The ForDiMHyS project is a program devoted to experimental studies and the model development of the kinetics of FORmation and Dissociation of Methane Hydrates in Sediments. The first part of the project which is presented in another paper (Bonnefoy and Herri, 2002) is designed to obtain experimental data on hydrate formation & dissociation under in-situ temperature and pressure conditions of methane hydrate in well constrained porous materials. The second part presented hereafter consists in modelling the flows inside the core; a specific numerical model has been developed to simulate the experimental set-up described in part one. The numerical model is 3D three phases and simulates the kinetics of hydrate dissociation and formation, taking into account the solubility of methane in water and the heat of phase transitions.