Dynamic Leidenfrost behaviors of different fluid drops on superheated surface: Scaling for vapor film thickness

Abstract

For an impact drop on a superheated surface, the dynamic Leidenfrost temperature, TLF, depends on several parameters such as impact velocity, vapor layer thickness, and thermophysical properties of the fluids. In this letter, we derived a scaling formula for TLF using the well-known balance relation between the pressures exerted by drop impact and evaporated vapor flow. As the TLF scale intrinsically requires estimating the vapor film thickness δv, it should be scaled based on the consideration of relevant physics postulated on the impact drop and evaporated vapor. Thus, for proper scaling of δv, we considered the drop–vapor interface deformation by drop inertial and surface tension forces during initial impact of drop. Results showed that δv could be scaled with drop diameter D0 and Weber number We. For drops with low We (<10), δv scaled to ∼D0We−1/4 and ∼D0We−2/5 for drops with higher We. The explicit scale for TLF agreed well with present experimental data.