An engineering-scale CFD-DEM coupled optimization analysis method based on engineering survey permeability data

Abstract

The present invention provides an engineering scale CFD-DEM coupling optimization analysis method based on engineering survey permeability data, including: according to actual engineering survey, obtaining actual permeability under actual particles, and constructing the relationship between the actual permeability and actual engineering equivalent particle size; constructing a seepage field geological model, and based on the coarse-graining theory, coarse-graining and amplifying the actual engineering equivalent particle size of the seepage field geological model, and obtaining the amplification factor; based on the flow-solid motion similarity criterion, obtaining the fluid density similarity coefficient and the viscosity coefficient similarity coefficient of the seepage field geological model; and establishing the engineering scale solid control equation, the engineering scale fluid motion control equation, and the engineering scale fluid-particle interaction control equation based on the fluid density similarity coefficient and the viscosity coefficient similarity coefficient of the seepage field geological model. According to the present invention, the coarse-graining theory and the flow-solid similarity theory are introduced to extend the coarse-grid fluid-particle fluid-solid coupling analysis model to geotechnical engineering scale applications.

Description

Technical Field

[0001] The present invention relates to the technical field of numerical simulation, and in particular to an engineering scale CFD-DEM coupling optimization analysis method based on engineering survey permeability data. Background Art

[0002] The discrete element method (DEM) has obvious advantages in studying large deformation and discontinuous deformation of rock and soil. In engineering-scale problems, the DEM model is established according to the actual rock and soil particle size. The number of DEM particles is in the hundreds of millions, which places high demands on computer hardware. Particles in the hundreds of millions need to be used on supercomputers and cannot be used on conventional computers. The large number of DEM particles leads to high computing costs and poor computing efficiency, which is one of the limitations of the particle-scale DEM method for engineering applications.

[0003] In the fluid-structure coupling model, based on the DEM method, combined with computational fluid dynamics (CFD;

[0004] The CFD-DEM fluid-solid coupling method is established in Computational Fluid Dynamics to simulate the migration of soil particles at the mesoscale under the action of liquid. The movement calculation of a large number of particles needs to consider the interaction between particles and the coupling between particles and fluid. It is repeatedly updated according to the set calculation time, which further increases the calculation demand and cost.

[0005] In order to solve the practical application of DEM method in engineering, it utilizes large-scale physical phenomena and ignores or averages some relatively minor physical phenomena in small scales. Coarse-grained amplification theory and similarity theory have been proposed, which partially solve the difficulty of applying DEM method in engineering scale models. For the application of CFD-DEM fluid-solid coupling method in engineering, it is necessary to further consider the coupling effect between fluid and particles, and at the same time, it is necessary to establish the connection between the physical and mechanical parameters of rock and soil bodies in engineering investigation and the microscopic material parameters of particles described in DEM model and the movement parameters of fluid in rock and soil media described in CFD model.

[0006] Among them, the physical and mechanical parameters of engineering survey rock and soil and the material parameters describing the microscopic particles in the DEM model are usually calibrated multiple times using the "trial and error method" through triaxial or shear standard tests. While ensuring the mechanical consistency of the DEM particles before and after the particle size is enlarged, there is currently no expression that can better describe the engineering survey permeability and CFD initial permeability in the CFD-DEM fluid-solid coupling method, as well as an optimization method for describing the corresponding engineering-scale DEM solid motion control equations, engineering-scale CFD fluid motion control equations, and engineering-scale CFD-DEM fluid-solid control equations. The application of the CFD-DEM method to engineering-scale model analysis is limited. Therefore, the present invention studies and designs an engineering-scale CFD-DEM coupling optimization analysis method based on engineering survey permeability data. Summary of the invention

[0007] Therefore, the technical problem to be solved by the present invention is to overcome the defect that the CFD-DEM method in the prior art cannot be well applied to engineering scale model analysis, thereby providing an engineering scale CFD-DEM coupling optimization analysis method based on engineering survey permeability data.

