between discrete particles and grids. The energy of the discrete particles mainly includes kinetic energy, potential energy, chemical bond energy and internal energy (here, the internal energy refers to the rotational energy, vibration energy and electronic energy inside the particle); when the particles interact with the grids, in addition to the collision effect, it is also necessary to determine whether the grids have adsorption and desorption sites and reaction sites to determine whether the adsorption and desorption and reaction processes of the current grid occur. The interaction process includes but is not limited to collision, adsorption, chemical reaction or desorption, etc. Each grid can contain one or more action sites, including adsorption and desorption sites and / or reaction sites, and the energy exchanged between the particles and the reaction sites of the grid (such as chemical reaction heat absorption / heat release, collision exchange energy, etc.) during each action process can be respectively denoted as dq i , the positive and negative of which can be self-agreed, such as setting the heat absorption of the site as positive and the heat release of the site as negative. In the above-mentioned action process, the temperature of the site will affect the size of dq i , and the energy transferred from the site to the particle will immediately act on or be marked on the corresponding parameters of the particle. In each time step, the heat conduction between the grids and the energy of the grid thermal radiation are denoted as dq j , and the positive and negative of which are agreed as above.

[0037] Therefore, in one time step, the sum of the heat absorption / release of all sites of each grid is denoted as dQ, and it satisfies dQ = ∑dq i + ∑dq j Therefore, each grid can be regarded as a heat source, which can be coupled with the heat transfer model of the solid material itself.

[0038] Preferably, the first energy action includes any one or a combination of at least two of collision exchange energy, reaction heat absorption, reaction heat release, adsorption heat, desorption heat or thermal convection, wherein a typical but non-limiting combination is a combination of collision exchange energy and reaction heat absorption, a combination of reaction heat absorption and adsorption heat, a combination of adsorption heat and desorption heat, a combination of thermal convection and collision exchange energy, and a combination of collision exchange energy and desorption heat.

[0039] Preferably, the second energy action includes heat conduction and / or heat radiation.

[0040] Preferably, the association between the substance and the discrete particle model and the finite element grid model in step (3) includes that the change of the substance of each grid in each time step includes a first change of the substance; the first change of the substance includes adsorption and / or desorption.

[0041] Preferably, the first change of the substance further includes the exchange of the substance in the reaction.

[0042] Preferably, step (3) further includes the establishment of initial conditions and boundary conditions.

[0043] According to a specific physical process mechanism or chemical reaction mechanism or a simplified physical or chemical reaction process, a calculation system model is established, which comprises a space region, a material structure, a physical process and / or a chemical process, initial conditions and boundary conditions, etc., and corresponding simulation parameters are determined. Specifically, discrete particle parameters and finite element grid parameters, as well as temperature, pressure, initial conditions, boundary conditions, adsorption types, chemical reaction paths, chemical reaction networks, energy transfer or conversion paths and sizes, etc. are included, so as to generate a calculation model.

[0044] Preferably, for the stable source gas phase and / or liquid phase, a component control region is set in the calculation model.

[0045] The present application can ensure that the temperature and components of the gas phase and / or liquid phase in the control region do not change, while being able to exchange and diffuse with the components in the simulation region in real time, which is suitable for simulating the interaction between fluid and aircraft surface, etc.

[0046] The present application does not have special limitations on the simulation calculation method and platform, and methods and platforms familiar to those skilled in the art can be used for calculation, or programs can be designed according to actual conditions for simulation calculation.

[0047] In the second aspect, the present application provides an interface calculation device based on a discrete particle-finite element grid coupling model, which can realize the interface calculation method based on the discrete particle-finite element grid coupling model in the first aspect.

[0048] The interface calculation device provided by the present application can realize simulation calculation with high accuracy in a short computing power, not only can realize the coupling of reaction, mass transfer and heat transfer process, but also can obtain the kinetic evolution process, and has wide application prospect.

[0049] Preferably, the interface calculation device comprises a discrete particle model establishment module, a finite element grid model establishment module, a model equation selection module, a calculation model construction module and a simulation calculation module.

[0050] The discrete particle model, the finite element grid model and the model equation obtained by the discrete particle model establishment module, the finite element grid model establishment module and the model equation selection module are used for the calculation model construction module to construct a calculation model; and the simulation calculation module uses the calculation model to calculate.

