Multiphase mixed fluid flow numerical simulation method, device, medium and equipment

Abstract

The invention discloses a multiphase mixed fluid flow numerical simulation method and device, a medium and equipment, and the method comprises the steps: building a lattice Boltzmann color model, and simulating multiphase fluid flow; establishing a non-Newtonian fluid constitutive equation and a surfactant convection diffusion equation; and coupling the lattice Boltzmann color model with the non-Newtonian fluid constitutive equation through fluid apparent viscosity, and coupling the lattice Boltzmann color model with the surfactant convection diffusion equation through interfacial tension to complete a numerical simulation process. According to the method, the lattice Boltzmann color model, the non-Newtonian fluid constitutive equation and the surfactant convection diffusion equation are coupled, so that the method can be conveniently expanded to solving of more kinds of non-Newtonian-Newtonian multiphase mixed fluid flow problems, and the reliability and applicability of multiphase mixed fluid flow numerical simulation are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fluid flow numerical simulation, and particularly relates to a multiphase mixed fluid flow numerical simulation method, device, medium and equipment. BACKGROUND

[0002] The fluid containing surfactants generally exhibits complex non-Newtonian rheological behavior, including shear thinning, shear thickening, yield stress and viscoelasticity, and how to effectively quantify them has always been the focus of research. Today, the rheological properties of non-Newtonian fluids are mainly measured by a rotary viscometer, and the consistency coefficient, rheological index and other rheological parameters are obtained by regression analysis. Although the experimental method can obtain the related characteristics of non-Newtonian fluids containing surfactants, the analysis process is complicated, and the changes of the surfactant migration at the phase interface and the velocity field cannot be accurately observed due to the limitation of observation means, so the understanding of the mechanism is still not thorough. As a supplement to the experimental method, the numerical simulation method has achieved preliminary success in the study of multiphase flow problems containing surfactants, but the existing numerical simulation method still has some shortcomings: the complex interface reconstruction is difficult to handle the complex topological deformation of the interface; the interface has large numerical dissipation, resulting in poor calculation accuracy and stability; and the interface grid encryption greatly increases the calculation amount. Since the problem of multiphase flow containing surfactants involves complex multi-field (concentration field, velocity field and phase field) coupling, it is of great theoretical significance and practical value to develop a numerical simulation method for the flow of multiphase fluid containing surfactants.

[0003] The existing numerical calculation method for multiphase flow, such as the interface tracking method (immersed boundary method, forward tracking method and boundary integral method), involves complex operations such as adding and deleting marker points, and is not suitable for simulating two-phase flow containing interface topological changes; the interface capturing method (horizontal set method, fluid volume method and phase field method) involves complex interface reconstruction and strong mass conservation constraints, resulting in non-smooth interface and low calculation efficiency, as well as artificially increasing the interface thickness and non-physical dissolution of droplets. In the prior art, Chinese patent CN119442741A discloses a numerical simulation method for multiphase and multi-component seepage flow based on a discrete fracture model; step 1, a mathematical model for multiphase and multi-component seepage flow is established and solved; step 2, the fracture model grid is discretized; step 3, the mass conservation equation is discretized; step 4, the conductivity between the matrix and the fracture is calculated; and step 5, a nonlinear equation set is established, and the solution is completed by using automatic differentiation technology and Newton iteration method.

[0004] In summary, the existing fluid flow numerical simulation technology cannot solve the flow problems of many types of non-Newtonian-Newtonian multiphase mixed fluids, and the reliability and applicability of the numerical simulation of multiphase mixed fluid flow are poor. SUMMARY

[0005] The application provides a multiphase mixed fluid flow numerical simulation method, device, medium and equipment, to solve the problem that the existing fluid flow numerical simulation technology is difficult to solve the problem of non-Newtonian-Newtonian multiphase mixed fluid flow of more types, and the reliability and applicability of the multiphase mixed fluid flow numerical simulation are poor.

[0006] To achieve the above object, the application provides a multiphase mixed fluid flow numerical simulation method, comprising the following steps:

[0007] Step S1, establish a lattice Boltzmann color model to simulate multiphase fluid flow.

[0008] Step S2, establish a non-Newtonian fluid constitutive equation and a surfactant convection-diffusion equation; the non-Newtonian fluid constitutive equation is used to obtain the relationship between fluid apparent viscosity and shear rate, and the surfactant convection-diffusion equation is used to describe the migration of surfactant at the interface of multiphase fluid.

[0009] Step S3, coupling the lattice Boltzmann color model and the non-Newtonian fluid constitutive equation through fluid apparent viscosity, coupling the lattice Boltzmann color model and the surfactant convection-diffusion equation through interfacial tension, and completing the numerical simulation process.

[0010] In a possible implementation, step S1 comprises:

[0011] Step S11, define the initial values of each physical quantity of the lattice Boltzmann color model, and divide the grid region.

[0012] Step S12, calculate the equilibrium distribution function of the lattice Boltzmann color model.

[0013] Step S13, based on the equilibrium distribution function, execute the collision process of different fluid particles.

[0014] Step S14, after executing the collision process, execute the recoloring process of different fluid particles.

[0015] Step S15, after executing the recoloring process, execute the migration process of different fluid particles.