[0008] In order to solve the above problems, the present invention provides an engineering scale CFD-DEM coupling optimization analysis method based on engineering survey permeability data, which comprises the following steps:

[0009] According to actual engineering survey, the actual permeability under actual particles is obtained, and the relationship between the actual permeability and the actual engineering equivalent particle size is established;

[0010] Construct a seepage field geological model, enlarge the actual engineering equivalent particle size of the seepage field geological model based on the coarse-graining theory, and obtain the enlargement coefficient;

[0011] Based on the similarity criterion of flow-solid motion, the similarity coefficient of fluid density and viscosity coefficient of the seepage field geological model is obtained;

[0012] Based on the fluid density similarity coefficient and viscosity coefficient similarity coefficient of the seepage field geological model, the engineering scale solid control equation, engineering scale fluid motion control equation and engineering scale fluid-particle interaction control equation are established respectively.

[0013] Preferably, the method for constructing the relationship between the actual permeability and the actual engineering equivalent particle size is:

[0014] According to the Kozeny-Carman extended equation containing clay, the relationship between the calculated engineering survey permeability and the actual engineering equivalent particle size is expressed as:

[0015]

[0016] Where p represents the actual engineering prototype, r p is the equivalent particle size corresponding to the permeability in actual engineering; k p is the actual permeability; m is the rock medium constant; α is the shape factor; C e is the pore structure influence coefficient; e is the porosity ratio.

[0017] Among them, when the rock and soil medium constant m is 0-0.1, 1 and 1.5 respectively, it is suitable for the calculation of sand, silt and clay respectively. When m=0, the Kozeny-Carman extended equation containing clay effect is the Kozeny-Carman classical equation.

[0018] Preferably, the coarse-graining amplification is as follows: introducing the coarse-graining theory, and calculating the equivalent particle size r of the actual engineering p Perform coarse-grained enlargement.

[0019] Preferably, the amplification factor is expressed as:

[0020]

[0021] Among them, λ r is the magnification factor, r c is the particle size of DEM after coarse-graining and enlargement, r p It is the actual engineering equivalent particle size.

[0022] Preferably, the seepage field geological model also includes: constructing the engineering survey permeability and the DEM model particle size r c relationship;

[0023] The engineering survey permeability and DEM model particle size r c The relationship is:

[0024] Select a number N of particles to be grouped as a whole coarse-grained particle. Under the condition that the density of the particles after the coarse-grained particle is the same as that of the fine particles in the actual project, the volume and mass of the coarse-grained particles before and after are the same, which can be expressed as:

[0025]

[0026] Assuming that the particle size distribution is the same, the actual number of engineering particles N P The number of particles N in the numerical model after coarse-graining c The relationship is:

[0027]

[0028] Under the condition that the average permeability of the fluid unit is consistent with the engineering survey permeability, the engineering survey permeability and the particle size r of the DEM model are c The relationship is expressed as:

[0029]

[0030] Preferably, the method for obtaining the fluid density similarity coefficient and the viscosity coefficient similarity coefficient of the seepage field geological model is:

[0031] Define the fluid density similarity coefficient as λ ρf , the viscosity similarity coefficient is λ μf ,

[0032] The particle size magnification factor is λ r :

[0033] λ ρf =λ r (18a)

[0034]

[0035] Preferably, the engineering scale solid motion control equation is:

[0036]

[0037]

[0038] Among them, m' p Indicates the mass of the particle calculated by the floating density. In the area without fluid action, the mass is calculated according to the dry density of the particle; I' p It represents the moment of inertia of the particle calculated according to the floating density. In the area without fluid action, the moment of inertia is calculated according to the dry density of the particle.

[0039] Preferably, the engineering scale solid control equation is:

[0040] The Darcy seepage control equation is improved, the particle size of the solid particles in the permeability is enlarged, and then the average permeability of each fluid unit is calculated. The engineering scale fluid control equation in the CFD-DEM fluid-solid coupling method is expressed as:

[0041]

[0042]

[0043]

[0044] Among them, k p is the engineering survey permeability, which changes accordingly with the change of porosity; μ is the fluid dynamic viscosity coefficient; r c represents the particle size in the DEM numerical model; r It indicates the particle size magnification factor for coarsening particles.