[0051] Compared with the prior art, the present application has at least the following beneficial effects:

[0052] (1) The interface calculation method based on the discrete particle-finite element grid coupling model provided by the present application can be applied to large space-time scale simulation calculation and the computing power time is significantly shortened;

[0053] (2) The interface calculation method based on the discrete particle-finite element grid coupling model provided by the application can obtain the energy exchange change with time in each process, such as adsorption, reaction, desorption or radiation, the participation of discrete particles in different processes, and the contribution of heat transfer, and can be applied to different systems, has high universality, and does not need to rely on empirical / semi-empirical models or limited experimental results, and can model and simulate the transfer and conversion processes of matter and energy in various complex gas phase and / or liquid phase and solid phase interaction processes; at the same time, according to the change of actual operation conditions and the like, the gas atmosphere, material properties and gas-solid interaction conditions can be conveniently modified, and the operation results are updated;

[0054] (3) The interface calculation device based on the discrete particle-finite element grid coupling model provided by the application can realize simulation calculation with high accuracy in a short computing power, can realize the coupling of reaction, mass transfer and heat transfer process, and can be used for research in multiple fields such as development of heat protection materials on the surface of aircraft, accurate prediction of aerodynamic heat and catalyst reaction kinetics, and has wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0055] Figure 1 is a combination schematic diagram of the discrete particle model and the finite element grid model established in Example 1.

[0056] Figure 2 is a schematic diagram of the five-center-point finite difference method used in Example 1.

[0057] Figure 3 is a graph of the loss efficiency of O atoms on the surface of SiO2 with time calculated by Application 1.

[0058] Figure 4 is a graph of the loss efficiency of O atoms on the surface of SiO2 with time calculated by literature.

[0059] Figure 5 is a graph of the change of the surface temperature of the solid with time calculated in Application 2.

[0060] Figure 6 is a graph of the change of the surface coverage of the adsorbed atoms on the solid with time calculated in Application 2.

[0061] Figure 7 is a graph of the change of the heat flux density of the adsorption / desorption heat in the gas-solid interaction process with time calculated in Application 2.

[0062] Figure 8 is a graph of the change of the time consumption per hundred steps with the number of central processing cores and the fitting graph in Application 3.

[0063] Figure 9 isFigure 8 The fitted curve is extended to a graph showing the variation in the number of central processing units up to 1 million.

[0064] In the figure: 1 - two-dimensional geometric plane model; 2 - simulation calculation area; 3 - component control area. DETAILED DESCRIPTION

[0065] The technical solutions of the present application are further illustrated below in conjunction with the drawings and through specific embodiments.

[0066] The present application is further described below. However, the examples described below are only simple examples of the present application and do not represent or limit the scope of protection of the present application, and the scope of protection of the present application is subject to the claims.

[0067] The present application provides an interface calculation method based on a discrete particle-finite element grid coupling model, which comprises the following steps:

[0068] (1) a discrete particle model is established for the gas phase and / or the liquid phase, and a finite element grid model is established for the solid phase;

[0069] (2) according to the actual interaction process between the gas phase and / or the liquid phase and the solid phase, any one or at least two combinations of the mass transfer, heat transfer or reaction between the interfaces are selected, and specific model equations are selected for the interaction process;

[0070] (3) according to the material and / or energy conversion process between the gas phase and / or the liquid phase and the solid phase, a correlation between the discrete particle model and the finite element grid model is established based on the model equations in step (3), and the construction of the calculation model is completed;

[0071] (4) simulation calculation is performed according to the calculation model in step (3).

[0072] Example 1

[0073] The present application provides an interface calculation method based on a discrete particle-finite element grid coupling model, which takes the catalytic reaction process of air and silicon dioxide material as an example, and the specific process is described as follows: in a high temperature environment, air dissociates, and a complex catalytic reaction process occurs on the surface of the silicon dioxide material, releasing a large amount of heat and causing the temperature of the material to rise.

