  This paper investigates the effect of permeability on two-dimensional
rectangular plates at incidences. The flow topology is investigated for
Reynolds number ($Re$) values between 30 and 90, and the forces on the plate
are discussed for $Re=30$, where the wake is found to be steady for any value
of the Darcy number ($Da$) and the flow incidence ($\alpha$). At $Re=30$, for a
plate normal to the stream and vanishing $Da$, the wake shows a vortex dipole
with a stagnation point on the plate surface. With increasing $Da$, the
separation between the vortex dipole and the plate increases; the vortex dipole
shortens and is eventually annihilated at a critical $Da$. For any value of
$Da$ below the critical one, the vortex dipole disappears with decreasing
$\alpha$. However, at low $Da$, the two saddle-node pairs merge at the same
$\alpha$, annihilating the dipole; while at high $Da$, they merge at different
$\alpha$, resulting in a single recirculating region for intermediate
incidences. The magnitudes of lift, drag, and torque decrease with $Da$.
Nevertheless, there exists a range of $Da$ and $\alpha$, where the magnitude of
the plate-wise force component increases with $Da$, driven by the shear on the
plate's pressure side. Finally, the analysis of the fluid impulse suggests that
the lift and drag reduction with $Da$ are associated with the weakening of the
leading and trailing edge shear layer, respectively. The present findings will
be directly beneficial in understanding the role of permeability on small
porous wings.
