Study On Dynamic Characteristics Of Two-phase Flow Based On MRT-GF-LBM And Fractional Order

Porous media is a common space occupied by multiphase materials and a combination of multiphase materials.It is a solid material with continuous macro and random micro distribution in the pore space.Fluid flows in porous media to form multiphase,which can be described mostly according to engineering thermos-physics,theoretical mechanics and mathematics,but the analysis of the flow characteristics of multiphase flow has always been a troublesome problem.The purpose of this study is to propose a mechanical analysis method of multiphase flow in porous media.Combined with LBM and fractional order,the meso-macro multi-scale two-phase flow dynamic model is established,and the method of fluid solid boundary treatment is improved to improve the accuracy of boundary treatment.The theory in this paper can be used in oil exploitation,fluid intelligent control,software development and calculation analysis.The main research contents are as follows:（1）In order to accurately describe the hydrodynamic characteristics,the constitutive equation of viscoelastic fluid with Soret-Dufour effect is established based on double fractional order.The analysis shows that the increase of fractional derivative in momentum equation increases the fluid velocity,The increase of fractional derivative in temperature and concentration equation makes heat and mass transfer stronger.（2）Using Lagrange form surface interpolation to improve GF-LBM,the accuracy of boundary treatment is at least more than second order.In this paper,the pressure conditions of nonequilibrium extrapolation are used to extrapolate the values of macro variables to the relevant ghost points in order to calculate the equilibrium and nonequilibrium parts of the unknown distribution function,which are verified by two cases:the flow around a cylinder and the natural convection of an adiabatic cylinder in a horizontal shell.In qualitative analysis,Karman vortex street is formed with the increase of Re;With the increase of Ra,a plume is formed above the cylinder;In quantitative analysis,C_D andN_u are used to evaluate.Through theoretical verification,the accuracy is improved compared with previous studies.（3）In order to simulate the dynamic characteristics of two-phase flow in porous media embedded in bifurcation network,this paper reconstructs porous media based on QSGS,and then combines fractional order and MRT-GF-LBM（Chapter 3）to establish a medium macro layered upgrading scheme to simulate fluid transport in porous media.In order to facilitate the solution,Crank-Nicolson and L1 algorithm are used to discretize the fractional derivative,and then Thomas algorithm is used to solve it,the results show that the increase of?a can increase the velocity,thicken the velocity boundary layer,and the increase of?can inhibit the heat conduction of the fluid.This study can not only combine the advantages of the two theories in the kinematic analysis of viscoelastic fluids,but also solve the problem that it is difficult to verify by experiments in mesoscopic.In addition,the lattice permeability is calculated based on LBM,and then the internal permeability of porous media is described.This method can be used in complex occasions where the cross-sectional area is difficult to calculate.（4）In order to verify the fractional order model of two-phase flow established in Chapter 4,a straight pipe test-bed is built in this paper,the peristaltic pump is used to provide pulsating pressure,andAl₂ O₃ mixed solutions with different volume fractions are configured for experiments.The collected experimental data are compared with the theory,and it is found that the theoretical and experimental data in this paper have the same change trend,which shows the rationality and correctness of this paper.