[0074] The interface calculation method specifically comprises the following steps:

[0075] (1) a discrete particle model is established for high temperature air gas, and the parameters set include: the gas density is 0.032 kg / m 3 ; the mass and diameter of the discrete particles are: O2(5.3138×10 -23g, 0.13996nm), N2 (4.6496×10 -23 g, 0.15027nm), NO (4.9817×10 -23 g, 0.14560nm), O (2.6569×10 -23 g, 0.12362nm), N (2.3248×10 -23 g, 0.11956 nm); the adsorption heats of gas atoms on the surface are: O (499.8 kJ / mol), N (530.8 kJ / mol); the bond energies of each gas molecule are: O2 (498.36 kJ / mol), N2 (945.33 kJ / mol), NO (630.57 kJ / mol);

[0076] A finite element mesh model is established for the silica material. Specifically, the silica material is a thin sheet structure with a certain thickness. The temperature gradient along the thickness direction within the material is not considered; therefore, a two-dimensional geometric planar model is used to represent it, such as... Figure 1 As shown, the simulation calculation region 2 is located on the upper part of the two-dimensional geometric plane model 1. The X and Y directions have periodic boundary conditions, each 70 nm in length, and the Z direction has a thickness of 1 μm. The uppermost region, with a thickness of 20 nm, is the composition control region 3, designed to ensure that the temperature and composition of the gas within this region remain constant, simulating a stable incoming gas flow. The density of reaction sites on the solid is 4.5 sites / nm. 2 The solid thickness is 10 nm, and the side length of the two-dimensional mesh is 10 nm; the surface emissivity ε of the solid is 0.8, and the density ρ is 2.2 g / cm³. 3 Specific heat c p Its thermal conductivity is 1124 J / (kg·K), and its thermal conductivity λ is 7.6 W / (m·K);

[0077] (2) Based on the actual interaction process between the gas phase and / or liquid phase and the solid phase, select the interaction process of three combinations of mass transfer, heat transfer and reaction between the interfaces, and select a specific model equation for the interaction process;

[0078] The mass transfer is comprised of three processes: collision, adsorption, and desorption; the heat transfer is comprised of thermal radiation and thermal conduction; and the reaction is a recombination reaction that occurs on a solid surface after the atoms of the dissociated air molecules.

[0079] Based on mass transfer and reaction characteristics, the Langmuir-Hinshelwood (LH) model equation and the Eley-Rideal (ER) model equation were selected, where ER represents spontaneous reactions, and the energy barriers for LH reactions are: OO reaction (300.96 kJ / mol), ON reaction (243.3 kJ / mol), and NN reaction (72.18 kJ / mol).

[0080] The heat radiated by the surface per unit time per unit area into space is σεΤ 4 where the Stefan-Boltzmann constant σ is 5.67032 x 10 -8 (W / m 2 ·K 4 ), and ε is the emissivity of the solid surface. The heat conduction is described by a two-dimensional active heat conduction equation, as shown in the following equation (1):

[0081]

[0082] where T is the temperature, F(x, y, t) represents the heat source intensity at different times and positions, t represents time, ρ is the density of the solid, c p is the specific heat capacity of the solid material, and λ is the thermal conductivity.

[0083] (3) According to the transformation process of matter and / or energy between the gas phase and / or the liquid phase and the solid phase, a correlation between the discrete particle model and the finite element grid model is established based on the model equation described in step (3), and the construction of the calculation model is completed;

[0084] Specifically, the transformation process includes atomic adsorption, molecular adsorption, chemical reaction, gas-solid collision, and thermal desorption, and is specifically as follows:

[0085] Atomic adsorption: when an atom acts on a reaction site and meets the adsorption condition (physical or chemical), the atom releases heat to the reaction site, and the movement speed of the atom after adsorption is determined according to the speed randomly generated according to the Maxwell speed distribution at the reaction site temperature, wherein the Maxwell speed is determined by the following equations (2)-(4), wherein u, v, and w are the velocity components of the particle in three directions, k is the Boltzmann constant, m is the mass of the particle, T w is the temperature of the solid surface, and ranf1-ranf5 are five independent random numbers, and the value range of each is [0, 1], and then the total kinetic energy E k is as shown in equation (5). The following models involve determining the particle movement speed (or kinetic energy) from the surface temperature, which are all performed according to this method:

[0086]

[0087]

[0088]

[0089]

[0090] Since the adsorbed atom can only move in two dimensions on the surface of the solid, the degree of freedom is reduced, so the normal velocity u = 0 is set, and thus the actual movement speed of the atom depends only on two-thirds of the translational energy. At this time, according to the total energy conservation, the energy is redistributed on different degrees of freedom by the Larsen-Borgnakke model, and the heat absorbed or released by the solid reaction site is calculated;

