In this work, the drag reduction (DR) performance of superhydrophobic composite coatings was investigated. The DR behavior for both short-term and long-term use was studied using a parallel-plate rheometer, and the morphology of the composite interface was studied by fluorescence staining. For short-term performance, the DR increased with higher silica NP content in the composition up to 40% by weight. The composite interface played a governing role in the DR of superhydrophobic coatings except for a very high particle loading sample. The surface topography effect on this composite interface was also studied. The increase in autocorrelation length was found to be related to the increased distance between wetted asperities and the decreased solid fraction. Furthermore, it was found that the reduced peak height also increased with autocorrelation length, providing a larger distance for meniscus sag and explaining the reason for increased DR with a larger autocorrelation length. Investigation of the long-term DR showed that sustainable DR can be provided by superhydrophobic coatings. In the case of the higher silica-loaded samples, the air plastron remained throughout the experiments and DR performance was retained. This has important implications for superhydrophobic coatings in DR for nautical applications.

中文翻译：

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超疏水复合涂层对层流减阻的影响

在这项工作中，研究了超疏水复合涂料的减阻（DR）性能。使用平行板流变仪研究了短期和长期使用的DR行为，并通过荧光染色研究了复合界面的形态。对于短期性能，DR随着组合物中二氧化硅NP含量的增加而增加，最高可达40重量％。复合材料界面在超疏水涂层的DR中起着主导作用，除了非常高的颗粒负载样品外。还研究了表面形貌对该复合界面的影响。发现自相关长度的增加与润湿的粗糙物之间的距离增加和固体分数减少有关。此外，结果发现，降低的峰高也随着自相关长度的增加而增加，从而为半月板凹陷提供了更大的距离，并解释了自相关长度更大时DR增加的原因。对长期DR的研究表明，超疏水涂料可以提供可持续的DR。对于较高的二氧化硅负载样品，在整个实验过程中仍保留空气塑料，并保留了DR性能。这对于航海应用中的DR中的超疏水性涂料具有重要意义。在整个实验过程中，空气塑料保持不变，并且DR性能得以保留。这对于航海应用中的DR中的超疏水性涂料具有重要意义。在整个实验过程中，空气塑料保持不变，并且DR性能得以保留。这对于航海应用中的DR中的超疏水性涂料具有重要意义。