[0016] In a possible implementation, in step S2, the use process of the non-Newtonian fluid constitutive equation comprises:

[0017] Step S211, establish a non-Newtonian fluid constitutive equation, and calculate the strain rate tensor and shear rate.

[0018] Step S212, calculate the apparent viscosity of the non-Newtonian fluid.

[0019] In a possible implementation, in step S2, the non-Newtonian fluid constitutive equation comprises: a power-law fluid constitutive equation, a Bingham fluid constitutive equation, or a Herschel-Bulkley fluid constitutive equation.

[0020] In a possible implementation, in step S2, the process of using the surfactant convection-diffusion equation comprises:

[0021] In step S221, a surfactant convection-diffusion equation is established, and an interface function is introduced.

[0022] In step S222, the surfactant convection-diffusion equation is time-discretized by using a semi-implicit Crank-Nicholson finite difference format, and is space-discretized by using a central difference format.

[0023] In a possible implementation, in step S3, the coupling of the lattice Boltzmann color model and the non-Newtonian fluid constitutive equation through fluid apparent viscosity comprises:

[0024] In step S31, the relaxation time in the lattice Boltzmann color model is updated according to the non-Newtonian fluid apparent viscosity calculated by the non-Newtonian fluid constitutive equation.

[0025] In a possible implementation, in step S3, the coupling of the lattice Boltzmann color model and the surfactant convection-diffusion equation through the interfacial tension comprises:

[0026] In step S32, the surfactant concentration calculated by the surfactant convection-diffusion equation and the interfacial tension in the lattice Boltzmann color model are coupled through a Langmuir state equation, and the interfacial tension is a non-Newtonian fluid interfacial tension.

[0027] In addition, to achieve the above object, the embodiment of the present application further provides a device for numerical simulation of multiphase mixed fluid flow, which comprises:

[0028] A multiphase fluid flow simulation module is configured to establish a lattice Boltzmann color model and simulate the multiphase fluid flow.

[0029] An equation establishment module is configured to establish a non-Newtonian fluid constitutive equation and a surfactant convection-diffusion equation; the non-Newtonian fluid constitutive equation is used to obtain the relationship between fluid apparent viscosity and shear rate, and the surfactant convection-diffusion equation is used to describe the migration of surfactant at the interface of the multiphase fluid.

[0030] The coupling module is used for coupling the lattice Boltzmann color model with the non-Newtonian fluid constitutive equation through fluid apparent viscosity, coupling the lattice Boltzmann color model with the surfactant convection-diffusion equation through interfacial tension, and completing a numerical simulation process.

[0031] In addition, to achieve the above object, the embodiment of the present application further provides a computer readable storage medium comprising instructions which, when executed on a computer, cause the computer to perform the multiphase mixed fluid flow numerical simulation method described in any embodiment of the present application.

[0032] In addition, to achieve the above object, the embodiment of the present application further provides a computing device, comprising: at least one processor, a memory and an input output unit; wherein the memory is used to store a computer program, and the processor is used to call the computer program stored in the memory to execute the multiphase mixed fluid flow numerical simulation method described in any embodiment of the present application.

[0033] The multiphase mixed fluid flow numerical simulation method in the present application has the following advantages:

[0034] By coupling the lattice Boltzmann color model, the non-Newtonian fluid constitutive equation and the surfactant convection-diffusion equation, the method can be easily extended to more types of non-Newtonian-Newtonian multiphase mixed fluid flow problem solving, and the reliability and applicability of the multiphase mixed fluid flow numerical simulation are improved.

[0035] By introducing a multi-relaxation time collision operator in the collision process, the stability of the collision process is improved, and the stability of the numerical simulation is improved.

[0036] The establishment of the surfactant convection-diffusion equation and the introduction of the interface function can be applied to the migration of surfactants with strong interface deformation.

[0037] The use of the semi-implicit Crank-Nicholson finite difference format for time discretization of the surfactant convection-diffusion equation and the use of the central difference format for spatial discretization of the surfactant convection-diffusion equation improve the solution accuracy of the surfactant convection-diffusion equation. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiment or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0039] Figure 1 Flowchart of the method for numerical simulation of multiphase mixed fluid flow considering the effect of surfactant provided in the embodiments of the present application;

[0040] Figure 2 Flowchart of the method for numerical simulation of multiphase mixed fluid flow considering the effect of surfactant provided in the embodiments of the present application;

[0041] Figure 3 Schematic diagram of the flow of non-Newtonian power-law fluid-Newtonian fluid between two plates driven by external force provided in the embodiments of the present application;

[0042] Figure 4 Comparison chart of the analytical solution and numerical simulation results of the flow rate of non-Newtonian power-law fluid-Newtonian fluid between two plates driven by external force when the rheological index of the non-Newtonian fluid is 1.5 provided in the embodiments of the present application;

[0043] Figure 5 Comparison chart of the analytical solution and numerical simulation results of the flow rate of non-Newtonian power-law fluid-Newtonian fluid between two plates driven by external force when the rheological index of the non-Newtonian fluid is 0.5 provided in the embodiments of the present application;

[0044] Figure 6 Schematic diagram of the flow of non-Newtonian Bingham fluid-Newtonian fluid between two plates driven by external force provided in the embodiments of the present application;