[0091] Molecular adsorption: molecules can be physically or chemically adsorbed on the surface. When chemical adsorption occurs, the molecule needs to have enough energy to first break the chemical bond, and the surface needs to have two adjacent adsorption sites for the generated atoms to be adsorbed respectively. The total energy absorbed and released in this process is calculated similarly to the atomic adsorption process;

[0092] Chemical reaction: when two adsorbed atoms on the surface meet, a reaction occurs to generate a molecule and leave the surface (L-H reaction process). This process will absorb energy from the surface, and the size is the difference between the adsorption heat of two atoms and the reaction heat. According to the total energy conservation, the energy of the newly generated molecule is calculated, and the kinetic energy of the newly generated molecule when it leaves the surface is determined according to the surface temperature, and the internal energy is redistributed. When a gas-phase atom meets an adsorbed atom, a reaction may occur to generate a molecule and leave the surface (E-R reaction process). This process will absorb energy from the surface, and the size is the difference between the atomic adsorption heat and the molecular bond energy. The rest is the same as above.

[0093] Gas-solid collision: when a discrete particle interacts with the surface, if the adsorption and reaction conditions are not met, the surface is treated as a boundary for the collision process. The collision model uses a diffuse reflection model, and the velocity of the particle after collision and reflection is determined according to the wall temperature, and then the energy absorbed or released from the wall is determined by the total energy conservation.

[0094] Thermal desorption: when the wall temperature rises, the energy of the adsorbed atom is high enough, greater than the adsorption heat of the atom, and then thermal desorption occurs and the atom leaves the surface. At this time, energy is absorbed from the reaction site, and the size is an adsorption heat.

[0095] Energy transfer: In a time step, the sum of the adsorption / heat release of all sites in each grid is denoted as dQ, and it satisfies dQ = ∑dq i + ∑dq j ; The energy exchanged between particles and grid reaction sites (such as chemical reaction heat absorption / release, collision energy exchange, etc.) can be denoted as dq i ; The energy of grid-to-grid heat conduction and grid heat radiation is denoted as dq j .

[0096] (4) Simulate according to the calculation model of step (3), such as Figure 2As shown, the equation in formula (1) is solved by using a five-center point finite difference method in the simulation calculation, wherein a discrete form of the equation in formula (1) is shown in formula (6) as follows:

[0097]

[0098] In formula (6), T(x, y, t) represents the temperature at different times and different positions, and △x represents the displacement difference in the x direction and the y direction in the five-center point finite difference.

[0099] The specific application is as follows:

[0100] Application 1

[0101] Based on the model and parameters provided in Embodiment 1, the specific incoming gas used in this application is a high-temperature gas containing O and O2 (molar ratio of 1:9), and the solid is simulated under isothermal wall conditions to simulate the loss efficiency of O atoms at different temperatures, and the simulation calculation is performed. The platform and platform configuration used are shown in Table 1.

[0102] Table 1

[0103] Platform Mole-8.5E Central Processing Units (CPUs) Intel Xeon E5-2680 v2 (2.80 GHz, 10 cores) Operating System (OS) CentOS release 6.3 (Final) Kernel: 2.6.32-279.el6 Compiler GCC: 4.4.6, Intel compiler: 14.0.0

[0104] The calculation results of this application are shown in Figure 3 From Figure 3 it can be clearly seen that the loss of O atoms on the SiO2 surface at low temperature is mainly due to the contribution of E-R reaction, and at high temperature, the L-H reaction becomes more and more important as the wall temperature rises.

[0105] To verify the effectiveness of the simulation calculation of the present application, the calculation results of this application are compared with the calculation results of Matthew et al. (Matthew MacLean, "Finite-rate surface chemistry model, I: Formulation and reaction system examples," 42nd AIAA Thermophysics Conference, 2011.). The simulation results of the literature are shown in Figure 4 From Figure 3 and Figure 4 it can be seen that the results of the present application are in good agreement with the existing literature, indicating the effectiveness and accuracy of the present model.

