Expansion of Injected Gas Bubble and Its Effects on Bath Mixing under Reduced Pressure

Abstract

The behavior of a single bubble was observed and the complete mixing time was measured under reduced pressure (∼1.33×10²Pa (1 Torr)) using a silicon oil model. The bubble expanded greatly and changed from oval to a spherical-cup shape. The complete mixing time tended to be constant independent of the stirring power of gas per unit bath volume in the low vessel pressure range (<6.66×10²Pa), because most of the expansion energy was dissipated and the mixing occurred near the bath surface; this was confirmed by observation of the flow.