WS1-4 気泡による流体抵抗低減(2)(EFDワークショップ:マイクロ・ナノバブル流れの最先端技術-気泡の発生・挙動・応用-,ワークショップ)

概要

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A variety of frictional drag reductions achieved by from microbubbles to large film-like bubbles are presented. The most curious fact found from their experiments is that the friction is so sensitively reduced by bubbles when the bubbles are smaller than the fundamental eddies in turbulence. This situation was, in the past, understood to be explained by homogenous model such as by Rheological expression because of less relative velocities between two phases. However the measurement results are unmatched with such a simplified theory. The discussion for the fluid dynamics mechanism is now advancing to extremely complicated model because of inevitable non-homogenous two-phase high-sheared turbulence. Despite to the knowledge accumulated to date, the key process hidden in the drag reduction still must be extracted to utilize the phenomenon as engineering technology that has already begun in maritime innovation. This report mentions how much the original bubbles have such potential to alter the boundary layer as well as the key phenomenon that triggers the effective drag reduction.
2007-11-17