Simulation Of Fluid Flow In Complex Channels By LBM Method

The single-phase fluid and two-phase fluid micro flow in the complex channel are common in the natural and industrial fields,which are the basic phenomena in the energy,chemical,environmental and other disciplines.There are two advantages to carry out the numerical calculation of this phenomenon with the macro-micro-combination idea,that is,to investigate the flow details at the micro scale and to calculate the overall seepage parameters at the macro scale.The lattice Boltzmann method,which is easy to deal with complex boundary,is widely used in this study and has great potential.However,in practical applications,there are still more difficulties in precise extraction of complex channels,reasonable determination of size,correct selection of flow models,effective coupling of micro forces and efficient realization of solution,etc.In view of that,the following studies are carried out in this paper:In this paper,based on the gray scale image of sandstone medium obtained by Micro-CT scanning experiment,the two channel model is accurately reconstructed and randomly extracted by the corresponding image processing algorithm,and the complexity of the two models are characterized by the equivalent conversion algorithm.Using LBM algorithm,the author studied the single-phase flow microfluidic calculations under different pressure gradients in two sizes of REV models in the way of C++ programming.What's more,the distribution characteristics of the flow velocity and pressure in the channel were visually demonstrated.And verified the absolute permeability value calculated by Darcy's Formula with the values measured in the experiment.The results show that the calculation of the single-phase microfluidic flow in the channel based on the combination of CT scanning technology and LBM algorithm has the advantages of visualizing the microscopic flow details and effectively measuring the macroscopic permeability value.Based on the "square-shaped drop become circle-shaped" simulation,it is verified that the relationship between the pressure difference,inside and outside the stable droplet,and the reciprocal of radius is consistent with the Laplace law.Further investigation shows that the intensity of fluid interaction is linear with the interfacial tension.Then the relationship between the wall false density and the wetting angle is studied based on the simulation of " the spreading of the square-shaped drop " on the surface of the wall.The above calculation lays a foundation for determining the interfacial tension and specific wettability in the two-phase flow microfluidic calculation of complex channels.Using the D2Q9 velocity model of SC-LBM method and the coupling method of micro force,the authors have carried out the numerical calculation of the two-phase fluid micro flow under three typical wetting conditions and two kinds of viscosity ratio in the two-dimensional or two-dimensional channel.The microcosmic flow details,such as the variation characteristics of the two-phase fluid interface in the channel and the occurrence of the two-phase flow,are emphatically investigated,and the macroscopic seepage parameters,such as the relative permeability and displacement efficiency calculated according to the whole and dynamic process of the model,are emphatically analyzed.According to this,the simulation calculation of the two phase interface evolution under the different wettability conditions in the three dimensional channel is carried out by using the D3Q19 velocity model of SC-LBM method.The characteristics of the two phases in the two types of channels are consistent,and the results are in conformity with the previous laboratory experiments.