基于改进QSGS-LBM法的各向异性重构土体的渗流模拟

Numerical simulation of anisotropically reconstructed soil seepage based on improved QSGS-LBM method

为解决传统四参数随机生长(quartet structure generation set, QSGS)方法重构模型与真实土体情况不符的缺陷,提出一种改进的QSGS方法,在综合考虑各向异性、孔隙率、土体颗粒大小情况下构建各向异性多孔介质模型.采用两点自相关函数法验证模型的有效性,并结合格子玻尔兹曼方法自编Matlab程序来模拟细观渗流过程.实验发现,各向同性模型和土体CT切片的两点相关系数最大差值是各向异性模型的2.5倍以上,且流体粒子在孔道中线处的渗流速度最大,达到0.03,在孔壁处渗流速度接近于0.结果表明,各向异性模型在孔隙结构和空间分布上更接近真实土体情况,流体在渗流后期出现大孔隙优先流现象和指进现象.

In order to solve the defect that the reconstruction model generated by the traditional quartet structure generation set(QSGS)method is inconsistent with the real soil condition,an improved QSGS method is proposed.The anisotropic porous medium model was constructed by considering anisotropy,porosity and soil particle size,and then the validity of the reconstruction model was verified by the two-point autocorrelation function method.Combined with the lattice Boltzmann method,the Matlab automatic program was used to simulate the meso-seepage process.It finds that the maximum difference of the two-point correlation coefficient between the isotropic model and the CT scan slice is more than 2.5 times that of the anisotropic model.The seepage velocity of fluid particles at the middle line of the channel is the largest,and its value can be reach 0.03,while the seepage velocity at the wall of the channel is close to 0.It shows that the anisotropic model is closer to the real soil in pore structure and spatial distribution.Pore preferential flow and finger-in phenomena exists in the later stage of seepage.