It is well known that marine animals such as shark and dolphin can swim quickly with very low drag due to their special structure of skin. The low drag in water for marine animals swimming is attributed to the follow factors.
Firstly, their streamline body results in the low pressure drag. Secondly, the mucus produced by skin can drive out the fouling as well as reduce the frictional drag. Thirdly, the micro-texture and toughness of skin lead to the decrease in turbulence so as to reduce the frictional drag.
On the supports of The National Natural Science Key Fund “The Design of Underwater Vehicle Surface and Their Drag Reduction Mechanism（51335010）”, many researches for effects of surface micro-texture on drag reduction have been conducted in the Key Laboratory of Marine Materials and Related Technologies.
The 3D printing technology has been used to fabricate micro-texture, the simulation and micro water-tunnel tests have been conducted to evaluation the drag reduction properties. It is found that the some micro-vortexes will been formed in the micro-texture. When the micro-texture has proper shape, it exhibits well drag reduction. According to this results, we have designed the hydrophilic coatings with micro-texture for drag reduction.
Besides, inspired by the mucus on skin, mucus-liked semi-solid coatings have be designed on the materials surface. The micro-been fabricated on the surface （ACS Appl. Mater. Interfaces,2014 6（2）PP 1053-1066))for stably storing the semi-solid coatings to avoid the loss of semi-solid coatingsstructure have . In this case, the drag reduction rate can be up to 30%. （Scientific Reports 7, Article number: 40038 (2017) doi:10.1038/srep40038）
Base on above results, low drag device was designed for cleanup of oil spill. （ACS Appl. Mater. Interfaces, 2015, 7 (47), pp 26184–26194；） And these drag reduction technology and method have also been used on the speedboats in order to evaluate the drag reduction the practically condition.
Prof. Zhixiang Zeng: zengzhx@nimte.ac.cn
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