Bio-replicated forming of the biomimetic drag-reducing surface based on underwater low-resistance scarfskins

Various forms of underwater low-resistance scarfskins provide abundant shape resources for the manufacturing of the biomimetic drag-reducing surfaces. The drag-reducing surface based on scale groove of shark skin is one of the issue researches. A new bio- machining technology named bio-replicated forming based on creatural scarfskins was presented in this paper. Taking the skin of Carcharhinus brachyurous as the template of the new-type biomimetic drag-reducing surface, the fundamental technologies and theories of bio-replicated forming were investigated. According to the existing problems of the traditional forming methods of the biomimetic drag-reducing surface based on the scale-grooves, such as low quality, low efficiency, high cost and low drag reduction effect, the new micro-embossing and micro-electroforming methods were put forward. Additionally, the problems on aggradation, deformation, infilling and demoulding of material were also solved. By means of the methods above, the highly vivid biomimetic shark-skin surfaces were fabricated. The analysis of the replication precision proves that the bio-replicated forming technology can be applied to the direct morphology replication of the firm creatural scarfskins. The water tunnel test of the flatplate sample pieces suggests that the drag reduction efficiency of the biomimetic shark-skin groove surface achieves 8.25% in maximum and 6.91% in average, which validates that bio-replicated forming has broad application value and prospect in the manufacturing of the biomimetic drag-reducing surface.