Under impact, as shown by recent studies, Oobleck suddenly changes from liquid to solid because of the activation of frictional contacts between the starch particles. In this article, they conclude that for Oobleck, waves do not arise from the effect of inertia, as for water, but from Oobleck's specific flowing properties. Their results are presented in a paper published on December 18 in Communication Physics. This surprising observation led the team to look for a scenario to explain their formation. These experiments revealed that for concentrated Oobleck, the onset of destabilization is different for destabilization in a Newtonian fluid such as water. The researchers measured the onset of wave appearance and their speed using controlled perturbation of the flow and laser detection to estimate the fluid film thickness. In order to unveil the origin of Oobleck waves, they conducted careful experiments with a mixture of cornstarch and water down an inclined plane. However, the scientists noted qualitative differences with water waves waves in Oobleck grow and saturate much faster. Similar waves can be observed on gutters and windows on rainy days. Researchers from Aix-Marseille University in France have now studied the regular and prominent surface waves that form when a Oobleck flows down an inclined slope (see Figure 1).
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