Velocity fluctuations of segmented flow in microchannels

This paper describes the velocity fluctuations of segmented gas–liquid flow in a microfluidic channel. The fluctuations are caused by pressure fluctuations associated with bubble formation and bubbles leaving the channel. Instantaneous bubble velocities were measured with a high speed camera at different locations in the channel. The observed transients could be decomposed into contributions of the pump, the inlet and the outlet. Experiments were performed for different velocities and bubble and slug lengths. A simple scaling analysis successfully predicted the order of magnitude of these fluctuations.