Longitudinal vortices sensitively govern the turbulent momentum transport in boundary layers. In order to obtain the fundamental knowledge on microbubble drag reduction mechanism, the interaction between the vortices and the bubbles are experimentally investigated in this study. The longitudinal vortex is generated artificially from a delta wing installed inside the shear layer in a channel. According to PTV measurement, the vorticity is reduced by presence of bubbles compared to the original.

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... ignificant displacement of the vortex core is also confirmed to explain the momentum transfer modification. Moreover, numerically simulated bubble trajectories on the measured velocity yields to high persistency of the interaction for small bubbles.