Planar laser fluorescence imaging of bubble detachment

When a gas bubble, slowly forming in a liquid, detaches from an orifice a small internal jet forms inside. The internal jet is difficult to image using a common shadowgraphy technique due to the curved bubble surface. This study investigates the application of planar laser induced fluorescence (PLIF) to image the internal jet of an air bubble in water, both as a standalone technique and in combination with shadowgraphy. PLIF is implemented using a high speed laser, high speed camera and high magnification to obtain time-resolved images visualising the internal jet development. The results show the internal jet growing rapidly after detachment and breaking up into numerous small droplets followed by the development of surface waves.