论文标题
氯化钠抑制有效的起泡拖动湍流taylor-couette流动
Sodium chloride inhibits effective bubbly drag reduction in turbulent bubbly Taylor-Couette flows
论文作者
论文摘要
使用泰勒（Taylor）几何形状，我们实验研究了盐对流动中存在气泡引起的阻力减少的影响。我们将扭矩测量与光学高速成像相结合，以将气泡尺寸与流动所经历的阻力相关联。先前的发现表明，一小部分空气（4％）会导致急剧减少（40％）。与以前主要使用淡水的实验室实验相反，我们将从淡水变为海水平均盐度。我们发现，减少阻力越来越受到盐度浓度的抑制作用。从淡水40％到海水的15％。工作流体中存在的盐会抑制聚结的事件，从而导致流量中较小的气泡，从而减少阻力减少。在临界盐度之上，增加盐度对流动中的气泡大小没有进一步的影响，因此流动所经历的阻力。我们的新发现表明了NACL对减少拖曳机制的重要性，并将进一步挑战海军建筑师在海洋船上实施有希望的空气润滑系统。
Using the Taylor--Couette geometry we experimentally investigate the effect of salt on drag reduction caused by bubbles present in the flow. We combine torque measurements with optical high-speed imaging to relate the bubble size to the drag experienced by the flow. Previous findings have shown that a small percentage of air (4%) can lead to dramatic drag reduction (40%). In contrast to previous laboratory experiments, which mainly used fresh water, we will vary the salinity from fresh water to the average salinity of ocean water. We find that the drag reduction is increasingly more inhibited for increasing salt concentration; going from 40% for fresh water to just 15% for sea water. Salts present in the working fluid inhibit coalescence events, resulting in smaller bubbles in the flow and with that, decreasing the drag reduction. Above a critical salinity, increasing the salinity has no further effect on the bubble sizes in the flow and thus the drag experienced by the flow. Our new findings demonstrate the importance of NaCl on the bubbly drag reduction mechanism, and will further challenge the naval architects to implement promising air lubrication systems on marine vessels.
