Bubble Drag Reduction Requires Large Bubbles

In the maritime industry, the injection of air bubbles into the turbulent boundary layer under the ship hull is seen as one of the most promising techniques to reduce the overall fuel consumption. However, the exact mechanism behind bubble drag reduction is unknown. Here we show that bubble drag red...

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Bibliographic Details
Published in:Physical review letters 2016-09, Vol.117 (10), p.104502-104502, Article 104502
Main Authors: Verschoof, Ruben A, van der Veen, Roeland C A, Sun, Chao, Lohse, Detlef
Format: Article
Language:English
Subjects:
Bubbles
Drag reduction
Fluid dynamics
Fuel consumption
Liquids
Surfactants
Turbulence
Turbulent flow
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Summary:In the maritime industry, the injection of air bubbles into the turbulent boundary layer under the ship hull is seen as one of the most promising techniques to reduce the overall fuel consumption. However, the exact mechanism behind bubble drag reduction is unknown. Here we show that bubble drag reduction in turbulent flow dramatically depends on the bubble size. By adding minute concentrations (6 ppm) of the surfactant Triton X-100 into otherwise completely unchanged strongly turbulent Taylor-Couette flow containing bubbles, we dramatically reduce the drag reduction from more than 40% to about 4%, corresponding to the trivial effect of the bubbles on the density and viscosity of the liquid. The reason for this striking behavior is that the addition of surfactants prevents bubble coalescence, leading to much smaller bubbles. Our result demonstrates that bubble deformability is crucial for bubble drag reduction in turbulent flow and opens the door for an optimization of the process.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.117.104502