Thermally-driven flows between a Leidenfrost solid and a ratchet surface

TL;DR

This study uses numerical solutions of the Boltzmann equation to analyze thermally-driven flows in Leidenfrost propulsion, finding that pressure-driven flow dominates over thermally-induced flows like thermal creep and edge slip.

Contribution

It reveals that thermally-induced flows are minor compared to pressure-driven flow in Leidenfrost propulsion on ratchet surfaces, contrasting previous assumptions.

Findings

Thermally-induced flows are dominated by thermal edge and stress slip.

Thermal creep flow is negligible in the propulsion mechanism.

Pressure-driven flow due to sublimation is the main propulsion factor.

Abstract

The significance of thermally-driven flows for the propulsion of Leidenfrost solids on a ratchet surface is studied based on a numerical solution of the Boltzmann equation. In contrast to a previous analysis, it is found that no significant thermal creep flow is established. Instead, the flow pattern is dominated by thermal edge and thermal-stress slip flow, the latter being directed opposite to thermal creep flow. However, in total thermally-induced flows only make a minor contribution to the propulsion of Leidenfrost solids on ratchet surfaces which is dominated by the pressure-driven flow due to the sublimating solid.