Physics

Two-phase flow

Tearing

Hele-Shaw flow

Mechanics

Microfluidics

Particle-laden flows

Open-channel flow

Capillary action

Volumetric flow rate

Flow focusing

Breakup

Capillary number

Flow (mathematics)

Thermodynamics

Physics of Fluids

We proposed the combined numerical and experimental study of the dynamics of droplets generation at shallow microfluidic T-junction, where the flow is strongly confined in the vertical direction. The numerical simulation is performed by employing quasi-2D Hele-Shaw approximation with an interface capturing procedure based on coupled Level-Set and Volume-of-Fluid methods. We investigate the effect of the capillary number, Ca, the channel geometry (cross section aspect ratio, χ), and the flow rate (disperse-to-continuous phases) ratio, Γ, on the dynamics of the droplet breakup. Depending on Ca, three distinct flow regimes are identified: squeezing, tearing and jetting. In the squeezing regime at low Ca, the size of the generated droplets depends on χ and Γ, while it is almost insensitive to Ca in agreement to previous studies. In the tearing regime at moderate Ca, the droplet size decreases as ∼Ca−1/3, while it is only a weak function of χ and Γ. Finally, in the jetting regime, the steady co-flow of both phases takes place at high enough Ca. The numerical predictions based on the Hele-Shaw flow approximation are in excellent agreement with our in-house experimental results, demonstrating that the proposed approach can be effectively used for computationally inexpensive and adequately accurate modeling of biphasic flows in shallow microfluidic devices.

Droplet generation at Hele-Shaw microfluidic T-junction