  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.
