Periodic Reporting for period 4 - DDD (Diffusive Droplet Dynamics in multicomponent fluid systems)
Período documentado: 2021-11-01 hasta 2022-10-31
The objective of the project was to better understand these multiphase and multicomponent fluid systems with relevant diffusive droplet dynamics, filling the gap and coming to a quantitative understanding of diffusive droplet dynamics and thus to illuminate the fundamental fluid dynamics of diffusive processes of immersed (multicomponent) (surface) droplets on multiple scales.
Another breakthrough is our work on the so-called Leidenfrost droplet, which also started off as sideline of the DDD project. Volatile drops deposited on a hot solid can levitate on a cushion of their own vapor, without contacting the surface. We proposed to understand the onset of this Leidenfrost effect through an analogy to nonequilibrium systems exhibiting a directed percolation phase transition. When performing impacts on superheated solids, we observed a regime of spatiotemporal intermittency in which localized wet patches coexist with dry regions on the substrate. We found a critical surface temperature, which marks the upper bound of a large range of temperatures in which levitation and contact coexist. In this range, with decreasing temperature, the equilibrium wet fraction increases continuously from zero to one. Also, the statistical properties of the spatiotemporally intermittent regime are in agreement with that of the directed percolation universality class. This analogy allowed us to redefine the Leidenfrost temperature and shed light on the physical mechanisms governing the transition to the Leidenfrost state. This is a totally different way of thinking of the Leidenfrost than it had been done for more than 250 years since the discovery of the effect. It really is a paradigmatic change. I