Drag Reduction Effect of Micro-Vortex on the Surface of Imitated Shark Skin

Surface frictional drag significantly impacts the performance of marine equipment, leading to increased energy consumption, reduced sailing speed, and potential equipment damage. As widely known, sharks, among the fastest fish in the ocean, possess skin covered with numerous tiny and dense scales. This paper simplified the scale structure of shark skin into four different patterned surfaces: lines, discontinuous lines, equal gradient riblet, and graded riblet. The flow field near these patterned surfaces was analyzed under both vertical and parallel flow conditions. It was observed that the drag reduction effect varied with the flow direction and patterned structure. Notably, the graded riblet exhibited an excellent drag reduction effect. This finding suggests a promising avenue for improving the efficiency of marine equipment.