CFD numerical simulation method for droplet-wall liquid film, electronic device and readable medium

Abstract

The application provides a kind of droplet-wall liquid film CFD numerical simulation method, electronic equipment and readable medium, it is related to computational fluid dynamics technical field.The application is by setting two-way coupling between discrete droplet solver and wall liquid film solver in the initial stage of simulation, gas-liquid mixture or pure gas phase solver is respectively one-way coupled with discrete droplet solver and wall liquid film solver, and gas-liquid mixture or pure gas phase solver is periodically interval operation, after the total liquid phase mass flow of target outlet is greater than or equal to threshold value, then continuously operate gas-liquid mixture or pure gas phase solver, and adjust the one-way coupling relationship between gas-liquid mixture or pure gas phase solver and discrete droplet solver and between gas-liquid mixture or pure gas phase solver and wall liquid film solver to two-way coupling, avoid invalid calculation before flow field is stable in simulation, and reduce complex calculation in numerical simulation simulation process, to greatly improve the calculation efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of computational fluid dynamics, and particularly relates to a CFD numerical simulation method for droplet-wall liquid film, an electronic device and a readable medium. BACKGROUND

[0002] Computational Fluid Dynamics (CFD) is an important tool for studying fluid flow, heat transfer, chemical reactions and other physical phenomena, and is widely used in aerospace, energy power, environmental engineering, nuclear power system design and other fields. CFD simulation software is a tool for simulating and analyzing fluid dynamics, heat transfer, chemical reactions and other physical phenomena. These software solves the control equations of fluid dynamics by numerical methods to analyze flow, heat transfer, mass transfer and other problems.

[0003] Currently, the mainstream CFD simulation method for two-phase three-field can completely describe the physical processes such as droplet collision, breakup, liquid film separation, but the calculation is time-consuming and cannot meet the rapid calculation requirements in industrial scenarios. SUMMARY

[0004] In order to alleviate, reduce or eliminate the above technical problems, the present application provides a CFD numerical simulation method for droplet-wall liquid film, an electronic device and a readable medium, which improves the calculation efficiency.

[0005] In a first aspect, the present application provides a CFD numerical simulation method for droplet-wall liquid film, comprising:

[0006] obtaining a geometric model of a simulation object, the geometric model having an inlet and an outlet;

[0007] establishing a two-phase three-field CFD simulation model for the geometric model and initializing flow field parameters, the two-phase three-field CFD simulation model including a gas-liquid mixture or pure gas phase solver, a discrete droplet solver and a wall liquid film solver;

[0008] starting the gas-liquid mixture or pure gas phase solver, the discrete droplet solver and the wall liquid film solver, setting the discrete droplet solver and the wall liquid film solver to be bidirectional coupling, and the gas-liquid mixture or pure gas phase solver being unidirectional coupling with the discrete droplet solver and the wall liquid film solver, so that the gas-liquid mixture or pure gas phase solver is not affected by the discrete droplet solver and the wall liquid film solver;

[0009] running the gas-liquid mixture or pure gas phase solver according to a preset period interval, and continuously running the discrete droplet solver and the wall liquid film solver; and

[0010] in response to a total liquid mass flow rate of a target outlet being greater than or equal to a threshold value, continuing to run the gas-liquid mixture or pure gas phase solver, and adjusting a one-way coupling relationship between the gas-liquid mixture or pure gas phase solver and the discrete droplet solver and between the gas-liquid mixture or pure gas phase solver and the wall film solver to a two-way coupling, wherein the total liquid mass flow rate of the target outlet is obtained according to an output result of the two-phase three-field CFD simulation model, and the target outlet is an outlet at which the simulation object outputs clean products.

[0011] In a possible implementation, the gas-liquid mixture or pure gas phase solver is configured to calculate movement of a gas-liquid two-phase mixture or pure gas phase; and / or

[0012] the discrete droplet solver is configured to calculate droplet trajectory, droplet collision and droplet breakup; and / or

[0013] the wall film solver is configured to calculate wall film formation, wall film flow and mass exchange.

[0014] In a possible implementation, the gas-liquid mixture or pure gas phase solver includes a VOF solver or a pure gas phase CFD solver; and / or

[0015] the discrete droplet solver includes a DPM solver; and / or

[0016] the wall film solver includes an EWF solver.

[0017] In a possible implementation, the output result includes a droplet mass flow rate, a film mass flow rate and an optional liquid mass flow rate in a gas-liquid mixture at the target outlet.

[0018] In a possible implementation, the establishing a two-phase three-field CFD simulation model for the geometric model and initializing a flow field parameter includes:

[0019] performing meshing on the geometric model; and

[0020] selectively setting each field related model and parameter, and setting a boundary condition of each field.

