Research Projects

In recent years there has been an increasing practical interest in creation of small toroidal drops and in their usefulness, which naturally led to the need to understand the scientific fundamentals of the appearance and behavior of such drops in various ambient flow fields. A primary conclusion emerging from the recent studies on dynamic behavior of Newtonian/Visco-plastic toroidal drops, embedded in linear viscous flow of an immiscible fluid, is that there exist stationary states for only a limited extent of the flow intensity, but that these states are absolutely unstable, and the drops exhibit either an inward collapse or extend their radius outward indefinitely. These dynamic patterns are observed irrespective of the drop viscosity relative to that of the suspending fluid. The research proposal suggests the examination of three modes to stabilize stationary toroidal drops once they are created in the flow. The three proposed methods are: (1) controlling dynamically the ambient flow field via adding a controlling element to the flow intensity thus keeping the toroidal structure near the unstable stationary states; (2) superimposing fields, that exhibit counter effects, i.e., collapse and divergence, on the toroidal dynamic structure, thus establishing intermediate stable stationary zones; (3) studying the dynamic structure of toroidal drops composed of visco-plastic materials in the viscous flow field, and their behavior following flow quenching. In this approach the dynamics is dictated by the competition between the restoring interfacial tensile forces and the resisting visco-plastic critical stress. These three effects can be applied separately or in parallel.