[0045] Preferably, the engineering scale fluid-particle interaction governing equation is:

[0046] Introducing the coarsening particle size magnification factor λ r Fluid density ρ in calculation of fluid-solid interaction forces f and the fluid dynamic viscosity coefficient μ f After correction, the fluid-particle interaction control equation in the CFD-DEM fluid-solid coupling engineering scale analysis method is expressed as:

[0047]

[0048]

[0049]

[0050]

[0051] The engineering scale CFD-DEM coupling optimization analysis method based on engineering survey permeability data provided by the present invention has the following beneficial effects:

[0052] 1. The present invention establishes the correlation between the engineering survey permeability and equivalent particle size of different rock and soil bodies (sand, silt and clay) through the Kozeny-Carman extended equation. Based on the equivalent particle size of the actual engineering survey permeability, the relevant similarity coefficient is equivalently calculated, which realizes the direct application of the rock and soil engineering survey permeability data and the CFD-DEM coupling method, and expands the application scenarios of the CFD-DEM coupling method;

[0053] 2. The present invention also calculates the correlation between the particle size magnification factor and the fluid density similarity coefficient and the viscosity coefficient similarity coefficient based on the coarse-grained theory and the flow-solid motion similarity criterion, by ensuring the consistency of the flow-solid interaction force of the "particle cluster" represented by the particle magnification, thereby improving the theoretical support for the engineering scale application of the CFD-DEM coupling method;

[0054] 3. The present invention also extends the coarse grid fluid-particle fluid-solid coupling analysis model to geotechnical engineering scale application by introducing coarse-graining theory and flow-solid similarity theory. The present invention is based on the CFD-DEM model, based on the correlation between the permeability of on-site engineering survey and the effective particle size of the DEM model, and under the condition of ensuring that the geometric size of the model is consistent with the actual engineering, the particle size is enlarged based on the coarse-graining theory, and then the relationship expression between the fluid density similarity coefficient and the viscosity coefficient similarity coefficient and the particle size magnification coefficient is derived according to the flow-solid motion similarity criterion, and the engineering-scale DEM solid motion control equation, the engineering-scale CFD fluid motion control equation, and the engineering-scale CFD-DEM fluid-solid control equation are established to solve the limitations of the CFD-DEM method for engineering-scale model analysis applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 It is a schematic flow chart of the engineering scale CFD-DEM coupling optimization analysis method for engineering survey permeability data of the present invention;

[0056] Figure 2 It is a schematic diagram of the DEM calculation model of Yonglian Tunnel established based on the engineering survey permeability and coarse-graining theory of the present invention;

[0057] Figure 3 The Yonglian Tunnel seepage field calculation model diagram of the present invention;

[0058] Figure 4 is the initial flow velocity vector distribution diagram of the present invention;

[0059] Figure 5 is the initial pore pressure distribution diagram of the present invention;

[0060] Figure 6 It is the particle displacement diagram at different times of the present invention. DETAILED DESCRIPTION

[0061] like Figure 1-6 As shown, the present invention provides an engineering scale CFD-DEM coupling optimization analysis method based on engineering survey permeability data, which includes the following steps:

[0062] According to actual engineering survey, the actual permeability under actual particles is obtained, and the relationship between the actual permeability and the actual engineering equivalent particle size is established;

[0063] Construct a seepage field geological model, enlarge the actual engineering equivalent particle size of the seepage field geological model based on the coarse-graining theory, and obtain the enlargement coefficient;

[0064] Based on the similarity criterion of flow-solid motion, the similarity coefficient of fluid density and viscosity coefficient of the seepage field geological model is obtained;

[0065] Based on the fluid density similarity coefficient and viscosity similarity coefficient of the seepage field geological model, the engineering scale solid control equation, the engineering scale fluid motion control equation and the engineering scale fluid-particle interaction control equation are established respectively. Specifically, the present invention introduces the coarse-graining theory and the flow-solid similarity theory, and extends the coarse-grid fluid-particle fluid-solid coupling analysis model to geotechnical engineering scale application. The present invention is based on the CFD-DEM model, based on the correlation between the permeability of the on-site engineering survey and the effective particle size of the DEM model, and under the condition that the geometric size of the model is consistent with the actual engineering, the particle size is enlarged based on the coarse-graining theory, and then according to the flow-solid motion similarity criterion, the relationship expression between the fluid density similarity coefficient and the viscosity coefficient similarity coefficient and the particle size magnification coefficient is derived, and the engineering scale DEM solid motion control equation, the engineering scale CFD fluid motion control equation, and the engineering scale CFD-DEM fluid-solid control equation are established to solve the limitation of the CFD-DEM method for engineering scale model analysis application.