[0045] Figure 7 Comparison chart of the analytical solution and numerical simulation results of the flow rate of non-Newtonian Bingham fluid-Newtonian fluid between two plates driven by external force provided in the embodiments of the present application;

[0046] Figure 8 Schematic diagram of the flow of non-Newtonian Herschel-Bulkley fluid-Newtonian fluid between two plates driven by external force provided in the embodiments of the present application;

[0047] Figure 9 Comparison chart of the analytical solution and numerical simulation results of the flow rate of non-Newtonian Herschel-Bulkley fluid-Newtonian fluid between two plates driven by external force provided in the embodiments of the present application;

[0048] Figure 10 Contact angles between the surfactant-containing droplet (solid line) and the surfactant-free droplet (dashed line) and the solid wall surface on the wall surface with different wettability provided in the embodiments of the present application;

[0049] Figure 11 Diagram of the change of surfactant in the process of non-Newtonian droplet migration under the action of shear force provided in the embodiments of the present application.

[0050] Figure 12A structural block diagram of an asynchronous network station sorting device provided by an embodiment of the present application is shown in the figure;

[0051] Figure 13 A structural schematic diagram of a medium provided by an embodiment of the present application is shown in the figure;

[0052] Figure 14 A structural schematic diagram of a computing device provided by an embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present application will be clearly and completely described in combination with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0054] As shown in Figure 1 and Figure 2 The embodiment of the present application provides a numerical simulation method for multiphase mixed fluid flow considering surfactant effect, which comprises the following steps:

[0055] Step S1, a lattice Boltzmann color model is established to simulate the flow of multiphase fluid.

[0056] Step S2, a non-Newtonian fluid constitutive equation and a surfactant convection-diffusion equation are established; the non-Newtonian fluid constitutive equation is used to obtain the relationship between the apparent viscosity of the fluid and the shear rate, and the surfactant convection-diffusion equation is used to describe the migration of surfactant at the interface of the multiphase fluid.

[0057] Step S3, the lattice Boltzmann color model is coupled with the non-Newtonian fluid constitutive equation through the apparent viscosity of the fluid, and the lattice Boltzmann color model is coupled with the surfactant convection-diffusion equation through the interfacial tension, and the numerical simulation process is completed.

[0058] Exemplarily, step S1 comprises:

[0059] Step S11, defining the initial values of various physical quantities of the lattice Boltzmann color model, and dividing the grid region.

[0060] Step S12, calculating the equilibrium distribution function of the lattice Boltzmann color model.

[0061] Step S13, based on the equilibrium distribution function, performing the collision process of different fluid particles.

[0062] Step S14, after performing the collision process, performing the recoloring process of different fluid particles.

[0063] Step S15, after performing the recoloring process, a migration process of different fluid particles is performed.

[0064] Exemplarily, in step S13, a multi-relaxation time collision operator is introduced in the collision process.

[0065] Specifically, the equilibrium distribution function is denoted as The collision process of different fluid particles is performed as follows:

[0066]

[0067] where f i ′(x,t) is the total distribution function of fluid particles after collision, f i (x,t) = f i,r (x,t) + f i,b (x,t) is the total distribution function of fluid particles before collision, f i,r (x,t) and f i,b (x,t) represent the distribution functions of non-Newtonian fluid and Newtonian fluid respectively, subscript i = 0, 1, …, 8 represents 9 discrete velocity directions, x is the position, t is the time, Ω i is the collision operator, is the force term, and the expression is:

[0068]

[0069] where I is the unit matrix, M is the conversion matrix, S is the relaxation diagonal matrix, Specifically:

[0070]

[0071] where w i is the weight, w0 = 4 / 9, w 1-4 = 1 / 9, w 5-8 = 1 / 36; c s is the sound speed; c i is the particle velocity, c0 = (0, 0), c 1,3 = (±1, 0), c 2,4 = (0, ±1), c 5,7 = (±1, ±1), F s is the interfacial force; σ is the interfacial tension coefficient; is the local interfacial curvature; is the surface gradient operator; is the interfacial unit normal vector; ρ N = (ρ r(x, t) - p b (x, t) + p r (x, t) + p b (x, t) is a phase field function identifying the interface position; δ t is the time step.

[0072] To consider the stability of numerical simulation of multiphase fluid flow, a multi-relaxation time collision operator is introduced, which is expressed as follows:

[0073]

[0074] where, is the equilibrium distribution function; p is the fluid density.

[0075] is the transformation matrix.

[0076] S is a relaxation diagonal matrix, which is expressed as follows:

[0077] S = diag(s0, s1, s2, s3, s4, s5, s6, s7, s8)

[0078] where, s 0,...,8 is the relaxation rate, The relaxation time τ is closely related to the dynamic viscosity η(p N ).

[0079]

[0080] where, p is the density of the mixed fluid; η(p N ) is the dynamic viscosity of the mixed fluid.

[0081] The fluid viscosity η(p N ) at the interface of multiphase flow is implemented to smooth transition based on the following formula to improve the stability of numerical simulation:

[0082]

[0083] where, η r and η b are the dynamic viscosities of non-Newtonian fluid and Newtonian fluid, respectively.

