Modeling Multiphase Flow with Phase Transitions in Porous Media Quan Bui Applied Math, Statistics, and Scientific Computation University of Maryland - College Park mquanbui@math.umd.edu Advisors Amir Riaz Department of Mechanical Engineering University of Maryland - College Park ariaz@umd.edu David Moulton Applied Math Group T-5 Los Alamos National Laboratory moulton@lanl.gov Abstract A new approach to model multiphase flow in porous media with phase appearance and disappearance is to use nonlinear complementarity constraints. In addition to the standard mass balance equations for mulitphase flow, a set of complementarity constraints are added in order to handle the phase transitions. This results in a larger system of nonlinear equations, which is non-smooth in general. The system is subsequently solved using a semi-smooth Newton method. In this project, we aim to investigate this new approach and implement it in Amanzi, which is a part of the Advanced Simulation Capability for Environmental Management (ASCEM) program. 1