多孔介质内流体流动的大涡格子Boltzmann方法研究

Study of flow in porous media by LES-LBM coupling method

为研究多孔介质内流动随Re数变化的特点,采用结合Smagorinsky亚格子模型的格子Boltzmann方法(LES-LBM)对多孔介质内流动进行了数值模拟.结果表明:多孔介质内的单相流动在高Re数时会表现出复杂的非线性现象;LES-LBM克服了传统LBGK方法模拟高Re数流动时容易产生数值不稳定的缺点,能清晰地描述出多孔介质内流动存在的3个区域,即低速时的线性达西区、过渡区和高速时的非线性二次区;不同Re下的流线图还说明微观的惯性作用最终导致了多孔介质宏观上的非线性现象,多孔介质流动呈现明显的多尺度特征.进一步分析计算结果可以证明:LES-LBM方法能准确地验证Darcy-Forchhimer阻力方程,Darcy-Forchhimer总阻力随Re数增加而增加,随孔隙率增加而减小,并且小孔隙率下的Forchhimer阻力占总阻力比例小于大孔隙率时的比例.

To study the variations of single-phase flow in porous media with various Reynolds, numerical simulations of the flow were carried out by using the large-eddy simulation（LES） based on lattice Boltz- mann method（LBM）. Results show that the single-phase flow in porous media has a complex non-linear phenomena at high Reynolds numbers; the LES-LBM coupling method is superior to the traditional lattice Bhatnagar - Gross - Krook （LBGK） method in numerical stability. This method can clearly shows three flow regimes in porous media when Reynolds numbers are increasing, which are the Darcy, the no-Darcy and the transition regimes. The streamlines at various Reynolds numbers show that the microscopic iner- tial effect leads to the macroscopic non-linear phenomena. The flow in porous media shows strong multi- scale features. Further analyses on the calculation results demonstrate that the LES-LBM method can veri- fy the Darcy-Forchhimer drag equation. The Darcy-Forchhimer drag increases with Reynolds numbers but de- creases with porosity, and ratios of Forchhimer darg increases quickly with porosity.