Study On Percolation Performance Of Fractal Porous Media Based On Renormalization Group Transformation Theory

Fluid flow and heat transfer phenomena in porous media are typical physical processes which is universal in the practice and application of industry and agriculture.Permeability is an important parameter to describe the conducting capacity of porous media and depends on the characteristics of pore structure.Due to the complexity of porous structure,the quantitative description of pore channel characteristics and the percolation performance of porous media are not enough.Therefore,it is very necessary for researchers to study the percolation performance of porous media in depth.On the basis of the fractal reconstruction models,the permeability of micro-pore structure is studied in this paper.The main contents and conclusions of this paper are as follows:First,the parameters of porous media,including porosity,particle shape,geometric size and arrangement,as well as the effect of particle caking on percolation,are numerically simulated.It is found in this study that with similar pore structure of porous medium,the permeability will increase with the increase of porosity,pressure and porosity is approximately exponential change law.The permeability increases with the particle size for homogeneous porous media composed of particles on the conditions of same porosity.Particle shape and arrangement will also have a certain effect on the permeability.The length and angle of particle chain formed by particle bond have great influence on the percolation performance,and the windward area is the main reason for the flow resistance.Secondly,based on the fractal characteristics of the real porous media,fractal geometry method is used to reconstruct the pore structure.Fractal porous models with typical pore distribution characteristics are established here.The CFD particle tracing technique is used to visualize the flow process in the fractal models.The motion mechanism of particles under the action of pressure and wall limitation in pore structure is analyzed.The random walk model in limited space is used to simulate the physical process of porous media.The results show that the fractal random walk method is feasible in describing the dynamic structural characteristics of porous structure.Finally,based on the fractal scale invariance characteristic,the method of the renormalization group transformation is applied to the numerical calculation of porous media percolation performance.We use the renormalization group transformation and neglect small scale details to coarsely visualize the porous media models.Based on maintaining similar structural features,we get coarse scale structures under different scales.A new method for calculating permeability of porous media based on renormalization group transformation is proposed,which simplifies the numerical calculation process and improves the computation efficiency.