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Preparation of Surface Drag Reduction Coatings and Research on the Factors

Author: DongHongYu
Tutor: ShiFeng
School: Beijing University of Chemical Technology
Course: Chemical Engineering and Technology
Keywords: hydraulic drag superhydrophobic drag reducingcoating electroless metal deposition technique polymer self-linkingtechnique
CLC: TQ637
Type: Master's thesis
Year: 2013
Downloads: 102
Quote: 0
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Abstract

Ships on the sea and underwater equipment suffer friction which is from the fluid when moving. It not only affects the ship’s moving speed, but costs navigation equipment amount of fuel to overcome resistance from the fluid in the course of navigation. Reducing the hydraulic drag resistance not only helps to improve the speed of the craft, and to enhance the energy efficiency, promote the progress of science and technology, strengthening national defense construction. Thus, it is necessary to improve the drag reduction technique. In recent years, superhydrophobic technology of drag reduction, as an emerging drag reducing method, receives a widespread concern by the scientists. Simple preparation process, moderate operating conditions and due to the excellent characteristics of the material itself of superhydrophobic drag-reducing coatings, they can capture the air layer which decreases the viscous resistance when moving, thus achieving drag reduction. However, superhydrophobic drag-reducing technique has some controversies currently, controversies mainly focused on two points:first, whether all kinds of superhydrophobic coatings can reduce the drag resistance; second, the specifications and parameters of superhydrophobic paint for drag reduction.Based on the current controversies, our paper centers on whether superhydrophobic coatings can really reduce the resistance, and we produce four kind of typical superhydrophobic surfaces through electroless metal deposition technique, self-crosslinking technique of polymers and other technological means. We notice separately on the surface morphologies, hydrophobic properties, and drag reduction characterization of the superhydrophobic coatings. We find that not all the superhydrophobic coatings can reduce the drag force; only the rough structures above the flat substrates has the ability of drag reduction. In addition, the adhesion strength value of the coatings is an important factor which affects drag reduction:the drag reduction behavior declining as the adhesion strength value increases; when the maximum adhesion strength of the superhydrophobic coatings reaches137.2μN, superhydrophobic surface reveal an increased drag force at which water droplets can hang upside down on the coating surface and would not fall off. Meanwhile, this article summarizes the technical factors and parameters of the superhydrophobic paint for drag reduction, and the mechanism and feasibility of practical application for drag reduction. Finally, the paper discusses the weakness of the technology currently. Hope our work can have a little contribution to the development of the marine ship drag reduction technology in the future.

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