Faraday instability in a surface-frozen liquid

Faraday surface instability measurements of the critical acceleration, ac, and wave number, kc, for standing surface waves on a tetracosanol (C24H50) melt exhibit abrupt changes at Ts=54°C, â4°C above the bulk freezing temperature. The measured variations of ac and kc vs temperature and driving frequency are accounted for quantitatively by a hydrodynamic model, revealing a change from a free-slip surface flow, generic for a free liquid surface (T>Ts), to a surface-pinned, no-slip flow, characteristic of a flow near a wetted solid wall (T<Ts). The change at Ts is traced to the onset of surface freezing, where the steep velocity gradient in the surface-pinned flow significantly increases the viscous dissipation near the surface.