The effect of nonlinear groundwater flow on DNAPL migration in a rough-walled single fracture

Understanding the migration of DNAPL in water-saturated fractured rocks is important for DNAPL remediation design, because it affects the distribution or phase structures of DNAPL that determine the pressure-saturation-conductivity relation and the transport pattern of dissolved DANPL in fractured rocks. The migration characteristic of DNAPL in a single fracture needs to be thoroughly understood for the fracture network scale phase structure. Previous researches concerned with the DNAPL migration in two-dimensional fracture networks with a constant aperture show that ambient groundwater flow as well as aperture variation and network geometry influences DNAPL migration. However, rough walls in a single fracture make nonlinear flow even in low Re, which may control the phase structure of DNPAL in a single fracture. In this study, we present experimental results to consider the effect of nonlinear groundwater flow in a rough-walled single fracture on DNAPL migration. A glass replica of a granite sample containing a rough single fracture is made, which allows the visualization of DNAPL migration process, and experiments are conducted over a range of Re. Observations are compared to the results of DNAPL migration tests that are conducted in two parallel glass plates over the same range of Re to characterize the effect of nonlinear groundwater flow on the phase structure of DNAPL in a single fracture.