[0021] In a possible implementation, the simulation object includes a cyclone separator, and the gas-liquid mixture or pure gas phase solver is configured to calculate movement of a gas-liquid two-phase mixture or pure gas phase.

[0022] In a possible implementation, the method further includes:

[0023] obtaining an output result of the two-phase three-field CFD simulation model in the last N simulation seconds of a simulation period, wherein N is an integer greater than or equal to 2; and

[0024] According to an output result of the N simulation seconds, a separation efficiency of the cyclone separator is calculated.

[0025] In a possible implementation manner, a calculation formula of the separation efficiency is as follows:

[0026] ,

[0027] wherein, is the separation efficiency; is a liquid droplet mass flow rate at the inlet; is a liquid droplet mass flow rate at the target outlet; is a liquid film mass flow rate at the target outlet; is a liquid phase mass flow rate in a gas-liquid mixture at the target outlet; t1 is a first simulation second in the N simulation seconds; and t2 is a last simulation second in the N simulation seconds.

[0028] In a second aspect, the present application provides an electronic device, comprising:

[0029] at least one processor; and

[0030] at least one memory having instructions stored thereon, which, when executed by the at least one processor alone or jointly, cause the electronic device to perform the method according to the first aspect.

[0031] In a third aspect, the present application provides a computer readable medium having instructions stored thereon, which, when executed by at least one processor of an electronic device alone or jointly, cause the electronic device to perform the method according to the first aspect.

[0032] In the present application, the discrete liquid droplet solver and the wall surface liquid film solver are bidirectionally coupled in an initial stage of simulation, the gas-liquid mixture or pure gas phase solver is unidirectionally coupled with the discrete liquid droplet solver and the wall surface liquid film solver respectively, and the gas-liquid mixture or pure gas phase solver is periodically and intermittently run. After the total liquid phase mass flow rate at the target outlet is greater than or equal to a threshold value, the gas-liquid mixture or pure gas phase solver is continuously run, and the unidirectional coupling relationship between the gas-liquid mixture or pure gas phase solver and the discrete liquid droplet solver and the wall surface liquid film solver is adjusted to bidirectional coupling. The invalid calculation before the flow field is stable in simulation is avoided, and the complex calculation in the numerical simulation simulation process is reduced, so that the calculation efficiency is greatly improved. BRIEF DESCRIPTION OF DRAWINGS

[0033] The accompanying drawings are included to provide a further understanding of the present application and are incorporated in and constitute apart of this application, illustrate embodiments of the present application and together with the description serve to explain the principles of the present application. In the drawings:

[0034] Figure 1 is a flowchart of a CFD numerical simulation method of droplet-wall liquid film provided by an embodiment of the present application;

[0035] Figure 2 is a model schematic diagram of a cyclone separator provided by an embodiment of the present application;

[0036] Figure 3 is a schematic diagram of running a continuous phase solver according to a preset periodic interval provided by an embodiment of the present application;

[0037] Figure 4 is a flowchart of another CFD numerical simulation method of droplet-wall liquid film provided by an embodiment of the present application;

[0038] Figure 5 is a schematic diagram of total liquid phase mass flow rate of a cyclone separator top outlet varying with time provided by an embodiment of the present application;

[0039] Figure 6 is a separation efficiency calculation result schematic diagram of a cyclone separator provided by an embodiment of the present application;

[0040] Figure 7 is a structural schematic diagram of an electronic device provided by an embodiment of the present application. DETAILED DESCRIPTION

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some examples or embodiments of the present application, and for those skilled in the art, the present application can also be applied to other similar scenarios without creative labor. Unless the context clearly indicates otherwise or otherwise stated, the same reference numbers in the drawings represent the same structure or operation.

[0042] As shown in the present application, unless the context clearly indicates otherwise or otherwise stated, the words "one", "a", "an", and / or "the" do not specifically refer to the singular, but also include the plural. Generally speaking, the terms "comprise" and "include" only indicate the inclusion of the steps and elements explicitly identified, and these steps and elements do not constitute an exclusive list, and the method or device can also include other steps or elements.

[0043] The foregoing is considered as illustrative only of the principles of the application. Other variations and modifications can be made to the embodiments disclosed in this application without departing from the spirit or scope of the application. Therefore, it is to be understood that this application is not to be limited to the particular embodiments disclosed, but is intended to cover any and all uses of the application, including modifications, adaptations, combinations, and guides that have or can become known or obvious from this disclosure. It is therefore requested that the scope of the application be determined not with reference to the above description, but with reference to the appended claims, along with their full scope of equivalents.

