Reducing Drag of Vehicles with Half-Stepped Cylinder Surfaces Part I: Numerical Optimization

Abstract

Aerodynamic drag is a major source of energy loss for vehicles, increasing fuel consumption, reducing the driving range of electric vehicles, and contributing to greenhouse gas emissions. For a vehicle, the major components of its drag are pressure and viscous drag. Engineers have developed a variety of strategies to reduce drag, including streamlined vehicle designs, surface modifications, and devices that alter airflow around the vehicle. This research focuses on reducing the viscous drag. Specifically, this study investigates whether microscopic surface features called half-stepped cylinder arrays can reduce skin friction by altering the turbulent boundary layer and promoting smoother airflow near the vehicle surface Using computational fluid dynamics simulations and numerical optimization, the researchers evaluated different cylinder sizes and spacing to identify a surface design that minimized skin friction on a simulated flat plate. The results indicate that when the cylinder’s dimensions are less than 1% of the boundary layer thickness, there is over 33% reduction in average skin friction. The findings demonstrate that carefully designed microscopic surface structures can substantially reduce skin friction in turbulent flows, which can contribute to improved aerodynamic efficiency and lower vehicle energy consumption. Although additional research is needed to validate these results on full-scale vehicles and under real-world operating conditions, this approach shows promise as a passive aerodynamic technology that could improve vehicle efficiency, extend electric vehicle range, and reduce transportation-related energy use and emissions.