Numerical Simulation of the Formation of a Jet and Droplets from a Capillary in a Co-Flowing Ambient Fluid

Formation of a liquid jet and droplets from a micro-capillary in another immiscible co-flowing ambient fluid is simulated numerically with a front-tracking/finite difference method. The transition from dripping to jetting is observed and the size of the resulting droplets is predicted. The predicted size in jetting mode is in close agreement with that from linear stability theory for a moving liquid jet in a co-flowing ambient fluid with the same speed as the jet. The transition between dripping and jetting are mapped on the diagram of the jet Weber number versus the ambient flow Capillary number. It is found that the viscosity ratio is an important parameter to distinguish the mode.