[0044] Furthermore, although the terms used in the present application are selected from generally known and used terms, some of the terms mentioned in the description of the present application can be created by the applicant in his or her own judgment. Accordingly, the detailed meaning of the terms can be determined with reference to the description of the present application to be used in conjunction with the accompanying drawings.

[0045] In the description of the present application, it is to be understood that the orientation words such as "front, back, upper, lower, left, right", "horizontal, vertical, perpendicular, horizontal" and "top, bottom" and the like indicated orientation or positional relationship are generally based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, without the opposite description, these orientation words do not indicate and imply that the indicated device or element must have a particular orientation or be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the scope of protection of the present application; the orientation words "inner, outer" refer to the inner and outer of the contour of each component itself.

[0046] For the convenience of description, spatial relative terms such as "over", "above", "upper surface", "upper" and the like can be used herein to describe the spatial positional relationship of one device or feature with other devices or features as shown in the drawings. It should be understood that the spatial relative terms are intended to include different orientations in use or operation in addition to the orientation of the device described in the drawings. For example, if the device in the drawing is inverted, the device described as "above" or "over" other devices or structures will be positioned "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below" orientations. The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein are interpreted accordingly.

[0047] It will be understood that when a component is referred to as being "on" or "connected to" or "coupled with" or "contacting" another component, it can be directly on, connected to, coupled with, or contacting the other component, or one or more intervening components can also be present. In contrast, when a component is referred to as being "directly on", "directly connected to", "directly coupled with", or "directly contacting" another component, there are no intervening components present. Similarly, when a first component is referred to as being "electrically in contact with" or "electrically coupled to" a second component, there is an electrical path between the first component and the second component that allows current to flow. The electrical path can include capacitors, coupled inductors, and / or other components that allow current to flow, even if there is no direct contact between electrically conductive components.

[0048] Flowcharts have been used herein to illustrate the operations performed by apparatuses or devices in accordance with embodiments of the present application. It will be understood that the operations previously or hereafter are not necessarily performed in the order shown. Instead, these steps can be processed in reverse order, or at the same time. Also, other operations can be added to, or removed from, these processes, or one or more steps can be removed from these processes.

[0049] CFD simulation of two-phase three-field flow of a simulation object using CFD simulation software can help engineers and researchers predict fluid behavior, optimize design, and solve problems. Here, "two-phase" refers to the gas and liquid phases, and "three-field" refers to the three flow fields of gas-liquid mixture or pure gas phase flow, droplet flow, and liquid film flow. Exemplarily, two-phase three-field includes "gas-liquid two-phase flow-discrete droplets-wall liquid film" or "pure gas phase single-phase flow-discrete droplets-wall liquid film" scenarios. However, the mainstream CFD simulation method for two-phase three-field flow can completely describe physical processes such as droplet collision, breakup, and liquid film separation, but the calculation is time-consuming and cannot meet the rapid calculation requirements in industrial scenarios.

[0050] Exemplarily, in refrigeration, heat pump, and other industrial systems, the refrigerant vapor-lubricating oil cyclone separator (RVOCS) is widely used due to its excellent separation efficiency, low operating cost, and moderate pressure loss. To vigorously strengthen and promote the design and operation of RVOCS, CFD simulation of the "gas-liquid mixture / pure gas phase-discrete droplets-wall thin liquid film" two-phase three-field flow in the separator is needed to accurately predict the droplet, liquid film distribution, and key performance parameters such as the top outlet liquid flow rate and liquid phase separation rate, in order to balance the separation efficiency, volume, and pressure drop of the separator. At the same time, numerical simulation is used to analyze the source and formation of the top outlet liquid, providing a basis for optimizing the structure of the separator.

[0051] Currently, the mainstream CFD simulation method for the "gas-liquid two-phase flow-discrete droplets-wall thin liquid film" three-field flow in the cyclone separator is the full-coupling simulation of the Volume of Fluid (VOF)-Discrete Phase Model (DPM)-Eulerian Wall Film Model (EWM). Although this full-coupling simulation method can more completely describe the physical processes such as droplet collision, breakage, and liquid film stripping, it still has significant technical challenges and deficiencies. For example, the gas phase flow rate in the cyclone separator can reach 20 m / s, and in order to ensure simulation accuracy, a very small calculation time step needs to be used to capture the dynamic changes in the flow field. In this process, the full-coupling simulation needs to solve the high computational cost Navier-Stokes equation (abbreviated as NS equation), the droplet Lagrangian trajectory equation, and the liquid film mass-momentum conservation equation in real time, and the momentum and mass exchange between the three need to be iteratively coupled. Therefore, the full-coupling simulation for a single working condition needs to continue for several weeks to reach a steady state, which is time-consuming and cannot meet the rapid calculation requirements in industrial scenarios. In addition, for the "pure gas single-phase flow-discrete droplets-wall liquid film" scene, the Navier-Stokes equation is usually used for CFD single-phase flow calculation, which also has the above problems.

