Fig. 2.

Variations of the wall shear stress τ_m as a function of the permeability-based Reynolds number Re_K: comparison between the CFD calculations of Cruel et al. and the analytical expressions proposed in the present paper (Eqs. 9–10). Inset: linear regression of Cruel et al. data ${\tau }_m/\left(\mu s{u}_s/{\epsilon }^2\right)$ versus Re_K