Flexible rings and rectangle structures floating at the surface of water are prone to deflect under the action of surface pressure induced by the addition of surfactant molecules on the bath. While the frames of rectangles bend inward or outward for
any surface pressure difference, circles are only deformed by compression beyond a critical buckling load. However, compressed frames also undergo a secondary buckling instability leading to a rhoboidal shape. Following the pioneering works of cite{Hu} and cite{Zell}, we describe both experimentally and theoretically the different elasto-capillary deflection and buckling modes as a function of the material parameters. In particular we show how this original fluid structure interaction may be used to probe the adsorption of surfactant molecules at liquid interfaces.
The present study aims to investigate the motion of buoyant rings in vertical soap films. Thickness differences and related bi-dimensional densities are considered as the motor leading to bi-dimensional buoyancy. We show how this effect can be re-int
erpreted thanks to surface tension profiles in soap films. We propose a model involving surface tension profiles in order to describe the motion of buoyant particles in vertical soap films, and compare it to experimental data.
We have studied the splashing dynamics of water drops impacting granular layers. Depending on the drop kinetic energy, various shapes are observed for the resulting craters. Experimental parameters that have been considered are : the size of the mill
imetric droplets; the height of the free fall, ranging from 1.5 cm to 100 cm; and the diameter of the grains. As the drop is impacting the granular layer, energy is dissipated and a splash of grain occurs. Meanwhile, surface tension, inertia and viscosity compete, leading to strong deformations of the drop which depend on the experimental conditions. Just after the drop enters into contact with the granular bed, imbibition takes place and increases the apparent viscosity of the fluid. The drop motion is stopped by this phenomenon. Images and fast-video recordings of the impacts allowed to find scaling laws for the crater morphology and size. This abstract is related to a fluid dynamics video for the APS DFD gallery of fluid motion 2010.