[0066] Specifically, the relationship between the actual permeability construction and the actual engineering equivalent particle size is:

[0067] According to the on-site geological survey, the macro-average permeability of the rock mass is measured. According to the Kozeny-Carman extended equation containing clay, the relationship between the engineering survey permeability and the actual engineering equivalent particle size is expressed as:

[0068]

[0069] Where p represents the actual engineering prototype, r p is the equivalent particle size corresponding to the permeability in actual engineering; k p is the actual permeability; m is a constant for a given rock medium; α is the shape factor; C e is the pore structure influence coefficient; e is the porosity ratio.

[0070] Among them, when the constant m of the given rock and soil medium is 0~0.1, 1 and 1.5, it is applicable to the calculation of sand, silt and clay respectively. When m=0, the equation is the Kozeny-Carman classic equation.

[0071] Specifically, the coarse-graining theory is introduced to calculate the equivalent particle size r of the actual engineering p After coarse-graining, the DEM particle size r c Equivalent particle size to actual engineering p The relationship is expressed as:

[0072]

[0073] Among them, λ ris the magnification factor, r c is the DEM particle size after coarse-graining, and c represents the numerical model after coarse-graining.

[0074] The number N is grouped into a whole coarse-grained particle. Under the condition that the density of the enlarged coarse-grained particle is the same as that of the fine particle in the actual project, the volume and mass of the coarse-grained particle are the same before and after the coarse-grained particle is expressed as:

[0075]

[0076] Assuming that the particle size distribution is the same, the actual number of engineering particles N P The number of particles N in the numerical model after coarse-graining c It is expressed as:

[0077]

[0078] Under the condition that the average permeability of the fluid unit is consistent with the engineering survey permeability, the engineering survey permeability and the particle size r of the DEM model are c The relationship is expressed as:

[0079]

[0080] Specifically, under the premise of ensuring that the seepage field model is consistent with the actual project permeability, project size, and boundary conditions, the velocity field and pore pressure field calculated from the seepage field in the fluid-solid coupling model and the actual seepage field will be consistent.

[0081] On this basis, in fluid-solid coupling, in addition to ensuring the consistency of the seepage field, it is also necessary to follow the fluid motion similarity criterion. The actual engineering model and the numerical model must have the same Newton number (Ne), Reynolds number (Re), Froude number (Fr) and Euler number (Eu) to make the two fluid systems similar.

[0082] However, in actual calculations, it is difficult to achieve strict similarity between two moving fluid systems. Therefore, it is difficult to achieve accurate calculations by simply ensuring that the non-dimensional parameters are the same.

[0083] In the seepage simulation of broken rock mass, the fluid movement is mainly dominated by viscous force. Therefore, the Reynolds number (Re) must be kept the same. In order to ensure the Reynolds number Re of the fluid-solid coupling model after the particle size is coarsened, p Equal, define the fluid-structure coupling numerical calculation fluid density The actual engineering fluid density The ratio is the similarity coefficient Numerical calculation of fluid viscosity coefficient using fluid-structure coupling The viscosity coefficient of the actual engineering fluid The ratio is the similarity coefficient According to the actual engineering and fluid-solid coupling numerical calculation model, the actual engineering Reynolds number is expressed as:

[0084]

[0085] Under the condition that the particle and flow field velocities of the actual engineering and the fluid-solid coupling numerical calculation model are the same, the similarity coefficient relationship between the actual engineering and the fluid-solid coupling numerical calculation model is expressed as:

[0086]

[0087] Among them, μ f is the dynamic viscosity coefficient of the fluid

[0088] In order to ensure that the N fine particles in the actual project and the single particle after coarsening are subjected to the same fluid force, the actual engineering and fluid-solid coupling numerical calculation model fluid-solid coupling force The need to be consistent;

[0089]

[0090] Interaction force between fluid and particles It consists of three parts: the drag force of the fluid, the force caused by the fluid pressure gradient, and the buoyancy of the fluid on the particle, expressed as:

[0091]

[0092] According to the coarse-grid fluid-particle coupling numerical analysis system, the fluid drag force It is defined as the drag force exerted by the fluid on the particle, always acting on the particle's center of mass, and the particle does not exert a rotational torque, expressed as:

[0093]

[0094] in, is the drag force on a single particle, is the average porosity of the fluid unit in which the particle is located, and χ is an empirical correction factor for the local average porosity; this correction term applies the force to high-porosity and low-porosity systems and a wide range of Reynolds numbers and is expressed as:

[0095]

[0096] Among them, C d is the resistance coefficient, ρ f is the fluid density, r is the particle radius, is the fluid velocity, is the particle speed.

