Experimental and numerical study of droplet generation in the normal and modified cross-junction

In this work, a visualization experimental combined with numerical approach was used to analyze the process intensification achieved by incorporating a rectangular obstacle into the downstream section of a cross-junction channel for droplet generation. A comparative experimental study was conducted to evaluate the performance of the droplet generation in the modified and normal cross-junction channel. Five typical flow regimes were observed, including squeezing, dripping, jetting, tubing and a first described tip-multi-breaking which differs from those previously reported in capillary devices. among these regimes, squeezing and dripping were found to be the preferred flow regime to generate monodisperse droplets with a variation coefficient of the droplet size less than 3 %. The presence of the rectangular obstacle in the modified channel increases the fluid resistance within the main channel, leading to a higher pressure drop before and on the obstacle, which induces the earlier appearance of necking stage and more prompt pinching-off of the thread in the modified channel. As a result, smaller monodisperse droplets with higher generation frequency were observed within a much wider distribution of squeezing and dripping regimes in the modified channel.