Knowing the experimental data of acLD, for different tested situations covering several stoppers diameters pd and densities pρ, loading factors θ and air interstitial velocities (necessary to calculate the Froude number fUfgUFr= ), these data were correlated through dimensionless numbers, as shown in Eq. (3). The fitting parameters α, β, γ, δ and η, are obtained through the application of a commercial software for nonlinear regression analysis.