Modeling the fragmentation of brittle object in turbulence*

The mechanism and the rate of fragmentation of plastic litters in the oceans are of paramount importance to model the fate of microplastic in open sea. The more likely scenario is a fragmentation of large plastic objects during storms after a fragilisation by UV radiation, salinity corrosion, ... From a fundamental point of view, this raise the question of the process of fragmentation within turbulent flow. This problem has been investigated for the fragmentation of particle aggregates but not for brittle object. Here we perform experiments and compelementary numerical simulations of the fragmentation of a single deformable objects that behaves elastically up to breakage. We exhibit a comprehensive fragmentation scenario, further modeled by an evolution equation. Our results demonstrate that the fragmentation process is limited at small scales by a physical cutoff length originating from the fluid-structure interactions between the objects and turbulence, and therefore independent of the brittleness of the fibers. This scenario leads to the accumulation of fragments with a typical length slightly longer than the cutoff scale, as smaller fragments are too short to be deformed and broken by turbulence.