Abstract
Aiming at aerodynamic drag reduction for transportation systems, a new active surface is proposed that combines a bionic nonsmooth surface with a jet. Simulations were performed in the computational fluid dynamics software STAR-CCM+ to investigate the flow characteristics and drag reduction efficiency. The SST K-Omega model was used to enclose the equations. The simulation results showed that when the active surface simultaneously reduced the skin friction and overcame the sharp increase of pressure drag caused by a common nonsmooth surface, the total net drag decreased. The maximum drag reduction ratio reached 19.35% when the jet velocity was 11 m/s. Analyses of the turbulent kinetic energy, pressure distribution, and velocity profile variations showed that the active surface reduced the peak pressure on the windward side of the nonsmooth unit cell, thereby reducing the total pressure drag. Moreover, the recirculation formed in the unit cell transformed the fluid–wall sliding friction into fluid–fluid rolling friction like a rolling bearing, thereby reducing the skin friction. This study provides a new efficient way for turbulent drag reduction to work.
Highlights
Flow control and drag reduction are important research focuses that should be fully considered in a range of engineering fields
Zhang et al [39] studied the broke the limitations in a single morphology and proposed a new nonsmooth surface inspired by drag reduction characteristics of a revolving body with a bionic jet surface, in which they achieved a sand dunes
The decrease in skin friction was accompanied by a sharp increase in pressure drag, which lead to a net increase in total drag
Summary
Flow control and drag reduction are important research focuses that should be fully considered in a range of engineering fields. Li et al [38] studied the drag reduction characteristics of bionic jet surfaces, in which they obtained a maximum drag reduction rate of 9.51%. Studied the drag reduction characteristics of a revolving body with a bionic jet surface, in which they achieved a maximum friction reduction rate of 10.8%. Zhang et al [39] studied the broke the limitations in a single morphology and proposed a new nonsmooth surface inspired by drag reduction characteristics of a revolving body with a bionic jet surface, in which they achieved a sand dunes. The study numerical simulations are analyzed, and the drag reduction mechanism of the active surface is broke the limitations in a single morphology and proposed a new nonsmooth surface inspired by sand explained with three aspects: Turbulent kinetic energy, pressure distribution, and velocity dunes. Physical Model Establishment and Hypothesis Verification problem of the rapid increase in pressure drag in designing nonsmooth surfaces and achieved better drag reduction effects
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