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Abstract: Inspired by the successful applications of biological non-smoothness, we introduced bionic non-smooth surfaces as appendices into vehicle body design, aiming to further reduce aerodynamic drag. The size range of the non-smooth units with pits and grooves was determined according to our analysis with the mechanisms underlying non-smooth unit mediated aerodynamic drag reduction. The bionic non-smooth units reported here were designed to adapt the structure of a given vehicle body from the point of boundary layer control that reduces the burst and the loss of turbulent kinetic energy. The engine cover lid and vehicle body cap were individually treated with the non-smooth units, and the treated vehicles were subjected to aerodynamic drag coefficient simulation tests using the computational fluid dynamics (CFD) analysis method. The simulation results showed that, in comparison with smooth surfaces, properly designed non-smooth surfaces can have greater effects on drag reduction. The mechanism underlying drag reduction mediated by non-smooth surfaces was revealed by further analyses, in which the effects of non-smooth and smooth surfaces were directly compared.

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