基于格子Boltzmann方法的饱和土壤渗流与传热数值模拟

Numerical simulation of seepage and heat transfer in saturated soils based on lattice Boltzmann method

利用随机多孔介质生成算法重构了与真实土壤外貌相近的多孔介质几何结构。通过引入不可压耦合双分布格子Boltzmann模型(lattice Boltzmann model,LBM)对孔隙尺度下单相饱和土壤渗流和传热进行了模拟。着重讨论了不同渗流压差、孔隙率、土壤固体颗粒尺寸分布对流动与传热的影响。结果表明:土壤渗流速度与渗流压差呈线性单调递增关系,平均温度随渗流压差增加而增大,但温升速率逐渐减缓;当孔隙率增大时,渗流速度增加,且当孔隙率大于0.58时,对流传热作用迅速增强,土壤温升速率显著加快;对于相同孔隙率,当土壤固相颗粒尺寸较大时,流动出现典型优先流效应;随着土壤固相颗粒尺寸减小,土壤温度变化逐渐趋于平缓,平均温度降低。

A random generation growth method was introduced to reconstruct the microstrueture of soil. The geometry of reconstruction was similar to real pore-scale structure of soil. A numerical study was then performed for simulation of pore-scale single phase saturated soil seepage and heat transfer process using lattice Boltzmann model （LBM）. Effects of different seepage pressure difference, porosity and particle size of porous media on flow and heat transfer were analyzed emphatically. The results indicate that both the seepage velocity and average temperature of soil increase with an increase in the seepage pressure difference, while the rising rate of temperature slows down gradually. With an increase in the porosity, the seepage velocity increases spontaneously , and when the porosity of soil is higher than 0.58, the effects of convective heat transfer and the rising rate of temperature are rapidly increasing. For the same porosity, when the soil particle size is larger, the phenomenon of typical preferential flow occurs. With a decrease in soil particle size, the soil temperature changes slowly and its average value decreases accordingly.