[0052] The embodiment of the present application proposes a CFD numerical simulation method for droplet-wall liquid film. The method sets a bidirectional coupling between the discrete droplet solver and the wall liquid film solver in the initial stage of simulation, a one-way coupling between the gas-liquid mixture or pure gas phase solver and the discrete droplet solver and the wall liquid film solver, and periodically interval operation of the gas-liquid mixture or pure gas phase solver. After the total liquid mass flow rate at the target outlet is greater than or equal to a threshold value, the one-way coupling between the gas-liquid mixture or pure gas phase solver and the discrete droplet solver and the wall liquid film solver is adjusted to bidirectional coupling. The method avoids invalid calculation before the flow field stabilizes in the simulation, reduces complex calculation in the numerical simulation process, and greatly improves the calculation efficiency.

[0053] Please refer to Figure 1 , Figure 1 A flow chart of a CFD numerical simulation method 100 for droplet-wall liquid film according to an exemplary embodiment of the present application is shown. It should be understood that the CFD numerical simulation method 100 can include additional steps not shown and / or some of the shown steps can be omitted, and the scope of the present application is not limited in this regard.

[0054] In step S110, a geometric model of a simulation object is obtained, which has an inlet and an outlet.

[0055] The simulation object can be any device requiring two-phase three-field flow CFD simulation. In one example, the simulation object includes a cyclone separator. An example of a cyclone separator's geometric model is shown below. Figure 2 As shown, the cyclone separator 200 has an inlet 201 and two outlets, namely a top outlet 202 and a bottom outlet 203. The bottom outlet 203 is the outlet of the bottom oil sump 210. The top outlet 202 is the outlet of the cyclone separator 200 that outputs the clean product, i.e., the outlet of the "clean" gas after the oil has been separated. It should be understood that in some other embodiments, the number and location of the inlets and outlets of the simulated object's geometry may be different from those of the other embodiments. Figure 2 The embodiments shown may differ, such as including only one outlet, or the outlet not being located at the top.

[0056] In step S120, a two-phase three-field CFD simulation model for the geometric model is established and the flow field parameters are initialized. The two-phase three-field CFD simulation model includes a gas-liquid mixture or pure gas phase solver, a discrete droplet solver, and a wall liquid film solver.

[0057] This application does not limit the method for establishing the two-phase three-field CFD model; the two-phase three-field CFD model can be established using existing methods. For example, establishing a two-phase three-field CFD simulation model for a geometric model and initializing the flow field parameters includes meshing the geometric model, selecting and setting relevant models and parameters for each field, and setting boundary conditions for each field.

[0058] In some embodiments, a gas-liquid mixture or pure gas phase solver is used to calculate the motion of a gas-liquid two-phase mixture or a pure gas phase. A discrete droplet solver is used to calculate droplet trajectories, droplet collisions, and droplet breakup. A wall liquid film solver is used to calculate wall liquid film formation, wall liquid film flow, and mass exchange. Specifically, when the two-phase three-field flow is "gas-liquid two-phase mixture - discrete droplet - wall liquid film", the gas-liquid mixture solver is used to calculate the motion of the gas-liquid two-phase mixture. When the two-phase three-field flow is "pure gas phase single-phase flow - discrete droplet - wall liquid film", the pure gas phase solver is used to calculate the motion of the pure gas phase.

[0059] In one example, the gas-liquid mixture or pure gas phase solver includes a VOF solver or a pure gas phase CFD solver, i.e., the VOF solver is used to calculate the motion condition of the gas-liquid two-phase mixture, and the pure gas phase CFD solver is used to calculate the motion condition of the pure gas phase. The discrete droplet solver includes a DPM solver, i.e., the DPM solver is used to calculate the droplet trajectory, droplet collision and droplet breakup. The wall film solver includes an EWF solver, i.e., the EWF solver is used to calculate the wall film formation, wall film flow and mass exchange.

[0060] At step S130, the gas-liquid mixture or pure gas phase solver, the discrete droplet solver and the wall film solver are started, the discrete droplet solver and the wall film solver are set to be bidirectionally coupled, and the gas-liquid mixture or pure gas phase solver is unidirectionally coupled to the discrete droplet solver and the wall film solver, respectively, so that the gas-liquid mixture or pure gas phase solver is not affected by the discrete droplet solver and the wall film solver.

[0061] At step S140, the gas-liquid mixture or pure gas phase solver is run according to a preset periodic interval, and the discrete droplet solver and the wall film solver are continuously run.

