Internal Jet Formation During Bubble Generation in Microchannels

Bubble generation is a very dynamic process including surface forces with fluid flow and structure interaction on short time and length scales. This study describes interaction effects during bubble generation in combination with bubble flow through a nozzle for redispersion purpose. At certain flow velocities and phase ratios, liquid jets within gas bubbles have been observed in microchannels, which origin from the rear tip of the bubble cap and penetrate through the whole bubble. The penetration of the filament or thread leads to bubble surface corrugation and causes bubble breakup, when the opposite cap of the bubble is hit. In the case of micronozzles behind the contact element, jet formation within the bubble is also caused by another bubble leaving the micronozzle and probably leading to a pressure disturbance acting on the just generated bubble. First data indicate major influence parameters in jet formation; however, systematic investigations are following.