[0084] After the collision process, the recoloring process of different fluid particles is performed as follows:

[0085]

[0086] where, f″ i,r (x, t) is the distribution function of fluid particles after recoloring; β is a separation parameter related to the interface thickness; p r and pb Density of non-Newtonian fluid and Newtonian fluid, respectively.

[0087] After the recoloring process, the migration process of different fluid particles is performed as follows:

[0088] f i,k (x+c i δ t ,t+δ t )=f″ i,k (x,t)

[0089] Where f i,k (x+c i δ t ,t+δ t ) is the distribution function of fluid particles after migration; k=r or b, when k=r represents non-Newtonian fluid, and when k=b represents Newtonian fluid.

[0090] The density and velocity of different fluids are obtained by summing the distribution functions based on the following formula:

[0091]

[0092] Where p k is the fluid density, f i,k is the distribution function of fluid after migration, and u is the fluid velocity.

[0093] Exemplarily, in step S2, the use process of the non-Newtonian fluid constitutive equation includes:

[0094] Step S211, establishing a non-Newtonian fluid constitutive equation, calculating a strain rate tensor and a shear rate.

[0095] Step S212, calculating the apparent viscosity of the non-Newtonian fluid.

[0096] Specifically, the strain rate tensor is denoted as S αβ , and the shear rate is denoted as The apparent viscosity of the non-Newtonian fluid is denoted as η k . In order to improve the stability of numerical simulation, the harmonic average method is used to calculate the apparent viscosity of different fluids at the phase interface.

[0097] Exemplarily, in step S2, the non-Newtonian fluid constitutive equation includes: power-law fluid constitutive equation, Bingham fluid constitutive equation, Herschel-Bulkley fluid constitutive equation.

[0098] Specifically, the non-Newtonian fluid does not comply with the Newtonian viscosity law, that is, the shear stress of the fluid and the shear rate are nonlinearly related, which shows phenomena such as shear thinning, shear thickening, time variation, and viscoelasticity. Three typical non-Newtonian fluid constitutive equations are established.

[0099] The constitutive equation of the power-law fluid is as follows:

[0100]

[0101] wherein, is the shear stress; is the shear rate; η0 is the viscosity coefficient; n is the rheological index, which represents the degree of deviation from the Newtonian fluid, when n = 1, the constitutive equation is simplified as the constitutive equation of the Newtonian fluid; when n < 1, it represents the shear thinning fluid; when n > 1, it represents the shear thickening fluid.

[0102] The apparent viscosity of the power-law fluid is as follows:

[0103]

[0104] The constitutive equation of the Bingham fluid is as follows:

[0105]

[0106] wherein, τ0 is the yield stress, η p is the plastic viscosity of the fluid.

[0107] The apparent viscosity of the Bingham fluid is as follows:

[0108]

[0109] When the applied shear stress is less than the yield stress of the Bingham fluid, the fluid does not flow and exhibits solid properties, and when the shear stress exceeds the yield stress, the fluid flows.

[0110] The constitutive equation of the Herschel-Bulkley fluid is as follows:

[0111]

[0112] In this equation, when n = 1, the fluid is simplified as a Bingham fluid; when τ0 = 0, the fluid is simplified as a power-law fluid.

[0113] The apparent viscosity of the Herschel-Bulkley fluid is as follows:

[0114]

[0115] Exemplarily, in step S2, the use process of the surfactant convection-diffusion equation includes:

[0116] Step S221, establishing a surfactant convection-diffusion equation, introducing an interface function.

[0117] Step S222, using semi-implicit Crank-Nicholson finite difference format to time-disperse the surfactant convection-diffusion equation, using central difference format to space-disperse the surfactant convection-diffusion equation.

[0118] Specifically, the surfactant convection-diffusion equation is as follows:

[0119]

[0120] Wherein, ψ is the surfactant concentration; D s is the surfactant diffusion coefficient.

[0121] In order to be coupled with the lattice Boltzmann color model, δ Γ = | ρ N | / 2 function is introduced in the surfactant convection-diffusion equation, and the surfactant convection-diffusion equation is further written as:

[0122]

[0123] Exemplarily, in step S3, coupling the lattice Boltzmann color model with the non-Newtonian fluid constitutive equation through the apparent viscosity of the fluid includes:

[0124] Step S31, updating the relaxation time in the lattice Boltzmann color model according to the apparent viscosity of the non-Newtonian fluid calculated by the non-Newtonian fluid constitutive equation.

[0125] Specifically, according to the apparent viscosity η k of the non-Newtonian fluid, the relaxation time τ in the multi-relaxation time collision operator Ω i in the lattice Boltzmann color model is corrected.

[0126] Exemplarily, in step S3, coupling the lattice Boltzmann color model with the surfactant convection-diffusion equation through the interfacial tension includes:

[0127] Step S32, coupling the surfactant concentration calculated by the surfactant convection-diffusion equation with the interfacial tension in the lattice Boltzmann color model through the Langmuir state equation, and the interfacial tension is the interfacial tension of the non-Newtonian fluid.

[0128] Specifically, the surfactant concentration ψ and the interfacial tension σ are coupled through the Langmuir state equation:

[0129]

[0130] Where σ0 is the interfacial tension of the fluid without surfactant, R is the universal gas constant, T is the absolute temperature, and ψ ∞ This represents the maximum concentration of surfactant at the interface.

