3-DIMENSIONAL SHAPE OF A DROP UNDER SIMPLE SHEAR-FLOW

The three-dimensional deformation of an isolated drop in an immiscible liquid phase undergoing simple shear flow was investigated by using a parallel-plate apparatus. The drop was observed by video-enhanced con trast optical microscopy, either along the vorticity direction or alon g the velocity gradient direction of the shear flow. An experimental m ethodology based on image analysis was especially developed to study i n a quantitative way the three-dimensional shape of the deformed drop, both under steady-state flow and during transients. Up to moderate de formations, the steady-state drop shape was well described within expe rimental error by an ellipsoid having three different axes. The deviat ion of drop shape from an ellipsoid at higher deformations was also ch aracterized in a quantitative way. Good agreement was found between th e experimental results of this work and numerical simulations reported in the literature. (C) 1998 The Society of Rheology. [S0148-6055(98)0 0902-X].