COALESCENCE OF FREELY SUSPENDED LIQUID-DROPS IN FLOW THROUGH A SMALL PORE

The coalescence of two freely suspended, neutrally buoyant liquid drops of unequal size is examined in low-Reynolds-number flow through a capillary 54 μm in diameter. The interaction between a pair of drops results in coalescence only when the upstream drop is sufficiently large. In these cases, a time scale associated with coalescence is measured for three different fluid systems. For two systems the coalescence time is a function of the size of the upstream drop, and data can be correlated based on a simple model that accounts for the interaction between the drops and the drainage of fluid between the drops. For the other system, which has the largest value of the suspending fluid viscosity, the coalescence time is independent of drop size. Furthermore, there is a large variation in the measured coalescence times among runs with similar experimental conditions. The results of this study are compared with those obtained previously for flow through a capillary with a diameter on the order of 1 cm. © 1991 Academic Press, Inc.