Gas-replenishing microstructured superhydrophobic surface for drag reduction

Hydrodynamic drag in marine engineering leads to high fuel consumption, increased emissions, and diminished operational efficiency. Superhydrophobic surfaces (SHS) are widely used for drag reduction, yet maintaining stable air films remains challenging. To overcome this challenge, we fabricated a grooved-microporous superhydrophobic surface (GMSHS) via nanosecond laser processing. Compared to its non-grooved microporous counterpart (MSHS), the GMSHS demonstrated superior hydrophobic durability, enhanced pressure resistance, and a maximum water contact angle of 160.3° ± 1.6°. Our investigation further revealed a nonlinear relationship between the gas injection rate and the drag reduction rate. By optimizing the injection parameters to balance air film stability with turbulence suppression, a maximum drag reduction of 32% was achieved. Additionally, simulation results confirmed that the GMSHS is more effective in trapping and retaining gas. The optimal efficiency for unidirectional gas permeation occurred with a conical pore taper angle of 15°. This work offers a viable strategy for sustained drag reduction on high-speed marine vessels.