Determination of the transition boundary between segmented and continuous flow patterns in microfluidic liquid-liquid flows using dimensional analysis

Microfluidic liquid-liquid flows exhibit a wide range of different flow patterns. The most important point in practical applications is the transition from the segmented to the continuous flow patterns, as well as the prediction of this transition for an arbitrary combination of fluids. This paper presents a detailed analysis of the existing experimental data on flow patterns of immiscible liquids and provides data generalization through dimensional analysis. It is shown that the previously proposed criterion (We 0.4 Oh 0.6 ) composed from Weber and Ohnesorge numbers provides a prediction on transition continuous-to-segmented flow with good accuracy if viscosity ratio λ = μ d /μ c is less than unity. For the viscosity ratio λ > 1, this criterion ceases to work, and additional experimental data are required to construct a generalizing parameter for microfluidic flow in such systems.