[0097] Drag coefficient Cd It is expressed as:

[0098]

[0099] Among them, Re p is the actual engineering Reynolds number.

[0100] In addition, the modified empirical factor χ is expressed as:

[0101]

[0102] Bring in drag Calculation formula (9)-(13):

[0103]

[0104] To ensure that the equation holds, the fluid drag force, pressure gradient force, and buoyancy force on the N particles in the actual project and on the single coarse-grained and enlarged particle in the numerical model are the same:

[0105]

[0106]

[0107]

[0108] Where, the drag coefficient C in equation (16a) is d and the modified empirical factor χ are functions of the Reynolds number. Under the premise of ensuring that equation (7) holds, the coefficients of the original model and the similarity model are the same. Assuming that the particle sizes of each particle are the same, and substituting them into equation (4), equation (16a) is simplified to:

[0109]

[0110] For the calculation of the pressure gradient force on the particles in equation (16b), assuming that the particle sizes of all particles are the same, and substituting them into equation (4), equation (16b) is always valid. For the calculation of the buoyancy of the fluid on the particles in equation (16c), the weight of the particles can be changed into the floating weight to bring about the same physical and mechanical effects. While ensuring that the size and particle volume of the original model and the numerical model are the same, the density of the particles below the water level is set to the floating density (ρ particle -ρ water ), where ρ water is the groundwater density, 1000kg / m 3 Combining equations (7) and (17), we get the similarity coefficient λ ρf and λ μf can be amplified by the particle size factor λ r It is expressed as:

[0111] λ ρf =λ r (18a)

[0112]

[0113] Specifically, the engineering scale solid control equation is established:

[0114] The existing particle motion control equation in the CFD-DEM fluid-solid coupling method is controlled by Newton's law and is expressed as:

[0115]

[0116]

[0117] in, represents the particle movement speed; t represents the numerical calculation time; It represents the contact force between particles, including particle-particle contact force and particle-wall contact force, and reflects the interaction between particles through the contact model; Represents the non-contact force between particles, mainly including van der Waals force, electromagnetic force and capillary force; represents the external force; represents the total fluid-particle interaction force acting on the particle; m p Indicates the particle mass; represents the acceleration due to gravity; represents the particle angular velocity; Represents the contact torque on the particle; I p represents the particle moment of inertia.

[0118] The existing solid motion control equation (19) is improved and the particle mass is calculated according to the floating density. The engineering scale solid motion control equation in the CFD-DEM fluid-solid coupling method is expressed as:

[0119]

[0120]

[0121] Among them, m' p Indicates the mass of the particle calculated by the floating density. In the area without fluid action, the mass is calculated according to the dry density of the particle; I' p It represents the moment of inertia of the particle calculated according to the floating density. In the area without fluid action, the moment of inertia is calculated according to the dry density of the particle.

[0122] The mutual collision motion between particles, that is, the force-displacement motion equation, equation (20a) The particle contact force between particles The contact torque on the particle in equation (20b) is The calculation needs to be performed based on the corresponding contact model.

[0123] Among them, the commonly used contact models include linear contact model, Hertz-Mindlin nonlinear contact model, etc.

[0124] Specifically, the engineering scale fluid motion control equation is established:

[0125] The Darcy seepage control equation is improved, the particle size of the solid particles in the permeability is enlarged, and then the average permeability of each fluid unit is calculated. The engineering scale fluid control equation in the CFD-DEM fluid-solid coupling method is expressed as:

[0126]

[0127]

[0128]

[0129] Among them, k p is the engineering survey permeability, which changes accordingly with the change of porosity; μ is the fluid dynamic viscosity coefficient; r c represents the particle size in the DEM numerical model; r It indicates the particle size magnification factor for coarsening particles.

[0130] Among them, the empirical coefficient C e and α 2 According to the corresponding permeability test results based on different engineering geological conditions, the corresponding empirical coefficients of different broken rock compositions will also be different.

[0131] Specifically, the governing equation for engineering-scale fluid-particle interaction is: Introducing the coarse-grained particle size magnification factor λ r Fluid density ρ in calculation of fluid-solid interaction forces f and the fluid dynamic viscosity coefficient μ f After correction, the fluid-particle interaction control equation in the CFD-DEM fluid-solid coupling engineering scale analysis method is expressed as:

[0132]

[0133]

[0134]

[0135]

[0136] Specifically, Figure 1-2As shown in the figure, based on the existing traditional CFD-DEM fluid-solid coupling control equation, according to the permeability data of on-site engineering survey, combined with the coarse-grained theory and the similarity criterion of fluid-solid motion, the fluid-solid coupling control equation of the engineering scale is obtained, and a similar model is established.

