Downstream persistence of frictional drag reduction with repetitive bubble injection
Downstream persistence of frictional drag reduction with repetitive bubble injection
复制标题
通过重复气泡注入减少摩擦阻力的下游持续性
DOI：
10.1016/j.oceaneng.2023.113807
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发表时间：
2023
影响因子：
5
通讯作者：
C.Kawakita
中科院分区：
文献类型：
--
作者：
T.Tanaka;Y.Oishi;H.J.Park;Y.Tasaka;Y.Murai;C.Kawakita
在一艘以8.0 m/s速度拖曳的36m长平底模型船的湍流边界层中，研究了使用重复气泡喷射减少摩擦阻力的方法。注入气泡的空气流速周期性波动，重复频率为0.5-2.0 Hz。减阻率达到24%，相对于传统的连续气泡注入方法提高了5%。对作用于底板的局部壁面剪应力的测量和气泡流动的光学可视化表明，气泡分散状态的转变导致了局部减阻的沿流衰减。通过使用重复气泡注入，可以将减阻效果的下游持久性提高15倍。全尺寸性能估计表明，对于超过130 m的长船体，重复气泡喷射提供的摩擦阻力减少约为连续气泡喷射所提供的7倍。
Frictional drag reduction using repetitive bubble injection is investigated in a turbulent boundary layer beneath a 36-m-long flat-bottom model ship towed at 8.0 m/s. Bubbles are injected with air flow rates periodically fluctuating at a repetition frequency of 0.5–2.0 Hz. The drag-reduction ratio reaches 24%, which is a 5% improvement relative to the conventional method of continuous bubble injection. Measurement of the local wall shear stress acting on the bottom plate and optical visualization of bubbly flow reveal that the transition of the status of bubble dispersion causes the streamwise decay of local drag reduction. The downstream persistence of the drag-reduction effect can be improved by a factor of 15 through the use of repetitive bubble injection. The estimation of the full-scale performance indicates that repetitive bubble injection provides approximately 7 times the frictional drag reduction provided by continuous bubble injection for long ship hulls exceeding 130 m.