PetraSim PetraSim is a graphical interface for TOUGH2, T2VOC, TMVOC, TOUGHREACT, TOUGH-Fx/HYDRATE, and TETRAD. These simulators are recognized for their powerful simulation capabilities involving fluid flow and heat transfer in porous and fractured media. The TOUGH2 codes have been applied to problems ranging from Yucca mountain groundwater flow to multi-component environmental remediation.