[0137] In order to verify the feasibility of the application of the engineering scale analysis method for water and mud inrush in broken rock mass, a water and mud inrush inrush solid coupling model was established by taking Yonglian Tunnel in Jiangxi Province, China as an example. According to the on-site engineering survey, the fault permeability is 1×10 -8 m 2 , porosity 0.34, combined with the relevant empirical coefficients and formula (1), the actual equivalent particle size of the fault is 0.042m, and the equivalent particle size d in the DEM model is set to h is 1.65 m, then according to the engineering scale similarity parameter calculation formula (2), the coarse-grained particle size magnification factor is λ r It is 39.28. After the particles are enlarged, according to formula (4), the total number of particles is reduced by 60605.83 times.

[0138] According to the site size, the three-dimensional size of the flow field calculation model is 60m×190m×190m, and the groundwater level is 50m below the surface of Yonglian Tunnel. Figure 3 As shown, the groundwater density is set to 1×10 3 kg / m 3 , the viscosity coefficient is 1×10 -3 Pa·s, the model surface is the free water surface as the inlet boundary, the tunnel face is the outlet boundary, there is no flow on other surfaces, the fluid motion in the tunnel is ignored, the entire model is fixed, and the mesh deformation is not considered.

[0139] Through the engineering scale solid control equation (20), the particle size magnification factor is substituted into the engineering scale liquid control equation (21), and the particle size magnification factor is substituted into the engineering scale particle-liquid interaction control equation (22) for coupling calculation. According to the set coupling times and time, the coupling calculation of the engineering scale CFD-DEM coupling method is completed; Figure 4 and 5 As shown in the figure, there is no flow field distribution in the tunnel. After the tunnel face is exposed, the formation of the face causes the underground seepage field to change. The groundwater in the surrounding rock converges to the excavation face and then forms a precipitation funnel. This is basically consistent with the pore pressure and flow velocity distribution law of the Yonglian Tunnel calculated by other scholars using COMSOL multi-physics software under the same flow field boundary, which illustrates the rationality of the engineering-scale fluid motion equation.

[0140] Figure 6Figure 2 is a graph of particle migration inside the fault at different times. With the "funnel" distribution of the secondary seepage field formed by the tunnel face and the groundwater level, the particle displacement of normal rock and fault broken rock mass is compared. It can be found that after the sudden water and mud disaster, the particles in the fault enter the tunnel from the tunnel face, while the particles in the rock area basically do not move. This is basically consistent with the findings of the on-site investigation. Under the action of water flow and gravity, the particles in the fault enter the tunnel from the tunnel face. With the development of time, the particle collapse area in the fault first occurs in front of the tunnel face. Then it develops 29° upward along the fault until it reaches the interface between the fault and the rock. Then the collapsed area in the fault expands along the fault dip until it reaches the surface. Then the entire fault collapses. The overall change in the particle migration law in the fault is basically similar to the particle change law in the numerical simulation of the Yonglian Tunnel by Shandong University based on the traditional CFD-DEM coupling model and the Fluent-EDEM fluid-solid coupling program framework (initial stage of catastrophic evolution, middle stage of evolution, and late stage of evolution), which illustrates the rationality of the engineering-scale solid motion and fluid-solid coupling control equations.

[0141] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and variations can be made without departing from the technical principles of the present invention. These improvements and variations should also be regarded as the protection scope of the present invention.

Claims

1. An engineering scale CFD-DEM coupled optimization analysis method based on engineering survey permeability data, characterized in that: The following steps are involved: According to actual engineering survey, the actual permeability under actual particles is obtained, and the relationship between the actual permeability and the actual engineering equivalent particle size is established; Construct a seepage field geological model, enlarge the actual engineering equivalent particle size of the seepage field geological model based on the coarse-graining theory, and obtain the enlargement coefficient; Based on the similarity criterion of flow-solid motion, the similarity coefficient of fluid density and viscosity coefficient of the seepage field geological model is obtained; Based on the fluid density similarity coefficient and viscosity coefficient similarity coefficient of the seepage field geological model, the engineering scale solid control equation, engineering scale fluid motion control equation and engineering scale fluid-particle interaction control equation are established respectively.

