A numerical investigation on the effect of length on wake flow asymmetry of a simplified heavy vehicle

This article examines the impact of the length of ground transportation system (GTS) model on the dynamics of its wake flow using improved delayed detached eddy simulation (IDDES) method at Re = 2.7 × 104. Four cases characterized by lengths of L, 0.5L, 0.375L, and 0.25L were examined to investigate the aerodynamic features of the GTS model. The validity of the method was confirmed by comparing the wake flow structure, probability distribution function (PDF), vortex core, and aerodynamic drag results of the baseline model with those obtained from the prior IDDES. As the length changes, distinct variations in vortex formations are observed at the wake. The rear base pressure coefficient gradient and PDF results show positive values for the L, 0.5L, and 0.375L cases, indicating they belong to the same flow regime, with asymmetrical flow characteristics. In contrast, the 0.25L case exhibits a zero pressure gradient, indicating symmetrical flow characteristics. Compared to the baseline (L), the total aerodynamic drag decreases by 6.9%, 8.7%, and 15.7% for 0.5L, 0.375L, and 0.25L, respectively. Consequently, the study of length variations on wake flow and aerodynamic characteristics of the GTS model provides essential guidance for engineers in designing and optimizing square-back vehicles.