[0131] For example, in step S3, the contact angle between the multiphase fluid and the solid wall is calculated using the Young equation.

[0132] Specifically, wettability boundary conditions are established to simulate the contact angle θ generated by the contact between the multiphase fluid and the solid wall. The interfacial tension of the multiphase fluid and the contact angle satisfy the Young equation:

[0133] σ0cosθ=σ sb -σ sr

[0134] Where, σ sb and σ sr These represent the surface tension between different fluids and solid walls.

[0135] Since surfactants alter the interfacial tension of fluids, a contact angle model that considers the surfactant effect is further established:

[0136]

[0137] To verify the correctness of the numerical simulation method for non-Newtonian-Newtonian multiphase mixed fluid flow using the Boltzmann color model of the non-Newtonian-Newtonian multiphase mixed fluid lattice established in this invention, a non-Newtonian power-law fluid-Newtonian fluid mixing system is used as an example for illustration:

[0138] like Figure 3 As shown, the space between the two plates is filled with two immiscible fluids. Gray represents non-Newtonian power-law fluids, and black represents Newtonian fluids, denoted by the letters red (abbreviated as r) and blue (abbreviated as b), respectively. The two fluids are symmetrically distributed along the x-axis, each occupying a portion of the total flow region. External force along the x-direction Driven by the flow, a multiphase fluid undergoes flow. When the flow reaches a steady state, the analytical solution for the velocity of the multiphase fluid along the x-direction is:

[0139]

[0140] Numerical simulations were performed using the Boltzmann color model of the non-Newtonian-Newtonian multiphase mixed fluid lattice established in this invention, with the rheological indices of the non-Newtonian and Newtonian fluids set as n. r =1.5 and n b =1, meaning the gray fluid and black fluid represent the shear-thickened fluid and the Newtonian fluid, respectively, and the initial viscosity ratio of the two phases is set to η. r / η b= 1, the driving force is set to

[0141] Similarly, the rheological index of the non-Newtonian fluid and the Newtonian fluid is set to n Figure 3 = 0.5 and n r = 1, that is, the gray fluid and the black fluid respectively represent the shear-thickening fluid and the Newtonian fluid, and other conditions are the same as above. b

[0142] Figure 4 And Figure 5 The comparison chart of the analytical solution and the numerical simulation result of the non-Newtonian power-law fluid-Newtonian fluid flow rate under the external force driving when the rheological index of the non-Newtonian fluid is 1.5 and 0.5 respectively is given, and it is found that they are in good agreement, the velocity curve of the shear-thickening fluid is sharp, and the velocity curve of the shear-thinning fluid is in the shape of a plunger. It is verified that the lattice Boltzmann color model of the non-Newtonian-Newtonian multiphase mixed fluid established by the application can correctly simulate the non-Newtonian power-law fluid-Newtonian fluid flow.

[0143] In order to further verify the correctness of the lattice Boltzmann color model in simulating the non-Newtonian-Newtonian multiphase mixed fluid flow, the non-Newtonian Bingham fluid-Newtonian fluid mixed system is taken as an example to illustrate:

[0144] As Figure 6 shown, the two plates are filled with two immiscible phases, the gray color represents the non-Newtonian Bingham fluid, and the black color represents the Newtonian fluid. Under the external force driving along the x direction, the multiphase fluid flows, the two fluids are symmetrically distributed along the x axis, and each occupies of the total flow area, the yield stress is set to τ0= 25 × 10 -8 When the flow reaches a steady state, the velocity of the multiphase fluid along the x direction is:

[0145]

[0146] Wherein,

[0147] Figure 7 The comparison of the analytical solution and the numerical simulation result is given, and it is found that they are in good agreement, which further verifies that the lattice Boltzmann color model of the non-Newtonian-Newtonian multiphase mixed fluid established by the application can correctly simulate the non-Newtonian Bingham fluid-Newtonian fluid flow.

[0148] Next, taking the non-Newtonian Herschel-Bulkley fluid-Newtonian fluid as an example, the correctness of the lattice Boltzmann color model in simulating the non-Newtonian-Newtonian multiphase mixed fluid flow is further verified.

[0149] ​As shown in Figure 8 the two plates are filled with two immiscible phase fluids, the gray represents the non-Newtonian Herschel-Bulkley fluid, and the black represents the Newtonian fluid. Under the driving of the external force in the x direction, the multiphase fluid flows, and when the flow reaches a steady state, the velocity analysis solution of the multiphase fluid in the x direction is:

[0150]

[0151] Figure 9 The analysis solution and the numerical simulation results are given, and it is found that the two still agree very well, which shows that the non-Newtonian-Newtonian multiphase mixed fluid lattice Boltzmann color model established in the application simulates the non-Newtonian Herschel-Bulkley fluid-Newtonian fluid flow correctly and reliably.

[0152] In this embodiment, the contact angle between the surfactant-containing droplet and the solid wall surface on the different wettability wall surfaces is simulated, and the contact angle between the surfactant-free droplet and the solid wall surface is also simulated as a control.

[0153] At the initial moment, one droplet is placed on the solid wall surface, and due to the different contact angles between the droplet and the solid wall surface, the droplet spreads or shrinks on the solid wall surface, and finally presents different morphologies.