[0062] The preset period can be set according to actual needs. Figure 3 A schematic diagram of the gas-liquid mixture or pure gas phase solver running according to the preset periodic interval is shown. In the Figure 3 In the embodiment shown, the gas-liquid mixture or pure gas phase solver is run when n = 1, and the gas-liquid mixture or pure gas phase solver is frozen when n = 0. Exemplarily, in one period, the ratio of the running time of the gas-liquid mixture or pure gas phase solver to the freezing time is 1:10.

[0063] At step S150, in response to the total liquid phase mass flow rate of the target outlet being greater than or equal to a threshold value, the gas-liquid mixture or pure gas phase solver is continuously run, and the unidirectional coupling relationship between the gas-liquid mixture or pure gas phase solver and the discrete droplet solver and the unidirectional coupling relationship between the gas-liquid mixture or pure gas phase solver and the wall film solver are adjusted to bidirectional coupling. The total liquid phase mass flow rate of the target outlet is obtained according to the output result of the two-phase three-field CFD simulation model. The target outlet is the outlet of the simulation object outputting the clean product.

[0064] The output results of the two-phase three-field CFD simulation model include the liquid droplet mass flow rate, the liquid film mass flow rate, and the liquid phase mass flow rate in the optional gas-liquid mixture at the target outlet. When the two-phase three-field flow is "gas-liquid two-phase flow-discrete liquid droplet-wall surface liquid film", the output results include the liquid droplet mass flow rate, the liquid film mass flow rate, and the liquid phase mass flow rate in the gas-liquid mixture at the target outlet, and the total liquid phase mass flow rate at the target outlet is equal to the sum of the liquid droplet mass flow rate, the liquid film mass flow rate, and the liquid phase mass flow rate in the gas-liquid mixture at the target outlet. When the two-phase three-field flow is "pure gas phase single-phase flow-discrete liquid droplet-wall surface liquid film", the output results only include the liquid droplet mass flow rate and the liquid film mass flow rate at the target outlet, and the total liquid phase mass flow rate at the target outlet is equal to the sum of the liquid droplet mass flow rate and the liquid film mass flow rate at the target outlet.

[0065] The following is further described with the gas-liquid mixture or pure gas phase solver, the discrete liquid droplet solver, and the wall surface liquid film solver respectively including the VOF solver, the DPM solver, and the EWF solver as examples. In this exemplary embodiment, the phase volume fraction transport equation in the VOF solver is used to track the volume fraction distribution of the first q phase in the calculation domain to identify the gas-liquid interface position. The mixture continuity equation is used to describe the mass conservation relationship of the gas-liquid mixture as a whole, and the two-phase mass change is reflected by the volume fraction weighting. The mixture momentum equation is used to describe the momentum change law of the gas-liquid mixture, including the effects of pressure, viscous force, gravity, and surface tension.

[0066] An example of the expression of the phase volume fraction transport equation is as follows:

[0067] .

[0068] wherein, α q is the volume fraction (0≤α q ≤1) of the first q phase; t is time; is the mixture flow velocity vector.

[0069] An example of the expression of the mixture continuity equation is as follows:

[0070] .

[0071] wherein, p is the mixture phase density.

[0072] An example of the expression of the mixture momentum equation is as follows:

[0073] .

[0074] wherein, p is pressure;p is the dynamic viscosity of the mixed phase; F surface is the surface tension; is the volume force.

[0075] The discrete droplet position equation in the DPM solver is used to track the trajectory of the discrete droplet in the flow field. The discrete droplet momentum equation is used to calculate the rate of change of the droplet velocity, which is the core equation of the Lagrangian method for tracking droplets.

[0076] An example of the expression of the discrete droplet position equation is as follows:

[0077] .

[0078] wherein, is the spatial position vector of the i-th droplet; i is the velocity vector of the i-th droplet. i An example of the expression of the discrete droplet momentum equation is as follows:

[0079]

[0080] .

[0081] wherein, is the mass of the i-th droplet; i is the interaction force between the liquids; is the drag force; is the turbulent diffusion force; g is the fluid density; p l is the droplet density. p

[0082] An example of the calculation formula of the drag force is as follows:

[0083] .

[0084] wherein, C d is the drag coefficient; is the diameter of the i-th droplet; is the fluid velocity vector.

[0085] The calculation formula of the drag force is used to calculate the size of the drag force of the fluid on the droplet, reflecting the influence of the relative motion of gas-liquid on the force of the droplet.

[0086] An example of the Schiller-Naumann drag force model is as follows:

[0087] .

[0088] wherein,​​​Re p is the liquid droplet Reynolds number.

[0089] The Schiller-Naumann drag model is used to accurately quantify the drag force in different flow regimes, improving the accuracy of droplet force calculation.

