Mechanism of Self-Induced Vibration of a Liquid Drop Based on the Surface Tension Fluctuation

Mechanism of self-induced vibration of a superheated liquid drop, which is levitated on a hot-plate with a thin vapor sheet in between, is analyzed experimentally and theoretically. Temperature distribution of a liquid drop at the surface and inside has been measured, and found not to be constant, which suggests dominance of the surface tension fluctuation. A model is proposed, where the liquid drop is assumed to be a thin liquid layer, and the potential flow is assumed inside the layer. The flow in the thin vapor sheet is assumed to be a superposition of Hele-Shaw flow and Couette flow. Magnitude of the surface tension is assumed to vary, due to the contact of the peripheral region of the drop with heated air surrounding it. Analysis based on this model gives stable stationary vibration with finite amplitude. The obtained vibrational amplitude agrees with experimental data.