[0154] Figure 10 The morphologies of the surfactant-containing droplet and the surfactant-free droplet on the different wettability solid wall surfaces at a steady state are given. It is found that compared with the surfactant-free droplet, the surfactant-containing droplet spreads more on the hydrophilic solid wall surface, and the contact angle at a steady state is smaller than the contact angle between the surfactant-free droplet and the solid wall surface; the surfactant-containing droplet shrinks more on the hydrophobic solid wall surface, and the contact angle at a steady state is greater than the contact angle between the surfactant-free droplet and the solid wall surface.

[0155] This is because the surfactant can reduce the interfacial tension of the droplet, and the interfacial tension σ of the surfactant-containing droplet is smaller than the interfacial tension σ0 of the surfactant-free droplet, that is, The contact angle between the surfactant-containing droplet and the solid wall surface is θ = arccos((σ sb -σ sr ) / σ), and the contact angle between the surfactant-free droplet and the solid wall surface is θ0 = arccos((σ sb -σ sr ) / σ0), so when θ0 < 90°, θ < θ0 < 90°, and when θ0 > 90°, θ > θ0 > 90°, and when θ0 = 90°, θ = θ0. This agrees well with the theoretical value, verifying the correctness of the model.

[0156] This embodiment simulates the migration of the liquid drop containing surfactant under the action of shear force.

[0157] The liquid drop is a non-Newtonian fluid, the fluid outside the liquid drop is a Newtonian fluid, the viscosity ratio of the non-Newtonian fluid to the Newtonian fluid is 1, the capillary number Ca = 0.8, the Reynolds number Re = 0.4, and the dimensionless time t * = γt, wherein γ = u w / H is the shear rate, and H is the distance between the upper and lower solid walls.

[0158] Figure 11 The surfactant changes during the migration of the liquid drop under the action of shear force, Figure 11 In (a), the shear thinning fluid; (b) Bingham fluid; (c) shear thickening fluid. The first to third rows of time are t * = 0, 6, 12. It can be seen that the surfactant gradually migrates to the vicinity of the tip of the liquid drop. The shear thinning fluid causes the apparent viscosity to decrease, resulting in an increase in the migration speed of the liquid drop; the shear thickening fluid causes the apparent viscosity to increase, resulting in a decrease in the migration speed of the liquid drop; and the migration speed of the Bingham fluid is between the two.

[0159] The embodiments of the present application can be easily extended to more types of non-Newtonian-Newtonian multiphase mixed fluid flow problem solving by coupling the lattice Boltzmann color model, the non-Newtonian fluid constitutive equation and the surfactant convection-diffusion equation, thereby improving the reliability and applicability of the numerical simulation of the multiphase mixed fluid flow.

[0160] By introducing a multi-relaxation time collision operator in the collision process, the stability of the collision process is improved, and the stability of the numerical simulation is improved.

[0161] The surfactant convection-diffusion equation is established, and the interface function is introduced, which can be applied to the migration of surfactant with strong deformation of the interface.

[0162] The semi-implicit Crank-Nicholson finite difference format is used to time-disperse the surfactant convection-diffusion equation, and the central difference format is used to space-disperse the surfactant convection-diffusion equation, thereby improving the solving accuracy of the surfactant convection-diffusion equation.

[0163] On the basis of the above embodiments, with reference to Figure 12 Another embodiment of the present application also provides a multiphase mixed fluid flow numerical simulation device, which can include the following modules:

[0164] The multiphase fluid flow simulation module 210 is used to establish a lattice Boltzmann color model and simulate the multiphase fluid flow.

[0165] The equation establishing module 220 is configured to establish a non-Newtonian fluid constitutive equation and a surfactant convection-diffusion equation; the non-Newtonian fluid constitutive equation is used to obtain the relationship between the apparent viscosity of the fluid and the shear rate, and the surfactant convection-diffusion equation is used to describe the migration of the surfactant at the interface of the multiphase fluid.

[0166] The coupling module 230 is configured to couple the lattice Boltzmann color model with the non-Newtonian fluid constitutive equation through the apparent viscosity of the fluid, and couple the lattice Boltzmann color model with the surfactant convection-diffusion equation through the interfacial tension, so as to complete the numerical simulation process.

[0167] On the basis of the above-mentioned embodiments, the embodiments of the present application further provide a computer readable storage medium, which refers to Figure 13 The computer readable storage medium shown is an optical disc 50, and a computer program (i.e., a program product) is stored on the optical disc 50; when the computer program is run by a processor, each step recorded in the above-mentioned method embodiments can be implemented, for example, establishing a lattice Boltzmann color model and simulating the flow of a multiphase fluid; establishing a non-Newtonian fluid constitutive equation and a surfactant convection-diffusion equation; the non-Newtonian fluid constitutive equation is used to obtain the relationship between the apparent viscosity of the fluid and the shear rate, and the surfactant convection-diffusion equation is used to describe the migration of the surfactant at the interface of the multiphase fluid; coupling the lattice Boltzmann color model with the non-Newtonian fluid constitutive equation through the apparent viscosity of the fluid, and coupling the lattice Boltzmann color model with the surfactant convection-diffusion equation through the interfacial tension, so as to complete the numerical simulation process. The specific implementation of each step will not be repeated here.

