“…In the case of linear model (for low or moderate flow velocity), the drag is uniquely represented by permeability of porous material and viscosity of fluid, while in the nonlinear model (for high flow velocity), an additional drag parameter (non-Darcy, Forchheimer or inertia coefficient) must be known (Hassanizadeh and Gray 1987;Zeng and Grigg 2006). An estimation of the two drag parameters is most frequently performed by steady flow methods using (i) extrapolation of experimental results to zero velocity limit (for determining permeability) and infinite velocity limit (for determining inertia coefficient) or (ii) finding the parameters at once by best fit of model prediction to experimental data throughout, e.g., the least-square method (Antohe et al 1997). When porous materials have high permeability, as for example foams or trabecular bones, the identification of the drag parameters can be related to relatively significant uncertainty in permeability measurements (Antohe et al 1997;Bhattacharya et al 2002;Sharma and Siginer 2010) which results from limited precision of controlling pressure gradient and/or flow velocities as well as from boundary effects, i.e., mainly friction loss in conduits.…”