[0106] Application 2

[0107] The application is based on the model and parameters of example 1, and the high-temperature gas adopts 5-component air, that is, contains oxygen molecules (O2), nitrogen molecules (N2), oxygen atoms (O), nitrogen atoms (N) and nitric oxide molecules (NO), the initial temperature of the gas is 5700K, and the initial solid temperature is 250K; the molar ratio of each component of the gas is:

[0108] N:O:N2:O2:NO=0.1051384:0.325525:0.5580423:0.0004246:0.0108697

[0109] The solid surface is a free convection and radiation boundary condition, and the gas-solid reaction process is simulated and calculated.

[0110] Figure 5 The solid surface temperature changes with time is given, from Figure 5 The solid surface temperature change with time can be obtained.

[0111] Figure 6 The coverage of adsorbed atoms on the surface changes with time is given, from Figure 6 It can be seen that with the progress of time, the atoms adsorbed on the solid surface can be quickly adsorbed to the solid surface in a short time, and then with the progress of the reaction, the gas phase produced by the reaction is desorbed from the solid surface, or with the increase of the solid surface temperature, the atoms originally adsorbed on the solid surface are desorbed from the solid surface, causing a significant decrease in the coverage of the subsequent solid surface, but with the reaction reaching equilibrium, the coverage of the solid surface no longer changes.

[0112] Figure 7 The heat flow density of the heat absorption / release in the gas-solid interaction process changes with time is given, from Figure 7 It can be directly seen from the figure that in a certain time period, which specific process causes the heat exchange, and the figure provides basic data for further optimizing the actual reaction process or accurately predicting the reaction.

[0113] It can be seen from the figure that through the simulation of the application, which process contributes most to the energy exchange in different stages, the proportion of adsorbed atoms participating in each process and the surface catalytic coefficient can be analyzed, and a new research model and means for accurately predicting the gas dynamic thermal environment from a microscopic point of view are provided.

[0114] Application 3

[0115] The application adopts the system of application 2 to carry out parallel computing, and evaluates the computing power required by the application. In the application, the single-process computing scale is 70nm*70nm*1um, and the number of particles contained in the single process is about 5000. The size of the X and Y directions is expanded while the size of the Z direction is kept unchanged. The physical time consumed by the system to evolve 100 time steps (1ps) under 160, 200, 240, 280, 320, 360 and 400 CPU cores is tested respectively, and the results are shown in Figure 8 As shown in the figure, the physical time required by the system with 160 CPU cores to evolve 100 time steps (1ps) is only 0.09133 seconds. According to the current parallel efficiency, it is predicted that the time consumed by the simulation scale of 1 million CPU cores to evolve 100 steps is 0.10801 seconds, as shown in Figure 9 The parallel efficiency of the million-core parallel computing is 81.74%, which indicates that the model has good parallelism.

[0116] It can be seen that the interface calculation method provided by the application has very high parallel efficiency and short simulation time, which is much higher than the efficiency of the molecular dynamics method using potential function, although a large number of gas molecules are set in the simulation process.

[0117] In summary, the interface calculation method based on the discrete particle-finite element grid coupling model provided by the application can model and simulate the coupling between various processes including chemical reaction and heat transfer in the gas-solid surface interaction process, and the transfer and conversion process between different forms of energy and matter. The parallel efficiency of 1 million CPU cores can reach more than 81.74%, and the prediction result is accurate and reliable, which greatly shortens the simulation calculation time.

[0118] The applicant declares that the detailed process and model algorithm characteristics of the application are illustrated by the above embodiments, but the application is not limited to the above detailed structure characteristics, that is, it does not mean that the application must rely on the above detailed model and algorithm characteristics to be implemented. Those skilled in the art should understand that any improvement of the application, equivalent replacement of the process model selected by the application, addition of auxiliary model, selection of specific calculation method or calculation model, etc. fall within the protection scope and disclosure scope of the application.

