Mass transfer at fracture intersections: An evaluation of mixing models

摘要: Models of solute transport in fractured geologic media that are based on the discrete network approach require a method be adopted for transferring mass through each fracture intersection. The two usual models partitioning between outflow branches crossing fractures assume either stream tube routing or complete mixing. A mathematical analysis two-dimensional, laminar flow intersection orthogonal with smooth walls is carried out to examine mixing process. Mixing ratios expressed terms local Peclet number (Pe = υr/D), where υ an average fluid velocity within intersection, r radius and D diffusion coefficient. As general observation concept does not properly represent transfer process at any value number. ratio equivalent may observed, but only particular geometries limited range Stream provide good approximation numbers greater than 1; some cases this limit as low 10−2. actual lower depends upon geometry bounding streamline separates into fractures, relation which enters There number, roughly 3 orders magnitude, extent dependent Pe