FRACK: A Freeware Flow and Transport Suite for Fractured Media

FRACK is a fractured media freeware flow and solute transport suite currently under development that is intended to serve as both a preand post-processor to MODFLOW. As a pre-processor, FRACK generates and maps networks of deterministic and/or stochastic fractures onto a regularly-spaced finitedifference grid, according to a fracture continuum method that closely approximates flow solutions to discrete fracture network (DFN) simulations. Thus, the methodology employed by FRACK is applicable to field sites where the DFN simulation approach is valid – flow through a rock mass occurs exclusively through sparse to intermediate networks of interconnected fractures. Moreover, unlike DFN, this methodology can also simulate flow and transport in fractured permeable rock. The solute transport postprocessor to MODFLOW is based on a version of the reliable random walk code RWHet, with specific revisions for simulating conservative and non-conservative particle trajectories through MODFLOW flow solutions. Prior applications of FRACK involving both 2-D and 3-D fracture networks will be used to demonstrate the similarity between fracture continuum and DFN flow solutions and the ability of this suite to capture anomalous transport behavior typical of highly heterogeneous media. Current and future capabilities of both the fracture network generator and mapping pre-processor and the random walk transport simulator are presented.