This study investigates the pressure drop in horizontal pipes packed with large particles that result in small pipe-to-particle diameter ratio both experimentally and numerically. Two horizontal pipes of 0.1905 and 0.0254 m ID filled with cylindrical or spherical particles are used to collect the experimental data for single and two-phase flows. The porosity has same value for both pipes when they packed with cylindrical particles which is 0.75, however has different values when packed with spherical particles, 0.7 for the large pipe and 0.57 for the small pipe. The Roe-type Riemann solver proposed by Santim and Rosa Int J Numer Methods Fluids 80 (9), 536–568, [36] which uses the Drift-Flux model is modified aiming to predict the pressure drop in porous media through the implementation of a new source term in the system of equations. Empirical models available in the literature are used to calculate the single and two-phase flows pressure drop. The motivation is to verify the solver capability to reproduce the two-phase flow pressure drop in porous media and to compare some empirical models existing in the literature against the experimental data provided modifying some empirical coefficients when necessary.