非饱和-饱和土壤中水分入渗的数值仿真模拟

Numerical simulation of infiltrating water in variably saturated zone

为了定量整体描述非饱和-饱和区域内水流入渗过程,在水分入渗理论基础上,基于V-G模型建立了非饱和-饱和区域内水流运动的数学模型,分别对水分在不同粒径大小土壤中的入渗过程进行模拟;分析结果表明:入渗水分进入土壤的初期,由于粒径较大的土壤中充气粗孔的阻隔,使得压力水头与粒径较小的土壤相比减小速率较慢;当进入渗漏与渗透阶段后,粗大孔隙中的空气基本被水分所驱替,渗透性较好的土壤中压力水头减小速率较大;毛细管带高度也是导致下渗速率不同的因素之一,毛细管高度越大,进入渗透阶段的时间越短,反映在压力水头的变化上则为压力水头变化速率降低。

According to theory of the infiltraing water in unsaturated zone,the mathematical model,definited for moisture’s movment,is established on the basis of V-G model,then numerical simulation is executed by computer,and the situation of moisture’s movment in two different soil partical diameters is obtained.The results indicate that variational rate of pressure head in soil which has larger partical diameter is more than that in soil which has smaller partical’s diameter just in early stage of infiltraion,because that pores which are filled with air in larger patical diameter soil inhibit water infiltration.When the infiltrating procedure changes into permeation,the air filled in pore is drived out of and the variational rate of pressure head in soil is as quickly as permeation.Besides,the capillary-height is another factor that influnces the rate of infiltration,the higher of the capillary-height,the shorter of the time become into permeation,and this also can be reflected by the vairational rate of pressure head.