Metasurface of Fluid Mechanics for Efficient Turbulence Drag Reduction

Abstract

Turbulence is a critical factor in global energy consumption and environmental protection. Riblets are a promising passive air drag reduction technique for turbulence. However, a large number of studies have shown that their drag reduction ability has reached a limit. Here, we propose the low-high-low riblets (LHLRs) as the metasurface of fluid mechanics to overcome the air drag reduction limit of riblets and investigate the mechanisms of turbulent drag reduction. The experiments show that the maximum air drag reduction ability of the LHLR metasurface of fluid mechanics represents a 91.6% higher reduction than optimal riblets with the same primary widths. Direct numerical simulation results for the LHLRs illustrate that the equivalent turbulence-free regions between the primary and secondary riblets optimize the turbulence distribution near the wall, which reveals a physical mechanism of turbulence under the effect of microstructures. This research provides a foundation for practical applications such as energy, environmental protection, and transportation.

Keywords: metasurface, turbulence, drag reduction, yardangs, low-high-low riblets