Abstract
Microbubble drag reduction has been observed in high Reynolds number turbulent flows. The interaction of microbubbles with the viscous sublayer seems to be of interest. In this study a microchannel on the order of 100 microns was used to simulate the shear rate of the near-wall region of a high Re flow. The interaction of the fluid flow with microbubbles at low void fraction in a microchannel was studied. The microbubble sizes ranged from approximately 10–50 microns. The liquid phase velocities were obtained by PIV measurement techniques. Electrolysis was used to generate bubbles within the channel and microbubble velocities in the flow were determined using separate cross correlation calculations. Simultaneous comparisons are made between the image-averaged bubble velocity and the image-averaged fluid velocity. Image processing techniques were utilized to both remove bubbles and decrease noise in the image. Results are shown comparing the fluid only velocity profile with the two-phase velocity profiles at three flow rates and two bubble generation cases. Results presented include the phase velocity differences, bubble size and bubble separation distances for three flow rates and three different bubble generation levels. It is seen that flow rates within the microchannel significantly reduce the average bubble size.