On physical mechanisms in chemical reaction-driven tip-streaming

In this work we provide a basic physical modeling of the spatiotemporal pattern of emulsification produced by chemical reaction-driven tip-streaming and observed by Fernandez and Homsy [Phys. Fluids 16, 2548 (2004)]. Features of this phenomenon-nonlinear autooscillations, a conical drop shape, tip-streaming, and droplet trajectory splitting-are addressed in this paper. In particular, the experimentally found regimes of self-sustained periodic motion and the transitions between them are explained with the help of a nonlinear relaxation oscillator model. An exact self-similar solution for the steady tip-streaming mode supports the suggested mechanism of a Marangoni-driven phenomenon. Finally, the ionic nature of the surfactant produced at the interface offers a reasonable explanation for the formation of a spray cone, which is due to repulsive electrostatic interactions between droplets. These features distinguish this phenomenon from standard tip-streaming. (C) 2004 American Institute of Physics.