When a liquid droplet touches a porous surface, its penetration is first inhibited by a short inertial phase, followed by a longer regime dominated by viscosity. Although the inertial phase governs the dynamics of penetration, it is nearly impossible to observe it on Earth, as drops must be very small to avoid being deformed by gravity. As a result, the inertial phase has so far only been studied
with numerical simulations, which our microgravity experiments intend to validate. In the ZARM drop tower, residual gravity is low enough to stage large centimetric drops, which our unique apparatus has successfully generated by separating two hemispheres coated with a water repellent. The student team from the Friedrich-Alexander-University (FAU) Erlangen-Nürnberg will use a high-speed camera to trace the penetration of large drops in several porous media and thus gauge the accuracy of simulations. We are supervised by Thorsten Pöschel and Jonathan Kollmer at the FAU, and we collaborate with Patrick Perré at the Ecole Centrale in Paris, who produced the numerical simulations, and Michel Louge at Cornell University, who helped with development of the experiment.
