(314b) Drop Breakage in Sinusoidal Constrictions: Analysis, CFD Simulation and Experimental Validation

Surface tension driven flow analysis in a core-annular geometry for arbitrary fluid viscosities leads to an evolution equation describing the temporal dynamics of the fluid-fluid interface. Its useful applications occur, for example, in environmental remediation and petroleum recovery. For sinusoidally constricted pores, a purely geometric criterion exists that enables or prohibits core fluid breakup in the neck of the constrictions. The geometrically favoring condition sets up capillary pressure gradients that ensure a continuous outflow of the core fluid from the neck into the ?crests? of the profile. Such behavior is indeed observed in the numerical solutions of the evolution equation, in CFD simulations, and in optical experiments carried out in a sinusoidal flow cell. The drop breakup is typically achieved through the formation and growth of ?wavy? disturbances from the initial interface profile, which touch the axis of the capillary in several places producing satellite drops. The final shapes of the profile just before the snap-off depend significantly on the slope of the initial configuration. Smaller slopes and thinner initial annuli slow down the breakup process. Finally, if the geometry prohibits the snap-off altogether, initial interface configurations decay into constant-radius surfaces. The main inferences of the analysis validate well (quantitatively) against CFD simulations and experiments.