The drag force typically rises with flow speed, except in cases like drag crisis or abrupt shape changes, such as wind-induced tree pruning. While pruning reduces drag sharply and maintains structural integrity, it is irreversible. An attractive alternative for abrupt shape change is snap-through events in flexible structures. Origami provides a promising framework for crafting such shape-morphing structures. By prescribing specific folds, one can achieve the desired kinematic pathway and mechanical properties, particularly multistability.
I will talk about bistable origami units capable of transitioning to a second stable state either by following the kinematic path or by utilizing a hidden degree of freedom arising from facet bending. These units can either deform continuously in flow with a snap-through event or maintain their shape before and after snapping to the second state. Both behaviours show a discontinuous evolution of drag with increasing flow speed. By adjusting geometrical and mechanical properties, we can modify and fine-tune the snapping event and the drag force experienced by the unit. I will show some experiments corroborated by a theoretical aero-elastic model that balances fluid forces with elastic forces. The talk will presents an origami design strategy for creating efficient passive deployable structures capable of controlling drag in fluid environments. For instance, I will demonstrate an origami structure functioning as a passive valve to regulate flow.