[0168] It should be noted that the examples of the computer readable storage medium can further include, but are not limited to, a phase change memory (PRAM), a static random access memory (SRAM), a dynamic random access memory (DRAM), other types of random access memory (RAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), a flash memory, or other optical or magnetic storage medium, which will not be described one by one here.

[0169] In addition, on the basis of the above-mentioned embodiments, the embodiments of the present application further provide a computing device, Figure 14 A block diagram of an exemplary computing device 60 suitable for implementing embodiments of the present application is shown, which can be a computer system or a server. Figure 14 The computing device 60 shown is only an example, and should not impose any limitation on the functions and use range of the embodiments of the present application.

[0170] AsFigure 14 As shown, the components of computing device 60 may include, but are not limited to: one or more processors or processing units 601, system memory 602, and bus 603 connecting different system components (including system memory 602 and processing unit 601).

[0171] The computing device 60 typically includes a variety of computer system readable media. These media can be any available media that can be accessed by the computing device 60, including volatile and non-volatile media, removable and non-removable media.

[0172] System memory 602 may include computer system readable media in the form of volatile memory, such as random access memory (RAM) 6021 and / or cache memory 6022. Computing device 60 may further include other removable / non-removable, volatile / non-volatile computer system storage media. By way of example only, ROM 6023 may be used to read and write non-removable, non-volatile magnetic media (…). Figure 14 Not shown in the image (usually referred to as a "hard drive"). Although not shown in Figure 14 The diagram illustrates that disk drives for reading and writing to removable non-volatile disks (e.g., "floppy disks") and optical disc drives for reading and writing to removable non-volatile optical discs (e.g., CD-ROMs, DVD-ROMs, or other optical media) can be provided. In these cases, each drive can be connected to a bus 603 that connects different system components via one or more data media interfaces. The system memory 602 may include at least one program product having a set (e.g., at least one) of program modules configured to perform the functions of the embodiments of this application.

[0173] A program / utility 6025 having a set (at least one) of program modules 6024 may be stored, for example, in system memory 602, and such program modules 6024 include, but are not limited to, an operating system, one or more application programs, other program modules, and program data, each or some combination of these examples may include an implementation of a network environment. Program modules 6024 typically perform the functions and / or methods described in the embodiments of this application.

[0174] The computing device 60 can also communicate with one or more external devices 604 (such as a keyboard, pointing device, display, etc.). This communication can be performed via the input / output (I / O) interface 605. Furthermore, the computing device 60 can also communicate with one or more networks (e.g., local area networks (LANs), wide area networks (WANs), and / or public networks, such as the Internet) via a network adapter 606. Figure 14As shown, the network adapter 606 communicates with other modules of the computing device 60 (e.g., the processing unit 601, etc.) through the bus 603 that connects the various system components. It should be appreciated that although not shown, other hardware and / or software modules could be used in conjunction with the computing device 60. Examples, include, but are not limited to, microcode, device drivers, redundant processing units, and external disk drive arrays, to name a few. Figure 14

[0175] The processing unit 601 performs various functional applications and data processing by running programs stored in the system memory 602, such as establishing a lattice Boltzmann color model, simulating multiphase fluid flow; establishing a non-Newtonian fluid constitutive equation and a surfactant convection-diffusion equation; the non-Newtonian fluid constitutive equation is used to obtain the relationship between the apparent viscosity of the fluid and the shear rate, and the surfactant convection-diffusion equation is used to describe the migration of the surfactant at the interface of the multiphase fluid; the lattice Boltzmann color model is coupled with the non-Newtonian fluid constitutive equation through the apparent viscosity of the fluid, and the lattice Boltzmann color model is coupled with the surfactant convection-diffusion equation through the interfacial tension, to complete the numerical simulation process. It should be noted that although several units / modules or sub-units / sub-modules of the asynchronous network station sorting device are mentioned in the foregoing detailed description, such division is merely exemplary and not mandatory. In fact, according to the embodiments of the present application, the features and functions of two or more units / modules described above can be embodied in one unit / module. Conversely, the features and functions of one unit / module described above can be further divided into a plurality of units / modules.

[0176] In the description of the present application, it should be noted that the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0177] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the system, device and unit described above can refer to the corresponding process in the foregoing method embodiments, which will not be repeated here.

[0178] In several embodiments provided in the present application, it should be understood that the disclosed system, device and method can be implemented in other ways. The device embodiments described above are only schematic. For example, the division of the units is only a logical function division, and there can be another division manner in actual implementation. For example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units or components shown or discussed can be indirect coupling or communication connection through some communication interfaces, devices or units, which can be electrical, mechanical or other forms.

[0179] ​The units described as separate components may or may not be physically separate, and the components displayed as units may or may not be physical units, i.e. may be located in one place, or may be distributed on multiple network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the embodiment scheme.

[0180] In addition, the functional units in each embodiment of the present application can be integrated in one processing unit, or each unit can be physically present separately, or two or more units can be integrated in one unit.

[0181] If the functions are realized in the form of software function units and sold or used as independent products, they can be stored in a non-volatile computer readable storage medium executable by a processor. Based on such understanding, the technical solutions of the present application essentially or the parts that contribute to the prior art or parts of the technical solutions can be embodied in the form of software products. The computer software product is stored in a storage medium, including a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), magnetic disk or optical disk, and various program code storage media.

