Light Nonaqueous‐Phase Liquid Movement in a Variably Saturated Sand

Abstract

AbstractNumerical simulations with the multifluid flow simulator STOMP are compared with quantitative results of a detailed lighter‐than‐water nonaqueous‐phase liquid (LNAPL) infiltration and redistribution experiment in a 1.67‐m‐long, 1‐m‐high, and 0.05‐m‐wide flow cell. The experiment was performed to test the ability of commonly used non‐hysteretic and hysteretic constitutive relations between relative permeability (k), fluid saturation (S), and capillary pressure head (h) to describe multifluid flow in two dimensions. The fluid and sand parameters necessary to apply the constitutive relations were obtained independently. The flow cell was filled with a homogeneous sand mixture under saturated conditions. After partial drainage of the sand, the LNAPL was slowly injected for 12 h from a small source area located at the surface. A dual‐energy gamma radiation system was used to determine LNAPL and water saturations at 255 locations during infiltration and redistribution. The results show a reasonable match between the experimental and numerical data, indicating that the constitutive relations used are adequate to describe relatively slow LNAPL infiltration and redistribution. The differences between the nonhysteretic and hysteretic simulations are small. This implies that hysteresis, a result of nonwetting fluid entrapment and pore geometry, was not important in this experiment.