Numerical investigation for the effect of deformation and dynamic pressure on the fast drainage of porous materials

Abstract

In the case of a fast drainage process, water movements result in a rapid change in capillary pressure and shrinkage of a porous material. Until now the models used to predict the deformation of most porous media are based on the quasi-static behaviour laws, and dynamic effects are completely neglected. In this paper, a fully coupled model with dynamic capillarity effect considered is proposed for unsaturated water-air flow within deforming porous media. Then, this model is validated with respect to documented experiment on investigation of dynamic capillarity effect in unsaturated sand. The Finite Element Method (FEM) and backward Euler method are used for the discrete approximation of the partial differential equations in space and time, respectively. Numerical results provided by dynamic model have high agreement with recorded experiment data. Moreover, numerical results also reveal that dynamic effects on capillary pressure could cause unexpected deformation (shrinkage) for porous media. All investigations suggest that dynamic effects on capillary pressure should be taken into account to predict unsaturated water-air flow and shrinkage for porous media.