Multi-bubble Formation and Pressure Characterization under Mixed Injection Conditions

This study investigates the bubble formation process and the associated pressure fluctuation characteristics under mixed injection conditions. The experimental findings demonstrate distinct bubble generation modes depending on the syringe size. Specifically, when employing a syringe with an inner diameter (I.D.) of 0.6 mm, no significant liquid level lowering is observed in the syringe, and bubble formation occurs exclusively in a dripping type. In contrast, when utilizing a 0.9-mm I.D. syringe, the bubble formation process exhibits a transitional behavior, initiating in a jetting type before transitioning to a dripping type. This transitional behavior, termed the jetting-to-dripping type, is characterized by an obvious lowering of the gas-liquid interface in the syringe. This study presents the development and validation of two distinct theoretical models to elucidate the pressure variations associated with bubble generation modes: the drip model and the jet model. The drip model demonstrated exceptional predictive accuracy in describing pressure characteristics during dripping-type bubble formation, showing remarkable congruence with experimental observations. In contrast, the jet model effectively captured the pressure fluctuation patterns associated with jetting-type bubble formation. Both models underwent validations across diverse experimental conditions, including variations in gas and liquid types, consistently demonstrating good predictive performance. Furthermore, the investigation systematically evaluated the influences of various parameters, specifically the gas chamber volume and gas supply rate, on the pressure dynamics during bubble formation. These findings provide valuable insights for the precise control and optimization of bubble generation processes in various scientific and industrial applications.