Séminaire Fluide: Ken Yamamoto (Osaka University)

Fluid seminars

Abstract:

Small Leidenfrost droplets move in a certain direction, which is determined by their asymmetric inner-flow direction (Bouillant et al., 2018). In addition, I found that the motion becomes more complicated when the temperature of hot substrate beneath the droplets is relatively low (see trajectories in the top  figure). In this study, the droplet motion in such condition was investigated by two different experiments.
The experiments revealed that small droplets moved in random zigzag directions, and their straight-running stability decreased as the droplet size and substrate temperature decreased. The mechanism was explained by a combination of the asymmetric flow and periodic generation of the Marangoni flow: (i) the asymmetric flow transports hot liquid to the droplet apex and a hot belt is formed (see the bottom figure), (ii) the Marangoni flow is generated from the droplet base toward a cold spot, which is the axis of the asymmetric flow, (iii) the asymmetric flow rotates in azimuthal (horizontal) direction as a result of an incorporation of the Marangoni flow.