Active drag reduction of a maglev train model using steady blowing jets

The active drag reduction (DR) of a maglev train (MT) model using steady blowing jets has been experimentally investigated. Extensive measurements were taken using force balances, pressure scanners, and particle image velocimetry with and without control. Based on these measurements, a comprehensive conceptual model of the flow around the MT model is proposed for the first time. This conceptual model identifies several predominant large-scale structures, including a recirculation region downstream of the tail nose, and four pairs of longitudinal vortices above and below it. To manipulate these structures, a total of 232 blowing configurations, with different blowing locations or blowing angles, were deployed on the tail car. The dependencies of DR on the blowing ratio and angle were determined based on the force data obtained simultaneously from two force balances. Only fifteen configurations may achieve a DR of greater than 1%, with a maximum of 7%. Targeted control of different dominant structures produced substantial modifications to the flow. Specifically, the optimal control achieved a DR of 7% by suppressing a predominant longitudinal vortex pair above the tail nose and preventing the merging of the wake vortices. Additionally, delaying flow separation at the nose tip and mixing high-momentum fluid with the boundary layer below the tail nose resulted in DRs of 3% and 5%, respectively. The maximum net power saving achieved by these steady jet configurations was 4%, corresponding to a DR of 6%.