The aerodynamic performance of heavy-vehicle platoons is strongly governed by wake interactions between adjacent vehicles. Although streamlining a leading vehicle can reduce its own drag, its effect on drag redistribution and the inflow environment of following vehicles remains insufficiently understood. This study experimentally investigates the aerodynamic trade-off induced by forebody streamlining of the leading vehicle in a three-vehicle platoon. Wind-tunnel experiments using 1/30-scale cab-over models were conducted at ReL = 4.4 × 10^5 for inter-vehicle gap ratios of G/L = 0.3, 0.5, and 0.7. Synchronized force measurements and particle image velocimetry were used to correlate individual vehicle drag coefficients with the spatial evolution of mean velocity and turbulent kinetic energy in the inter-vehicle wakes. The streamlined leading vehicle reduced the platoon-averaged drag coefficient at all tested spacings, with a maximum reduction of 12.7% at G/L = 0.3. However, the drag coefficient of the first following vehicle increased by up to 9.5%, indicating that the aerodynamic benefit was not uniformly distributed across the platoon. PIV results showed that leading-vehicle streamlining weakened the wake deficit and supplied higher-momentum inflow to the first following vehicle, thereby reducing its wake-shielding benefit. The turbulent kinetic energy upstream of the first following vehicle also decreased, indicating a lower-fluctuation but aerodynamically unfavorable inflow condition. These results demonstrate that leading-vehicle streamlining produces a system-level aerodynamic trade-off by reducing the net platoon drag while increasing the drag burden on the immediately following vehicle.

Understanding the transport behavior of microplastic particles in flotation systems is critical for enhancing their removal efficiency in wastewater treatment processes. Here, we investigated the particle‐lifting effect of a bubble‐chain system on polystyrene (PS) particles under continuous rising flow conditions. A custom‐built chamber equipped with syringe‐driven needle injectors generated successive air bubbles with mean equivalent diameters of 3.21 and 2.81 mm. As the number of bubbles ( N ) increased from 1 to 10, the nondimensionalized vertical displacement ( L _z ) of PS particles increased from 5.29 to 7.66 and 4.53 to 6.07 for 3.21 and 2.81‐mm bubbles, respectively. Correspondingly, the nondimensionalized total displacement ( L _total ) increased from 5.58 to 8.31 and 4.78 to 6.52, showing maximum increases of 44.8% and 48.7%, respectively. As the number of bubbles increased, the axial motion of the particles was significantly enhanced, which was attributed to the vertical expansion of the flow field, the increase in vorticity, and the formation of asymmetric flow structures as identified through particle image velocimetry (PIV) analysis. The formation of overlapping vortices within bubble‐chain systems substantially broadens the effective hydrodynamic field, facilitating improved flotation of microplastic particles. This extended flow structure provides a quantifiable framework for enhancing the efficiency of dissolved air flotation (DAF) technologies, particularly in applications targeting microplastic separation.

This study emphasizes the potential risk posed by microplastics, particularly in tap water. Numerous studies have reported the removal of microplastics, but the limitations in addressing this issue remain challenging. To tackle this problem, a new method is introduced using tandem flexible structures (FSs) for microplastic removal. The present study focused on understanding the hydrodynamic characteristics between FSs to utilize microplastic removal. This comprehension of fluid flow and FSs offers valuable insights for improving the efficiency of microplastic removal methods. Therefore, the optimal conditions for removing microplastics were experimentally investigated inside the FSs gap region. Based on the gap distance and height, the flow structures between FSs were investigated. A small secondary vortex structure that could trap particles from upstream was continuously maintained behind the upstream FSs under certain geometric conditions. It is shown that this vortex structure has an effective way of confining the particles from upstream. The persistency of a small secondary vortex was also evaluated. This study may be helpful to researchers working on microplastic removal and FSs with a tandem arrangement.