毛细饱和带横向渗流数值模拟

Numerical Simulation of Lateral Flow in Capillary Saturation Zone

自主编写计算机程序构建了分别基于达西定律和非线性渗流规律的渗流数值模拟技术,并开展了稳定毛细条件下多孔介质中的横向渗流实验,揭示了多孔介质毛细饱和带中渗流流场的分布特征及其变化规律:1在渗透性良好的多孔介质毛细饱和带中的渗流,当补排水水位差增大时,总水势等势线在各区域均增大,分布得更为密集;压力势水平向梯度在各区域亦均增大;压力势垂向梯度在上升流动区增大,在下降流动区减小,在中部近水平流动区变化不大;毛细饱和带厚度在上升流动区减小,在下降流动区增大,在中部近水平流动区变化很小,且仍近似等于水静止时的毛细饱和带厚度。2在低渗透性多孔介质毛细饱和带中的低速渗流,在整个渗流区域,按达西定律推算的相同总水势值的等势线比按非线性渗流规律推算的更靠近排泄区;在水势梯度较小的区域,按达西定律计算出的总水势等势线分布比按非线性渗流规律推算的更稀疏;反之,在水势梯度较大的区域,按达西定律计算出的总水势等势线分布比按非线性渗流规律推算的更稠密;结果表明,以非线性渗透规律为基础的数学模型对低渗透多孔介质毛细饱和带中低速渗流规律的刻画更为准确。

Based on Darcy law and non-linear flow law,the numerical simulation technology of water flow in saturated-unsaturated zone was constructed by independent writing computer programs.The experiment of lateral flow in porous media under the condition of stability capillary was conducted by using numerical simulation technology.The distribution characteristic and its variation regularity of flow field in capillary saturation zone of porous media was indicated as follows：（1）For the lateral flow in good permeability porous media under the condition of stable capillary,the equipotential line distribution of total water potential in flow field becomes more intense when the water level difference between supply area and drainage area increases,while the total water potential gradients increase in flow field and horizontal pressure potential gradients increase also.Vertical pressure potential gradients increase in rising flow area,and decrease in falling flow area,and change little in the central nearly horizontal flow area,while the thickness of the capillary saturation zone decreases in the rising flow zone,and increases in the down flow zone,and changes little in the central nearly horizontal flow area and remains approximately the thickness of the capillary saturated zone when water is still.（2）For the low speed lateral flow in low permeability porous media under the condition of stable capillary,in the whole the flow area,total water equipotential line simulated by using the mathematical model based on Darcy＇s law is closer to the discharge area than the one simulated by using the mathematical model based on nonlinear flow law.In the zone with less water potential gradient,the total water equipotential line distribution calculated according to Darcy＇s law is sparser than the one calculated according to non-linear flow law.On the contrary,in the zone with more water potential gradient,the total water equipotential line distribution calculated according to Darcy＇s law is denser than the one calculated according to non-linear flow law.The results show that the numerical simulation model based on the non-linear flow law could describe more accurately than the law of low speed lateral flow in low permeability porous media under the condition of stable capillary.