Turbulent Drag Reduction Research on Biomimetic Surfaces Based on the Microstructural Characteristics of Shark Skin

In engineering fields such as aviation, shipping, and high-speed rail, system operational efficiency and energy consumption are largely determined by turbulent drag. The drag reduction design of shark skin-inspired micro-groove structures have opened up new avenues for improving aerodynamic efficiency, optimizing flow field characteristics, and saving energy, representing a highly promising research hotspot in the field of functional micro-structured surfaces. Addressing the issue of drag reduction for V-shaped grooves (frictional Reynolds number 85-695), this paper employs Design of Experiments (DOE) combined with high-precision numerical simulation to clarify the influence of groove height (h), groove width (s), and inflow velocity (U) on the drag reduction rate for bionic microgroove surfaces. The drag reduction mechanism is further revealed through the analysis of vorticity distribution, vortex core position, boundary layer velocity distributions, pulsating velocity fields, and Reynolds stress distributions. When the dimensionless height h⁺ and width s⁺ range from 8.50 to 29.75, these grooves can effectively reduce resistance. A maximum drag reduction rate of 12.33% is achieved at h⁺ = s⁺ = 25.29 and a flow velocity of 80.7 m/s (frictional Reynolds number 599). At low flow velocities, larger groove dimensions are favorable for drag reduction. In contrast, smaller groove dimensions are required under medium-to-high flow velocity conditions. The optimal microstructural dimensions of V-shaped grooves decrease as the inflow velocity increases. V-shaped grooves can lift turbulent vortex coherent structures, reduce pulsating velocities in the streamwise, normal, and spanwise directions, and decrease the peak values of Reynolds stress in the near-wall region. The results can provide a quantitative basis for the design and engineering applications of biomimetic riblet drag-reducing surfaces.