On the drag reduction of road vehicles with trailing edge-integrated lobed mixers

Trailing edge-integrated lobed-mixing geometries are proposed as a viable method for road vehicle aerodynamic drag reduction. Experiments are conducted on a 1/24th-scale model, representative of a Heavy Goods Vehicle, at a width-based Reynolds number of 2.8 × 105. A broad range of pitches and penetration angle values is examined, with detailed comparisons also made to high-aspect-ratio rear tapering. Changes to mean drag coefficients and wake velocities are evaluated and assessed from both the time-independent and time-dependent perspectives. Results show significant drag reductions for lower pitches at higher penetration angles, where the performance of regular tapering is found substantially degraded. The mechanisms responsible for drag reduction are identified to be reductions in the wake size and a shift in the vertical wake balance. The former is shown to be a result of the enhancement in inboard momentum close to the trailing edges through the generation of pairs of counter-rotating streamwise vortices, with the latter attributed to the downstream evolution of the vortices. Overall, these results identify such geometries to be suitable for improving vehicle drag while minimising the losses in internal space.

IMPACT OF FREIGHT TRANSPORTATION ON CD. JUÁREZ ENVIRONMENT AND REVIEW OF AERODYNAMIC DRAG REDUCTION DEVICES FOR HEAVY TRUCKS

En la actualidad, el estudio de como disminuir las emisiones de gases de efecto invernadero de todos los sectores, incluido el transporte es muy importante. El propósito de este trabajo es estudiar el impacto ambiental del transporte de carga en Cd. Juárez y revisar los dispositivos de reducción de arrastre aerodinámico para camiones pesados para tener un mayor entendimiento de que tecnologías o prácticas pueden ser implementadas en el transporte de carga para reducir el arrastre aerodinámico sin afectar el desempeño de los vehículos.

Understanding the Aerodynamic Benefits of Drafting in the Wake of Cyclists

A new approach is presented to characterize the aerodynamic benefit from riding in the wake of another cyclist at different downstream locations. The method presented uses the dynamic pressure deficit in the wake of a cycling mannequin to estimate percentage drag savings. In the experiments, the time-averaged velocity behind a cycling mannequin was recorded in 1 × 0.95 m cross-planes by two four-hole pressure (Cobra) probes for four static leg positions (0°, 90°, 180°, and 270°). It was found that the wake of the cycling mannequin propagated to one side or the other as it developed downstream, depending on the strength of the two large-scale counter-rotating streamwise vortical structures shed off the hips of the mannequin. In the near wake, the complex wake dynamics resulted in an inaccurate prediction of the relative drag reduction based upon a dynamic pressure deficit. However, as the wake developed and stabilised further downstream, the dynamic pressure deficit was found to provide a reasonable estimate of the aerodynamic drag reduction of riding in the wake of the lead rider.