基于水气二相流的稳定饱和-非饱和渗流模拟研究

非饱和带的渗流过程实质上是水、气两种流体在土壤孔隙中相互替代的过程,因此采用水-气二相流模型求解饱和-非饱和渗流问题更加合理.根据水、空气的质量守恒定律和达西定律,结合多相流理论建立水-气二相流模型,采用高效的积分有限差分法求解,给出精确模拟水相、气相边界的处理方法.通过求解Muskat稳定渗流问题得到逸出面长度与解析解基本一致,验证了水气二相流模型的有效性;由孔隙水压力、孔隙气压力和毛细压力的分布可知,稳定渗流中气相的影响几乎可以忽略,而非稳定渗流中气相的影响有待进一步研究.

Research on simulation of steady saturated-unsaturated seepage based on water-air two-phase flow theory

In general, there are two kinds of fluids (water and air) through saturated-unsaturated porous media in seepage process, so the water-air two-phase flow model is regarded as a better numerical model to obtain the refined solution to saturated-unsaturated seepage problem. Taking into account the movement of air flow and water flow the numerical model is developed. Using the integral finite difference technique, a fully implicit simultaneous computation code is developed, which is used to simulate the Muskat problem. By comparing the calculated value of seepage face and theoretical value of seepage face, the accuracy of the model is verified. The distributions of pore water, air pressure and capillary pressure indicate that for steady state seepage problem, the effect of air phase can be considered as a passive phase, but for unsteady state seepage problem, the effect of air phase should be paid more attention to.