Noncirculatory fluid forces on panels with porosity gradients

This Note determines the unsteady non-circulatory forces on an arbitrarily deforming panel with a Holder-continuous porosity distribution. An analytical expression for the non-circulatory pressure distribution is presented and evaluated for the special cases of uniform and variable-porosity panels undergoing harmonic deformations, where special attention is paid to the influence of the panel end conditions. These results constitute the first major step towards a complete linearized, unsteady aerodynamic theory for lifting porous bodies, which may have potential application to the performance estimation of biologically-inspired swimmers and fliers and to the future assessment of aeroelastic stability and flow noise production of porous airfoils.