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大孔隙结构的建立和大孔隙流的渗流模拟能定性和定量的解释大孔隙流的产生机理及其动态变化过程。采用CT扫描获取斜坡非饱和带大孔隙域,基于不考虑外力项的格子Boltzmann方法,通过确定离散速度模型、平衡态分布函数和分布函数的演化方程三大组成部分,其中边界条件与计算假设依据染色示踪试验设定,定性定量化研究二维大孔隙流的渗流过程,研究结果表明:该方法能清晰定量化描述大孔隙流湿润前锋的推进过程,大孔隙效应明显,渗流场流速随着时间推移逐渐趋于稳定,大孔隙效应逐渐减弱;在连通性较好、孔径较大的区域流体流速较快,且在大孔隙中心流速最大,往两侧逐级递减;下层深度处的流体流量和流速往往受控于上一层大孔隙的孔径尺度。格子Boltzmann方法的应用能为大孔隙流特别是三维渗流过程的研究提供新手段。
The establishment of macropore structure and the seepage simulation of macropore flow can qualitatively and quantitatively explain the generation mechanism of macropore flow and its dynamic change process. Based on the Lattice Boltzmann method which does not consider the external force term, a large-scale macroscopic domain of unsaturated zone is obtained by CT scanning. The three components of the evolutionary equation of equilibrium velocity distribution function and distribution function are determined. The boundary conditions and calculation assumptions are based on The experimental results show that this method can clearly and quantitatively describe the advancing process of the macropore flow wetting front, and the macropore effect is obvious. The flow velocity of the seepage field increases with the increase of The time lag gradually stabilized and the macropore effect gradually weakened. In the area with good connectivity and large pore diameter, the fluid flow velocity was faster and the flow velocity was the largest in the center of the macropore and gradually decreased on both sides. The fluid flow at the depth of the lower layer And the flow rate is often controlled by the pore size of the upper macropores. The application of the lattice Boltzmann method can provide a new method for the research of macropore flow, especially the three-dimensional seepage process.