LIGHT NONAQUEOUS-PHASE LIQUID MOVEMENT IN A VARIABLY SATURATED SAND

Numerical simulations with the multifluid flow simulator STOMP are com pared with quantitative results of a detailed lighter-than-water nonaq ueous-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 nonhysteretic and h ysteretic constitutive relations between relative permeability (k), fl uid saturation (S), and capillary pressure head (h) to describe multif luid flow in two dimensions. The fluid and sand parameters necessary t o apply the constitutive relations were obtained independently, The fl ow cell was filled with a homogeneous sand mixture under saturated con ditions, After partial drainage of the sand, the LNAPL was slowly inje cted 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 sa turations at 255 locations during infiltration and redistribution, The results show a reasonable match between the experimental and numerica l data, indicating that the constitutive relations used are adequate t o describe relatively slow LNAPL infiltration and redistribution, The differences between the nonhysteretic and hysteretic simulations are s mall. This implies that hysteresis, a result of nonwetting fluid entra pment and pore geometry, was not important in this experiment.