[0182] Finally, it should be noted that: the above-described embodiments are merely specific embodiments of the present application, used to illustrate the technical solutions of the present application, and not to limit them. The protection scope of the present application is not limited thereto, although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any skilled person familiar with the technology in the art can modify or easily think of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed by the present application, or make equivalent replacements to some of the technical features; and these modifications, changes or replacements do not make the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be limited by the protection scope of the claims.

[0183] In addition, although the operations of the method of the present application are described in a specific order in the accompanying drawings, this does not require or imply that the operations must be performed in that specific order, or that all of the shown operations must be performed to achieve the desired result. Additionally or alternatively, some steps can be omitted, a plurality of steps can be combined into one step, and / or one step can be divided into a plurality of steps.

Claims

1. A method for numerical simulation of a multiphase mixed fluid flow, characterized by, The method comprises the following steps: Step S1, establishing a lattice Boltzmann color model to simulate multiphase fluid flow; Step S2, establishing a non-Newtonian fluid constitutive equation and a surfactant convection-diffusion equation; the non-Newtonian fluid constitutive equation is used to obtain the relationship between fluid apparent viscosity and shear rate, and the surfactant convection-diffusion equation is used to describe the migration of surfactant at the interface of multiphase fluid; Step S3, coupling the lattice Boltzmann color model with the non-Newtonian fluid constitutive equation through fluid apparent viscosity, and coupling the lattice Boltzmann color model with the surfactant convection-diffusion equation through interfacial tension, to complete the numerical simulation process.

2. The multiphase fluid flow numerical simulation method of claim 1, wherein, Step S1 comprises: Step S11, defining initial values of physical quantities of the lattice Boltzmann color model, and dividing a grid region; Step S12, calculating an equilibrium state distribution function of the lattice Boltzmann color model; Step S13, performing a collision process of different fluid particles based on the equilibrium state distribution function; Step S14, performing a recoloring process of different fluid particles after the collision process is performed; Step S15, performing a migration process of different fluid particles after the recoloring process is performed.

3. The multiphase fluid flow numerical simulation method of claim 1, wherein, In step S2, the use process of the non-Newtonian fluid constitutive equation comprises: Step S211, establishing a non-Newtonian fluid constitutive equation, and calculating a strain rate tensor and a shear rate; Step S212, calculating non-Newtonian fluid apparent viscosity.

4. The multiphase fluid flow numerical simulation method of claim 1, wherein, In step S2, the non-Newtonian fluid constitutive equation comprises: a power-law fluid constitutive equation, a Bingham fluid constitutive equation, and a Herschel-Bulkley fluid constitutive equation.

5. The multi-phase fluid flow numerical simulation method of claim 1, wherein, In step S2, the use process of the surfactant convection-diffusion equation comprises: Step S221, establishing a surfactant convection-diffusion equation, and introducing an interface function; Step S222, using a semi-implicit Crank-Nicholson finite difference format to perform time discretization on the surfactant convection-diffusion equation, and using a central difference format to perform spatial discretization on the surfactant convection-diffusion equation.

6. The multi-phase fluid flow numerical simulation method of claim 1, wherein, In step S3, coupling the lattice Boltzmann color model with the non-Newtonian fluid constitutive equation through fluid apparent viscosity comprises: Step S31, updating a relaxation time in the lattice Boltzmann color model according to non-Newtonian fluid apparent viscosity calculated by the non-Newtonian fluid constitutive equation.

7. The multi-phase fluid flow numerical simulation method of claim 1, wherein, In step S3, coupling the lattice Boltzmann color model with the surfactant convection-diffusion equation through interfacial tension comprises: Step S32, coupling surfactant concentration calculated by the surfactant convection-diffusion equation with interfacial tension in the lattice Boltzmann color model through a Langmuir state equation, and the interfacial tension is non-Newtonian fluid interfacial tension.

8. A device for numerical simulation of a flow of a multiphase mixture, characterized in that The method comprises: A multiphase fluid flow simulation module, configured to establish a lattice Boltzmann color model to simulate multiphase fluid flow; An equation establishing module is configured to establish a non-Newtonian fluid constitutive equation and a surfactant convection-diffusion equation; the non-Newtonian fluid constitutive equation is used to obtain a relationship between fluid apparent viscosity and shear rate, and the surfactant convection-diffusion equation is used to describe migration of surfactant at an interface of a multiphase fluid; A coupling module is configured to couple the lattice Boltzmann color model with the non-Newtonian fluid constitutive equation through fluid apparent viscosity, and couple the lattice Boltzmann color model with the surfactant convection-diffusion equation through interfacial tension, so as to complete a numerical simulation process.

9. A computer-readable storage medium, characterized in that, The computer program product comprises instructions which, when executed on a computer, cause the computer to perform the multiphase mixed fluid flow numerical simulation method of any one of claims 1-7.

10. A computing device, comprising: The computing device comprises: at least one processor, a memory, and an input / output unit; The memory is configured to store a computer program, and the processor is configured to invoke the computer program stored in the memory to execute the multiphase mixed fluid flow numerical simulation method of any one of claims 1-7.

Images