Simulation On Mesoscopic-scale Flow In Pores Of Saturated Porous Media Using Lattice Boltzmann Method

Fluid flow in porous media has been put in researches for extremely attention in a number of fields, such as geology, oil and gas, material engineering, chemical engineering, biological engineering, mechanical engineering, medicine and environmental protection, etc. The fluid has been generally assumed that flowing in the whole space of porous media using traditional methods for macroscopic-scale, namely seepage, which does not pay attention to the specific flow within the actual pores. With the deepening of the research on porous media flow, people no longer content about researches on macro-scale flow based on the assumption of the seepage. By means of microscopic and mesoscopic experiment methods, people gradually unveiled the porous media with complex pores structure, researches on microscopic or mesoscopic mechanism for macroscopic phenomena has been put on the agenda.Lattice Boltzmann Method (LBM) with molecular kinetics theory, the theory of statistical mechanics based on the Boltzmann equation and discrete speed model is established to simulate the particles’movement within the pores space, through numerical solution of distribution function, thereby gaining the macro flow information. LBM provides a new Method to study on fluid flow, which is gradually applied in the porous media flow, multiphase and multi-components flow, blasting and burning, chemical reaction flow, micro-scale or nanoscale flow, biological engineering, mechanical engineering, and other fields.This article achieves the single relaxation, isothermal, incompressible standard LBM algorithm in MATLAB, then simulates the fluent flow in column group by regularly arranged and digital core by 3D reconstruction based on fine sands CT scan imaging results using LBM. The details are as follows:(1) The paper finds out that the results by LBM simulation perfectly match with the existing results by analyzing the simulation about the pore-scale flow in porous media composed of regular arranged cylinders array using LBM, and comparison with others conclusions.(2) The paper gives a modifierformulaapplying to calculatingpermeability of porous media composed of regulartriangle arranged cylinders array based on LBM simulation results and Lee and Yang’s permeability formula about cylinders array square arranged. The modifierformula has a smaller relative error when compared with LBM simulation results.(3) The paper gives a new formula which could be used to calculate the permeability of porous media composed of square arranged cylindroids array, based on LBM simulation results, which could consider different ratios of long to short half axises and inclination angles of long axis of ellipses.(4) The paper simulates the flow in directional (0°～90°) alignment porous media composed of square arranged cylindroids array with random ratio of long to short half axis and inclination angle of long axis of every ellipse.(5) Based on digital core by reconstruction of silty sand with sheet-shape grains using CT scan imaging, the paper simulates the flow in pores of saturated silty sand when flow velocity is low using LBM. The permeability results of the silty sand sample using LBM coincides better with the measured permeability, which are in the same order of magnitude.