  We perform direct numerical simulations of turbulent flow at friction
Reynolds number $Re_\tau \approx 500-2000$ grazing over perforates plates with
moderate viscous-scaled orifice diameter $d^+\approx40$--$160$ and analyse the
relation between permeability and added drag. Unlike previous studies of
turbulent flows over permeable surfaces, we find that flow inside the orifices
is dominated by inertial effects, and that the relevant permeability is the
Forchheimer and not the Darcy one. We find evidence of a fully rough regime
where the relevant length scale is the inverse of the Forchheimer coefficient,
which can be regarded as the resistance experienced by the wall-normal flow.
Moreover, we show that, for low porosities, the Forchheimer coefficient can be
estimated with good accuracy using a simple analytical relation.
