The Geometry of the Vapor Layer Under a Leidenfrost Drop

TL;DR

This study investigates the shape and fluctuations of the vapor layer beneath Leidenfrost drops, revealing that the vapor pocket geometry mainly depends on drop size rather than substrate temperature.

Contribution

It provides detailed measurements of the vapor layer geometry and fluctuations, advancing understanding of the Leidenfrost effect's physical mechanisms.

Findings

Vapor pocket geometry depends mainly on drop size.

Measured vapor layer radius, curvature, and height using laser interference.

Non-axisymmetric interface fluctuations observed.

Abstract

In the Leidenfrost effect, liquid drops deposited on a hot surface levitate on a thin vapor cushion fed by evaporation of the liquid. This vapor layer forms a concave depression in the drop interface. Using laser-light interference coupled to high-speed imaging, we measured the radius, curvature, and height of the vapor pocket, as well as non-axisymmetric fluctuations of the interface for water drops at different temperatures. The geometry of the vapor pocket depends primarily on the drop size and not on the substrate temperature.