Water waves in granular rafts – WAWRAFT

The presence of particles at the surface of a liquid can drastically alter its properties. Particles can stabilise an interface, preventing droplets from coalescing and enhancing emulsion stability. On a different scale, fragmented sea ice interacts with ocean waves, potentially dissipating, reflecting, or diffusing them. These examples illustrate how floating objects impact various contexts, but despite their significance, the mechanical properties of particle-covered surfaces remain largely unexplored.

Granular rafts, made up of millimetric to centimetric grains floating at a liquid's surface and held together by capillary forces, present a model system to investigate the physics of particle-laden interfaces. Granular rafts are a powerful experimental platform to study the mechanical behaviour of particulate 2D materials, in particular to understand their interaction with surface waves. Indeed, waves offer a non-destructive method to characterise the properties of a material, but it is also possible to create a wave-controlling structures, to steer waves at will.

I will use 3D printed particles that can be easily tailored to present specific capillary interactions, which in turn will enable me to create both ordered and disordered rafts with a controlled microstructure. I will then send surface waves on those rafts to probe their mechanical properties. By measuring the wave fields, I will be able to extract valuable information on the effective elasticity of the rafts, but also on more complex wave phenomena, such as bandgaps, i.e. a range of frequencies that are not allowed to propagate in the medium.

Understanding and controlling these effects will be relevant for various applications, at an environmental level to provide insight for ice floe-wave interactions in polar regions, or in industrial processes that involve droplet manipulation and emulsion stabilisation for instance.