Abstract
In this work, we explored self-propulsion of a Leidenfrost drop between non-parallel structures. A theoretical model was first developed to determine conditions for liquid drops to start moving away from the corner of two non-parallel plates. These conditions were then simplified for the case of a Leidenfrost drop. Furthermore, ejection speeds and travel distances of Leidenfrost drops were derived using a scaling law. Subsequently, the theoretical models were validated by experiments. Finally, three new devices have been developed to manipulate Leidenfrost drops in different ways.
Highlights
The testing results on the three devices, together with those of the second and third experiments, have validated two of the theoretical predictions: i) once Leidenfrost drops contact two non-parallel sidewalls, they move towards the diverging end of the corresponding structure; and ii) these drops have ejection speeds with an order of 10 cm/s when a non-parallel structure has a mm-scaled gap
We explored the behavior of a Leidenfrost drop between two non-parallel sidewalls of a structure through theoretical and experimental investigations
According to the derived theoretical model, once a Leidenfrost drop has contact with the two sidewalls of the structure, it is capable of self-transporting towards the diverging direction of the structure on a horizontal plane
Summary
Following a line of reasoning used in refs[6,12,27], we derive Laplace pressure to find moving conditions. According to the first assumption, across drop thickness, the gravity effect on Laplace pressure Subsequently, both Edges 1 and 2 iasrneecgolnecsitdeder. Since R1 and R12 are, respectively, in the same order as the plate gap and drop radius, according to the above second assumption, R1 is much smaller than R12, which has been previously validated by our experimental results in ref.[14] (see its Fig. 2). There exists a gravity-induced pressure gradient along the longitudinal direction of the drop. It is ρg sinβ, where ρ and g, respectively, denote mass density of the liquid and gravitational acceleration. The resultant gradient of liquid pressure is positive along the direction from Edges 1 towards 2.
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