Capillary number Ca = μv/γ controls dripping vs jetting
Regime: — | Droplet size: —
At a T-junction, a dispersed phase enters the main channel. The Capillary number Ca = μv/γ sets the balance
between viscous drag and surface tension. Low Ca (dripping): interfacial tension dominates, large periodic droplets.
High Ca (jetting): viscous forces dominate, a jet forms that breaks via Rayleigh-Plateau instability into small droplets.
Critical Ca_c ≈ 0.3 for most systems. Droplet size L ∝ (Q_d/Q_c)·Ca^(-α) in dripping regime.