The structure of turbulent fluid flow involving gas bubble (Measurement of the fluid flow in the vicinity of bubble by PIV

An experimental investigation on flow around and in the wake region of a single bubble and two similarly sized air bubbles confined in a channel with downward flow of water was conducted. Velocity measurements of the flow field in the vicinity of bubble's surface, were made using a one CCD camera based Digital Particle Image Velocimetry (DPIV) system using fluorescent particles as tracer for visualization. A second CCD camera was used to detect the bubble's shape and trans- lational motion via back-lighting from a square array of infrared LEDs. In this way both the two- dimensional flow field and the corresponding instantaneous position and shape of the bubble were measured simultaneously. The results reveal that the difference in wake structure between bubble and solid occurs in the vicinity of the interface defining to the bubble's oscillatory motion. Moreover it was shown that the turbulence generated by wake interaction played a significant role in the wake of two bubbles.