2. The engineering scale CFD-DEM coupled optimization analysis method based on engineering survey permeability data according to claim 1, characterized in that: The method for constructing the relationship between the actual permeability and the actual engineering equivalent particle size is: According to the Kozeny-Carman extended equation containing clay, the relationship between the permeability calculated for engineering investigation and the actual engineering equivalent particle size is expressed as: Where p represents the actual engineering prototype, r p is the equivalent particle size corresponding to the permeability in actual engineering; k p is the actual permeability; m is the geotechnical medium constant; α is the shape factor; C e is the pore structure influence coefficient; e is the porosity ratio; Among them, when the rock and soil medium constant m is 0-0.1, 1 and 1.5 respectively, it is suitable for the calculation of sand, silt and clay respectively. When m=0, the Kozeny-Carman extended equation containing clay effect is the Kozeny-Carman classical equation.

3. The engineering scale CFD-DEM coupled optimization analysis method based on engineering survey permeability data according to claim 1, characterized in that: The coarse-graining amplification is as follows: the coarse-graining theory is introduced to calculate the equivalent particle size r of the actual engineering p Perform coarse-grained enlargement.

4. The engineering scale CFD-DEM coupled optimization analysis method based on engineering survey permeability data according to claim 1, characterized in that: The amplification factor is expressed as: Among them, λ r is the magnification factor, r c is the particle size of DEM after coarse-graining and enlargement, r p It is the actual engineering equivalent particle size.

5. The engineering scale CFD-DEM coupled optimization analysis method based on engineering survey permeability data according to claim 1, characterized in that: The seepage field geological model also includes: constructing engineering survey permeability and DEM model particle size r c relationship; The engineering survey permeability and DEM model particle size r c The relationship is: Select a number N of particles to be grouped as a whole coarse-grained particle. Under the condition that the density of the particles after the coarse-grained particle is the same as that of the fine particles in the actual project, the volume and mass of the coarse-grained particles before and after are the same, which can be expressed as: Assuming that the particle size distribution is the same, the actual number of engineering particles N P The number of particles N in the numerical model after coarse-graining c The relationship is: Under the condition that the average permeability of the fluid unit is consistent with the engineering survey permeability, the engineering survey permeability and the particle size r of the DEM model are c The relationship is expressed as:

6. The engineering scale CFD-DEM coupled optimization analysis method based on engineering survey permeability data according to claim 1, characterized in that: The method for obtaining the fluid density similarity coefficient and viscosity coefficient similarity coefficient of the seepage field geological model is: The fluid density similarity coefficient is defined as The viscosity similarity coefficient is The particle size magnification factor is λ r ,but:

7. The engineering scale CFD-DEM coupled optimization analysis method based on engineering survey permeability data according to claim 1, characterized in that: The engineering scale solid motion control equation is: Among them, m' p Indicates the mass of the particle calculated by the floating density. In the area without fluid action, the mass is calculated according to the dry density of the particle; I' p It represents the moment of inertia of the particle calculated according to the floating density. In the area without fluid action, the moment of inertia is calculated according to the dry density of the particle.

8. The engineering scale CFD-DEM coupled optimization analysis method based on engineering survey permeability data according to claim 1, characterized in that: The engineering scale solid governing equation is: The Darcy seepage control equation is improved, the particle size of the solid particles in the permeability is enlarged, and then the average permeability of each fluid unit is calculated. The engineering scale fluid control equation in the CFD-DEM fluid-solid coupling method is expressed as: Among them, k p is the engineering survey permeability, which changes accordingly with the change of porosity; μ is the fluid dynamic viscosity coefficient; r c represents the particle size in the DEM numerical model; r It indicates the particle size magnification factor for coarsening particles.

9. The engineering scale CFD-DEM coupled optimization analysis method based on engineering survey permeability data according to claim 1, characterized in that: The governing equation for the engineering-scale fluid-particle interaction is: Introducing the coarsening particle size magnification factor λ r Fluid density ρ in calculation of fluid-solid interaction forces f and the fluid dynamic viscosity coefficient μ f After correction, the fluid-particle interaction control equation in the CFD-DEM fluid-solid coupling engineering scale analysis method is expressed as:

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