Claims

1. A method for interface calculation based on a discrete particle-finite element mesh coupling model, characterized in that, The interface calculation method includes the following steps: (1) For the interface system, a discrete particle model is established for the gas phase and / or liquid phase on one side of the interface, and a finite element mesh model is established for the solid phase on the other side of the interface. (2) Based on the actual interaction process between the gas phase and / or liquid phase and the solid phase, select any one or at least two combinations of mass transfer, heat transfer or reaction between the interfaces, and select a specific model equation for the interaction process; the specific model equation is a model equation selected based on diffusion, adsorption, desorption, reaction mechanism, reaction conditions and heat transfer process in particle and surface interaction. (3) Based on the transformation process of matter and / or energy between the gas phase and / or liquid phase and the solid phase, establish the correlation between matter and / or energy in the discrete particle model and the finite element mesh model based on the model equations described in step (2), and complete the construction of the computational model; the correlation of energy between the discrete particle model and the finite element mesh model in step (3) includes: the energy change of each mesh in each time step includes a first energy change and a second energy change; the first energy change is the first energy action of the discrete particles on the mesh in the time step; the second energy change is the second energy action of the adjacent mesh on the mesh; the correlation of matter between the discrete particle model and the finite element mesh model in step (3) includes: the matter change of each mesh in each time step includes a first matter change; the first matter change includes adsorption and / or desorption; (4) Perform simulation calculations according to the calculation model described in step (3).

2. The interface calculation method according to claim 1, characterized in that, In step (1), the discrete particles in the discrete particle model include any one or a combination of at least two of the following: point particles, particles with regular geometric structures, or particles with irregular geometric structures.

3. The interface calculation method according to claim 1, characterized in that, The parameters of the discrete particles mentioned in step (1) include any one or at least a combination of two of the following: mass, position, atomic diameter, molecular diameter, translational velocity, thermal velocity, chemical bond energy, dangling bond energy, adsorption heat, rotational energy, vibrational energy, or electronic energy.

4. The interface calculation method according to claim 1, characterized in that, The finite element mesh model mentioned in step (1) includes a two-dimensional surface mesh model or a three-dimensional mesh model.

5. The interface calculation method according to claim 1, characterized in that, The parameters of the finite element mesh model in step (1) include mesh shape, mesh size, material density, material specific heat capacity, material thermal conductivity, material surface emissivity, heat absorbed by the mesh, heat released by the mesh, and material temperature.

6. The interface calculation method according to claim 5, characterized in that, The parameters of the finite element mesh model also include the size and shape of the reaction sites.

7. The interface calculation method according to claim 5, characterized in that, The parameters of the finite element mesh model also include the size and shape of the adsorption sites.

8. The interface calculation method according to any one of claims 1 to 7, characterized in that, The mass transfer in step (2) includes any one or a combination of at least two of diffusion, adsorption or desorption.

9. The interface calculation method according to claim 1, characterized in that, The heat transfer includes any one or a combination of at least two of thermal radiation, thermal conduction, or thermal convection.

10. The interface calculation method according to claim 1, characterized in that, The reaction includes any one or a combination of at least two of the following: gas-phase and / or liquid-phase reaction, gas-solid catalytic reaction, liquid-solid catalytic reaction, or gas-liquid-solid three-phase catalytic reaction.

11. The interface calculation method according to claim 1, characterized in that, The computational model described in step (3) adopts a real spatiotemporal scale or a dimensionless scale.

12. The interface calculation method according to claim 1, characterized in that, The energy includes any one or a combination of at least two of the following: kinetic energy, potential energy, chemical energy, electromagnetic energy, radiant energy, or thermal energy.

13. The interface calculation method according to claim 1, characterized in that, The first energy action includes any one or a combination of at least two of the following: collisional energy exchange, reaction endothermic, reaction exothermic, adsorption heat, desorption heat, or thermal convection.

14. The interface calculation method according to claim 1, characterized in that, The second energy effect includes thermal conduction and / or thermal radiation.

15. The interface calculation method according to claim 1, characterized in that, The first material change also includes the exchange of substances in the reaction.

16. An interface computing device based on a discrete particle-finite element mesh coupling model, characterized in that, The interface computing device can implement the interface computing method based on the discrete particle-finite element mesh coupling model as described in any one of claims 1 to 15.

17. The interface computing device according to claim 16, characterized in that, The interface computing device includes a discrete particle model establishment module, a finite element mesh model establishment module, a model equation selection module, a computational model construction module, and a simulation calculation module. The discrete particle model, finite element mesh model, and model equations obtained by the discrete particle model establishment module, finite element mesh model establishment module, and model equation selection module are used to construct the computational model in the computational model construction module; the simulation computation module uses the computational model for calculation.

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