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In Situ Grafting Hydrophilic Polymeric Layer for Stable Drag Reduction
Langmuir ( IF 3.7 ) Pub Date : 2019-05-14 00:00:00 , DOI: 10.1021/acs.langmuir.9b00321 Chaoguo Tian 1 , Xingwei Wang , Ying Liu 1 , Wufang Yang 2 , Haibao Hu , Xiaowei Pei , Feng Zhou 2
Langmuir ( IF 3.7 ) Pub Date : 2019-05-14 00:00:00 , DOI: 10.1021/acs.langmuir.9b00321 Chaoguo Tian 1 , Xingwei Wang , Ying Liu 1 , Wufang Yang 2 , Haibao Hu , Xiaowei Pei , Feng Zhou 2
Affiliation
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Developing drag reduction techniques has attracted great attention because of their need in practical applications. However, many of the proposed strategies exhibit some inevitable limitations, especially for long period of adhibition. In this work, the dynamic but stable drag reduction effect of superhydrophilic hydrogel-coated iron sphere falling freely in a cylindrical water tank was investigated. The absolute instantaneous velocities and displacements of either the hydrogel-encapsulated or unmodified iron sphere falling freely in water were monitored via a high-speed video. It was revealed that, in the range of Reynolds number from 104 to 106, the optimized hydrogel-coated iron sphere with uniform stability could reduce the resistance by up to 40%, which was mainly due to the boundary slip of water and the delayed boundary separation that resulted from the coated hydrogel. Besides, the deliberate experiments and analysis further indicated that the superhydrophilic hydrogel layer accompanied by the emergence of the drag crisis has largely effected the distribution of flow field at the boundary around the sphere. More importantly, the drag reduction behavior based on the proposed method was thermodynamically stable and resistant to external stimulus, including fluidic oscillator and hydrodynamic pressure. The effective long-term drag reduction performance of the hydrophilic substrate can be expected, correspondingly, and also provides a novel preliminary protocol and avenues for the development of durable drag reduction technologies.
中文翻译：
用于稳定减阻的原位接枝亲水性聚合物层
由于减阻技术在实际应用中的需求，因此发展起来引起了极大的关注。但是，许多提议的策略都表现出某些不可避免的局限性，尤其是对于长时间的禁制。在这项工作中，研究了在圆柱形水箱中自由下落的超亲水性水凝胶包覆的铁球的动态但稳定的减阻效果。通过高速视频监控水凝胶包裹的或未改性的铁球在水中自由下落的绝对瞬时速度和位移。结果表明，在雷诺数从10 4到10 6的范围内，经过优化的具有均匀稳定性的水凝胶包覆的铁球可将阻力降低多达40％，这主要是由于水的边界滑移和包覆的水凝胶导致的边界分离延迟所致。此外，经过深思熟虑的实验和分析还表明，伴随着阻力危机的出现的超亲水性水凝胶层极大地影响了流场在球体边界处的分布。更重要的是，基于所提出的方法的减阻行为是热力学稳定的，并且对包括流体振荡器和流体动力压力在内的外部刺激具有抵抗力。相应地，可以预期亲水性基材的有效的长期减阻性能。
更新日期：2019-05-14
中文翻译：
用于稳定减阻的原位接枝亲水性聚合物层
由于减阻技术在实际应用中的需求，因此发展起来引起了极大的关注。但是，许多提议的策略都表现出某些不可避免的局限性，尤其是对于长时间的禁制。在这项工作中，研究了在圆柱形水箱中自由下落的超亲水性水凝胶包覆的铁球的动态但稳定的减阻效果。通过高速视频监控水凝胶包裹的或未改性的铁球在水中自由下落的绝对瞬时速度和位移。结果表明，在雷诺数从10 4到10 6的范围内，经过优化的具有均匀稳定性的水凝胶包覆的铁球可将阻力降低多达40％，这主要是由于水的边界滑移和包覆的水凝胶导致的边界分离延迟所致。此外，经过深思熟虑的实验和分析还表明，伴随着阻力危机的出现的超亲水性水凝胶层极大地影响了流场在球体边界处的分布。更重要的是，基于所提出的方法的减阻行为是热力学稳定的，并且对包括流体振荡器和流体动力压力在内的外部刺激具有抵抗力。相应地，可以预期亲水性基材的有效的长期减阻性能。
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