Figure 2.
Creation of a liquid plug due to the surface tension induced capillary instability. (A) Less viscous core fluid is injected into tube, displacing the more fluid already in the tube, and leaving behind a uniform film whose thickness depends on Ca ; (B) The injection described in (A) is stopped, and the surface-tension instability ensues as shown in (C)–(F). From Cassidy et al. (1999).