Jet impact on a soap film

LG14014E - We experimentally investigate the impact of a liquid jet on a soap film. We observe that the jet never breaks the film and that two  qualitatively different steady regimes may occur. The first one is a refraction-like behavior obtained at small incidence angles when the jet crosses the film and is deflected by the film-jet interaction. For larger incidence angles, the jet is absorbed by the film, giving rise to a new class of flow in which the jet undulates along the film with a characteristic wavelength. Besides its fundamental interest, this study presents a new way to guide a micro-metric flow of liquid in the inertial regime and to probe foam stability submitted to violent perturbations at the soap film scale.

Geometric Mechanics of Curved Crease Origami

LT13067 - Origami has been widely applied to fields in structural engineering, architecture, and design, contributing to solutions of many practical problems of these fields. Although the idea that a sheet of paper can be folded along an arbitrary curve seems unfamiliar, such folds have been incorporated into origami sculptures for quite some time, and are also seen in decorative and functional boxes such as the McDonald's Fries Box. Though the crease of an open closed fold lies flat on the plane, a closed crease buckles dramatically and appears mechanically stiff. Previous work has described the geometry of curved folds. For the first time, we have presented an analytical and simulation model of the mechanics of curved fold origami. We show that it is the interaction between the geometry of the fold, the mechanical tendency to avoid in-plane stretching, and the bending energy of the sheets that produce both the three-dimensional shapes observed and the mechanical stiffness.