Design and testing of a passively adaptive inlet

Mechanical instabilities and elastic nonlinearities are emerging engineering means for designing shape-changing devices. In this paper, we exploit the taxonomy of post-buckling behaviours of a glass-fibre panel to design an adaptive air inlet that passively regulates the fluid flow into a connected duct. The adaptive component controls the inlet aperture by snapping open and closed depending on the velocity and pressure of the surrounding fluid. Sensing, actuation and control is entirely governed by the characteristics of the post-buckled component. Post-buckling stresses - induced in the composite panel by suitably applying compressive and bending loads - create the intrinsic characteristics of stability required for the panel to snap-through and snap-back. Furthermore, the associated post-buckled shape creates the aerodynamic pressure fields required for actuation. This design concept is explored and validated here by means of wind tunnel experiments. The passive actuation and control mechanism presented is particularly valuable for fluid control applications where simplicity and mass-minimisation are critical.