FIG. 3.

Oscillatory mode (f = 1–15 Hz) co-flow droplet generation at the lowest flow rate levels with We = 0.010 and Ca = 0.020. (a) Droplet images at different oscillation frequencies with repeatable patterns. (b) Effect of oscillation frequency on the number of generated droplets and their dimensionless diameter (d/d_o). Upon increasing the oscillation frequency, transverse drag increased and subsequently led to an overall droplet size reduction. Meanwhile, the lateral motion of the nozzle exposed the growing droplet to a variable axial drag, and the droplet breakup occurred at different sizes at different locations.