Mid- and large-size road vehicles are responsible for high levels of green-house gas emissions, due to their poor aerodynamic designs. To alleviate this environmental and health risk, we propose a low-cost, noninvasive morphing vehicle design toward improved aerodynamic efficiency and reduced emissions. Using a generic pickup truck as the base geometry, morphing is accomplished by retrofitting a flexible structure over its cargo bed region, enabling active deformation and interaction with the airflow. The shape morphing process is optimized through a combined parametric genetic algorithm – computational fluid dynamics framework, enabling continuous morphing across a range of driving speeds. The optimal structural shapes lead to a reduction in the aerodynamic drag force between 8.7% and 10.1%.

Analysis of the velocity, vorticity, and pressure distributions around the vehicle further elucidated the drag reduction mechanism. The retrofitted structure compressed the size of the low-pressure circulation bubble in the cargo bed and wake regions and reduced the size and strength of the counter-rotating vortical flows in the wake, resulting in an increased back-pressure and a decreased drag force. This is corroborated by direct quantification of the aerodynamic loading on the vehicles, where the morphing structure was observed to elicit an increase in the pressure on the rear window and the tailgate.