[0090] The thin liquid film mass conservation equation in the EWF solver is used to describe the mass conservation relationship of the wall liquid film, considering the mass increase caused by droplet impact and the mass loss caused by splashing, ensuring the mass conservation of the liquid film. The thin liquid film momentum conservation equation is used to calculate the momentum change of the liquid film, describing the flow behavior of the liquid film along the wall.

[0091] An example of the expression of the thin liquid film mass conservation equation is as follows:

[0092] .

[0093] wherein, h l is the liquid film thickness; is the liquid film average velocity vector; is the mass flux of the i th impacting droplet to the liquid film; is the mass flux of the i th droplet splashing out of the liquid film; is the mass flux of the i th droplet shearing off from the liquid film; is the surface gradient operator.

[0094] An example of the expression of the thin liquid film momentum conservation equation is as follows:

[0095] .

[0096] wherein, P L is the liquid film pressure; is the viscous shear force on the interface; p l is the droplet phase dynamic viscosity; is the tangential momentum source caused by droplet impact; is the tangential momentum source caused by droplet splashing; is the contact angle force; is the gravitational acceleration vector.

[0097] An example of the calculation formula of the liquid film pressure is as follows:

[0098] .

[0099] wherein, is the wall normal vector; It is the surface tension coefficient; p imp Impact pressure; p spl This refers to the splash pressure.

[0100] The formula for calculating liquid film pressure is used to calculate the total pressure on the liquid film and is a key input parameter of the liquid film momentum equation.

[0101] Examples of formulas for calculating the impact pressure and splash pressure of a droplet are shown below:

[0102] , .

[0103] in, For the first i The velocity vector of each impacting droplet; For the first i The velocity vector of the splashing droplets.

[0104] The formulas for calculating the impact pressure and splash pressure of droplets are used to quantify the normal pressure exerted on the liquid film by droplet impact and splash, which affects the morphology and flow of the liquid film.

[0105] Examples of calculation formulas for the tangential momentum sources caused by droplet impact and droplet splash are shown below:

[0106] , .

[0107] in, This is the tangent vector of the wall.

[0108] The formula for calculating the tangential momentum source caused by droplet impact and splash is used to calculate the tangential momentum input generated by droplet impact and splash on the liquid film, which affects the flow velocity and direction of the liquid film along the wall.

[0109] Please refer to Figure 4 , Figure 4 A flowchart of a CFD numerical simulation method 400 for droplet-wall liquid film is shown. The CFD numerical simulation method 400 includes the following steps.

[0110] In step S410, during the initial stage of the simulation, the DPM solver and EWF solver are set to bidirectional coupling, while the VOF solver is unidirectionally coupled to both the DPM and EWF solvers, and runs periodically. The total liquid mass flow rate at the target outlet is monitored in real time. When the total liquid mass flow rate at the target outlet is greater than or equal to a threshold, the simulation enters a fully coupled phase to ensure subsequent simulation accuracy. Otherwise, the simulation time (time) is increased by the time step (dt), and the previous calculation continues.

[0111] At step S420, in the full coupling stage, the VOF solver is continuously run, and the one-way coupling relationship between the VOF solver and the DPM solver and the VOF solver and the EWF solver is adjusted to bidirectional coupling, and the mass and momentum exchange among the three fields is solved in real time. Until the simulation time time is greater than the total length T_period of the pre-set simulation period.

[0112] The method provided in the embodiments of the present application has a deviation of less than 3% from the existing full coupling simulation result, and is consistent with the droplet size distribution and the outlet liquid mass flow trend measured by experiments, and the precision meets the engineering design requirements.

[0113] In one example embodiment, for Figure 2 As shown in the cyclone separator 200, the output results of the two-phase three-field CFD simulation model include the liquid droplet mass flow at the target outlet (i.e., the top outlet 202), the liquid film mass flow, and the liquid phase mass flow in the gas-liquid mixture. The total liquid phase mass flow at the top outlet 202 of the cyclone separator 200 is equal to the sum of the liquid droplet mass flow, the liquid film mass flow, and the liquid phase mass flow in the gas-liquid mixture at the top outlet 202. Figure 5 A schematic diagram showing the change of the total liquid phase mass flow at the top outlet 202 over time is shown. From Figure 5 It can be seen that before 18s, the total liquid phase mass flow at the top outlet 202 is low, almost 0, at this time the internal flow field of the model has not been fully formed, the VOF solver is in a periodic freezing (i.e., periodic interval running) state, and the coupling relationship between the VOF solver and the DPM solver and the EWF solver is one-way coupling. When it is monitored that the total liquid phase mass flow at the top outlet 202 is greater than or equal to a threshold value, the VOF solver ends the periodic freezing and continuously runs, and the coupling relationship between the VOF solver and the DPM solver and the EWF solver is adjusted to bidirectional coupling.

