Numerical Experimental Study On The Influence Of Particle Shape On The Seepage Characteristics Of Porous Media

The permeability characteristics of porous media are significantly influenced by particle shape,which also dictates the fluid’s flow path within the pore structure.Examining the effect of particle shape on these permeability characteristics can not only expand our knowledge of the seepage mechanism of porous media,but also supply theoretical guidance for the prevention of seepage in earth-rock dams and the prevention measures used in engineering construction.The permeability characteristics of porous media are investigated in this paper,with porosity,tortuosity and particle shape being the research objects.Firstly,PFC3D software is used to establish the pore medium model with complex particle shape,and then the Tianhe No.2calculation platform is used to conduct LBM seepage simulation.With the help of theoretical analysis,a permeability prediction model based on the traditional Kozeny-Carman model is established.After that,through self-designed constant water head test equipment,the indoor penetration test is conducted on the target sample prepared by 3D printing technology.The test results are compared with the results of the prediction equation in this paper and the traditional Kozeny-Carman prediction equation to discuss the accuracy of the permeability analysis model proposed in this paper.The main work and conclusions of this paper are as follows:（1）Select two groups of ellipsoidal particle shapes（Oblate,a=b>c;Prolate,a=b<c）for research,and the shape parameterψ（ratio of sphericity to roundness）is used to quantitatively analyze the particle shape from a three-dimensional perspective.Nine sets of ellipsoidal particle cluster（Clump）templates are generated by filling geometry,and then the pore medium model composed of ellipsoidal particles is generated by calling the template.The pore structure of the model is extracted by Avizo software to analyze the influence of particle shape on the pore specific surface area.The model’s pore-specific surface area rises with the divergence of ellipsoidal particles from the sphere,and the alteration of oblate ellipsoidal particles is more conspicuous than that of prolate ellipsoidal particles,as evidenced by the results.（2）Verify the accuracy of the LBM program used through numerical simulation and indoor penetration testing.Import the model particle information into LBM for seepage simulation,and study the influence of particle shape on the permeability characteristics of porous media.Results showed that,as porosity increases,the permeability of porous media test rises with different shape parametersψ（ratio of sphericity to roundness）,while the change trend flattens with the decrease of shape parametersψ（ratio of sphericity to roundness）.At the same porosity,the permeability decreases with the decrease of shape parameters,indicating that the permeability of the sample with the particle shape deviating from the sphere’s internal pore structure is worse.The special structure of prolate ellipsoid particles causes accumulation between them when they fall freely,thus not significantly altering the surface area of their pore structure.Therefore,compared with oblate ellipsoid particles,the permeability difference between different shape parameters of prolate ellipsoid particles is small.（3）The numerical simulation results are used to carry out linear fitting with the commonly used porosity function and tortuosity function respectively,and the porosity function and tortuosity function that has the highest correlation with permeability is obtained.On this basis,the shape correction coefficient CF is obtained by inverse calculation,and is linearly fitted with the shape parameterψand the aspect ratio respectively.The permeability prediction model of porous media,which takes into account porosity,tortuosity,and particle shape,is established by the Kozeny-Carman model.The results show that the porosity function n³/（1-n）² and tortuosity functionτ₆ have a very high linear correlation with permeability.The shape parameterψis more suitable for describing the shape correction factor CF than the aspect ratio.（4）Metal 3D printing technology is employed to ready the desired porous media sample.The indoor permeability test,conducted with the self-crafted constant head test equipment,was used to determine the permeability of the sample.This was then compared to the prediction results of this equation and the traditional Kozeny-Carman equation.The results indicated that the prediction model in this paper,within the permissible error range,was more accurate than the traditional Kozeny-Carman model and was closer to the test results.