A numerical simulator based on the discrete network model approach has been developed 12 to simulate drainage processes in a water-saturated porous medium. To verify the predictive 13 potential of the approach to simulate the unstable migration of adense nonaqueousphase liquid 14 (DNAPL) at the pore scale, the numerical model was applied to laboratory experiments 15 conducted on a sand-filled column. The parameters relative to pore body size and pore throat 16 size used in the construction of the equivalent network were derived from discrete grain-size 17 distribution of the real porous medium. The observed water retention curve (WRC) was first 18 simulated by desaturation of the network model.The good agreement of the modelled WRC 19 with the experimental one highlights that the applied approach reproduces the main 20 characteristics of the real pore space. The numerical model was then applied to rate controlled 21 experiments performed on a homogenous sand-filled column to study the gravity-driven 22 fingering phenomenon of immiscible two-phase flow of water and a DNAPL. The numerical 23 results match within 10% based on the standard deviation with the experiments. They correctly 24 reproduce the effect of several system parameters, such as flow mode (upward flow and 25 2 downward flow) and the flow rate, on the stability of the water/DNAPL front in a saturated 26 porous medium.