[0114] According to the output results described above, the separation efficiency of the cyclone separator 200 can be calculated. For example, the output results of the two-phase three-field CFD simulation model at the last N simulation seconds of the simulation period are obtained, where N is an integer greater than or equal to 2, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, etc. Then the separation efficiency of the cyclone separator is calculated according to the output results of the N simulation seconds. For example, the calculation formula of the separation efficiency is as follows:

[0115] ,

[0116] wherein, is the separation efficiency; is the liquid droplet mass flow at the inlet; is the liquid droplet mass flow at the target outlet; liquid film mass flow rate at the target outlet; liquid phase mass flow rate in the gas-liquid mixture at the target outlet; t 1 1st simulated second among the N simulated seconds; t 2 last simulated second among the N simulated seconds.

[0117] Figure 6 The separation efficiency calculation results of the cyclone separator provided by the embodiments of the present application are shown. The horizontal dashed line in the figure represents the average value of the separation efficiency of the last 3s of simulation, which is used to evaluate the separation performance of the cyclone separator. From the figure, it can be seen that the calculated separation efficiency presents a fluctuating trend and tends to be relatively stable over time. Figure 6 It can be seen that the calculated separation efficiency presents a fluctuating trend and tends to be relatively stable over time.

[0118] An embodiment of the present application also provides an electronic device 700 as shown in the figure. According to the embodiment, the electronic device 700 can include an internal communication bus 701, a processor 702, a read-only memory (ROM) 703, a random access memory (RAM) 704, and a communication port 705. When applied to a personal computer, the electronic device 700 can also include a hard disk 706. Figure 7 Figure 7 The internal communication bus 701 can realize data communication between the components of the electronic device 700. The processor 702 can make judgments and issue prompts. In some embodiments, the processor 702 can be composed of one or more processors. The communication port 705 can realize data communication between the electronic device 700 and the outside. In some embodiments, the electronic device 700 can send and receive information and data from the network through the communication port 705.

[0119] The electronic device 700 can also include different forms of program storage units and data storage units, such as the hard disk 706, the read-only memory (ROM) 703 and the random access memory (RAM) 704, which can store various data files used by the computer processing and / or communication, and possible program instructions executed by the processor 702. The processor 702 executes these instructions to make the electronic device 700 perform the CFD numerical simulation method 100 or the CFD numerical simulation method 400. The results processed by the processor 702 are transmitted to the user device through the communication port 705 and displayed on the user interface.

[0120] The electronic device 700 can also include different forms of program storage units and data storage units, such as the hard disk 706, the read-only memory (ROM) 703 and the random access memory (RAM) 704, which can store various data files used by the computer processing and / or communication, and possible program instructions executed by the processor 702. The processor 702 executes these instructions to make the electronic device 700 perform the CFD numerical simulation method 100 or the CFD numerical simulation method 400. The results processed by the processor 702 are transmitted to the user device through the communication port 705 and displayed on the user interface.

[0121] ​In addition, another aspect of the present application provides a computer readable medium storing computer program instructions, which, when executed by at least one processor of an electronic device, alone or in combination, cause the electronic device to perform the CFD numerical simulation method 100 or the CFD numerical simulation method 400.

[0122] Aspects of the present application can be implemented in, completely, by hardware, completely, by software (including firmware, resident software, micro-code, etc.), or by combinations of hardware and software. The above hardware or software can be referred to as a "data block", "module", "engine", "unit", "component", or "system". The processor can be one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DAPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, or combinations thereof. In addition, aspects of the present application can be implemented as a computer product located in one or more computer readable media, which includes computer readable program code. For example, the computer readable medium can include, but is not limited to, magnetic storage devices (e.g., hard disk, floppy disk, magnetic tape...), optical disks (e.g., compact disk CD, digital versatile disk DVD...), smart cards, and flash memory devices (e.g., card, stick, key drive...).

[0123] The computer readable medium can contain a propagated data signal with computer program code embodied therein, for example, in baseband or as part of a carrier wave. Such propagated signal can take a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. The computer readable medium can be any computer readable medium except for a transitory, propagating signal per se. The program code can be propagated by any suitable medium, including, but not limited to, wireless, wire line, optical fiber cable, RF, or similar medium, or any suitable combination of the foregoing.

[0124] The foregoing description has been set forth in terms of particular embodiments and is meant to be illustrative only, as the application disclosed above can be modified, improved, and supplemented by those skilled in the art. Accordingly, various modifications, improvements and additions can be made thereto without departing from the spirit and scope of the application as set forth in the following claims.

