Laser Induced Biomimetic Fish Scale Arrays Composite With Superhydrophobic Nanoscale SiO₂ Particles for Drag Reduction

Reducing surface friction resistance (SFR) is beneficial for the performance of high-speed marine equipment surfaces. To reduce SFR, a biomimetic surface was developed through a collaborative multi-process strategy involving a combination of laser ablation and spraying techniques. Initially, biomimetic fish scale (BFS) arrays with five different spacing (s) values were fabricated on an aluminium (Al) substrate using laser ablation, which was then replicated with polydimethylsiloxane (PDMS). Subsequently, a mixture of superhydrophobic nanoscale SiO₂ particles (SH-SiO₂), PDMS and n-hexane solution was uniformly sprayed onto the BFS surface to enhance its hydrophobic properties. The morphology of these biomimetic surfaces was characterised using a scanning electron microscope (SEM) and ultra-depth field microscope. The drag reduction (DR) performance of the biomimetic surfaces was evaluated within a Reynolds (Re) number range of 4.2 × 10⁴–2.2 × 10⁵ in a circulating water tunnel. The results indicated that a drag reduction rate of 11.82% was achieved with the modified BFS at s = 300 μm and Re = 1.7 × 10⁵. Additionally, the drag reduction mechanism of the modified BFS surface was analysed using the computational fluid dynamics (CFD) method. The excellent drag reduction performance was attributed to the combined effects of the ‘rolling bearing’ caused by streamwise vortices, high-low velocity streaks and the velocity slip effect caused by hydrophobic properties at the interface. These findings offer a novel approach for creating multi-effect coupled drag reduction surfaces.