| Wed January 27th 2016 16:00 – 16:30 ZH286 | Seminar | Bubble deformability is crucial for drag reduction Ruben Verschoof |
Details:In the naval industry, air lubrication is seen as one of the most promising techniques reducing the overall fuel consumption. It is known that a small percentage of bubbles can reduce the overall drag in channel flow, flat plates, Taylor-Couette flow, and various other systems. Even though its clear relevance for the naval industry, the exact mechanism behind this bubbly drag reduction is not known. Hitherto, different mechanisms were studied in various systems with different conditions, so it is hard to disentangle the relevant drag reduction mechanism.In this study, we add surfactant to a bubbly Taylor-Couette flow, to change the bubble properties while keeping all other flow parameters and fluid properties identical. We found that when the bubbles where large and deformable, the drag reduction was large, whereas small and stiff bubbles did not cause any drag reduction - at gas volume fractions up to 4%. | ||