[0125] Furthermore, this application uses specific terms to describe embodiments of the application. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic related to at least one embodiment of the application. Therefore, it should be emphasized and noted that "an embodiment," "one embodiment," or "an alternative embodiment" mentioned twice or more in different locations in this specification do not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of the application can be appropriately combined.

[0126] Similarly, it should be noted that, in order to simplify the description of the present application and thus aid in the understanding of one or more embodiments of the invention, the foregoing description of the embodiments of the present application sometimes combines multiple features into a single embodiment, drawing, or description thereof. However, this disclosure method does not imply that the subject matter of the present application requires more features than those mentioned. In fact, the embodiments have fewer features than all the features of the single embodiments disclosed above.

[0127] Although this application has been described with reference to specific embodiments, those skilled in the art should recognize that the above embodiments are only used to illustrate this application, and various equivalent changes or substitutions can be made without departing from the spirit of this application. Therefore, any changes or modifications to the above embodiments within the scope of the essential spirit of this application will fall within the scope of this application.

Claims

1. A CFD numerical simulation method of a droplet-wall liquid film, characterized by, The method comprises: obtaining a geometric model of a simulation object, the geometric model having an inlet and an outlet; establishing a two-phase three-field CFD simulation model for the geometric model and initializing flow field parameters, the two-phase three-field CFD simulation model comprising a gas-liquid mixture or pure gas phase solver, a discrete droplet solver and a wall film solver; starting the gas-liquid mixture or pure gas phase solver, the discrete droplet solver and the wall film solver, setting the discrete droplet solver and the wall film solver to be bidirectionally coupled, and the gas-liquid mixture or pure gas phase solver to be unidirectionally coupled to the discrete droplet solver and the wall film solver respectively, so that the gas-liquid mixture or pure gas phase solver is not affected by the discrete droplet solver and the wall film solver; running the gas-liquid mixture or pure gas phase solver at a preset period interval, and continuously running the discrete droplet solver and the wall film solver; and in response to a total liquid phase mass flow rate of a target outlet being greater than or equal to a threshold value, continuously running the gas-liquid mixture or pure gas phase solver, and adjusting the unidirectional coupling between the gas-liquid mixture or pure gas phase solver and the discrete droplet solver and the wall film solver to bidirectional coupling, wherein the total liquid phase mass flow rate of the target outlet is obtained according to an output result of the two-phase three-field CFD simulation model, and the target outlet is an outlet through which the simulation object outputs clean products.

2. The method of claim 1, wherein, the gas-liquid mixture or pure gas phase solver is configured to calculate movement of a gas-liquid two-phase mixture or pure gas phase; and / or the discrete droplet solver is configured to calculate droplet trajectory, droplet collision and droplet breakup; and / or the wall film solver is configured to calculate wall film formation, wall film flow and mass exchange.

3. The method of claim 1, wherein, the gas-liquid mixture or pure gas phase solver comprises a VOF solver or a pure gas phase CFD solver; and / or the discrete droplet solver comprises a DPM solver; and / or the wall film solver comprises an EWF solver.

4. The method of claim 1, wherein, the output result comprises droplet mass flow rate, film mass flow rate and optionally liquid phase mass flow rate in a gas-liquid mixture at the target outlet.

5. The method of claim 1, wherein, the establishing a two-phase three-field CFD simulation model for the geometric model and initializing flow field parameters comprises: meshing the geometric model; and selectively setting each field related model and parameter, and setting each field boundary condition.

6. The method of any one of claims 1-5, wherein, the simulation object comprises a cyclone separator, and the gas-liquid mixture or pure gas phase solver is configured to calculate movement of a gas-liquid two-phase mixture or pure gas phase.

7. The method of claim 6, wherein, The method further comprises: obtaining an output result of the two-phase three-field CFD simulation model at the last N simulation seconds of a simulation period, wherein N is an integer greater than or equal to 2; and calculating separation efficiency of the cyclone separator according to the output result of the N simulation seconds. the calculation formula of the separation efficiency is:

8. The method of claim 7, wherein, The method comprises: ， wherein, is the separation efficiency; is the droplet mass flow rate at the inlet; is the droplet mass flow rate at the target outlet; is the liquid film mass flow rate at the target outlet; is the liquid phase mass flow rate in the gas-liquid mixture at the target outlet; t1 is the 1st simulated second of the N simulated seconds; t2 is the last simulated second of the N simulated seconds.

9. An electronic device, comprising: at least one processor; and ​ ​ at least one memory having instructions stored thereon, the instructions, when executed by the at least one processor alone or in combination, causing the electronic device to perform the method of any one of claims 1-8.

10. A computer readable medium characterized by The computer readable medium has instructions stored thereon, the instructions, when executed by at least one processor of an electronic device alone or in combination, causing the electronic device to perform the method of any one of claims 1-8.

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